Ecology of Insular Southeast Asia: The Indonesian Archipelago

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Prelims-N52739.fm Page i Friday, August 11, 2006 12:21 PM

Ecology of Insular

Southeast Asia

THE INDONESIAN ARCHIPELAGO

Prelims-N52739.fm Page ii Friday, August 11, 2006 12:21 PM

Illustrations by Rolito M. Dumalag Hilongos, Leyte, Philippines

Desktop publishing by Elvira Bulawan-Gorre Leyte State University, Visca, Baybay, Leyte, Philippines

Prelims-N52739.fm Page iii Friday, August 11, 2006 12:21 PM

Ecology of Insular

Southeast Asia

THE INDONESIAN ARCHIPELAGO

Edited by Prof. Dr. Friedhelm Göltenboth, Biologist

University of Hohenheim, Stuttgart, Germany

Dr. Kris H. Timotius, Biologist

Universitas Kristen Satya Wacana, Salatiga, Indonesia

Dr. Paciencia Po Milan, Biologist

Leyte State University, Visca, Baybay, Leyte, Philippines

Dr. Josef Margraf, Biologist

Jinghong, Yunnan, PR China

Amsterdam • Boston • Heidelberg Paris • San Diego • San Francisco

•

London • New York • Oxford

• Singapore • Sydney • Tokyo

Prelims-N52739.fm Page iv Friday, August 11, 2006 12:21 PM

Elsevier Radarweg 29, PO Box 211, 1000 AE Amsterdam, The Netherlands The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, UK

First edition 2006 Copyright © 2006 Elsevier B.V. All rights reserved No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publisher Permissions may be sought directly from Elsevier’s Science & Technology Rights Department in Oxford, UK: phone (+44) (0) 1865 843830; fax (+44) (0) 1865 853333; email: [email protected]. Alternatively you can submit your request online by visiting the Elsevier web site at http://elsevier.com/locate/permissions, and selecting Obtaining permission to use Elsevier material Notice No responsibility is assumed by the publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. Because of rapid advances in the medical sciences, in particular, independent verification of diagnoses and drug dosages should be made Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN-13: ISBN-10:

978-0-444-52739-4 0-444-52739-7

For information on all Elsevier publications visit our website at books.elsevier.com

Printed and bound in The Netherlands 06 07 08 09 10

10 9 8 7 6 5 4 3 2 1

Contents PREFACE

vii

ACKNOWLEDGEMENTS I

16 Tropical Lowland Evergreen Rainforests 297

17 Special Forest Ecosystems 385

18 Mountain Forests 401

ix

INTRODUCTION V

F. GÖLTENBOTH & W. ERDELEN

1 Geography and Geology 3

2 Climate 17

II

AQUATIC ECOSYSTEMS Marine Ecosystems

AGROECOSYSTEMS AND HUMAN

ECOLOGY

19 Ecology of Rice Fields and Other

Land Use Systems 417

F. GÖLTENBOTH, W. KOCH & J. SAUERBORN

20 Social Ecology 465

F.GÖLTENBOTH, S. SCHOPPE & P. WIDMANN

3 Seagrass Beds 31

4 Coral Reefs 47

5 Open Oceans 71

6 Deep Sea 85

Freshwater Ecosystems

GLOSSARY 501

F. GÖLTENBOTH

F. GÖLTENBOTH & P. LEHMUSLUOTO

7 Lakes 95

8 Rivers 139

III

F. GÖLTENBOTH

BIBLIOGRAPHY 520

F. GÖLTENBOTH

TABLE OF ABBREVIATIONS 541

F. GÖLTENBOTH

ECOTONES AND SPECIAL

ECOSYSTEMS

9 Shore and Tidal Flats 171

CONVERSION FACTORS

F.GÖLTENBOTH, S. SCHOPPE & P. WIDMANN

10 Mangroves 187

F.GÖLTENBOTH & S. SCHOPPE

11 Estuaries and Soft Bottom Shores 215

543

F. GÖLTENBOTH

INTERNATIONAL SYSTEM OF UNITS OF

MEASUREMENTS, OR SI 544

F. GÖLTENBOTH

F.GÖLTENBOTH & S. SCHOPPE

12 Caves 229

GEOLOGICAL TIME TABLE AND

SYSTEMATICS 546

F. GÖLTENBOTH

13 Small Islands Ecology 239

F. GÖLTENBOTH

14 Grasslands and Savannas

F. GÖLTENBOTH & P. WIDMANN

267

F.GÖLTENBOTH & P. WIDMANN

INDEX

550

IV FOREST ECOSYSTEMS F.GÖLTENBOTH, G. LANGENBERGER & P. WIDMANN

15 Beach Forests 281

v

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Preface The Tropical Ecology of South East Asia- The Indonesian Archipealago is designed to be a teaching tool. Above all we see the workings of natural selection in the form and function of every living thing and we do know that the majority of primary production on this globe takes place in the tropical ecosystems. Each dicipline has also its own history- also Tropical Ecology. While in the 1970s only a few

major areas of Indonesia. These books compiled during the 1980s and 1990s the information available from various places and various publications and pushed forward the interest in the ecology of the Indonesian Archipelago, one of the most diverse, complex and extremely interesting biogeographical regions of the world.

SUBTROPICAL AND TEMPERATE CLIMATE LESS THAN 0.5

DESSERT

Figure 1.

0.5 - 3.0

GRASSLAND, DEEP LAKES, MOUNTAIN FORESTS, AGRICULTURE

TROPICAL CLIMATE 3 - 10

10 - 25

TROPICAL RAINFOREST, RICEFIELDS, SHALLOW LAKES

0.5 - 3.0

LESS THAN 1.0

CORAL REEF MANGROVES

DEEP SEA

Distribution of global primary production as annual production in 1,000 kj/m2 (after Odum, 1963).

books were available concerning tropical ecology, none was in existence specifically for the Indonesian Archipelago. This lack of information for the interested scientific community changed when the Environmental Management Development in Indonesia Project (EMDI) started to publish the series of special books concerning the ecology of the

Environmental awareness has penetrated so far both the minds of the interested layman , university curricula and government policy. An understanding of the components of ecosystems and the manner in which they interact is central to studying the environment and to conduct sound resource management (Dardak, 1984 in Whitten et al., 1984).

vii

In writing a textbook about The Ecology of South East Asia - specifically the Indonesian Archipelago we had the following objectives in mind: 1. To provide an up-to-date textbook cover ing the major concepts of basic ecology at the undergraduate level because the better of the existing books are too large or specific for many undergraduate courses. 2. To illustrate the principles of basic ecology mainly with examples of tropical organisms and tropical ecosystems found in the Indo nesian archipelago. 3. To give a broad view of the natural systems, applied and human ecology of one of the most outstanding biogeographical regions of the world. The environmental impact of rapid cultural changes in the Indonesian archipelago can only be fully understood in an ecological context. In scanning the available literature it was found that more recent ecological literature on tropical issues of the Indonesian archipelago are very rare with the exception of the

EMID books. There is a severe paucity of any suitable textbook to complement lectures , seminars and laboratory sessions at the university and college level. This fact is unfortunate given the enourmous needs for more information for a better understanding of the ecological and environmental laws, principles and interactions to avoid unnecessary environmental stress in an archipelago under rapid development. This textbook will be useful to teachers of the classes in the subject matter and their students , and also to working ecologists who would like to gain an overview about insular ecology of the vast Indonesian Archipelago. Readers who have not experienced any basic introductory classes in biology or ecology may consult the book´s glossary to understand the specialized terminology that is sometimes used. Finally , we do hope that this book will encourage environmental awareness and provide sufficient stimulation to stem the decline of living quality caused by unnecessary environmental destruction throughout the Indonesian Archipelago.

FRIEDHELM GÖLTENBOTH University of Hohenheim Stuttgart, Germany

viii

Acknowledgments

We would like to thank the following friends and colleagues who reviewed draft chapters or were even involved in drafting paragraphs and figures of various chapters: Prof. Dr. Walter Erdelen for reviewing all the major chapters of the book, and giving substantial comments to make the book more readable and pleasing; Prof. Dr. Gernot Bretschko and Dr. Pasi Lehmusluoto for their comments concerning the river and lake chapters; Dr. Sabine Schoppe for proof reading and correcting particularly the chapters dealing with marine ecosystems; Prof. Dr. Andreas Schulte, Prof. Dr. Albert Reiff and Dr. Gerhard Langenberger for their profound screening of the chapters dealing with forests; and the late Prof. Dr. Werner Koch and Prof. Dr. Joachim Sauerborn for their substantial support in reviewing the chapters of agro-ecological content and human ecology. There is no doubt that the book has been markedly improved by their comments and inputs. Any remaining mistake or heresies are probably where we ignored their advice. Our very special thanks go to: Peter Widmann, MSc for his substantial contribution to many chapters; Rolito M. Dumalag a freelance scientific artist illustrator of Hilongos, Leyte, Philippines, who made all the figures illustrating in an excellent manner the various aspects of tropical ecology of South East Asia and the basic principles of general ecology; and to Elvira B. Bulawan-Gorre of the Leyte State University, Visca, Baybay, Leyte, Philippines who professionally produced the desktop version of this publication. Partial financial support during the first time of writing came from the ViSCA-GTZ Applied Tropical Ecology Project which is gratefully acknowledged. If any readers have comments or criticisms of the material or approach used in this book, we would be most grateful if you would communicate your ideas and suggestions to us. THE EDITORS ix

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Ecology of Insular SE Asia • The Indonesian Archipelago

1

CHAPTER I

Introduction

S

ituated upon the equator, and bathed by tepid water of the great tropical oceans, this region enjoys a climate more uniformly hot and moist than almost any other part of the globe, and teams with natural productions which are elsewhere unknown (Wallace, 1869). This short sentence expresses the still fascinating encounter to the scientific or casual visitor to these thousands of islands of the Indonesian archipelago. All major ecosystems of the tropics can be found here and the miriads of habitats harbour most probably more organisms and ecological secrets than already have been revealed since the first systematical studies were made by naturalists like G.E. Rumphian (1627 -1702) or Sir Alfred R. Wallace (1854 - 1862). Considering the already huge amount of information collected by various expedition and accumulated in impressive long shelves in libraries it is surprising that the ecosystem and biodiversity of the Indonesian archipelago remains largely unknown and generally unavailable to students and teaching staff on the textbook level. It is therefore the main objective of this textbook to introduce students to the fascinating environment of the Indonesian archipelago. It is hoped that it will serve the interested student and public at large providing an overview of all major ecosystems with special focus on ecological basic processes including impacts of the activities of man.

Introduction

2

Göltenboth, Timotius, Milan and Margraf

GEOGRAPHY AND GEOLOGY


THESIS In 1996 the Republic of Indonesia officially declared itself an archipelagic nation. The approximately 17,000 islands and the seas between the islands shape the country. “Tanah air”, land and water, is officially combined by this proclamation. The Indonesian archipelago is often called an island continent and the boundaries are the result of the colonial past and not due to natural boundaries between different peoples or due to geographical factors. More than 300 different ethnic groups are living in Indonesia. They differ in language and cultural background, comprising people with more than thousand years of cultural heritage, like the Javanese, and stone age tribes in West Papua who even do not yet know that they are living in the Indonesian archipelago. For many people, Indonesia is fascinating and frightening at the same time. Landscapes of outstanding beauty are threatened by active volcanoes. Earthquakes and tsunamis are part of the day-to-day life of many of the islanders. The megalopolis of Jakarta is mushrooming into the surrounding environment with a steady accelerating speed producing a wide range of problems, including shortage of drinking water and far reaching pollution. The overpopulated areas of Java, Madura and Bali have reached their carrying capacity already decades ago and people are moved to the outer islands in one of the worldwide biggest migration programs under peaceful conditions (Program Transmigrasi). In some areas the richness of the natural environment is threatened by large scale deforestation projects, huge mining activities or the on-going misuse of natural resources. Indonesia is often called the country of people who are at the same time beyond description happy or miserable ( Raffles, 1817). It is called a nation in waiting or a sleeping giant (Schwarz, 1994).

3

1


Friedhelm Göltenboth and Walter Erdelen

Introduction

4


THE NAME AND THE PEOPLE On August 17, 1945 the independent fighters for a free “Dutch East India” under the leadership of Dr. Hatta and Sukarno gave the newly proclaimed republic the name Indonesia. The Indonesian archipelago is about 5,219,270 km 2, including the independent East Timor. About 17,508 islands for this archipelago was first used by the British ethnologist J.R. Logan in his book entitled “The ethnology of the Indian archipelago and eastern Asia”, issued in 1850. In 1922 the organized students of Dutch East India gave themselves the name: Perhimpunan Indonesia. This was a political program stressing the desire to be one nation and one country with one language. The state emblem, the Garuda eagle, holds the national motto saying Bhinneka Tungal Ika or “Unity in Diversity”. This refers to the fact that some 250 different languages are spoken by over 300 officially recognized ethnic groups. While the coastal regions have always been open to new cultural influences through migration and trade, the interior of the islands have provided secure havens for local cultures for long periods. Three major cultural forms can be recognized: Firstly the great stratified state societies based on irrigated rice cultivation, particulalry those of the Javanese, Sundanese, Madurese and Balinese. Secondly , the smaller coastal states based on a combination of trading and fishing as well as irrigated rice. For instance those of the Mollucans and Sulawesi people. Thirdly, the indigenous subsistence farmers, hunters and gatherers inhabiting the forested areas with their village -based societies, like the Dayak in Kalimantan or the Papuans in West Papua. With an estimated population in 1998 of more than 200 million people Indonesia is the fourth most populous nation in the world. Despite the fact that since the 1980’s a decline in the population growth rate is observable the demographic momentum built into the Indonesian age pyramid will ensure a substantial population growth with estimated population numbers of 254 million by the year 2020


and a peak population of about 354 million at the end of the next century (Hugo, 1996). GEOGRAPHICAL LOCATION AND MAJOR GEOGRAPHICAL SECTIONS Indonesia is the largest archipelagic state of the world with about 5,219,270 km2, including East Timor. About 17,508 islands, of which about 6000 are inhabited, form the landmass of about 1,919,270 km2 encircled by about 3.3 Mio km2 of territorial seas (Rigg, 1996). The arc of islands surrounds single seas and straits which are more of connecting than separating nature between the single islands. After Greenland, the biggest islands of the globe belong partly to Indonesia, like the Western part of New Guinea called West Papua and the Southern part of Borneo, called Kalimantan. The arc of islands connects the Asian mainland with the Greater Australian continent. They sit on the submerged Sunda Shelf in the western parts of Indonesia with the islands of Sumatra, Java , Madura, Bali , Kalimantan, Riau, Bangka and Belitung, forming the islands of the transition area with Sulawesi, Lombok, Sumba, Sumbawa, Flores, Timor and the Molluccas or sit on the Sahul Shelf south of the equator, for instance West Papua. The north-to south distance is about 1,770 km while the EastWest distance is about 5,152 km or 1/8th of the circumference of the globe (Fig. 1.1) The highest mountain in Indonesia is the 5,029 m-high Mt. Jayawijya or Puncak Jaya or Gunung Jaya in West Papua. One of the longest rivers is the Kapuas River in Kalimantan with more than 700 km, the largest lake is Lake Toba in Northern Sumatra with 1,146 km2, the deepest lake is Lake Matano in Sulawesi with 590 m depth and the deepest sea is the Banda Sea with more than 7,000 m depth , while the Java Sea shows an average of 40 m depth only. Indonesia covers only 1.3% of the Earth’s surface yet harbors 10% of all flowering plants, 12% of the world’s mammals, 16% of the world’s reptiles


FIGURE 1.1.

5

Geographical location of the Indonesian archipelago.

and amphibians, 17% of all birds and more than 25% of known marine and freshwater fish species (Stone, 1994). GEOLOGY The surface of the earth consists of a mosaic of continental (sima), and oceanic (sial) plates made up of crust and an upper mantle which form the lithosphere. Oceanic plates may be 60 km thick and continental plates about 100 km. These plates are in continous movement over the partially molten hot layer beneath called the asthenosphere where the magma originates from which it is ejected by active volcanoes in form of lava (Rigg, 1996). The Indonesian archipelago is comprised of three major plates:

• The Eurasian Plate in the west including the Sunda shelf area. • The Pacific Plate with its two attached minor plates the Philippine plate and the Caroline plate and its subduction zone along the Pacific coastline of the Philippines and New Guinea. • The Indo-Oceanic-Australian Plate with its subduction zone along the Indian Ocean side of the arc of islands from Sumatra to the Sahul shelf area in East Indonesia (Fig. 1.2). The tensions created by the collision of these plates power the volcanic events in the entire Indonesian archipelago and are responsible for the mountain and landscape forming processes. This process started about 150 million years ago when, what is now some parts of the Western

Introduction

6


FIGURE 1.2.

Tectonic plate boundaries in South and South East Asia with subduction zones where one part of the earth’s crust is forced below another at the junction of two tectonic plates (after van Bemmelen, 1970).

Indonesian islands and Western Sulawesi, split off Gondwanaland and drifted northwards. As Gondwanaland continued to disintegrate, New Guinea was gradually pushed further north, ahead of Australia. About 15 million years ago, a part of New Guinea went its separate way, drifting westwards until it collided with another landmass of the west to form present-day Sulawesi. Thus the western parts of Sulawesi were originally part of South East Asia while Sulawesi’s eastern arms were derived from the Australian land mass. At approximately the same time, the first small islands emerged from the sea where the West Javan Plateau is situated today. Further tectonic movements caused more land to rise up on Java and Borneo whose South Western and South Eastern


parts where islands in the Tethys Sea. Timor and the islands of the outer Banda arc, Buru, Seram and Tanimbar, were all once part of the northern margin of the ancient Australian continent and were bent westward by the movements of the northwarddrifting Australian plate (Whitten et al., 1987). In this area of South East Asia two areas, continental Asia and continental Australia are welded together by an active process of mountain building. The Sunda Mountains is one of the greatest coherent mountain belts of the world and consists of two parallel belts of mountain arcs, island-festoons and submarine ridges. The inner one has a volcanic nature whereas the outer one is non-volcanic. It streches inside of present day Indonesia from the noose formed by the Banda arcs in the East along the


Lesser Sunda Islands, Java, Sumatra to the Andamans and Nicobars in the Indian Ocean and meets the Himalayan system in Burma (van Bemmelen, 1970). The Circum Australian System of mountains extends along the central axis of New Guinea. Primary movements of the plates and secondary upward thrust that occured at different geological times along the length of the Sunda Mountain System formed also the chain of islands for instance along the Western coast of Sumatra. A very deep trough falling to the Indian-Ocean-Australian Plate, was

FIGURE 1.3.

7

formed to the west of these islands (Verstappen, 1973). Until today volcanic activity, both on land and beneath the sea, is a continuing process in this region. The entire area of Indonesia is relatively unstable and 500-1,000 earthquakes per year can be recorded. More than 170 volcanoes of the 300 volcanic mountains are still active and 49 are in the fumarole and solfatare phase (Fig. 1.3) Each earth movements and, more recently, volcanic activity have had a great influence on the physical development of Indonesia. An “arc of fire” runs

Schematic cross-section through the Indonesian archipelago (after Huxley, 1988).

Introduction

8


from the northern tip of Sumatra through Java and Nusa Tenggara out into the Banda Sea. The majority of the volcanoes are formed by layers of ashes and lava. The surrounding soils of these so-called stratovolcanoes are very fertile and therefore very attractive for farmers despite the steady existing threat by eruptions, earthquakes and mudstreams. Dormant volcanoes often show colorful crater lakes. Lakes are also a dominant feature in another type of volcanic landscape, the caldera. Calderas are the result of an implosion of the surface underneath an emptied volcanic oven. Lake Toba, lake Maninjau on Sumatra, the Idjen and Bromo area in East Java have been formed after such a cataclysmic event leading to the formation of large calderas. One of the most striking examples of a cataclysmic volcanic eruption in recorded history was the catastrophe of the eruption of the Krakatau island in 1883. The submarine eruption of this island in the Sunda Strait between Sumatra and Java killed about 36,000 people and fast stretches of coastal areas were completely devastated due to a Tsunami wave more than 20 m high. In 24 hours more than 18 km3 of ashes and volcanic pebbles were blown into the atmosphere covering 827,000 km2 of adjacent land areas with ashes (Thornton, 1996) (Fig. 1.4). When during the August 26, 1883 events sea water burst into the emptied magma chambers of the Krakatau, a devastating wave was formed and the sound of the explosion was recorded as far away as Sri Lanka, the Philippines and even Western Australia. Since then a new island, up to 200 m above sea level, was formed from underneath the sea crater at about 260 m depth. The completely devastated leftovers of former Krakatau island were after 14 years already colonized by 132 species of insects and birds and 61 species of plants. In 1815, Gunung Tambora on the island of Sumbawa blasted away the top 1,800 meters of its peak. It threw out 80 km3 of ashes which killed about 90,000 people (Stone, 1994) and cooled the


Earth enough to cause the “year without summer” of 1816, leading to worldwide hunger. This eruption is recorded as the most massive one ever recorded. Mineralization processes of the volcanic activities over geological periods lead to substantial deposits of tin, nickel, magnetite, zircon, copper, gold, silver, mercury and other rare minerals. During the Tertiary enormous amounts of sediments accumulated in regional troughs. These Tertiary sediments are the storage material for fossil fuels like crude oil and gas which are mined today in Aceh in Northern Sumatra, Lampung in Southern Sumatra, in Eastern Kalimantan and in the Vogelkop Peninsula of Irian Jaya. In some areas of Southern Sumatra, Eastern Kalimantan, Central Sulawesi and Irian Jaya coal can be mined. In some areas in Java phosphate deposits, deriving originally from the phosphate rich excrement’s of cave dwelling bats and birds, have been accumulating over time and are mined today. GEOMORPHOLOGY AND SOILS On of the associated thrusts of the collision of the Indian subcontinent with continental Asia caused the uplift of the Barisan mountains that run the length of Sumatra, the mountain ranges of Java, Bali and the Lesser Sunda Islands. During the Oligocene andesitic volcanism transformed the landscape which was further shaped by faulting and creation of rift valleys during Pliocene and Pleistocene. The Quaternary volcanic activity covered wide areas with ashes being the mother material for soils of today, for instance on Sumatra, Java and Bali (Whitten et al., 1984). The geomorphological features of the main islands of Indonesia can shortly be decribed as follows: Sumatra with a land area of about 473,000 km2 has 93 peaks with Mt. Kerinci being the highest with 3,805 m a.s.l. North-eastern of the Barisan range, largely composed of sedimentary rocks, low hills and plains form the landscape. Further east alluvial plains were formed by sediments coming


FIGURE 1.4.

9

The development of Krakatau Island in the Sunda Strait between Sumatra and Java ( after Thornton, 1996).

Introduction

10


mainly via transversing south-east flowing rivers like the Musi, Indragiri, Kampar and Baruman River. Sumatras soils are generally not very fertile. Waterlogging poses in vast areas of the eastern plains a problem, while the foothills of the Barisan range tend to be heavily leached. The island of Java is about 1,000 km in length and some 200 km in width and is punctuated by a line of volcanoes running the length of the island. The highest of these volcanoes is Mt. Semeru with 3,676 m. The Central Javan Mt. Merapi is one of the most active volcanoes. Nutrient rich lava and ash from Java’s volcanoes account for the fertile soils of the foothills and the Northern plains, particularly in Western and Central Java. This contrasts with the shallow soils and soluble rocks of the limestone karst areas in the northeast and southeast, and the acidic and leached soils of the southern hills. All major rivers run from the mountain ranges northward into the Java Sea. With the exception of the Brantas River in East Java the rivers are all relatively short. Bali is a comparably small island with just 5,561 km2. Most of the rivers on Bali flow from the Central highlands with their volcanoes, like Mt. Batur and the highest Mt. Agung (3,140 m), through the foothills into the Indian Ocean. The rich and fertile soils allow two rice crops per year. The north of the island has a much drier climate and the mountains drop steeply to the sea, with only a narrow coastal lowland strip. Kalimantan, or Indonesian Borneo, embraces the southeastern two-thirds of the island. With the exception of the Meratus Mountains in the southeast and limestone outrcops in the west much of Kalimantan consists of vast areas of not very fertile alluvial soils. They have been formed on the shallow parts of the Sunda Shelf. A network of rivers that originate in the central mountains dissect this lowlands. The two largest river networks are the east flowing Mahakam and the west flowing, and longest, the Kapuas. The numerous other large rivers, like the Mendawai River, Kahayan River and Barito River drain south into the Java Sea.


On Sulawesi there are few lowland areas. Most of the island is above 500 m with 11 active volcanoes in the Minahasa Region of North Sulawesi. Deep valleys disect the uplands and fast flowing rivers run through them like the 200 km long Lariang. Soils are usually poor because of high levels of magnesium and heavy metals, if the mother material is not covered by volcanic ashes like in the South of Sulawesi. The islands of Nusa Tenggara stretch over 1,300 km, divided into two arcs: the longer volcanic northern arc with Lombok, Sumbawa, Komodo, Flores, Solor Island, Alor Island and Kalbahi, and the shorter southern one consisting of Sumba, Savu, Roti and Timor formed from raised coral reefs and sedimentary rocks. While the volcanic soils of the northern arc are generally fertile, the southern arc islands comprise barren limestone plains and sparse savannas with less productive soils due to lack of rain. On all these islands there are few permanent water courses, with river and streams beds filling up and disappearing in the rainy and airy season, respectively. The about 1,000 islands forming the Moluccas, vary from small uninhabited atolls to large island, like Seram with 18,400 km2. The northern and central islands have active volcanoes and are naturally covered with tropical forest.The Aru Islands are composed of mangrove swamps and tidal salt marshes. From an ecological point of view that part of new Guinea belonging to Indonesia, named West Papua, can be divided into three geographic regions: a mountainous zone; the coastal lowlands; and the interior lowlands. The mountain range runs from northwest to southeast and is made up of numerous peaks, 11 exceeding 4,800 m. Mt. Jayawijaya is the highest mountain in Indoensia with 5,029 m. Permanent snow and a glacier exist on this mountain. In addition to the central range a coastal range or Van Rees Mountains form a natural barrier between


the north and south of the island. In the north of the central mountain range a large swampy area pushes the northern plains into a relatively thin belt along the coast. The enormous network of the Mamberamo River transports the water from the Central mountain range to the Pacific Ocean. To the south of the central range there are a few plains before the mountains reach the sea while in the east, large coastal swamps separate the mountains from the sea. These swamps are crossed by huge meandering rivers like the Utumbuwe River, the Baliem River, the Kampung River and the Digul River. Single areas like the Baliem valley in the highlands, the homeland of the Dani tribe, have very fertile soils. The swampy areas in the South are the center of Sago-based tribal societies like the Asmats. BIOGEOGRAPHY After the sea level rise at the end of the Pleistocene glacial period the present island situation was formed. This rise of the sea level with the corresponding isolation of the single islands is responsible for the very unique distribution pattern of animals and plants in the Indonesian archipelago. Therefore the Indonesian archipelago is subdivided into three distinctive areas: • The Sunda Shelf area in the West including Sumatra, Java, Madura, Bali and Borneo. • The transition or Wallacea area including Sulawesi. • The Austro-Melanesian area consisting mainly of West Papua. The flora and fauna of most of the islands of this archipelago tells of ancient affiliations. The animals of the Great Sunda islands of Java, Sumatra and Borneo are characteristically Asian with tigers, elephants, tapir, deer, monkeys and squirrels. In contrast, the island of New Guinea has no indigenous placental mammals other than bats, rats and the sealiving dugong (MacKinnon,1992b). Fossil evidence shows that lowering and raising of the sea level happened several times during the

11

Pleistocene. The periodic lowering and raising of sea levels meant that connections between mainland Asia and the islands of the Sunda Shelf, and between Australia and the islands of the Sahul Shelf, were periodically broken. During the periods of geographical isolation species of plants and animals, many of them new colonizing species, spread and quickly filled vacant niches. New species arriving in successive waves then had to content with already established species, and each had to find a new niche if the preferred habitat was already occupied, or adapt to living under sub-optimal conditions. Java, for example, supported a rich Pleistocene fauna. In addition to species still present today and their ancestral forms, the Java fauna included bears, hyenas, elephants, tapirs, antelopes, giant pangolins and orang utans, whose distribution in the present Oriental region is much more limited today. For the purpose of zoogeography the world is divided into six realms. Indonesia falls into two of them: the Oriental Realm and the Australian Realm. Confined within the boundaries of the oriental realm are leaf monkeys (Fam. Cercopithecinae), gibbons (Fam. Hylobatidae) and flying lemurs (Fam. Cyancephalida). Only one family of birds is endemic to this realm, the family Irenidae with the Fairy blue birds (Irena sp.), the Leafbirds (Chloropsis sp.) and the Ioras (Aegithina sp.) The center of evolution of this bird family is Sumatra. The Isthmus of Kra, marking the boundary between the Sunda Region and Mainland or Continental Asia, is an obvious regional boundary which coincides with a change in vegetation which is also reflected in the fauna. At this isthmus 375 genera of plants reach their northern limit and 200 genera their southern limit. The Sunda, Transition, and Sahul Region today supports a wide range of vegetation types, a broad altitudinal range of vegetation types, and high faunal and floral species diversity. For example, 4,600 flowering plants are recorded for Java while West

Introduction

12


Papua has approximately 9,000 species of flowering plants of which some 90% are endemic. The history of the area is also reflected in the percentage of combined total of plant and animal species shared for example between the major parts of the Sunda region (FAO and MacKinnon, 1982) (Table 1.1-1.2). Big gaps do exist particularly in the knowledge of present days invertebrate fauna and it is not possible to state precisely why the tiger never managed to get from Sumatra to Borneo or the lesser mouse deer from Sumatra to Java. Also scientific issues like “split distribution” inside a given area without any obvious natural boundaries like big rivers or mountain ranges, are unexplainable with the recent knowledge. Such a “split distribution “can be observed in the area of Lake Toba in Sumatra where a SW-NE boundary runs through the lake: only north of the boundary leaf monkeys, white headed gibbons and organg-utans are found, only south tarsier and tapir. TABLE1.1.

Composition of mammal fauna of various islands in Indonesia (after Whitten et al., 1988).

Island

Total number of mammal species recorded

Borneo Sulawesi Flores Moluccas Irian Jaya

TABLE 1.2.

Plants Birds Mammals

149 109 20 53 55

Percentage of shared plant and animal species between major parts of the Sunda Region (after FAO and MacKinnon, 1982).

Sumatra - Malaysia

Sumatra - Borneo

49 74 63

45 66 55


Sumatra Java - Java - Borneo 37 49 43

27 37 36

The feature of repeated waves of colonization and specialization of plants and animals is very vividly displayed in Indonesia. Early explorers and naturalists were puzzled by the extremely high and divergent levels of species found in the region. Among the first to document systematically these important discoveries was the Victorian naturalist and voyager, Alfred Russel Wallace, a contemporary of Charles Darwin. In Indonesia, Wallace noticed that in Lombok and on islands of the east one could find cockatoos, parrots and marsupials. In contrast, monkeys, tigers, elephants and rhinoceros were found on Bali and on islands further west. He expressed these findings in his book “The Malay Archipelago” the following way: “We have here a clue to the most radical contrast in the archipelago, and by following it out in detail a line among the islands, which shall so divide them that one-half shall truly belong to Asia, while the other shall no less certainly be allied to Australia. I term this the “Indo-Malayan” and “AustroMalayan” division of the archipelago” (Wallace, 1869). This important faunal boundary, separating Bali from Lombok and extending northwards through the Makassar Strait, separating Borneo from Sulawesi including Palawan Islands is dubbed the “Wallace Line” in his honor. While the Indonesia flora is predominantly Malesian throughout the archipelago, determined by natural factors such as rainfall, altitude and latitude, the distribution of faunal elements more closely reflects ancient land connections, with placental mammals being found in the west and marsupials in the east (Fig 1.5). The most characteristic tree family of the tropical lowland evergreen rainforest in Southeast Asia is the family of Dipterocarpaceae. As documented by fossil imprints of leaves and fruits found in Southern Sumatra (Ashton, 1982), dipterocarp trees have occurred in Southeast Asia since the Tertiary.


FIGURE 1.5.

13

The floral regions of South East Asia and the most important zoogeographical lines in the Indonesian Archipelago (after Huxley,1988). Wallace’s Line : Boundary of predominantly continental Asian fauna Weber’s Line: 50% Line of continental Asian fauna and Australo-Melanesian fauna Lydekker’s Line : Boundary of predominantly Australo-Melanesian fauna The floral region of Malesia is subdivided into 3 subregions: (1) West Malesia with Southern Thailand, Peninsula Malaysia, Sumatra, Borneo and the Philippines; (2) East Malesia with Sulawesi, the Mollucas and West Papua ; (3) South Malesia with Java, Bali and the Nusa Tenggara islands including Timor

Examples of Major Endemic Species 1 Orang Utan in Sumatra and Kalimantan 2 Javan Rhinoceros in Western Java 3 Proboscis Monkey in Southern and Central Kalimantan 4 Flying Frog in Kalimantan 5 Black Macaca in Northern Sulawesi 6 Babirusa in Central and Northern Sulawesi 7 Anoa in Central and Northern Sulawesi 8 Komodo Dragon on Komodo Island 9 Long-horned Beetle in the Moluccas

Examples of Australian-Melanesian Fauna 1 0 Cuscus in Sulawesi 1 1 Yellow-crested Cockatoo in Timor Island 1 2 Tree Kangaroo in West Papua Examples of Oriental Fauna 1 3 Tapir in Malaysia and Sumatra 1 4 Sumatran Rhinoceros in Sumatra 1 5 Flying Lizard in Sumatra, Java, Kalimantan and Sulawesi 1 6 Giant Rat in Nusa Tengara Islands

Introduction

14


1a 1b

2a 2b

3a 3b

4a 4b

A Arboreal animals 1a Thomas Leaf monkey (Presbytis thomasi) 1b Cuscus (Phalanger orientalis) 2a Flying squirrel (Petaurista petaurista) 2b Sugar glider (Petaurus breviceps) 3a Prevost’s squirrel (Callosciurus prevostii) 3b Possum (Distoechurus pennatus) B Terrestrial animals 4a Leopard cat (Felis bengalensis) 4b New Guinea quoll (Dasyurus albopunctatus) 5a Hourse shrew (Suncus murinus) 5b Red cheeked dumart (Sminthopis sp.) 6a White-bellied rat (Niviventer cremoriventer) 6b Striped bandicoot (Microperoryctes longicauda) C Grassland animals 7a Banteng (Bos javanicus) 7b Agile wallaby (Macropus agile)

5a 5b

6a 6b

7a 7b

FIGURE 1.6.

Representatives of animals occupying the same niche in Western Indonesia and in West Papua forests (after MacKinnon, 1992).



The Dipterocarpaceae make the majority of large trees in the evergreen lowland forests of Sumatra, Kalimantan and Java while the Nusa Tenggara Islands of Eastern Indonesia show seasonal monsoon forest and savanna grasslands. With altitude, successive vegetation zones can be found from mangrove forest, tropical lowland evergreen rainforest, montane and upper montane forest followed by moss forests and subalpine vegetation above the tree line at about 3,200-3,800 m a.s.l.. Inland swamps support a specific type of forest and heath forests or kerangas are found specifically in Kalimantan. With the advent of man the pressure on the natural environment started. Before the arrival of man, South East Asia, with the exception of beaches, tidal flats and the tops of some high mountains, was completely covered by forests. Two species of early man occurred on Java and their fossilized remains have been found near Sangiran and Trinil, respectively, in Central Java: Meganthropus and Homo erectus (Pithecanthropus) are the oldest known remains of mankind in Asia dating back at least 1.3 million years and 400,000-500,000 years, respectively.

TABLE 1.3.

Island

Today the population pressure together with a range of undesirable developments has led to enormous problems concerning the environment in the Indonesian archipelago. Only about 52% of the primary forests are left and the rest is under a steadily increasing pressure. With the forest trees the rich and diverse associated fauna and flora vanish. Estimations of loss of mammal species on some of the larger Sunda Islands are given in Table 1.3. Most water bodies on the densely populated islands, like Java and Bali, are highly polluted and even entire coastal areas, like the Jakarta Bay, are not any more safe. Mussles and crustaceans, but even fish from these areas are not any more safe to be consumed due to high concentration of heavy metals in their flesh. Even good quality drinking water is not any more available for all people at any time, because the aquivers are polluted or salt water intrusion has taken place. Not the destructive and wasteful way of natural resource use must be followed but the wise use of these resources is a must to avoid a complete depletion of the given environment and the end of the carrying capacity of it.

Estimation of loss of mammal species for four islands of the Sunda region (after German Bundestag, 1990).

Area in km2

Original number of species

Current number of species Absolute %

Sumatra

425,485

51

43

84

Borneo

751,709

51

31

61

Java

126,806

50

21

42

5,443

32

4

13

Bali

15

Introduction

16


SUMMARY The Indonesian archipelago is an "Island Continent" with about 17,508 islands and 3.3 Mio km2 of territorial seas. The highest mountain of South East Asia, Mt. Jayawijya with 5,029 m a.s.l., the longest river of South East Asia, the 700 km long Kapuas River in Kalimantan, the largest lake of South East Asia, the 1,146 km2 Caldera-type lake Toba in Northern Sumatra, the most active volcano, Mt. Merapi in Central Java, all these geographical locations are part of the Indonesian archipelago. Major tectonic plate boundaries influence this area between continental Asia and Australia. More than 300 volcanoes, about 170 still active, are part of the "arc of fire". There activities have transformed the landscape of the Sunda shelf area, the Wallacea and the Sahul shelf area and their ejections have, and still do, influence the geomorphology and soils. The flora and fauna of the Indonesian archipelago is unique and many endemic species do occur. There are three distinct biogeographical areas: the continental Asia - influenced Sunda shelf area, separated by the Wallace - line from the Wallacea or transition area and the Australian - influenced Sahul shelf area. Not only the fauna and flora is outstanding, but also the fact that Central Java is the place where the oldest remains of mankind in Asia, Meganthropus and Homo erectus have been excavated. The population pressure on the environment is reaching in some locations disastrous proportions, leading to the biggest fluctuation processes of people under peaceful conditions in form of transmigration from overpopulated areas to less populated regions of the archipelago.



THESIS It is said that most parts of Indonesia have no weather worthwhile to be mentioned but a climate only. Climate is following a rather monotonous annual cycle : Rainy season follows dry season. Others point out that nowadays no predictable climatic pattern can be observed at all. Torrential rains causing extensive flooding of previously unknown dimension interchange with prolonged dry seasons and El Niño events resulting in water shortages and extensive forest fires. Even global climatic changes are blamed to be the reason of some disastrous climatic events in the Indonesian archipelago. Nevertheless, the distribution of plants and animals is not only determined by geological accidents and geography of mountain and water barriers, but also by altitude, latitude, rainfall quantities and patterns, and temperature. Human influence, like deforestation is not only contributing to the change of the landscape but also of the climate on a local and global scale. The appearance of acid rains are certainly manmade events. They do occur in the highly industrialized areas of Indonesia.

17

2 CLIMATE Friedhelm Göltenboth and Walter Erdelen

MAJOR PRESENT CLIMATIC FACTORS The most important feature of tropical climate is the continuous warmth. Most climatologist agree that the boundary of tropical climate coincides with a mean temperature of 18oC for the coldest month. The tropical zone is defined by the geometry of the globe in its orbit. Being roughly a spherical planet circling the sun in an elliptical orbit, the globe receives energy radiation over a wide spectrum, some of which we perceive as light. Mostly the short wavelength radiation is absorbed by the earth’s surface , which is warmed and in turn emits longwave radiation thus heating the lower atmosphere and initiating convection. During convection, warmed air of the lower atmosphere rises while cooler air

Introduction

18


moves in to replace it. This effects of convection directed by the rotational or Coriolis force of the globe, drive our weather systems. Because the earth is tilted at 23 1/2° to the perpendicular in its orbit, the latitude of the overhead sun progresses during the year from the Tropic of Cancer at 23°30’ North on the solstice in June to the Tropic of Capricorn at 23° 30’ South in December. The tropical region, where the sun passes overhead twice a year, lies between these extremes and has a largely internal climate system. This internal climate system is powered by the convection effects around the meteorological equator, creating low pressure zones. As the warm air rises it cools and hence loses carrying capacity for water vapor which condenses, forming stratocumulus or cumulonimbus clouds, and falls ultimately as rain. Rotational forces divide the rising air flow, which move towards the poles at high altitudes before descending again at sub-tropical latitudes, north and south of the meteorological equator, creating surface high pressure. Since air flows always from high pressure areas to low pressure areas, low level winds or trade winds return towards the equator. Their convergence defines the Inter-Tropical Convergence Zone (ITCZ) which moves north and south, following the sun. If the ITCZ moves southwards during November, and from December to about March lies at around 5-10o South, winds veering from northeast to northwest as they curve into the ITCZ. This is the time of the commonly called Northeast Monsoon for the Indonesian archipelago. The ITCZ moves north wards again during May, so that from June to September a reverse airflow curves across the equator to become broadly southeast winds extending to the ITCZ at around 15° North. This is the time of the commonly called Southwest monsoon and therefore typically the movements of the ITCZ produce an alternation of wet and dry season each year for most of the Indonesian archipelago.

CLIMATE

However, the climate is in many cases and at many locations unpredictable and the rainy seasons in April-May and November-February can be prolonged or shortened. Also topography has a strong local influence on the weather but on average a temperature range between 22° and 32° as a diurnal range can be observed and about 2,300 - 4,000 mm rainfall per year (Fig. 2.1). Various attempts have been made to characterize climates and to map them. The most widely known and used world classification is that of Köppen (1936) distinguishing five world type climates. Within them distinctions were made on seasonal incidents and amount of rain. The Indonesian archipelago belongs to class A , the tropical rainy climate. This is characterized by a mean temperature (t) of the coldest month above 18o C and annual total precipitation over 20 x (t) mm for winter rains or 20 x (t+14) mm for summer rains. This large group of climates is subdivided as follows: Af for hot damp forest climates with mean rainfall of the driest month not less than 60 mm (e.g. Balikpapan, Kalimantan) Am for monsoon type forest climates with less than 60 mm rainfall in the driest month (e.g. Surabaya, Java) Aw for periodically dry savanna climates with less than 60 mm rainfall in the driest month (e.g.Kupang, Timor) A serious limitation of the Köppen system is that the moisture regime cannot be characterized solely by water increased by precipitation, because the amount lost by evaporation and by transpiration of plants is also very important . Mohr (1933) attempted to include these factors in a scheme developed for Indonesia in which any month with over 100 mm of rain is regarded as wet because the precipitation is exceeding the evaporation, any month with less than 60 mm as dry, because the evaporation is exceeding the precipitation. Months with 60 mm to 100 mm are

19


b a

a b c d e f g h

c d Name (500m) 23 °C 1950 mm f °C

mm

h

Name of station Altitude above sea level Mean annual temperature Mean annual precipitation Drought periods Monthly precipitation higher than 100 mm Monthly mean temperature Humid periods

g

e

Monthly mean of rainfall in mm above 100 mm Monthly mean of temperature in oC

Month

Dry periods

12

11

10

9

8

13 7

14 6

15

1

FIGURE 2.1.

No.

1 2 3 4 5 6 7 8

2

3

4

5

Climatic diagrams for major stations in the Indonesian archipelago (after Walter and Lieth, 1967).

Name of Station

Jakarta /W-Java Salatiga /C-Java Surabaya /E-Java Malang /E-Java Kupang /W-Timor Dili /E-Timor Monokwari /Irian Jaya Ambon /Moluccas

Altitude a.s.l. (m)

Mean Temp. (°C)

Mean Precip. (mm)

No.

8 580 7 445 45 1 19 4

26.2 23.0 26.8 23.7 26.6 27.8 26.2 26.2

1793 2589 1533 1945 818 818 2491 3475

9 10 11 12 13 14 15

Name of Station

Manado /N-Sulawesi Balikpapan /E-Kalimantan Pontianak /W-Kalimantan Medan /N-Sumatra Balige /N-Sumatra Pematang Siantar /N-Sumatra Padang /W-Sumatra

Altitude

Mean

Mean

a.s.l. (m)

Temp.

Precip.

2 2 3 25 1150 400 7

(°C) 26.7 25.7 26.7 25.9 20.9 24.4 26.4

(mm) 3576 2230 3180 2015 2258 3130 4453

Introduction

20


moist, because the precipitation is more or less in balance with the evaporation. By using the Mohrs’s index (Q) seven successively drier climatic regimes, A-G, can be distinguished for the Indonesian archipelago (Schmidt et al., 1951): Mohr’s Index : Dry months

Q = —————————— x 100

Wet months

FIGURE 2.2

A B C and D E and F G and H

: : : : :

wettest regime with Q = 0 - 14.3; perhumid regime with Q = 14.3 - 33.4; slightly seasonal regimes with Q = 33.3 - 100; seasonal regimes with Q = 100 - 300; strongly seasonal driest regimes with Q > 300; semiarid to arid (Fig. 2.2).

Despite the fact that only little data from meteorological stations away from the coasts of most of the islands in Indonesia are available, the major vegetation types do correspond with the established climatic regime.

Simplified map of the rainfall types of South East Asia based on Mohr’s Index. The two perhumid core areas, corresponding to the western and eastern rain-forest blocks, are separated by a zone of more seasonal climates running north to south through the center of the archipelago (after Whitmore, 1984).

CLIMATE


The wettest climates occur in two great blocks lying about the equator and they roughly coincide with the Sunda and Sahul continental shelves. Sumatra and Borneo are the heartland of the western wet block and West Papua of the eastern wet block. In the center of the archipelago lies a northsouth zone of seasonally dry climates with Sulawesi, the Moluccas and the even drier Lesser Sunda Islands, including parts of Eastern Java and Bali. The Lesser Sunda Islands are seasonally very dry, owing to the dry south western monsoon which blows off Australia during the middle months of the year. Particularly over forested areas convectional rain is very important, usually in the afternoon and coming characteristically as heavy thunderstorms, affecting only small areas and preceded by a build up of cumulonimbus clouds. An important feature is the high degree of cloudiness, with an average of 5.2 tenths in the zone 0°- 10°North and 5.6 tenths in the zone 0°- 10°South (Richards, 1952). Another characteristic is the small range of temperature at the ground with diurnal ranges rarely exceeding 11° C and very high temperatures in excess of 37° C occurring rarely or not at all. SPECIAL CLIMATIC ISSUES The general climate is measured by meteorologists under standard conditions in a shaded screen in the open at about 1 m above ground. It is only one of a whole family of climates which could be measured and is chosen because it is approximately what is experienced by a human being in the open. Diurnal Fluctuations While in most of the locations throughout the Indonesian archipelago the annual fluctuations in temperature are very small with an average of 2-3° C the daily variations can be more than 5 to 6° C.

21

The natural cover of the area plays further a significant role in the daily regime of temperature and humidity. For example, in the canopy area of a evergreen tropical rainforest the humidity drops from about 95% nocturnal value to about 60% daytime value while the temperature rises from about 22° C to more than 30° C . However, in the ground floor level of the same forest the humidity remains more or less at a 90% saturation level throughout the day and night and the temperature does not show any substantial fluctuation. Daily variations in both the temperature and the humidity are greatest in the drier month particularly if the sun is not obscured by clouds. Altitudinal Changes The differences in temperature between locations are caused mainly by altitude. The rate of temperature decrease is generally about 0.6° C per 100 m. However, this average rate varies considerably from place to place with season, time of day, water vapour content of the air, exposure to wind and vegetation coverage. MICROCLIMATIC FEATURES There is a whole series of climates within an ecosystem each with a whole series of aspects. These microclimates can be considered under the aspects of air movements, precipitation, temperature, relative humidity, saturation deficit, evaporation, light and carbon dioxide (Richards, 1952). The microclimates vary vertically, horizontally and through the diurnal and annual cycle. They do have an important influence on the communities living in a given environment, whether on the niche level or the habitat level. THE WATER BALANCE Besides rainfall (P) and evapotranspiration (E) the soil also plays an important role in the water balance. Some rain runs off the surface or at depth (R = run-

Introduction

22


off) and some may be stored in the soil and the change in storage is expressed as D S. The whole water balance, therefore, may be expressed as the equation: P=E+R+DS The water balance plays an important role in the lives of plants and animals and in their distribution. Even in areas where it is believed that water is always freely available, like in tropical rainforest areas, was recently found that periods of water deficit occur, whose frequency, duration, and severity varies from year to year (Whitmore, 1984). It has been found that extreme climatic events of rare occurrence can be more important and critical to the fauna and flora than averages. Such events can be characterized by cool nights, extremely heavy rainstorms, extreme drought periods, heavy winds, El Niño and La Niña events. EL NIÑO - SOUTHERN OSCILLATION (ENSO) AND LA NIÑA - SOUTHERN OCILLATION (LNSO) A coherent pattern of oceanic and atmospheric fluctuations have been detected and this phenomenon is called the Southern Oscillation. These anomalies typically last about a year and are characterised by dislocations of rainfall distribution in the tropics, bringing drought to some regions and torrential rains to others (Roplewski,1989) (Fig. 2.3). Related anomalies extend high into the atmosphere and major changes in the ocean currents and temperatures are also related to the oscillation. During the one extreme of the oscillation, called El Niño, the sea surface temperatures (SSTs) in the Eastern Equatorial Pacific are very warm at the surface, while during the other extreme, called La Niña, the Eastern Equatorial Pacific surface water is cold. Heavy rainfall and flooding is then observed over areas usually affected by drought during El Niño events.

CLIMATE

ENSO and LNSO is the result of interactions between the tropical oceans, especially the Pacific, and the atmosphere. El Niño and La Niña events are the extremes of the ENSO and LNSO phenomenon, respectively. By using the standardized differences in pressure between Tahiti and Darwin (Australia) the Southern Oscillation Index (SOI) can be calculated giving a relatively clear pattern of both events for the region. El Niño events occur when the SOI has large negative values; La Niña events occur when the SOI has large positive values (Fig. 2.4). A major El Niño event occurred in 1982-83 with severe droughts in Indonesia, resulting in month long excessive fires particularly in Kalimantan. The drought started in April 1982 and lasted until at least January 1983. At the same time unusually heavy rainfall occurs in the central and east Pacific. A similar event occurred in 1997-98. During the drought period man-made fires turned into uncontrollable forest fires throughout Kalimantan, Sumatra, Sulawesi and Java. Harvest failures and thick haze over most of South East Asia resulted in crop failures and heavy health problems for many people throughout South East Asia. One feature of rainfall fluctuations in areas influenced by ENSO is a large interannual variability and that wide areas suffer from the same rainfall anomaly at the same time. Further droughts and pluvial or wet periods tend to last about 12 months or so and this sets the time-scale of the rainfall fluctuations. A biennial cycle has been recorded showing that El Niño events are often preceded and/ or followed by La Niña events and vice-versa. Besides the rainfall the temperature is also influenced mainly due to the lack of cloud cover during El Niño events, leading to increased radiational cooling. In 1982 and 1997 frosts occurred throughout the highlands of West Papua. While the winds of the north-east monsoon during the northern summer tends to be weaker the south-west monsoon over western Indonesia tends to be stronger during an El Niño event.


23

Above: El Niño Phase in 1997/98 Below: La Niña Phase C Vertical circulation

Co Cold oceanic water

Wa Warm oceanic water

EQUATOR 0°

EQUATOR 0°

FIGURE 2.3.

Transpacific circulation patterns during El Niño and La Niña Phases (after Nicholls, 1993).

Introduction

24


30

SOUTHERN OSCILLATION INDEX

20 10 0 -10 -20

-30

1970

72

74

76

78

EL NIÑO PERIODS

FIGURE 2.4

82

84

86

88

LA NIÑA PERIODS

Monthly means of Southern Oscillation Index (SOI) between 1970 and 1990 giving the El Niño and La Niña events (after Nicholls, 1993).

By monitoring the SOI a certain predictability of ENSO and LNSO phases is possible. Whether global climatic changes do have any impact on the ENSO and LNSO is not yet clear and certainly predicting the changes is still impossible. The South East Asian Region is likely to continue to be affected in much the same way as it is now. The pressure on the environment due to a steadily increasing population combined with the high variable climate produced by ENSO and LNSO can yield further rapid and irreversible changes to the environment. The El Niño - La Niña event affects the climate, natural vegetation and wildlife, agriculture, human

CLIMATE

80

health and economies of many of the countries bordering the Pacific and Indian Ocean. It has an important and well-documented role in controlling the interannual climatic variations in the Indonesian archipelago. Besides massive tree deaths and forest fires in Kalimantan, crop failures due to frosts in the highlands of West Papua, also cholera outbreaks due to lack of water in many areas of Indonesia was recorded during the El Niño events in 1997-98. PALAEOCLIMATIC FEATURES The climate of Indonesia today is quite unlike the climate which dominated the region during most of the Quaternary and earlier (Whitmore, 1981).


Tropical and subtropical conditions, with the animals and plants associated with them, extended further away from the equator during the Tertiary than they do now and this has influenced the present distribution pattern of animals and plants (Whitten et al., 1988). The pattern of rising and falling temperatures during the Quaternary had a great impact on the global and local hydrological cycles (Fig. 2.5). The area of South East Asia with its largely extended shelf areas, the Sunda Shelf, and the area of the Sahul Shelf between Australia and New Guinea, formed a dry land mass by only 40 m drop of the sea surface. Ocean currents which now enter the Indonesian archipelago through the Torres Strait, the South China Sea, the narrow straits between many of the Lesser Sunda Islands and the straits between Mindanao and Sangihe-Talaud Islands would have been blocked and their buffering effect on climate would have been lost. The Makassar Straits and the Sulawesi Sea would have been much more enclosed but the currents entering the Molucca Sea and Banda Sea would have been nearly unobstructed. The Sunda and Sahul area would have experienced a more continental climate with greater diurnal temperature range, lower rainfall and lower humidity. It has been estimated that rainfall about 11,000 years ago was only 30% of present values in the equatorial zone and 18,000 years ago the temperatures at sea level were about 2-3 degrees lower on average than present, leading to the lowering of the tree line in Sumatra for about 300-500 m below present. The lowering of the sea level had certainly a very great effect on the coral reefs killing most of the reefs and eroding them away by wave action. Since the end of the latest ice age the sea level rose on

25

average with 3-15 mm per year and the vertical growth of corals has been able to keep pace with this (Barnes et al.,1982). The most northerly position of the Intertropical Convergence Zone (ITCZ), were the rising air of the northern and southern hemisphere meet, was probably more south of its present position that is roughly over the equator. During the northern hemisphere winter time the ITCZ was further south than today resulting in a more drier and seasonal climate with lower rainfall and humidity and greater seasonal changes in mean daily temperatures for the Indonesian archipelago (Verstappen, 1980). There are indications that during the Pleistocene sea levels could have reached up to 25 m above present levels and the most recent sea level maxima detected were 4,500 and 1,600 years ago when sea level was 5 m and 2.5 m higher, respectively (Klerk, 1983). SUMMARY The climate of this tropical zone, stretching over more than 5,000 km along the equator, is characterized by a mean temperature (t) of the coldest month above 18 °C and annual total precipitation over 20 x (t) mm for winter rains and 20 x (t + 14) mm for summer rains. Special climatic events do occur. The most prominent one is the El Niño and La Niña - Southern Oscillation even leading to extended droughts and heavy rains, respectively. Palaeoclimatic features have lead to the formation of the archipelago with lowering and rising sea levels during most of the Quaternary.

Introduction

26


FIGURE 2.5.

CLIMATE

Schematic drawing of the major hydrological cycles under warm and cool conditions. The surface of the sea rose and fell at least four times with a maximal of 150 m due to four successive ice ages and their inter-glacial periods, respectively. The final ice-age ended about 15 000 years ago.

CHAPTER II


27

Aquatic Ecosystems

A

quatic ecosystems comprise two major biomes: freshwater ecosystems,

like lakes and rivers; marine ecosystems, such as seagrass beds, coral

reefs, soft bottom surfaces, open ocean and deep sea.

They are all connected by the flow of fresh water draining in the oceans

and by the evaporation over the seas raining down on land.

There are major differences betweenf resh waters and oceans aside from the obvious discrepancies in size and salinity: The oceans, due to the evolutionary processes of life on earth, harbour an extraordinary rich diversity of ancestral life forms. The fresh waters, compared to the oceans, offer habitat for little diverse life forms, but provide the essence of life for the whole world of terrestrial organisms. To accept this concept, we have to stretch our mind to imagine that all land could well be considered a fresh water habitat. From the viewpoint of soil inhabiting organisms (e.g. in the wet tropics who have to thrive under 3 to 8 meter of rainfall equally distributed through the year), this is surely no exaggereation.

Aquatic Ecosystems

28


SEAGRASS BEDS


29

MARINE ECOSYSTEMS

M

arine ecosystems are a specific part of the aquatic global system. Ninety-six percent of all water reserves of the globe are marine water. All the ecosystems from the shoreline to the deep sea have to deal with the salinity of the water. The oceans harbor major habitats for many lifeforms and one of the richest and most diverse ecosystems has developed here: the reefs of tropical shallow waters. All the marine ecosystems whether shorelines, tidal flats, seagrass beds, coral reefs, open oceans and deep seas are interconnected by the forces governing marine oceanic environments. Climate forces and the hydrological cycle bind sea and land.

Aquatic Ecosystems

30


SEAGRASS BEDS


THESIS Seagrass beds have long been neglected in ecosystem research and only recently the functional linkages between coastal reefs and mangrove communities attracted considerable research not only in Indonesia. Superficially, seagrass beds resemble mixed or monospecific meadows, but their only common fea ture with terrestrial meadows is their high primary productivity. This resemblence ends when we look at the herbivores. While terrestrial grasslands abound with grazing animals, remarkably few specialized herbivores directly feed on the living biomass ofseagrasses. Instead, a food chain depending almost completely on detritus has developed in seagrass beds. This is possible not only because of the internal detritus, but also because the plants are sieving out particles from the seawater originating from other ecosystems (Fig. 3.1). Some scientists, however, view seagrass areas more as a part of the reefassociated communities rather than a separate ecosystem due to the great variation in areal dimension (Shepphard et al., 1992).

31

3 SEAGRASS BEDS Friedhelm Göltenboth, Sabine Schoppe and Peter Widmann

OVERVIEW ‘Seagrasses’ are the only marine flowering plants or seed-bearing plants in shallow waters. They are phanaerogames and no true grasses, rather they comprise two different monocotyl families that usually include species growing in freshwater environments like Vallisneria spp. or Hydrilla spp. in the family of Hydrocharitaceae (den Hartog, 1958). Plants belonging to the seagrasses are among the few plants that have developed in limnic and marine environments independently and parallel (den Hartog,1970; King et al., 1990). They were well established throughout the shallow waters of the Jurassic Tethys Sea were specification occured (Mukai, 1993). Today two families occur in Indonesian waters, the Hydrocharitaceae and the Potamogetonaceae. Unlike algae, they consist of true roots, leaves and an internal lignified vascular transport system for nutrients, water and gases

Aquatic Ecosystems

32


FIGURE 3.1.

Insight into a seagrass bed.

1 Sea horse Hippocampus sp. (Fam. Syngnathidae) 2 Sea cucumber Synapta sp. (Fam. Synaptidae) 3 Hole of Mantis shrimp Odontodactylus syllarus (Fam. Squillidae) 4 Round tipped seagrass Cymodocea rotundata (Fam. Potamogetonaceae) 5 Nodular Starfish Protoreaster nodosus (Fam. Oreasteridae) 6 Mermaid's Fan Padina sp. (Fam. Dictyotaceae) 7 Starfish Archaster typicus (Fam. Archasteridae) 8 Mussel Chlamya sp. (Fam. Pectinidae) 9 Sea urchin Diadema setosum (Fam. Diadematidae) 10 Fiber-strand grass Holodule sp. (Fam. Potamogestonaceae) 11 Dugong Dugong dugon (Fam. Dugonidae)

SEAGRASS BEDS


(Fortes, 1990). In the temperate genus Zostera, female as well as male flowers develop. Pollen is simply released into the water body and hits the female flower by chance (Morton and Morton, 1983). Only scattered information exist on seed dispersal, but seeds are most likely dispersed by water currents. Anyway, vegetative reproduction with rhizomes plays a more important role, than sexual propagation (Tomlinson, 1974). Seagrasses form distinctive ecosystems commonly referred to as seagrass beds. At mangrove dominated coastlines seagrass communities often provide a functional link and a buffer between the seaward coral reefs and the inshore mangroves, but can grow as well in suitable situations within coral reefs and tidal zones, including mangroves. Seagrass beds are found most commonly on soft bottoms between fringing reefs and the mangrove zone. So far 58 species out of 12 genera are described scientifically (Kuo and Comb,1989). In many coastal areas of Indonesia mixed seagrass communities composed of 8-9 species are common. For the explanation of the modern distribution of seagrasses two hypothesis are proposed and discussed: • The vicariance hypothesis proposed by McCoy and Heck (1976) stresses plate tectonics, climate chages, extinction and species-area relationships. • The Centre-of-origin-hypothesis explains the modern distribution by radiation from a region of highest diversity (den Hartog, 1970). The center of seagrass distribution is proposed to be “Malesia” in the tropical Indo-West Pacific region. This hypothesis, however, is highly unlikely. Two types of seagrass beds can be distinguished: Seagrass beds that are permanently submerged and seagrass beds that are exposed during low tides. Some seagrasses that occur in both kinds have developed two distinguishable morphotypes. There

33

is a specific zonation of intertidal seagrass communities observable. Further, seagrasses are characterized by the absence of stomata, retention of thin cuticle, schizogenous development of the lacunar system, hydrophilous pollination and the presence of diaphragmas in the lacunar system. ECOSYSTEM FUNCTIONS Though seagrass beds are no massive structures, they reduce wave and current energy. They seem to be more resistant to storms than coral reefs or mangroves (Hatcher et al., 1989). Due to their extensive root and rhizome systems, seagrasses are very efficient in stabilizing soft bottom sediments and therefore prevent coastal erosion. They not only dissipate incoming wave energies but efficiently protect seaward habitats, like coral reefs, due to filtration effects. Seagrass beds form habitats for many species because of their structural complexity. They provide shelter for fishes and substratum for sessile and hemisessile organisms. Seagrass beds are nursery areas for fish and shrimp with economical value as human food (Fortes, 1990a). Seagrasses develop extensive networks of roots and rhizomes which are very effective in trapping nutrients. Since water movement is slowed down, also particulate organic matter (POM) is caught between the shoots. Seagrass beds belong to the most productive marine ecosystems and play a vital role in coastal nutrient dynamics. Hence, they are connected to the yields of local fisheries, and also to neighboring ecosystems like coral reefs. They also serve as feeding ground for some highly endangered species like the dugong Dugong dugon or the green turtle Chelonia mydas. This ecosystem is not an isolated entity, but interacts with adjacent ecosystems in a complex manner and through several mechanisms (Fig. 3.2). Seagrass communities habour a wide range of benthic, demersal and pelagic organisms that are

Aquatic Ecosystems

34


FIGURE 3.2.

Major types of interactions between seagrass beds, mangroves and coral reefs. 1 2 3 4 5

Human impact Animal migration Particulate Organic Matter (POM) Nutrients, Dissolved Organic Matter (DOM) Physical

either permanent residents or transients. The transient species are frequently juvenile stages of numerous organisms that seek food and shelter during critical parts of their life cycle, or they may be daily visitors that use seagrass meadows as feeding grounds (Tomascik et al., 1997). ABIOSIS Seagrass beds develop on soft bottoms in the photic

SEAGRASS BEDS

zone of marine waters. Regarding temperature, seagrasses are more euryoecious than hermatypic corals, hence they do not only occur in tropical, but also in temperate seas. Flowering, fruiting and germination of seeds are most probably being triggered by abiotic factors (Fig. 3.3) like daylength, temperature, rainfall or exposition to sun and air due to unusual low tides (Fortes, 1990b). Density of shoots of seagrasses is correlated with the water

35


I

II

A

B

C

D

E

F

G

H

I

340

373

394

386

397

388

366

367

353

10

3

5

5

5

4

10

12

12

19

22.5

22.5

22

21.5

23

21.5

22.4

21

32.5

33.5

34.2

35

34.6

34

34.5

33

30

trace

163.2

73.1

151.4

561.4

176.1

289.9

422.9

61

FEB

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

1 2

3 4 5

6

FIGURE 3.3.

Phenology of the tropical eelgrass Enhalus acoroides in dependence on some abiotic factors (after Fortes, 1990a). I Habit of the plant II Set of recurring events 1 Daylight (h) 2 Day-minus tide (h) 3 Minimum temperature (T min oC) 4 Maximum temperature (T max oC) 5 Total rainfall (mm) 6 Month A Lowest growth rate; smallest number of leaves

temperature, whereas productivity depends on the daylength (Fortes, 1990a). At least four species, namely the tropical eelgrass Enhalus acoroides, the toothed seagrass Cymodocea serrulata, the fiber strand grass Halodule uninervis and the small spoon grass Halophila minor have developed two varieties each, one stenoecious and one euryoecious respecting the factors daylength, tides, rainfall, and temperature (Fortes, 1990a). The latter forms are more suited to inhabit extreme environments like intertidal portions of reefs, whereas the former dwell in more stable, permanently submerged surroundings. Connected to these adaptations are also differences in tolerance to changing salinities

B C D E F G H I

Peak biomass production; growth rate; greatest number of leaves Peak pollen discharge; flowering Fruit initiation; flowering Peak fruiting; flowering Peak seed dispersal Appearance of new leaves; shoots Peak biomass, production, growth rate; greatest number of leaves Lowest biomass production

and oxygen contents. In fact, anaerobic and aerobic processes in seagrass sediments occur very close to each other. BIODIVERSITY Producers The most productive plants in the seagrass beds are the seagrasses themselves (Fig. 3.4). The per area production can even exceed that of phytoplankton in the areas (Ryther, 1969). From the Philippines production rates of 1.65 g C (dry weight) · m-2 · day1 have been recorded. This is comparable to terrestrial crops like rice, corn or wheat (Largo, 1992; McRoy and McMillan, 1977). The highest production rate

Aquatic Ecosystems

36


was recorded for the tropical eelgrass Enhalus acoroides with 1.4 g Cm-2 · day1 and a leaf growth of up to 1.1 cm · day-1. Turnover time of the biomass was 115 days, meaning during 16 weeks the standing crop is replaced once completely. The productivity of Indonesian seagrasses is seasonal with two peaks from March to May and from July to November (Fortes, 1990a). Associated with seagrasses are higher algae with Caulerpa, Gracilaria, Gelidiella and Sargassum being important genera (Fig. 3.5). Species composition of macroalgae associated with seagrass beds is dependent on substrate type and degree of exposure. The greatest diversity is found on reef flats of patch reefs and coastal reefs (Verheij and Erftenmeijer, 1993). Epiphytic algae directly growing on the seagrass leaves and competing for light with their host plants are more inconspicuous. These microalgae, mostly diatoms and filamentous algae (Klumpp et al., 1992), may be more important as a source of food for herbivores as are the seagrasses themselves (Hatcher et al., 1989). A significant portion of the total primary production in seagrass meadows can be attributed to the epiphtic cyanobacteria and algae. The surface area occupied by these epiphytes is up to 20 times that of the sediment surface area. Eigtheen major algae species can be found on the blades while only 9 species of epiphytes were found on stems. Particularly, coraline encrusting algae, cyanophyta and rhodophyta are found. Both the epiphytic and epibenthic communities are integral components of the three-dimensional seagrass environment. Consumers In general, four major faunal groups are recognized (Howard et al., 1989): • Infaunal group living within the sediment. • Motile epifaunal group mostly associated with the surface sediment layer. • Sessile epifaunal group as attached organisms to any part of a seagrass plant.

SEAGRASS BEDS

• Epibenthic faunal group consisting of mobile fauna within the seagrass bed. Further, seven major characteristics of fish assemblages associated with seagrasses were identified (Bell and Pollard (1989): • The diversity and abundance of fish in seagrass meadows are usually higher than on ajacent bare subtrates like sand, coral rubble and mud. • The duration of the fish-seagrass association varies among species and life-cycle stages. • Seagrass meadows are important nursery grounds for many commercially important fish species. • Zooplankton and epifaunal crustaceans are a major nutrient pool for seagrass-associated fish, with plant, detrial and infaunal components of the seagrass food web being under-utilized by fish. • Vertical differences in species composition occcur in most seagrass beds. • The relative abundance and composition of fish species in seagrass beds are dependent on the type and proximity of adjacent habitats, as well as on day-night cycles. • Fish assemblages from different seagrass meadows are often different, even when the two habitats are adjacent. Of the 360 fish species associated with seagrass meadows, a total of 78 seagrass-associated fish species were recorded in the Kepulauan Seribu (Hutomo and Martosewojo, 1977) and classified into four main categories: • Full-time residents which spawn and spend most of their lives in seagrass beds like Apogon margaritophorus. • Residents which spawn outside the seagrass beds like Halichoeres leparensis, Gerres macrosoms, Synathoides biaculeatus. • Residents which occur in seagrass beds only during their juvenile stages like Siganus canaliculatus, S. virgatus, Scarus sp. Abudefduf sp., Pelates quadrilineatus.


1.1

1.2

2

3.1

1.3

3.2

5

FIGURE 3.4.

37

1.4

4.1

4.2

6

Some seagrass species of Indonesian shallow waters.

1 Halophila spp. (Fam. Hydrocharitaceae): Four species are found in the Indonesia archipelago: 1.1 H. decipens Ostenfeld, is monoecious; 1.2 H. spinulosa (R.Brown) Ascherson; 1.3 H. ovalis (R.Brown) Hooker, is a dioecious pioneering species, growing until 20 m depth; 1.4 H. minor (Zollinger) den Hartog, is dioecious, H. decipiens and H. spinulosa are relatively rare, but form monospecific meadows. They have stricter environmental requirements preferring clear water and are distributed between intertidal areas down to 40 50 m depth. 2 Thalassia hemprichii (Ehrenberg) Ascherson (Fam. Hydrocharitaceae): This is the most abundant seagrass on various substrate types. It shows a narrow depth distriburtion from lower eulittoral to 4-5 m depth. It forms often monospecific meadows with extensive network of roots and rhizomes essential for high-energy habitats with high-velocity tidal currents exceeding 2 m.sec-1 . 3 Cymodocea spp. (Fam. Potamogetonaceae): Two species do occur in the Indonesia archipelago: 3.1 C. rotundata Ehrenberg and Hemprich ex Ascherson. Most abundant in shallow-water moats of fringing reefs; 3.2 C. serrulata (R.Brown) Ascherson and Magnus. Highly tolerant to subaerial exposure and very common in intertidal reef flats between 3-6 m depth. 4 Holodule spp.(Fam. Potamogetonaceae): Both species are found in Indonesia with similar distribution on muddy or fine-grained calcareous sands: 4.1 H. uninervis (Forskal) Ascherson is considered a typical pioneer species; 4.2 H. pinifolia (Mikki) den Hartog 5 Thalassodendron ciliatum (Forskal) den Hartog (Fam. Potamogetonaceae) is relatively rare in the western part of Indonesia . It grows mostly in stable sublittorial environments. It shows highly lignified woody rhizoms and roots and a branched erect stem. Branching seems to be related to the energy of the water producing short branches in high-energy environments. 6 Syringodium isoetifolium (Ascherson) Dandy (Fam. Potamogetonaceae) is widely distributed. It is a subtidal species sensitive to exposure and desiccation. It seems to be the preferred seagrass for Dugong dugon.

Aquatic Ecosystems

38


1.1

1.2

1.3

1.4

1.5

1.6

1.7

2.1

2.2

2.3

2.4

FIGURE 3.5.

2.5

2.7

Some macrophytic algae typically found in seagrass beds.

1 Chlorophyta or Green Algae 1.1 Enteromorpha intestinalis (L.) Link: Good for consumption 1.2 Ulva lactuca (L.): Good for consumtion 1.3 Caulerpa racemosa (Forsk.) J.Agardh: Excellent for consumption 1.4 Caulerpa sertularoides (Gmelin) Howe: Good for consumption 1.5 Caulerpa taxifolia (Vahl) C. Agardh: Good for consumption 1.6 Halimedia dicoidea Decaisne: Mostly lightly calcified 1.7 Neomeris annulata Dickie: Thallus strongly calcified

SEAGRASS BEDS

2.6

2 Phaeophyta or Brown Algae

2.1 Colpomenia sinuosa ( Roth) Derbes & Solier: For consumption

2.2 Dictyota cervicornis Kuetz.: For consumption

2.3 Padina australis Hauck

2.4 Padina minor Yamada: Source of algin

2.5 Padina tetrastromatica Hauck: For consumption

2.6 Sargassum crassifolium J.Agardh

2.7 Turbinaria ornata (Turner) J. Agardh: For consumption


3.1

3.2

3.5

3.3

3.6

39

3.4

3.7

FIGURE 3.5, continuation...

3 Rhodophyta or red algae 3.1 Galaxaura oblongata (Ellis & Solander) Lamouroux: Source of sulphated polysaccharides 3.2 Gelidiella acerosa (Forskal) Feldman & Hamel: Source of agar 3.3 Chondrococcus hornemannii Lyngby: Source of carrageenan 3.4 Hypnea cervicornis J. Agardh: Source of agar 3.5 Gracilara eucheumoides Harvery : Source of agar 3.6 Gracilaria coronopifolia J. Agaqrdh: Source of agar 3.7 Eucheuma alvarezii Doty: Source for agar

• Occasional residents or transients. High seagrass biomass is usually an indicator for a high number of fish and a diverse species composition. Only few specialized animals are feeding mainly on seagrasses like some sea urchins as Diadema setosum, rabbitfishes (Fam.Siganidae), parrotfishes (Fam. Scaridae), surgeonfishes (Fam. Acanthuridae), the green turtle Chelonia mydas and the dugong Dugong dugon. This is due to the fact that seagrasses contain high amounts of cellulose which

is difficult to break down into sugar without the help of microorganisms. In case there are sufficient hiding places available, herbivores are able to control the density of seagrasses (Ogden et al., 1973). The largest two herbivores in seagrass beds are a reptile and a mammal, respectively: the green turtle Chelonia mydas ( Fig. 3.6) and the dugong Dugong dugon (Fig. 3.7) which possess symbiotic microorganisms in their guts. These organisms help to break down the plant matter and therefore make it digestible for their hosts. Usually only 10 -15% of

Aquatic Ecosystems

40


FIGURE 3.6.

Chelonia mydas (Fam. Cheloniidae).

This species is widely distributed in tropical and subtropical waters, near continental coasts and around islands. It is a typical solitary nektonic animal that occasionally forms feeding aggregations in shallow water areas with abundant seagrsses or algae. This species migrates from rookeries to feeding grounds which are sometimes several thousand kilometers away. In western Indonesia the peak nesting season of Chelonia mydas is from November to April. Females usually return to the same bach from which they emerged as hatchlings to lay their eggs. Usually there is a two-year breeding interval and 2 to 5 clutches of eggs are laid. They lay about 100 eggs per clutch. Incubation takes about 48 to 70 days. Hatching and emergence occur simultaneously and mostly at night. There is high predation throughout the life-cycle of green turtles. The green turtles, like all other neric turtles are endagered; turtles and their products are protected through national laws in Indonesia.

the seagrass biomass is utilized directly by herbivores, the rest is consumed as detritus or is exported to other systems (Hatcher et al., 1989) (Fig. 3.8). Only relatively small fish up to a length of 20 cm live permanently in seagrasses, among them several species of cardinalfishes (Fam. Apogonidae), snappers (Fam. Lutjanidae), wrasses (Fam.Labridae), blennies (Fam.Blenniidae) and gobies (Fam.Gobiidae). The pipefishes (Fam.Syngnathidae) and sea horses (Fam.Hippocampidae) are extremely difficult to spot, since they camouflage by adopting color and shape of the surrounding vegetation. Some terrestrial animals also utilize seagrasses as food like the wintering flocks of ducks, such as the Tadorna tadorna. The echinodermata fauna is the most

SEAGRASS BEDS

conspicuous component of the benthic seagrass communities. Rather common in Indonesian seagrass areas are the sea stars, Protoreaster nodosus (Fig. 3.9) and Linckia laevigata. Most echinoderms feed at night. Usually all representatives of the echinoderm class like Asteroidea, Echinoidea, Holthuria, Ophiuroidea and Crinoidea are present. Molluscs, especially bivalves are among the most common invertebrates in seagrass beds. Up to 20-60% of epiphyte biomass is utilized by epifaunal communities dominated by gastropods (Klumpp et al., 1984). Up to 70 species of molluscs can be recorded in Indonesian seagrass beds with gastropods like Pyrene versicolor, Strombus labiatus and Cymbiola vespertilio being the more abundant ones. Common bivalves to be found are Anadara


FIGURE 3.7.

41

Dugong Dugong dugon ( Müller, 1778) (Order Sirenia, Fam. Dugongidae, Sub. Fam. Dugonginae).

The Dugong dugon is the largest and only true extant marine herbivorous mammal. It belongs to the Order Sirenia together with the three species of riverine and eurhyhaline manatees.They are closly related to the Proboscidae or elephants. They seem to become more than 70 years old with body length up to 3 m and a weight of 400 kg. Sexual maturity is not reached before the 9-10 year. Only one calf is born after a gestation period of 12-13 month. Neonates are about 1-1.4 m long and weigh 20-35 kg (Marsh et al., 1984). The calving interval is estimated to range from three to seven years. The streamlined body has short, rounded fore flippers and whale like flukes. The large head has small eyes, no external ear pinnae and the nostrils are located on top of the snout. Sinus-type hairs are scattered all over the extremely thick and smooth skin. The teeth are replaced throughout its life span The gut-passage-rate is one of the slowest in any mammal. They forage at maximum depth of 3-4 m in both sublittoral and intertidal areas. The mean submerged time is 4.6 min. They live in herds up to several hundred individuals.

scapha, Trachycardium flavum , Macta sp. and Pinna bicolor (Mudjiono and Sudjoko, 1994) Other animals belonging to the infauna are predators, as are most polychaetes or the mantis shrimps (Stomatopoda) whose holes are easily recognized by the piles of sand surrounding it. Key components of seagrass food webs are crustaceans. They built an important link between the primary producers and higher trophic levels. Up to 28 species of crustaceans were recorded for seagrass beds including amphipods like Apseudeus chilkensis and Eriopsia elongata. Stomatopods, such as Pseudosquilla ciliata and Odontodactylus scyllarus are active and voracious mollusc predators. To this group of mollusc predators belongs also the box crab Calappa sp.

Seagrass beds are also critical habitats for the juvenile stages of Portunus pelagicus a crab of economically value. The fifth pair of legs in this family of Portunidae is adapted for swimming and acts as propeller. Paneid prawns and spiny lobsters like Panulirus ornatus depend on seagrass beds for food and shelter during the postlarval and juvenile stages of their life cycle. The meiofauna consists mainly of infauna like nematodes, foraminiferans, copepods, ostracods, turbelarians and polychaetes. Actively emerging meiofauna consists of copepods, nematodes, amphipods, cumaceans and ostracods. Benthic foraminifera are often abundant and usually dominated by the suborders Miliolina and Rotaliina.

Aquatic Ecosystems

42


Shore birds

B1

Leaf blade fragments

Mulch for land Coral reefs; crops mangroves

Drift and export

A

Sinking and decay High primary production and growth

C

F1

H5 G B2

Epizoan suspension feeders

H3

Zooplankton

D1

Drift and export

H2 DOM

F2 H1

B3

Phytoplankton

H4

E2

Roots binding sediments

D2 Detritus

E1 Infaunal deposit feeders

POM

FIGURE 3.8.

Simplified food web of seagrassbeds in Indonesia involving herbivores and detritivores (after Fortes, 1990a).

Mammalia Fishes

: A) Dugong dugon : B1) Siganus vermiculatus B2) Canthigaster bennetti B3) Juvenile fishes : C) Hawksbill turtle, Eretmochelys imbricata : D1) Black sea urchin, Diadema sp. D2) Holothuria nobilis : E1) Oxypode sp. E2) Juvenile shrimp : F1) Calocalanus sp. F2) Euphausia sp.

Reptilia Echinodermata Crustacea Zooplankton

SEAGRASS BEDS

Phytoplankton, algae and seagrasses: H1) Chaetoceros sp. H2) Thalassiosira sp. H3) Navicula sp. H4) Sargassum sp. H5) Thalassia hemprichii DOM Dissoved organic matter G Aufwuchs on blades of Enhalus sp. POM Particulate organic matter


FIGURE 3.9.

43

Protoreaster nodosus (Fam. Oreasteridae).

It is a common, pominent sea star in seagrass beds and seaweed areas from 1-30 m depth throughout South East Asia. It prefers to feed on shells and gastropods, but also feeds on sponges, soft corals and other small invertebrates. It reproduces sexually, releasing eggs and sperms into the water.

A sessile or semisessile epifauna is associated with seagrasses that consists mainly of filter feeders or animals which are browsing on attached algae and other animals. The hemisessile browsers of the epiphytic algae are usually active during night. They remove up to about 60% of the biomass (Klumpp et al., 1992) and may therefore play a significant role in enhancing the rate of photosynthesis of the seagrasses by grazing the covering epiphytes. Decomposers Sea cucumbers are among the most conspicuous decomposers and are feeding presumably on dead leaf material. The scavenging sea star Protoreaster nodosus can occur in amazing densities in shallow portions of seagrass beds. It is also a carnivore, commonly feeding on the invertebrate infauna. Not much is known of the microbiological activities, especially in the bottom, but undoubtedly they play a central role in the decomposition of organic matter in

this ecosystem. Rapid decomposition of plant material through bacterial and microbial action produces the main bulk of detrital material which fuels the main pathway through which primary production is channeled to higher trophic levels. The detrital material or coarse particulate organic matter (CPOM) is consumed by a variety of deposit-feeding, benthic organisms. The particulate organic matter (POM) is the major food source for filter-feeding organisms. As organic matter in sediments undergoes mineralization, phosphate is released into interstitial porewater where it becomes available for absoption through the seagrass root system. This is very important under the aspect that usually phosphate is the limiting nutrient in seawater. NUTRIENT AND ENERGY FLOW Depending of the current regime, nutrients are trapped or released in seagrass beds. Seagrass beds are dynamic systems occupying a variety of habitats

Aquatic Ecosystems

44


each under a unique set of environmental conditions and usually these ecosystems act as a sink of nutrients. Energy in form of sunlight is stored as organic matter via photosynthesis of the producers, predominantly the seagrasses themselves. Light can be an important factor limiting seagrass production and distribution vertically and horizontally. Seagrasses, unlike most other macrophytes, can trap two dissolved nutrient pools, the interstitial water surrounding their roots and rhizomes, and the seawater in the water column. Beginning from these plants two different cycles of nutrients have developed. The more substantial involves the already dead leaf biomass of the seagrasses and leads to a detritivore-dominated cycle. Biomass refers to the above and below-ground plant material and is ususally expressed in grams dry weight per square meter (gDW·m-2). Standing crop refers to above-ground plant material only, and is the most frequently given production parameter estimate. Biomass and standing crop estimates show high variability due to difference in habitat concerning the substrate type, turbidity, nutrient pulses, salinity fluctuations and trophic status. In general, average biomass densities in seagrass beds vary between 1 g DW·m-2 and 2,479 g DW·m 2 . About 85-90% of the productivity is decomposed this way. The remaining 10-15% comprise still living leaves grazed by herbivores. This is the herbivoredominated cycle. Both cycles include microbial decomposers which make the nutrient available to the producers in form of minerals (Fig. 3.10). Highly productiv systems, like seagrass beds, will be nutrient-limited either by nitrogen or phosphorus. Phosphorus is most likely the limiting nutrient, since nitrogen fixation can produce suffient quantities of usable nitrogen to maintain high production rates. Sulphate reduction processes in the partly anoxic sediments is one of the processes through which phosphate is reduced from the ferric to ferrous form, thus releasing phosphate and dissolved ammonia in this process. It is believed that less than 10% of the net production is exported from seagrass meadows,

SEAGRASS BEDS

the rest being retained within the system (Nienhuis et al.,1989). Seagrass communities seem to be primarily self-sustaining systems. It is believed that seagrass beds play a key role in global sulphur and nitrogen cycles through sulphate reduction and nitrogen fixation. The carbon fixation through photosynthesis and organic matter accumulation is calculated as primary production. Both, the Gross Primary Production (GP) and the Net Primary Production (NP) are related to each other with the simple equation: NP = GP - Ra Ra = Respiration of the autotrophs Thus NP is the amount of energy left after accounting for the respiration or energy consumption during metabolism of the autotrophs. The measured and calculated NP in some Indonesian seagrass beds can be given with 60 mg C·m 2 ·day-1 to 1,060 mg C ·m-2 .day-1 or a maximum annual NP of about 387 g C·m-2 (Lindeboom and Sandee, 1989). The attachment of an extensive epiphytic flora on the blades of the seagrasses considerably increase the production of the system. HUMAN INFLUENCE AND ECOLOGICAL STATUS While natural environmental stresses like cyclones, volcanic eruptions, tsunamis, pests, diseases , as well as seagrass population and community interactions certainly influence the ecosytem, the most destructive impacts come from man. Seagrass beds are heavily affected by mining activities, near-shore dredging and filling activities due to deposition of silt and toxic runoff (Fortes, 1990a, Hatcher et al., 1989). Like all marine ecosystems in shallow waters, seagrass beds may be heavily affected by oil spills. Industrial effluents like heavy metals are accumulated


in the blades of seagrass species. Further, highly toxic subtances like dioxins and chlorinated aromatic hydrocarbons are flushed in a steady increasing amount from pulp-and-paper factories into the coastal systems. Seagrass beds are prone to conversion into fish and shrimp ponds or tambaks. The use of pesticides to clear the tambaks before being stocked with fry and the eutrophication effects if tambaks are flushed have destructive effects on nearby seagrass beds. Although seagrasses are adapted to siltation to a certain degree, they can not bear the huge sediment loads that often are washed to the sea originating from deforested watersheds.

FIGURE 3.10.

45

Increased levels of diluted nutrients may lead to an extensive growth of epiphytic algae. The host plants may consequently not receive enough sunlight any more and subsequently may die (Hatcher et al., 1989). Anthropogenic eutrophication is a serious threat to all tropical coastal ecosystems. Via cultivated ricefields along the coastal plains, untreated sewage, contaminated ground water and agricultural runoff sometimes with enourmous amounts of nutrients like nitrogen and phosphate, subsidies and enter coastal waters. While in principle these nutrients are beneficial for the growth of the seagrasses, too high levels stimulate an excessive growth of phytoplankton, causing so-called “blooms”. These

Simplified model of nutrient and energy flow in seagrass beds (after Ott, 1988). 1 2 3 4 5 6

Phytoplankton : Chaetoceros lorenzianus Zooplankton : Stenhelia inopinata Invertebrata : Nereis sp. (Polychaeta) Invertebrata : Ocypode sp. Vertebrata : Parapercis cylindrica Vertebrata : Egretta sacra

DOM M ME NS POM

Dissolved organic matter Microorganisms Meiofauna Nutrients Particulate organic matter

Aquatic Ecosystems

46


blooms can substantially reduce the photosynthetic activity of the seagrasses and in extreme cases lead to their gradual destruction. Non-sustainable fishing methods, especially dynamite fishing, damage seagrasses. Seagrass beds are extensively gleaned for their invertebrate organisms throughout South East Asia. Several economically important holothuroid species like Holothuria sp. and Actinopyga sp. as well as the sea urichin Tripneustes gratilla are sharply declining. It is doubtful that this form of exploitation is sustainable. Some of the seagrass-dwelling organisms are endangered, since they are overexploited by man like the shell Strombus, several sea cucumbers, the green turtle Chelonia mydas and the dugong Dugong dugon. Because of their high demand in the traditional Chinese medicine, almost all species of sea horses are under threat in Indonesian waters. IMPLICATION FOR EIA STUDIES The distribution of seagrass beds in Indonesia is still insufficiently known. Thus, mapping of existing meadows is necessary. Fortes (1990a) proposed the following classification for seagrass beds: • Pristine seagrass meadows: Usually far away from human settlements. High priority for protection, utilization only for recreational or scientific purposes. • Disturbed seagrass meadows: Strongly influenced by man. Control measures should ensure sustainable use. • Altered seagrass meadows: Partly or completely converted to salinas or ponds. Could be rehabilitated if appropriate. • Emergent seagrass meadows: Strongly influenced by extreme physico-chemical conditions. Density and species composition of seagrass beds can shift, caused by natural fluctuations. In order to assess human impact, the reasons of these natural fluctuations must be known beforehand.

SEAGRASS BEDS

Conservation of seagrass beds is much more effective and much cheaper than restoration by transplantation. SUMMARY Seagrass beds are highly productive ecosytems in shallow marine waters. However, this high productivity can only be utilized directly by a limited set of herbivores, since the living plant matter of the seagrasses is difficult to break down because of its high content in cellulose. Thus, most of the matter and energy flow passes through a detritivore cycle, after free living microorganisms already broke down at least part of the dead leaves. Indonesian seagrass beds are not only important nurseries for fish and shrimp, but also are feeding habitat for two spectacular marine vertebrates: the green turtle and the dugong. A specialized epifauna and -flora which utilizes the seagrasses as substrate also contributes considerably to its biodiversity.


THESIS Since they are accessible and conspicuous, sometimes even spectacular ecosystems, coral reefs belong to the relatively well studied ecosystems in Indonesia. However, this did not prevent their extensive destruction in the past. Only just recently protection and recreation are considered when fish catches have declined sharply and diving tourists who are contributing considerably to the income of the country were complaining about damaged reefs. Still, in remoter parts illegal overexploitation and destruction is going on, often tolerated, sometimes even promoted by local officials.

4 CORAL REEFS Friedhelm Göltenboth, Sabine Schoppe and Peter Widmann

OVERVIEW Out of several reef building organisms like red algae (Rhodophyta), sponges (Porifera), and molluscs (Mollusca), corals are by far the most important in terms of productivity. In Indonesia the total area of coral reef is estimated to be 7,500 km2 (KLH, 1992). At least 8 phyla of sessile and mobile invertebrates are usually found in the reef areas of the Indonesian archipelago. While Darwin’s monumental work on structure and evolution of coral reefs is generally credited with the pioneering coral reef research (Darwin, 1882), the work of Niermeyer (1911) is credited as being the first to call attention to the existence of atolls and barrier reefs in the Indonesian archipelago. Four major types of reefs can be distinguished: Fringing reefs, barrier reefs, atolls and platform or patch reefs. The most widely distributed is the fringing reef (Fig. 4.1) that develops in shallow waters around islands. Beginning from the landward side it consists of the tidal pool area, the reef flat, and the reef slope with usually the highest density and diversity in corals facing the open ocean (Figs. 4.2- 4.3). In barrier reefs the tidal pools and the reef flat are replaced by deep lagoons. Barrier reefs form over geological eras whenever islands submerge below the water surface due to tectonic processes.

Aquatic Ecosystems

48


FIGURE 4.1.

Zonation of a typical fringing reef (after Ott, 1988).

This type of reef is only found in the Togian Islands in Central Sulawesi. When an island has submerged completely, an atoll is formed with a more or less ring shaped reef crest ridge depending on the form of the vanished island. This reef crest separates a central lagoon from the open ocean. Only a few atolls have formed in Indonesia waters, but the third largest of the world is the Taka Bone Rate Atoll in the Flores Sea of Southern Sulawesi with about 2,220 km2. In barrier reefs as well as in atolls permanent islands can build up consisting entirely of coralline material.

CORAL REEFS

The theory of the evolution of atolls out of fringing reefs and barrier reefs was developed by Charles Darwin (Fig. 4.4). Darwin’s theory of barrier reef and atoll formation through subsidence and upward growth of coral was an impressive feat of deductive logic. This theory requires that the slow subsidence of the foundation, normally a volcanic island, is matched by the upgrowth of the coral. Only in 1951 this theory was finally proved by a 1,340 m deep bore at Enewetak Atoll in the Marshal Islands of the Pacific where the underlying volcanic foundation was stuck at 1408 m (Ladd, 1973). The coralline material was proved to be of Eocene age.


FIGURE 4.2.

49

Insight into a coral reef slope area. 1 2 3 4 5

Hard coral Lobophyllia sp. (Fam. Mussidae) Hard coral (Ord. Scleractinia) Calcareous red algae (Fam. Corallinaceae) Hard coral Porites sp. (Fam. Poritidae) Sponge Haliclona sp. (Fam. Chalinidae)

6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Basslet Pseudanthia sp. (Fam. Serranidae) Sponge Clathria sp. (Fam. Clathrinidae) Hard coral Oulophyllia sp. (Fam. Faviidae) Hard coral Acropora sp. (Fam. Acroporidae) Hard coral Montipora sp. (Fam. Acroporidae) Hard coral Porites sp. (Fam. Poritidae) Hard coral Favia sp. (Fam. Faviidae) Hard coral (Ord. Scleractinia) Tubeworm Branchiomma sp. (Fam. Sabellidae) Sponge Latrunculia sp. (Fam. Latrunculiidae) Hard coral Acropora sp. (Fam. Acroporidae) Damselfish Pomacentrus sp. (Fam. Pomacentridae) Black-bar puller Chromis retrofasciata (Fam. Pomacentridae) Hard coral Merulina sp. (Fam. Merulinidae) Oriental sweetlips Plectohinchus orientalis (Fam. Haemulidae) Golden sergeant Amblyglyphidodon aureus (Fam. Pomacentridae)

Aquatic Ecosystems

50


Figure

Growth Form

Example of Species (species name in bold is the drawing)

Digitate Coral

Montipora stellata Porites sp. Pocillopora sp. Hydriophora sp. Dendrophylla sp.

Massive Coral

Favites flexuosa Favia sp. Goniastrea sp. Quelastrea sp. Platygyra sp. Galaxea sp. Diploastrea sp. Lobophyllia sp. Symphyllia sp.

Encrusting Coral

Hydrophora microconos

Folious Coral

Turbinaria veniformis Pectinia sp. Pavona sp.

Branching Coral

Turbastrea micranthus Goniopora sp. Heliopora sp.

Table Coral

Acropora hyacinthus Pachyseris sp. Echinopora sp. Merulina sp.

Free -Living Mushroom Coral

Fungia concinna Heliofungia sp. Herpolitha sp. Polyphylla sp.

FiFIGURE 4.3. Comparison of growth forms of hard corals.

CORAL REEFS

Euphyllia sp. Plerogyra sp. Physogyra sp. Treachyphyllia sp.


1

2

3

FIGURE 4.4.

Formation of an atoll (3) out of a fringing reef (1) and a barrier reef (2) (after Darwin, 1882). The original island submerges due to tectonic processes.

51

Today still three more theories are discussed: • The glacial - control theory (Daly, 1915, Kuenen, 1947) (Fig.4.5 A1 and A2). This theory of reef formation is based on the fact that sea levels have fluctuated widely up and down during Earth’s long geologic history. During the last glacial period maximum global sea levels may have been as much as 120 m below present-day values, thus exposing large areas of formerly submerged foundations to rapid subaerial erosion and weathering. Consequently most reef-building corals were killed. During the following warmer period since then the sea level continued to rise and coral growth kept pace with the rising sea levels and barrier reefs and atolls were eventually formed. In fact this is not a contradiction to Darwin’s theory, because Darwin explains how reefs originated and Daly’s theory explains how sea-level changes and erosion could cause surface features (Sheppard, 1983). • The Antecedent-Platform Theory (Hoffmeister and Ladd, 1944): This theory proposes that barrier reefs and atolls can develop on any suitable pre-existing platform provided it is located within the euphotic zone where biotic and abiotic conditions permit coral recruitment and growth. This anticipation is highly unlikely and does not comply with most observations at least in the Indonesian archipelago (Tomascik et.al., 1996). • The Karstic-Saucer Theory (Purdy, 1974) (Fig. 4.5, B1 and B2): The basic premise of this theory is that the characteristic annular or saucer-like shapes of atolls, as well as the general surface features of barrier reefs, are derived from a generally flat, carbonate antecedent platform, which, while subaerially exposed during relative sea-level drops, was karstified by rainfall and percolating water (Guilcher, 1988). This process produced a

Aquatic Ecosystems

52 Göltenboth, Timotius, Milan and Margraf

CORAL REEFS

FIGURE 4.5.

Reef building theories (after Daly, 1915, Kuenen, 1947, Purdy, 1974).

I Sea Level; II Basement or foundation; III Limestone A1) Glacial-controlled theory of Daly’s applied to the formation of atolls (after Daly, 1915): (1) Formation of an atoll during the last interglacial: a) rim of the atoll; b) pinnacles; c) lagoon; (2) The destroyed reef during at the glacial maximum: a) Truncated platform; (3) Newly developed reef on the truncated platform: a) rim of the atoll; b) pinnacles; c) lagoon A2) Glacial control subsidence theory applied to fringing reefs and barrier reefs (after Kuenen,1947): (1) A barrier reef (a), a fringing reef (b), a lagoon (c) and a fore-reef talus (d) formed in pre-glacial times; (2) Abraded barrier reef formed of still living corals (a), remnants of a fringing reef (b), aggraded lagoon (c), fore-reef talus (d); (3) Post glacial time with a newly built barrier reef (a1) and lagoon reef (a2), new fringing reef (b), lagoon and new lagoon deposits (c), and fore-reef talus (d)

B2) Karst-induced antecedent platform theory by Purdy as applied to the formation of atolls (after Purdy, 1974 in: Tomascik et al., 1996): (1) Atoll formation in pre-glacial period; (2) Exposed atoll reef area during the maximum of glacial period: a) karstification; b) rainfall; (3) Post -glacial period with regrowth of coral: a) rim of the atoll; b) lagoon

53

Aquatic Ecosystems

B1) Karst-induced antecedent platform theory by Purdy as applied to the formation of barrier reefs (after Purdy,1974 in:Tomascik et al.,1996): (1) Fringed reef during pre-glacial times; (2) Exposed fringed reef during the maiximum of glacial period: a) land runoff; b) karstification; c) rainfall; (3) Present day situation after newly grown corals: a) Barrier reef; b) pinnnacle reefs; c) lagoon


Figure 4.5 continuation...

54


characteristic saucer-like morphology, with a central lagoon, surrounded by a slightly elevated outer rim, breached by gullies. Inter reef-channels, drowned dolins and blue holes commonly observed are also produced by this process. Platform reefs, patch or table reefs can form whenever solid bottom of the sea reaches the photic zone so that there is enough light to allow the establishment of corals with phototrophic zooxanthellae. This kind of reefs are formed in the area of the Pulau Seribu in the Jakarta Bay in the Java Sea. In contrast to fringing and barrier reefs that only grow in one dimension to the seaward side, platform reefs grow in two dimensions (Schuhmacher, 1988). Once a platform reef has reached a certain size the corals in the central parts may die, since they get cut off more and more from the nutrients, plankton and oxygen of the open sea water body. Another but less frequent type of reefs is the sinous reef with a lagoonlet. ECOSYSTEM FUNCTIONS Of all marine ecosystems coral reefs are the richest in species. The net productivity is one of the highest of all ecosystems. Due to their calcified skeletons corals are involved in the formation of new land. This is especially true for the atolls which entirely consist of coral material. Coral reefs protect the land by dampening wave energy. They form living breakwaters, hence they are able to “repair” damages after storms without help of man. They act as sinks for nutrient from land. Moreover there are also links in nutrient and energy flows between other marine ecosystems, especially seagrass beds and mangroves. Reefs are most important habitats, breeding nurseries and feeding grounds for certain fishes, crustaceans, echinoderms and molluscs useful for man. They form a source of building material,

CORAL REEFS

provided they are managed carefully to prevent overexploitation. Calcium carbonate (CaCO3 ), the product of calcification, is a sink for carbon dioxide but whether it is contributing to the reduction of global warming by using up carbondioxide in a significant bigger portion than is released to the atmosphere by the calcification process is still not yet decided (Ware et al., 1992). Abiosis Coral reefs are restricted to areas where the annual minimum temperature does not drop below 200C and the annual maximum temperature does not exceed 270C. Hence, the centers of coral reef distribution are situated in the tropical Atlantic and Indo-Pacific. Extremely high salinity or inflow of freshwater also limit their occurrence. In addition, hermatypic corals are susceptible to siltation. They are usually absent in the vicinity of large river deltas shedding large quantities of turbid water. Due to the photosynthetic activity of the endosymbiotic algae, coral reefs can only develop in shallow water were sunlight can still penetrate. Depending on the transparency of the water corals might reach a maximum depth of 90 m. Most coral larvae need a hard bottom substrate for establishment. The composition of the coral fauna depends largely on the substrate of the bottom, the water depth, wave action and exposure of the site. The reef edges are the most densely settled locations, because they are best exposed not only to the plankton, but also to the nutrients and the oxygen of the open sea water body. Biodiversity The Indo-Pacific region is one of the centers of coral diversity and the Indonesian archipelago includes both Philippine and Australian coral genera. Outstanding reef areas of different types are found particularly in the Eastern parts of the Indonesian archipelago, like the Moluccans, Sulawesi and East Nusantara Islands.


Producers Probably the most important producers are the zooxanthellae of the genus Symbiodinium that live as endosymbionts inside the inner cell layer of coral polyps. These zooxanthellae obtain a number of benefits, mainly living space in a well protected habitat as well as a continuous supply of basic nutrients, like phosphate, calcium and nitrate and other metabolic byproducts, like urea and amino acids. In addition the host organism supplies unlimited amounts of carbon dioxide which is a product of the animal’s respiration. Another source of inorganic carbon for the photosynthesis of the zooxanthellae is the sea water. Zooxanthellae can tap both the inorganic and the organic fractions of dissolved nutrients. Not only hermatypic but also some non reefbuilding (ahermatypic) coral species and even other groups of animals, like several species of sponges, flatworms and molluscs can contain zooxanthellae. The close association between plant and animal enables an efficient exchange of nutrients with only minimum loss. In one square centimeter of a coral polyp, between 1 x 106 to 5 x 106 zooxanthellae have been counted (Schuhmacher, 1988). The zooxanthellae provide the polyp with products derived from the photosynthesis process, like carbohydrates, glycerin and also secondary products, like amino acids. In addition, the host polyp benefits through the efficient removal of excreted material. Certainly the most significant benefit that hermatypic corals derive from the symbiotic association is the enhancement of the calcification process, which is essential to coral skeletal growth (Muscatine et al., 1984). CaCO3 forms the limestone of the coral skeleton. The building process of the calcareous coral skeletons is enhanced, since the zooxanthellae deprive the system of carbon dioxide (CO2) and therefore the reaction shifts to the right side of the following equation: Ca2+ + 2 HCO3- —> Ca(HCO3)2 —> Ca CO3 + CO2 + H2O

55

As a result of the symbiosis, light is one of the most important factors in determining depth distribution of reef-building corals (Fig. 4.6). Most corals release their gametes, simultaneously at night a few days after full moon (Harrison, 1984). Simultaneous spawning of the corals gives them the maximum opportunity for successful fertilization (Whitten et al., 1996). Calcareous algae, like the green Halimeda (Chlorophyta) and some red algae (Rhodophyta) also contribute considerably to the stabilization of the reef. The latter also occur in permanently shaded parts of the reef and in deeper protions of the reef slope. Several species of green algae live within the calcereous skeletons of the hard corals. Their biomass can even exceed that of the symbiotic algae (Ott, per. comm.). They are only of limited importance in the food chain since they can only be exploited to a certain extent by the parrotfishes (Fam. Scaridae), which are able to bite off and devour lumps of massive coral skeletons. Higher forms of algae, like some species of Caulerpa, Turbinaria, Padina or Valonia and even seagrasses, like Halodule sp., Halophila sp. and Cymodocea sp. grow preferably on the reef flat and in the lagoon (Berner, 1990). Planktonic algae contribute as well to the nutrient inflow into the system. Special adaptations can be found as growth patterns like the highly branched Acropora and Pocillopora species usually found as wave breakers. Waves break when the height is in the ration of 3:4 with the water depth, e.g. 30 cm high waves will break in water 40 cm deep. Further down on the reefs edge particularly flat, lightly inclined table-like forms can be observed, allowing a maximal light reception like the Montastrea species. Others form a kind of trunk expanding into a table, like Acropora tabulata. Competition for space can be observed leading even to interspecies aggression between coral species. The soft corals of the genus Alcyonaria emit toxic substances like sarcophytoxid, cembren terpene-flexibilid and furanochinone which even

Aquatic Ecosystems

56


Ca++

Ca++

CO2

SEA WATER IN BODY CAVITY ZOOXANTHELLA WITH BENDED CHLOROPLAST

ENTODERM

CO2

Ca++

HCO3 Ca (HCO3)2

EKTODERM

CaCO3 + H2CO3

CHITINOUS MATRIX WITH PRIMARY CRISTALS

CALCEOUS SKELETON

FIGURE 4.6.

Carbon cycle and nutrient exchange between coral polyps and zooxanthellae (after Schuhmacher, 1988).

can kill neighbouring Acropora species. Another soft coral Capnella imbriata, produces substances like capnella preventing them from being eaten by fish (Fig 4.7). The horn coral of the genus Plexaura produces the toxin postglandine A2 which efficiently protects them from being eaten by fish. One of the most toxic substances is produced by zoantharian species belonging to the family Zoanthidae. The encrusting zoanthid genusPalythoalives in symbiosis with marine bacteria (Vibriones) and they produce the polypeptide palytoxin, a very toxic substance leading to haemolysis in higher organisms. Nevertheless, fishes like the scrawled filefish Alutera scripta (Fam. Monacanthidae) can digest tissue of the anemone and even accumulate the toxin in his digestive tract without any harm to the fish.

CORAL REEFS

There seems to be a tendency that many typical coral reef fishes are very aggressive towards individuals of the same group. The diverse colours of many of the coral fishes are signals for the triggering of the respective territorial behaviour. Juvenile stages have mostly not this signal colouration and can therefore move freely in the various microhabitats of the reef. Consumers Because of the very limited resources especially in nutrient and space, coral reefs are highly competitive ecosystems. The inhabitants of reefs try to avoid competition through adaptation to highly segregated ecological niches. Some 450 nominal scleractian coral species or hard corals thrive in Indonesian


57

HARD CORAL Acropora sp.

OH O O O

H

O

KILLING

H O SARCOPHYTOXID Sarcophyton sp.

FLEXIBILID

SOFT CORAL Liobophytum sp.

H

H

OH

OAC

H H

AcO REPELLING

O OO

O

DENTICULATOLID

CAPNELLAN

Acanthurus achilles

FIGURE 4.7.

Some examples of toxins in use for various purposes by some inhabitants of the coral reef (after Mebs, 1989).

marine waters. The most important genera in number of species are Acropora with 104 species, Montipora with 39 species, Porites with 24 species, Fungia with 23 species and Goniophora with 14 species (Tomascik et al., 1996). True invertebrate herbivores which feed on algae are predominantly sea urchins, molluscs and several micrograzers (Berner, 1990). However, the

most important herbivores are several families of fishes, especially the surgeonfishes (Fam. Acanthuridae) and the rabbitfishes (Fam. Siganidae) that often occur in large schools. Animals which feed on corals are both carnivores and herbivores, as they are not able to prey on the polyps without devouring the symbiotic algae and vice versa. The most important invertebrate browsers

Aquatic Ecosystems

58


CNIDOCIL

FIGURE 4.8.

Mechanical parts of the defence mechanism of Cnidarians including corals, sea anemones and jellyfish species. 1 ) Surface section of a coral species with expanded polyps 2 ) Longitudinal section through an anthozoan polyp 3 ) Ectodermal layer of the cnidarian tissue with one type of nematocytes uncharged (a) and after charge (b)

on corals are polychaetous annelid worms, gastropods, sea urchins, sea stars, and crustaceans (Glynn, 1990). All corallivores must be able to deal with the nematocystes, highly specialised cells the cnidarians developed for defense and for catching prey (Fig. 4.8).

CORAL REEFS

These cells contain microscopic darts, sticking filaments and poisons, mostly polypeptides which in some species can be even fatal for humans. Some of the corallivores have not only adapted to this defense mechanism, but are even able to use it for their own defense by exposing the nematocystes of


FIGURE 4.9.

59

(I) Some animals specialized in feeding on hard corals: (1) Parrotfish (Scarus prasiognathus); (2) Beaked butterflyfish (Chelmon rostratus); (3) Crown-of-thorns starfish (Acanthaster planci); (4) Nudibranch snail (Phyllidia sp.) (II) Animals living on or in corals: (5) Giant clam (Tridacna maxima); (6) Christmas tree worm (Spirochaetus giganteus); (7) Endolithic algae; (8) Red spider crab (Menaethius orientalis); (9) Arceye hawkfish (Paracirrhites arcuatus).

their prey on their own body surfaces. Some nudibranch gastropods of the genera Glaucilla and Glaucus are an example for this phenomenon. They incorporated fully developed nematocystes

and collect them in special cells called cleptocnides located at the end of the filamentous body tentacles. How the snail manages to digest these cells without discharging them and locate them in these special

Aquatic Ecosystems

60


most exposed regions of their body is unknown. The corallivore crown-of-thorns starfish Acanthaster planci undergoes temporal mass reproductions and therefore can devastate large reef areas (Endean and Cameron, 1990). Among the fishes, specialized coral feeders have evolved like the parrotfishes with their beak-like jaws (Fig. 4.9). that bite off lumps of the limestone skeletons including the polyps and the endolithic algae. They defecate almost pure coralline sand, and thereby are important contributors to the natural erosion of coral reefs. The beaked butterflyfish Chelmon rostratus with its forcep-like jaws is able to prey on polyps and other small invertebrates in narrow crevices. This species belongs to the Chaetodontidae family that is closely associated with coral reefs and therefore can serve as bioindicators for the structural condition of the ecosystem in Environmental Impact Assessments (EIA). Carnivores form an extended end of the food chain that almost never ends with secondary consumers but rather with tertiary consumers or even on higher levels. If these predators occur in high densities they may control their prey and therefore play a role in preventing overexploitation of corals and algae by coralivores and herbivores. Conspicuous predators of higher rank in reefs are the Black-tipped Reef Shark Carcharinus melanopterus, lionfishes Pterois sp., groupers like Plectropomus sp. or barracudas Sphyraena sp. To get a view of the proportions between producers and consumers, the biomasses of the respective trophic levels range between 703 g·m-2·yr-1 for the producers and 11 g·m-2·yr-1 for the secondary consumers (Fig. 4.10) for a reef in the Pacific. A simplified model of the trophic relationships of coral reef fish shows the interrelationships of major contributors to reef communities (Fig. 4.11). Decomposers Crustaceans, molluscs and echinoderms are the most important animal groups feeding on detritus in the reef. The brittlestars are especially effective

CORAL REEFS

detritivores which are generally active during nighttime. The mineralisation is predominantly accomplished by bacteria (Ducklow, 1990). NON-TROPHIC RELATIONSHIPS Scleractinian corals, as we see them today, first appeared in the Triassic oceans about 240 million years ago (Archituv and Dubinsky, 1990). If we include reef-structures built by prokaryotic marine organisms, like stomatolites from cyanobacteria then the first appearance of reefs date back about 3000 Mio years ago. One example of this kind of reefs is found in Lake Motitoi on Satondo Island in Eastern Indonesia. The reef building metazoans have since evolved complicated and fine tuned interspecies relationships that do not necessarily need to involve feeding and being eaten. A few examples could be cited. Some plants and animals use coral colonies as substrates, refuge or perches. Some even live inside the coral’s skeletons. Lithophytic algae and some polychaetous worms make crevices in the limestone by active drilling. Others may simply be overgrown by corals. To this group belong tubeworms (Fam. Sabellidae), Christmas Tree Worms (Spirobranchus, Fam.Serpulidae), Spaghetti worms (Fam. Terebellidae), barnacles (Fam. Pyrgomatidae). The giant clams Tridacna sp. may become simply overgrown leaving just enough space to allow SECONDARY CONSUMERS 11 g • m-2 • yr-1

PRIMARY CONSUMERS 132 g • m2 • yr1

PRODUCERS 703 g • m-2 • yr-1

FIGURE 4.10.

Food pyramid in a coral reef in Enewetak Atoll, Pacific. The biomass per square meter for the different trophic levels are given (after Berger, 1991).


61

1 ) Large piscivore shark 2 ) Small piscivore 3 ) Midwater piscivore, Carangids 4 ) Benthic invertebrate feeder, Butterfly fish 5 ) Coral feeder, Parrotfish 6 ) Midwater invertebrate feeder, Damselfish 7 ) Detritus feeder, Gray Mullet 8 ) Herbivores, Surgeonfish

FIGURE 4.11.

Trophic relationships of coral reef fish (after Nybakken, 1982).

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exchange of water for feeding and breathing. The enlarged opening parts contain numerous sometimes very colourful zooxanthellae. Tridacna gigas is already extinct around Java and in most parts of Western Indonesia despite the fact that these clams can produce a billion eggs at a single spawning, a number more than any other creature recorded. These clams start off as males and reach maturity after only 5 years. They then become female and mature again a few years later. Tridacna gigas may grow up to 200 kg weight with up to 60 kg of living tissue. Some custaceans like the cirripedia Pyrgoma and Lithotrya drill actively into living or dead corals. One shell species is even living in the body of the solitary coral genus, Fungicava. In contrast to the relative unspecifity of many of the reef dwelling organisms a very great number of biotic relations can be observed including commensalism and mutualism. Highly mutualistic relationships evolved between shrimps of the genera Lysmata sp. and Stenopus sp. and reef fishes, the former removing ectoparasites from the latter. The cleaner wrasses Labroides sp. are also in the “barber business” and help other fishes to stay healthy by removing their ectoparasites. The wrasses benefit from their “customers” by being fed without having to leave the same coral cover. The blenniid Aspidontus taeniatus shows almost the same coloration pattern as the cleaner wrasse Labroides dimidiatus (Fig. 4.12), but it harms its hosts by biting off pieces of skin instead of cleaning. This mimicry can only be successful, as long as the numbers of the blenniids is low, compared to the number of the wrasses, so that the good experiences of the fish being cleaned prevail over the bad ones. With ongoing research more and more examples of these cleaning symbiosises are discovered. Another kind of mimicry is observable between a sea snake, the banded sea snake Laticauda colubrina reknown for their very fatal neurotoxin erabutoxin b and the harlequin snake eel, Myrichthys

CORAL REEFS

FIGURE 4.12. Some organisms that remove ectoparasites from fishes: 1 2 3 4

Cleaner shrimp (Lysmata amboinesis) Cleaner shrimp (Stenopus hispidus) Cleaner wrasse (Labroides dimidiatus) and Its mimic the Sabre-toothed blenny (Aspidontus taeniatus) 5 Cleaner pipefish (Doryrhamphus janssi)

colubrinus. The harmless eel shows the same banded feature as the deadly but fortunately very unagressive snake. Individuals of the Humbug fish, Dascyllus aruanus (Fam. Pomacentridae), hide in the branches


63

FIGURE 4.13. Humbug fish (Dascyllus aruanus) hiding between the branches of a coral (Acropora sp.)

of the hard coral Acropora sp. (Fig. 4.13) together with crustaceans. The clownfish Premnas biaculeatus (Fam. Pomacentridae) specifically lives with the anemone Entacmaea quadricolor and even defend their host against potential attackers. They themselves are not threatened by the cnidarians of the anemone because they are coated with slime from the anemone itself. They are attracted to the specific anemone by chemical substances like Amplysinopsin or Amphikuemin excreted by the anemone. NUTRIENT AND ENERGY FLOW The paradox of coral reefs is that they form an ecosystem with high productivity, despite a nutrient poor environment. This only works out since the nutrients in the system are recycled and conserved,

as was already being demonstrated for the coral polyps and their zooxanthellae. Nitrogen, phosphorus and probably silicon are the elements that limit the productivity of reef ecosystems, however, their relative abundance is still much lower than those of other essential elements (D’Elia and Wiebe, 1990). The sources of nitrogen in the reef are terrestrial runoff, including sewage, oceanic and geothermal upwelling, groundwater, and biological fixation by cyanobacteria. The short term sinks of this element are the biota. The greatest loss of nitrogen is by denitrification, a process which synthesizes N2, a gas which can easily escape from the system into the atmosphere (Fig. 4.14). Main sources and sinks of phosphorus are sediments like calcite and aragonite, where both fixation and release are dominated by physicochemical processes. Terrestrial runoff

Aquatic Ecosystems

64


FIGURE 4.14.

Bacteria

2

Cyanophycea

3

Foraminifera

4

Hard corals

5

Algae

6

Tubeworms

7

Urchins

8

Fishes

Simplified model of the nitrogen cycle in coral reefs.

originating from uplifted sediments or from bird guano deposits can be locally important sources of phosphorus (Fig. 4. 15). Silicon is not an essential element for reef growth itself but it is crucial to many organisms like diatoms, silicoflagellates, radiolarians and several sponges which may contribute to reef productivity (D’Elia and Wiebe, 1990). A surplus in

CORAL REEFS

1

nutrient, however, easily destroys the fine tuned system, since corals are easily be outcompeted by algae. The gross primary production of coral reefs is about 3,000 - 7,000 g carbon · m-2 · yr-1 or 30 t · ha-1·yr-1. This is balanced by very high respiration so that the net primary production is about 300 - 1,000 g carbon · m-2 · yr-1 (Mann, 1982).


65

1

Bacteria

2

Foraminifera

3

Hard corals

4

Algae

5

Protozoa

6

Urchins

7

Tubeworms

8

Fishes

FIGURE 4.15. Simplified model of the phosphorus cycle in coral reefs.

Corals provide substantial amounts of mucous materials to their environment and this nutrious material is consumed by many organisms either directly or after breakdown by microorganisms. Efficient filters like the ascidians of the genus Didemnum (Fam. Axinellidae), Haliclona (Fam. Chalinidae) or Strongylacidon (Fam.

Desmacididae) have therefore certainly a good nutrient supply living in a coral reef. Many invertebrates and fishes live from the meadowlike encrusting algae like gastropoda and some sea urchins. The suspended material in the water is food for many suspension feeders like tube worms, basket stars and brittle stars. The coral reef is an example

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66


of a system with many very fine tuned internal cycles like coral-zooxanthellae, nitrogen fixing cyanobacteria-gastropods-nutrients for algae, tychozooplankton-corals-slime production (Fig. 4.16).

FIGURE 4.16.

Nutrient and energy-flow-diagram of a coral reef (after Ott, 1988). CR M N O2 org. PO

CORAL REEFS

HUMAN INFLUENCE AND ECOLOGICAL STATUS As coral reefs are slow regenerating ecosystems, with an average growth rate of 1-3 mm up to 3-10 cm. yr-1, they are particularly prone to even minor disturbances. One of the most serious reasons for the decline of coral reefs in Indonesia is siltation due to deforestation. Not only the photosynthesis of the

Calcium release Microorganisms Nitrogen Oxygen Organic phosphate

PO PP TZP NS

Phosphate Pelagic predators Tychozooplankton Nutrients


zooxanthellae is hampered by the influx of turbid water in coastal waters, but also the colonies themselves may die due to deposition of sediments. Jakarta Bay in Java is only one example of this effect. Corals are heavily affected by silt that originates from the degraded uplands. The physical structure of coral reefs is frequently destroyed by unsound methods of fishing, especially dynamite and muro-ami fishing or with big vessels. Cyanide and other chemicals that are commonly used to poison fish also have a severe effect on the rest of the biocoenosis. Overfishing and excessive gleaning of the reef flats are commonplace. Single species with a high market value like rock lobsters (Panulirus sp.), several groupers of the family Serranidae, or trepang (several species of sea cucumbers) are scarce everywhere or are locally extinct already. The skeletons of hard corals are excessively harvested for construction purposes, for extraction of lime, and more and more for an international market as souvenirs. The same is true for several other reef inhabitants such as sea snakes, sea turtles and some coral fishes that are traded as pet fish. With a growing number of people interested in outdoor and recreational activities, reefs are increasingly affected by snorkelers and scuba divers, who collect marine organisms, spear-fish, dump waste and accidentally destroying corals. Even more serious damage is caused by grounding boats or by anchoring in reefs. With ongoing industrial and agricultural development reefs face increasing damage by pollutants like heavy metals, pesticides, and fertilizer. Other sources of pollution are large settlements with no sewage plants. Even extensive freshwater flooding can affect reefs negatively. Offshore drilling activities may enhance the chances of oil spills with probably disastrous effects for reefs and other marine ecosystems (Berger, 1991). Man’s impact on coral reefs may not always be direct and obvious. The human removal of natural

67

predators such as the triton snail (Charonia tritonis) may lead to population outbreaks of the crown-of thorn starfish (Acanthaster planci) which can lead to the destruction of vast reef areas (Endean and Cameron, 1990). Since 1987 a number of snails like triton (Charonia sp.), helmetshell (Cassis cornuta) and the Green Snail (Turbo marmoreus), and shells, like Mother of Pearl (Trochus niloticus) and Cephalopoda like (Nautilus niloticus) are protected. Unfortunately, it is commonly said they are “paper protected”. The establishment of marine sanctuaries is therefore a very needed countermeasure for an on-going destructive impact on the marine ecosystems (Fig. 4.17) Effects caused by the man-made climatic change, like increase of acidity in sea water due to rising carbon dioxide concentrations may have a fatal synergistic effect in combination with other stresses (Wilkinson and Buddemeier, 1994). A quite recent phenomenon observed in coral reefs is ‘bleaching’, a discoloration of reef-building corals caused by the loss of the endosymbiotic zooxanthellae from the coral tissue, leading in extreme cases to coral death (Glynn, 1993). Some researchers believe there is a connection between bleaching and the higher rate of highly energetic ultraviolet radiation caused by the partial destruction of the ozone layer or the increasing mean temperature of the oceans. It is known that 2-30 C above the average sea water temperature for a period of 1-2 months time can lead to even selective “bleaching” events where single colonies of corals, like Acropora and Pocillopora, are bleached. One of these events was observed in 1983 in the Java Sea. The most recent bleaching event was observed in 1998 wherein large reef areas died all over the Indo West Pacific. Coral “bleaching” caused by the loss of zooxantellae, however, can be reversed if the unsuitable conditions occur only for a short time. In some areas artificial reefs have been built consisting of used tires, dumped cars or ships. Their placement and use is not without controversy despite

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FIGURE 4.17.

Coral reef sanctuary demarcated with buoys.

the fact that after 5 years usually about 15% of the surface provided is covered with corals and epiphytes and after 18 years up to 80% can be covered. Usually fewer fish species, a greater biomass and density of individuals can be observed in comparison to natural reef (Gomez et. al., 1982). It should be considered that artificial reefs should be at least 1 km away from any natural reef, near an alternative food source, on flat or gently sloping sand in water with good visibility at a depth of 15-25 m, protected from excessive wave action. Fishery at artificial reefs should be managed, otherwise they will contribute to further overfishing.

CORAL REEFS

IMPLICATION FOR EIA STUDIES Coral reefs have high biodiversity. As to species richness of corals, reef fishes and molluscs Indonesian coral reefs are ranking among the first on a worldwide scale (Rubec, 1988; Veron, 1986). Hence, the conservation of the ecosystem is of outstanding importance for preservation of biodiversity, not only on a national, but also on a global scale. Coral reefs are regenerating slowly. Even shortlasting impacts may cause long-lasting damages that need decades or even centuries to recover. Conservation is easier and much cheaper than the restoration or the replacement with artificial reefs


which do not hold such high biodiversities as natural reefs. As the environment of coral reefs naturally is very stable, reefs are easily affected by sudden changes of abiotic factors, like salinity, temperature, oxygen content, and water transparency. Coral reefs are “low input ecosystems” concerning flow of matter (D’Elia and Wiebe, 1990). Emissions of chemicals, especially of nutrients and poisons can therefore easily disrupt the system. High productivity of coral reefs is based on a high turnover rate of nutrients within the system, they are therefore not adapted to a high loss of matter. Hence, any extraction of resources, be it by fishing, mining of limestone, harvesting of algae, catching of aquarium fish, should be managed on the basis of data on natural regeneration of the respective resource. For the assessment of environmental impact meanwhile a set of indicator organisms has been identified, e.g. butterflyfishes to assess structural diversity or bryozoans to assess long term pollution (Scholz, 1990). With many “new” threats such as climatic changes possibly affecting coral reefs, even reefs in remote areas without any direct human impact should be monitored carefully.

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algae. Only because of this close cooperation between polyps and plants through exchange of nutrients it is possible to form such a highly complex and diverse ecosystem in an environment that is relatively poor in nutrients. This diversity is not only accomplished by providing the base of the food chain, but also by forming a complex three-dimensional structure of calcified colonies that serve as substrate and refuge for a variety of algae, invertebrates and fishes. The outstanding biodiversity in coral reefs is attributed to a fine tuned annidation of the single species that could take place in a quarter of million years. This highly complex system can be easily disturbed by human interference. For local fisheries coral reefs belong to the most important fishing grounds, though, they are easily destroyed by nonsustainable methods of exploitation.

SUMMARY Coral reefs are highly productive ecosystems in an environment which is stable but poor in nutrients. Presently the most severe impacts on coral reefs in Indonesia are siltation caused by terrestrial runoff due to deforested hinterlands, non-sustainable methods of marine resource exploitation, namely dynamite, cyanide and big vessel fishing. Highest priority should be given to the conservation of still intact or only slightly damaged reefs, since restoration is expensive, time consuming and not always possible. Coral reefs are predominantly formed by hermatypic scleractinian corals and hydrocorals that live in symbiosis with zooxanthellae or dinoflagellate

Aquatic Ecosystems


OPEN OCEAN


THESIS The area called the Indo-Pacific ocean is considered to be the “largest ecological system on earth” (Sheppard et al.,1992). The Republic of Indonesia claims to be an archipelagic state with 1.9 million km2 land area and 7.9 million km2 sea area including 17 508 islands supposed to be under national sovereignty. If this archipelagic concept will be adopted, open marine waters would be the largest ecosystem in Indonesia. Despite the fact that these seas are poor in nutrients and therefore not very productive, they play an outstanding role in securing food resources in form of marine pelagic organisms.

5 OPEN OCEAN Friedhelm Göltenboth, Sabine Schoppe and Peter Widmann

OVERVIEW The world’s ocean is the largest ecosystem, covering almost 71% of the globe’s surface and holding 1.4 billion km3 of water. Out of the total amount of oceanic areas, the Pacific Ocean holds 49.9%, the Indian Ocean 20.5%, and the Atlantic Ocean 29.6%. While these enormous bodies of water are called oceans, the inter island areas are called marginal seas. Therefore, all the sea basins in the archipelago of Indonesia belong to the category of marginal seas. Four major sea basins have been identified for the territory of Indonesia: 1. The Banda Sea Basin. Where the IndoAustralian, Eurasian, and Pacific plates meet, the Banda Sea is located with its two basins. The deepest point is greater than 7 km, while the majority of the sea floor lays between 4-5 km. 2. The Sulu Sea Basin. Located to the north from the Banda Sea Basin, this basin is subdivided into two parts separated by a distinct submerged ridge. On average, the depth is betweeen 3.7-4.4 km. 3. The Celebes Sea Basin. It is a marginal basin with a flat sea floor with an average depth between 4-5 km. It is located between Sulawesi and the Philippines.

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4. The South China Sea Basin. It is thought that this basin is the result of continental margin rifting. It is located between Borneo and mainland Asia. Included into these basin areas are sedimentary basins. About 61 such basins can be found in the Indonesian archipelago. For an island state like Indonesia, the open sea has a more prominent significance than for other states. This is demonstrated by the presence of a baseline coastal length of about 80,719 km, a continental shelf area of about 1,500,000 km2, and its position in a strategic location with respect to global ocean circulation patterns. The interactions between the Pacific Ocean and the Indian Ocean reigned by a monsoonal climate explain to a great extent the high marine biodiversity of this archipelagic region. The Indonesian throughflow between the Pacific Ocean and the Indian Ocean acts like a filter and transformer of the water properties. This has consequences to global thermohaline circulation, the distribution of sea surface temperature and the air/ sea transfer of heat driving partly the global atmospheric circulations as well as on the entire ecosystem of the creatures living in the seas and on their shores. While water from the Pacific Ocean moves steadily through the archipelago to the Indian Ocean, no Indian Ocean water reaches the Pacific Ocean. This throughflow pattern provides an avenue for Pacific Ocean biota to penetrate far into Indonesian seas, while Indian Ocean biota can only be found in the southeastern seas (Tomascik et al.,1997). In this chapter, only those parts of the water body which receive enough sunlight to allow photosynthesis will be treated. This is called the photic zone or the epipelagial. Under clear water conditions, this region extends to a maximum depth of 200 m. However, only 10% of this whole water body is productive. The compensation layer marks the limit, where productivity of the plants equals their respiration. The deeper portion of the water body is

OPEN OCEAN

referred to as deep sea. The edge of the continental shelf is also sometimes being used to define the border between the epipelagial and the deep sea. This edge is also situated at a depth of approximately 200m. The water body over the continental shelves is called neritic zone, whereas the water body over deep ocean floors is named oceanic. ECOSYSTEM FUNCTIONS Open seas have a major impact on the climate of the earth. They have a stabilizing and balancing influence on the temperature, since currents are transporting energy in form of heat from the equatorial regions to the other parts of the globe. They are the main source of water in the atmosphere and a sink for carbon dioxide and hence, reduce the global “glass house effect”. Open seas are influencing regional and local weather events. Winds coming from open seas, usually bring rain. Typhoons come into existence as a result of differences in temperature between oceans and the atmosphere. Open seas serve as habitat to a highly specialized community of pelagic organisms and feeding ground for others. Currents of open oceans are a means of transportation for dispersal stages, not only of marine organisms, but also for some seeds of land plants like coconut Cocos nucifera or Indian Almon Terminalia catappa. Animals are actively migrating in open seas but also reach other habitats by drifting on pieces of wood and other debris. Especially in island states, the open seas are important waterways for humans as well. Open seas are one of the most important sources of animal protein for human consumption. In Indonesia, about 60% of protein consumed by the population are derived from fisheries. About 90% of Indonesian marine landings are attributed to artisanal fisheries for direct consumtion (Riopelle, 1995).


Abiosis The waters of the Indonesian seas are primarily an extension of the waters of the Pacific Ocean (Godfrey et al., 1993). The dynamical processes operating in the Indonesian archipelago provide a tendency towards the development of a three - layer system which can be described by its density: The surface layer (0-200 m) with a density of 6km. Accordingly the aphotic pelagic environments are defined as: • Bathypelagial (its upper layer 0.2 - 1 km is called Mesopelagial): 0.2 - 4 km • Abyssopelagial: 4 - 6 km • Hadopelagial: > 6 km The mean depth of the world’s ocean is 3.792m, well within the aphotic zone. The abyssal comprises more than two thirds of the ocean’s floor surface. The greatest depth of about 11.000 m was measured in the Challenger Deep, east of the Philippines. Most ocean floors outside the continental shelves and slopes are soft bottoms, predominantly covered with inorganic clay or biogenic oozes consisting of skeltal remnants from diatoms, radiolarians, foraminiferans and pteropods. Rocks and terrestrial sediments are much rarer. Not all ocean floors are flat, sometimes terrace-like structures and even seamounts or canyons occur. The mid-ocean ridges that form

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86


FIGURE 6.1.

Ecological structure of the marine environment (after Tardent, 1993).

submarine mountain ranges are situated in the spreading zones of the large oceans. However, these ridges with their own unique deep sea communities do not occur within South East Asian waters. ECOSYSTEM FUNCTION Deep sea is the ultimate sink for matter. Sedimentation can lead to thick depositions which eventually results in the forming of solid rock. Deep seas have an influence on the world’s climate, since they are connected to the epipelagic zone by currents. They also form a major sink for carbon dioxide in form of limestone, and hence diminish the glasshouse effect.

CORAL REEFS

Deep seas are habitats for unique organisms, most of them probably still unknown to science. Some deep sea organisms like threadfins (Fam. Polynemidae) are regularly fished for human consumption in South East Asia. Deep seas can be a source of mineral resources, like oil or manganese nodules. Abiosis The characteristic feature of the deep sea is the absence of light. Radiation still penetrates in the mesopelagial, the upper portions of the bathyal, but not enough to support photosynthesis. Temperature is declining with increasing depth. However, this decline is not steady. In tropical


waters there is a thermocline at about 80 to 150m where temperature drops markedly (Fig. 6.2). It reaches near freezing at the bottom. Water has its greatest density at 4ºC and when its salinity is high. Some of the water, even in the South East Asian deep sea, originates from antarctic regions, where it drops to greater depths while becoming cooler and heavier with the onset of the polar winter.It has been proven that deep sea water is relatively rich in oxygen. The hydrostatic pressure increases by 1 bar or 5 10 pascal per 10 m. This pressure can create problems, especially for vertically mobile organisms. Body liquids and gasses are getting compressed while descending and are increasing their volumes while ascending which subjects tissues of organisms to severe stress. The deep sea environment seems not to be that stable as previously thought. Turbidity currrents are

FIGURE 6.2.

Temperature in relation to depth in tropical marine waters.

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creating erosion-deposition regimes similar to those of estuaries. Strong surface flows created by strong currents or storms do also perturbate the deeper zones. These storms called eddies are analogous to typhoons in the atmosphere but can persist for months and even years (Gage and Tyler, 1991). BIODIVERSITY Producers Like in other ecosytems the producers are that part of organisms able to produce organic matter. Due to lack of light, no photoautotroph producers can exist in the deep sea. Most communities are totally dependent on organic matter in form of dead or alive organisms originating from the photic zone. However, in situations where CH4 or H2S are emitted from the lithosphere due to volcanic activities, unique communities which are totally independent of sunlight as a source of primary energy have evolved. The basis of these communities is formed by chemoautotroph bacteria. These bacteria make use of anorganic compounds such as CH4 and H2S for the synthesis of organic carbon. H2S and CH4, on the other hand, originate from hydrothermal vents. These bacteria live in endosymbiosis with pogonophore worms and mussels which participate from the synthesis of organic matter. On the other side, the bacteria are provided with CO2, sulfid, nutrients and oxygen (Childress et al., 1991). Yet it is not known, if these communities which have been found next to hydrothermal vents on the mid ocean ridges of the Pacific and the Atlantic do occur also in South East Asian deep sea waters. Consumers and Decomposers In deep sea environment it is not always possible to distinguish between consumers and decomposers, since even typical carnivores of shallow waters like sea stars, seem to feed on living organisms, carrion and detritus alike. For this reason both trophic groups are treated in the same paragraph. Gage and Tyler

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(1991) arrange the benthic fauna in errant and sessile megafauna which can be easily recognized from photos made from research submersibles, and the smaller animals that can not be recorded with those method. The subsequent account of taxa follows their work on benthic deep sea biology. In terms of biomass the most important group of benthic errant megafauna are the echinoderms, especially the brittlestars and basket stars (Ophiuroidea) which predominatly feed on particulate organic matter (POM) and plankton. The omnivorous sea cucumbers (Holothurioidea) belong either to the epi- or infauna and have even evolved some pelagic forms. Other important taxa belonging to the errant megafauna are worms of the phyla Annelida, Hemichordata and Echiurida, sea spiders (Chelicerata), Crustacea with spectacular species like the the giant scavenging amphipod Eurythenes gryllus (Fig. 6.3) and cephalopods. Some species of fish are also restricted to the bathyal zone. Apart from rays, most of them have a more or less elongated, eel-like appearance. The sessile megafauna usually is restricted to areas with rocks, manganese nodules or boulders.

FIGURE 6.3.

Sponges (Porifera), Cnidaria, sea lilies and feather stars (Crinoidea) are among the sessile megafauna. They are typical passive suspension feeders. These are filter feeding on plankton and POM from the surrounding waters without creating currents by their own body movements in contrast to the active suspension feeders like the deep sea barnacles (Fam. Scalpellidae), the moss animals (Bryozoa) and the lamp shells (Brachiopoda). The feeding strategy of sea squirts (Ascidiacea) is situated somewhere in between, since they augment currents with own pumping movements of their body. The macro- and meiofauna contribute considerably to the biodiversity of deep sea environments, with the bristle worms (Polychaeta) being the dominant group, followed by crustaceans and molluscs. This diversity probably could evolve over geological eras in a widely stable environment so that finely tuned interspecies interactions could come into existence. However, it could be demonstrated that the deep sea is not that stable, as it was supposed to be. So other explanation brought forward to explain this unexpected diversity include the theory of biological disturbance. Large carnivores

The giant scavenging amphipod (Eurythenes gryllus, Fam. Lysianassidae) reaches a length of up to 14 cm. The animal has a world wide distribution and is part of a highly mobile fauna that is attracted by large food falls on the ocean floor. These amphipods posesses mouthparts adapted to slicing, biting and chewing, but since in the guts of caught specimens sediment was found, scavenging might not be the exclusive way of life (after Gagne and Tyler, 1991).

CORAL REEFS


may control population numbers of their prey, so that the food resource of the latter would not be the limiting factor any more. This could allow the coexistence of species with virtually the same ecological niche. The pelagic fauna of the aphotic zone consists of nekton and zooplankton. They form a ‘nutrient bottleneck’ between the productive photic zone and the deep sea benthic community where detritus accumulates. Fishes found in this habitat have the strangest forms that so far have been found on earth with often large heads and disproportionately large teeth. These are scavengers and carnivores that are adapted to exceptionally large and scarce prey. Since they have very expandable body cavities, they can feed on large prey which sometimes exeeds their own body weight (Fig. 6.4). To attract their food, some have developed special organs which emitt light. This is caused by the chemical reaction of a substance called luciferin which with the help of the enzyme luciferase sets free energy in form of a cold light. Bioluminescence can be generated by the organism itself or with the help of endosymbiotic bacteria. It most probably also serves for the attraction of possible mates. Since also plankton is attracted by light, planktivores sometimes use this means of concentrating food. Other predators rely on other senses like chemoreceptors, organs that receipt density differences in surrounding water or ultrasonic orientation to spot their prey or mates. The gulper Euypharynx pelecanoides is the only species within the family Eupharyngidae. They are the only teleosteen fishes with 5 gill arches and 6 gill slits. They have a giant mouth but minute teeth. The pectoral fins are minute, too. The black animals seem to catch its prey fishes by just opening the mouth. Its light organs might function as attractant to the prey. Most individuals are known from the tropical Atlantic where they occur between 1400 and 2800 m depth.

FIGURE 6.4.

89

Some pelagic deep sea fishes found in Southeast Asian waters.

1 Gulper (Euypharynx pelecanoides, Fam. Eupharyngidae) Total length - 62 cm 2 Viperfish (Chauliodus sloanei, Fam. Chauliodontidae) Total length - 30 cm 3 Slickhead (Alepocephalus owstoni, Fam. Alpocphalida) Total length - 25 cm 4 Hatchetfish (Sternoptyx pseudobscura, Fam. Sternoptychidae) Total length - 6 cm

Aquatic Ecosystems

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The Viperfish Chauliodus sloanei of the family Chauliodontidae has a long and slender body. The yaw is broad with long teeth of uneven length, those of the lower jaw are directed backward. The animal possess light organs in the mouth and big eyes. It occures in all oceans. Alepocephalus owstoni like all other species of the family Alepocephalidae is a cosmopolitan deep sea fish of the bathypelagial. The head is slender, eel-like and without scales. They too pocess light organs. Sternoptyx pseudobscura belongs to the family of Sternoptychidae of which so far 45 species are described. The body is short and laterally compressed. The eyes are big and the mouth slit is horizontal. NUTRIENT AND ENERGY FLOW With the exception of the hydrothermal vents mentioned above, all energy and matter that can be used by organisms originates from the photic zone of the open sea. It reaches the deep sea in form of living organisms, carrion, particulated organic matter (POM) or dissolved organic matter (DOM). Only a fraction of the minerals that accumulate in the deep sea are recycled to ecosystems with primary production. Much is deposited in the sediments and thus are eliminated from the nutrient cycle for geological eras. This might happen as well with organic material including the solar energy which is ‘trapped’ in it, as can be seen by the large depositions of crude oil all over the world. This oil originates from plankton organisms which were not decomposed after being imbedded in the ocean floor. Deep sea organisms which at least partly during nighttime feed in the epipelagial may also play a role in the enrichment of deep sea environments with nutrients (Fig. 6.5-6.6). HUMAN INFLUENCE AND ECOLOGICAL STATUS The deep seas are still the least human-influenced ecosystems on earth. However, it is to be expected that deep sea exploitation will increase in future. The following three forms of utilization are carried

CORAL REEFS

out already or are in a state of exploration: • Fishery for deep sea organisms. The impact that this form of exploitation may have on the stocks can not yet be quantified. • Deep sea sediments may contain minerals which are in high demand, liker manganese, but because of high costs, no exploitation of this resources is carried out presently. • Deep seas are sometimes regarded as dumps for human waste which is too costly or too dangerous to be treated on land. Gage and Tyler (1991) distinguish four types of waste which are dumped in deep seas: 1. dredge spoil, 2. sewage sludge, 3. pharmaceuticals and industrial waste, 4. low level radioactive wastes. IMPLICATION FOR EIA STUDIES Since impact on the deep sea in Indonesian waters seems not to be very strong at the moment, no EIAs are usually carried out focussing on this ecosystem. If utilization in the future should increase, the following aspects should be taken in account: • The knowledge of fishery stocks of exploitable organisms from the deep sea is very limited. Most probably most species occur at low densities and reproduce and grow slowly. The limits of sustainable use may then been reached very early. • Mining of deep sea minerals may not only have an effect on the benthic community in the deep sea floor, but also on the epipelagial, since mother ships of mining ships most probably discharge tailings which may contain high concentrations of heavy metals. • Whereas dumping of dredge spoil and sewage sludge to a certain degree are regarded to cause only little impact, disposal of pharmaceuticals, industrial waste and radioactive wastes may be potential hazardous, not only for the deep sea environments, but also for the connected environments (Gage and Tyler, 1991).


FIGURE 6.5.

91

Simplified model of nutrient and energy flows in deep sea environments (after Ott, 1988). C M

multiple times ingested feces of consuments microorganisms

MF meiofauna POM particulate organic matter

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FIGURE 6.6.

Simplified model of nutrient flow between the marine photic and aphotic zones.

SUMMARY Deep seas are no lifeless zones, as was suspected until the last century. Virtually all ecosystems of the marine aphotic zones are dependent of the primary production of the epipelagial. Animal communities in deep sea environments can be relatively diverse.

CORAL REEFS

Specialization to certain feeding niches however,

seems to occur only exceptionally.

The deep portions of the Indonesian marine

waters are presently the ecosystems least influenced

by man.


93

FRESHWATER ECOSYSTEMS

F

reshwater is a vital resource, regardless of any religious addiction. It is regarded by Muslims as the origin and prosperity of all life and as a spiritual blessing by Balinese Hindus (Whitten et al., 1996). The importance of water is exemplified in the religious belief of Indonesians. For example, for Dewi Danau, the goddess of the water, a temple is placed right in lake Bratan on the island of Bali. All aspects of freshwater from quantity, quality to allocation and storage, have been of increasing concern over the last couple of decades. Freshwater accounts for only 2.6% of all water on earth and 2.06% is held in ice caps and glaciers, 0.59% as groundwater, 0.0001% in rivers and 0.007% in lakes.

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LAKES



THESIS Recently, tropical lakes seemed almost as complete a mystery to science as 30 years ago. The study of Indonesian lakes, however, began with Ruttner and Thienemann’s Sunda Limnological Expedition back in 1928-29. Indonesian lakes can be grouped in three major categories: firstly those built by volcanic action, secondly those like fault lakes, solution lakes, landslide lakes, floodplain lakes, and thirdly coastal lakes with a historical connection to marine environments. The first group consists of oligotrophic, saline, acid and eutrophic lakes and has in some cases developed a unique endemic fauna. The second group is a characteristic feature of the bigger outer islands of Indonesia, while the third group was originally inhabited by a true saltwater community which became adapted to freshwater conditions. Most lake communities are endangered mostly through side effects of logging and other human activities and the introduction of strongly competitive exotic fish, molluscs and water plants.

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7 LAKES Friedhelm Göltenboth and P. Lehmusluoto

OVERVIEW Out of the approximately 50 million lakes of the globe only 10% are located in tropical areas, because lakes of glacial origin, forming the majority of lakes, are rare around the equator (Lewis, 1995). Hutchinson (1957) listed, on the base of geomorphology and origin 76 different types of lakes, sorted into 12 major categories. In Indonesia 7 categories of lakes based on the classification of Hutchinson occur: 1. Tectonic basins e.g. Danau Diatas in Sumatra. 2. Lakes associated with volcanic activities, e.g. Lake Toba in Sumatra. 3. Lakes formed by landslides, e.g. Lake Rawa Pening in Central Java. 4. Lakes due to fluviatile action, e.g. Lakes in the Kapuas River Area in Kalimantan. 5. Lakes of mature floodplains, e.g. Lake Tempe in Sulawesi.

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6. Lakes associated with shoreline and landslides, e.g. Lake Sentani in Irian Jaya 7. Lakes formed by organic accumulation, e.g. Peat Swamp Lakes in Kalimantan Under ecological aspects lakes can be classified into three categories (Odum, 1986): 1. According to their productivity from oligotrophic to eutrophic lakes. 2. According to very specific features like volcanic lakes, meromictic lakes or salt lakes. 3. According to their origin, like man-made lakes or reservoirs. There are some indications that tropical lakes appear to have the following features (Lewis, 1995): 1. They are more efficient in producing phytoplankton biomass on a given nutrient base. 2. They tend to be nitrogen- rather than phosphorus-limited. 3. Their organisms are relatively inefficient in passing primary production to the highest trophic levels 4. Are in general relatively similar in composition to temperate lakes in phytoplankton and zooplankton but differ markedly in species diversity. In contrast to the global aspect that the most common type of tropical lake is the riverine lake, here in the Indonesian archipelago the volcanictectonic lakes are the most important group of lakes. The total area of the 521 natural lakes of Indonesia is more than 5,000 km2 or about 0.25% of the country’s land surface (Giesen, 1994) (Fig. 7.1). The state of the Indonesian lakes is varying, but the most extreme features so far recorded are found in two lakes on Bali, the Bratan and Batur lake (Table 7.1). The world’s largest Caldera-type lake, Lake Toba (Fig. 7.2) in Northern Sumatra, covers an area of about 1,130 km2, including the island of Samosir with 639.8 km2 and the island of Pardepur

LAKES

TABLE 7.1

Range of some chemical and and physical variables found in Indonesian lakes (after Lehmusluoto et al., 1995b). 1 2 3 4 5 6 7

Parameter

Lake Toba (North Sumatra)

Lake Diatas (West Sumatra)

Lake Ranao (West Sumatra)

Lake Rawa Pening ( Central Java)

Lake Bratan (Bali)

Lake Batur (Bali)

Lake Mantano (Central Sulawesi)

Minimum Maximum

Physical Parameters Conductivity [μS.cm-1] 225 pH 7.54 Transparency [m] 0.74 Chemical parameters Total nitrogen [mg.1-1 N] 0.141 -1 Nitrate nitrogen [mg.1 N] 0 Total phosphorus [mg.1-1 P] 0 Phosphate Phosphorus [mg.1-1 P] 0 Sulfate [mg.1-1 SO4] 0.53 -1 Calcium [mg.1 Ca] 1.905 Biological parameters Chlorophyll - a [mg.m-3] 0.576

1.74% 8.86 197 0.696 0.0272 0.0853 0.0803 6506 326 5.595

with 7 km2. About 1,500 - 2,000 km2 of material was ejected before the top of the volcano collapsed about 75,000 years ago. The Maar lakes at Gunung Lamongan in East Java belong to the group of smallest natural lakes with 0.1 km2 for Lake Bedali, 0.3 km2 for Lake Lamongan and 0.4 km2 for Lake Pakis. While Lake Toba is the ninth deepest lake in the world with 529 m, Lake Matano in Central Sulawesi is the seventh deepest lake with 590 m and the only Indonesian lake having a cryptodepression of 280 m. By far the largest, but not permanent bodies of water are formed by floodplains like those in Southern Sumatra with about 200,000 ha, Kalimantan with up to 480,000 ha in the Barito area or in Irian Jaya the Wasur and Rawa Biru floodplains with up to 431,000 ha (Fig. 7.3).


FIGURE 7.1

Location of map of major lakes and reservoirs in the Indonesian archipelago (after Lehmuluoto et al., 1995b).

SUMATRA 1 Laut Tawar Lake 2 Toba Lake 3 Maninjau Lake 4 Diatas Lake 5 Dibawah Lake 6 Singkarak Lake 7 Kerinci Lake 8 Ranau Lake JAVA 9 10 11 12 13

97

Saguling Reservoir Cirata Reservoir Jatiluhur Reservoir Dama Reservoir Sempor Reservoir

14 15 16 17 18 19 20 21 22 BALI 23 24 25 26 27

Mrica Reservoir Rawa Pening Lake Gajah Mungkur Reservoir Kedung Ombo Reservoir Sengguruh Reservoir Lahor Reservoir Sutami Reservoir Wlingi Reservoir Selorejo Reservoir Tamblingan Lake Buyan Lake Bratan Lake Batur Lake Palasari Reservoir

LOMBOK 28 Segara Anak Lake

37 Matano Lake 38 Towuti Lake

FLORES 29 Tigawama Lake IRIAN JAYA (West Papua) 30 Sentani Lake SULAWESI 31 Tondano Lake 32 Limboto Lake 33 Lindu Lake 34 Poso Lake 35 Sidenreng Lake 36 Tempe Lake

Aquatic Ecosystems

98


A relatively big group of lakes in Indonesia are maars: lakes of volcanic origin filled with water, after a big explosion formed an almost round lake. Particularly in East Java many of the lakes have developed in this way, like Lake Lamongan. In addition to the crater or maar lakes there are also"banana-shaped" caldera lakes. The only major coastal or barrier lake in Indonesia, formed after blockage by a landslide and uplifting of an entire bay of the sea, is Lake Sentani in Irian Jaya.

FIGURE 7.2

LAKES

The development of Lake Toba from a volcanic caldera which, after it collapsed, filled with water (after van Bemmelen, 1970).

ECOSYSTEM FUNCTION The most important functions of lakes inside of an environment can be grouped into three major categories: 1. Retention of water run off from surrounding catchment areas reflecting the activities in the area(Fig. 7.4). 2. Habitat for specific flora and fauna and therefore part of the system of biodiversity and gene pool protection (Fig. 7.5). 3. Source for human utilization of fish, shells, crabs, shrimps, water fowl, and water plants. Likewise, for irrigation, hydro-power, recreation, navigation and household requirements. The common morphological organizations of a lake are: A relatively flat bank, the eulittoral zone, is followed by a steeper part, the infralittoral zone. Further down follows the profundal zone. The area of the surface of the water is called the neustic zone, while all the rest of the body of water is called the pelagic zone. The entire area of the lake bottom is called the benthic zone (Fig. 7.6). These features are often varied and in many of the large lakes the bank is often quite steep. The kind of substratum of the benthic zone is a major factor for the habitat. At the surface of the substrate the following areas can be distinguished: 1. Muddy surface areas or epipelon respectively endopelon if the areas in the mud itself are referred to.


FIGURE 7.3

99

Riverine, phytogenetic or oxbow lakes are occassionally formed in lowlands by the movements of big rivers during flash floods.

Aquatic Ecosystems

100


FIGURE 7.4.

Retentional function of a lake and impact of man on the catchment area of a tropical lake.

2. Sandy areas or epipsammon respectively endopsammon if the areas in the sand itself are referred to. 3. Rocky areas or epilithon respectively endolithon if the areas between the rocks itself are referred to. 4. Areas on submerged plants or epiphyton respectively endophyton if areas inside the plant are referred to. Therefore the littoral provides plenty of different microhabitats. The benthic zone has a relatively small importance in most of the major deep lakes in Indonesia compared to the shallow lakes.

LAKES

Abiosis In a lake, the development and the effects of physico chemical gradients can be particularly clear. The radiation impinging on the surface of the water is partly absorbed and reflected by the body of water. The penetration of the radiation is often interferred by suspended particles or tripton, and organisms. The total of this floating, suspended material in natural waters is called seston and often forms layers inside the body of waters. The upper layers of water absorb most of the radiation and are therefore also heated up most. Without movement of the water the absorbed energy remains at the place of absorption, because the


relativly low ability of heat conduction of water transfers the energy only very slowly down to deeper water levels. Mainly through the energy of wind, mixing of different layers of water is achieved. In Indonesia, lake water temperature is also relatively high in deeper parts of the lakes and the greatest difference between the surface water temperature and the temperature of the deepest layer is about 3.8 °C (Lehmusluoto,1997). Highest water temperature was recorded with 28.3 °C in Lake Rawa Pening in Central Java. The lowest hypolimnion temperature with 20.1°C was recorded in Lake Bratan in Bali (Fig. 7.7). The lakes show circulation of their water, but in a very irregular pattern compared with lakes in temperature climate. The circulation and stratification properties of lakes are used to categorize them according to Hutchinson (1957) in the following way: Polymictic lakes which may circulate during the somewhat cooler northeast monsoon period, are mostly high altitude lakes or very shallow, e.g. Lake Batur in Bali. Oligomictic lakes are lakes with significant stable stratification and therefore no regular mixing of the water occurs, e.g. Lake Toba in Northern Sumatra and most other deeper Indonesian lakes. Meromictic lakes are lakes with a permanent and stable stratification were no mixing ever occurs under normal conditions, mostly due to chemical stratification, e.g. Lake Singkarak in Sumatra. The meromictic lakes may be seen as hazardous lakes if the ratio lake depth : lake area is great, because in their hypolimnion huge amount of ammonia, carbon dioxide and hydrogen sulfide may be trapped and accumulated. If a sudden circulation would happen, for example due to tectonic events, the amount of gases released into the environment could be even fatal to the people living around the lake. For the Singkarak Lake, for example, an amount of 140,000 t of carbon dioxide and about 18,000 t of hydrogen sulfide has been calculated in 1994 (Terangna et al., 1994).

101

Overturns of lakes have been recorded for Lake Bratan in 1994, Lake Lamogan in 1976 (Green et al., 1995) and the largest reservoir in Indonesia, Jatiluhur in West Java, in 1996. These causes extensive fish killings. All biotic and abiotic factors interact with each other in a given ecosystem (Figs. 7.8-7.9). When stratification develops, an epilimnion, a thermocline, and a hypolimnion are formed. The hypolimnion serves as a nutrient trap, while primary production is limited to the upper zone (Fig. 7.10). When the entire epilimnion is homogenized during windy weather, nutrients are returned to the surface from the compartment below the secondary thermocline, stimulating primary production. This process is called atelomixis or oligomixis and may contribute in a major way to high primary production of a lake. However, secondary thermoclines are usually short - time events. In general, the absolute level of primary production is higher in tropical lakes, compared to temperate lakes by a factor of 2. However, this is relatively seldom the case. Each lake exchanges gases with the atmosphere through its surface. While the atmosphere contains about 21% oxygen, 78% nitrogen and 0.03% carbon dioxide, in water the carbon dioxide content is much higher. Under standard conditions of about 1,013 milibar (mbar) or Hekto Pascal (hP) the following gas concentrations can be found as saturation concentrations (Fig. 7.11); (Table 7.2). If the lake water temperature rises, the oxygen supply for the organisms can turn critical, because TABLE 7.2.

Saturation concentrations of watersoluble gases under standard pressure conditions (after Lampert and Sommer, 1993).

Gas

0°C

10°C

Oxygen [mg/l]

14.5

11.1

8.9

7.2

Nitrogen [mg/l]

22.4

17.5

14.2

11.9

1.0

0.7

0.5

0.4

Carbondioxide [mg/l]

20°C

30°C

Aquatic Ecosystems

102

LAKES


Figure 7.5.

Major members of the lake community in the shallow, mesotrophic Central Javanese lake Rawa Pening.


103

Main producers and consumers of the mesotrophic lake Rawa Pening, Central Java: 1 2-4

Mammalia:

1

Aves:

2 3 4

5 6-9

Amphibia: Pisces:

5 6 7 8 9

10-13

Insecta:

10 11 12

14 15-16

Arachnid: Crustacea:

17-20

Mollusca:

13 14 15 16 17 18 19 20

Pipistrella imbricata (Fam. Vespertilionidae) Collocallia linchi (Fam. Apodidae) Halcyon cyanoventris (Fam. Alcedinidae) Lonchura maja (Fam. Ploceidae) Rana erythrea (Fam. Ranidae) Aplocheilus panchax (Fam. Aplocheilidae) Channa striata (Fam. Channidae) Clarias batrachus (Fam. Clariidae) Trichogaster pectoralis (Fam. Belontiidae) Belostoma indica (Fam. Belostomatidae) Ptilomera sp. (Fam. Gerridae) Crocothemis servilia (Fam. Libellulidae) Libellulidae-Larva Spider Nephila sp. Macrobrachium rosenbergii (Fam. Palaemonidae) Caridina laevis (Fam. Atyidae) Pila polita (Fam. Ampulariidae) Egg Cluster of Pila polita Corbicula javanica (Fam. Corbiculaceae) Anodonta woodiana (Fam. Unionidae)

21

Hydrozoa:

21

22

Porifera:

22

Chlorohydra viridissima (Fam. Hydridae) Spongilla lacustris (Fam. Spongillidae)

Representatives of the macrophyta community: 23 24 25 26 27 28

Rhynchospora corymbosa (Fam. Cyperaceae) Ceratophyllum demersum (Fam. Ceratophyllaceae) Hydrilla verticillata (Fam. Hydrocharitaceae) Salvinia cucculata (Fam. Salviniaceae) Eichhornia crassipes (Fam. Pontederiaceae) Nymphoides indica (Fam. Gentianaceae)

A-E Representatives of the plankton, macro-benthic and macro-pelagic community of invertebrata: Phytoplankton species (A): Fam. Desmidiaceae: Cosmarium bioculatum Cosmarium granatum, Staurastrum sp. Zooplankton species (B): Ostracoda: Stenocypris sp. Copepoda: Eudiaptomus gracilis (Fam. Cyclopidae) Rotifera: Colurella sp. Benthic species (C): Larval stages of Chironomus sp. (Fam. Chironomidae) Pelagic/semi-pelagic species (D): Subneustic stages of Anopheles sp. (Fam. Culicidae) Larva and pupa and the neustic imago (E) Semi-pelagic larva of Chaoborus sp. (Fam. Chaoboraceae)

Aquatic Ecosystems

104


FIGURE 7.6.

Schematic drawing of the lacustrine zonation.

the respiration activity is rising but the solubility of oxygen is declining. In shallow lakes this phenomenon can be recorded by measuring during a 24 hour cycle the oxygen and carbon dioxide concentrations (Fig. 7.12). Due to the photosynthetic activity, these two curves are reciprocal to each other. Today, due to the ever increasing necessity to monitor the extent of pollution of a given body of water, dissolved oxygen (DO) and biological oxygen demand (BOD) are often recorded parameters. Because oxygen and carbon dioxide are reciprocal, the oxygen concentration and the carbon dioxide concentrations are important factors influencing biological production.

LAKES

Nitrogen and phosphorus seem to play a certain role in all freshwater ecosystems as limiting factors. They are the key candidates for general nutrient limitation of phytoplankton. Nitrogen limitation is more important and more widespread in tropical than in temperate lakes. While soluble reactive phosphorus is usually measurable in significant amounts, inorganic nitrogen is often below detection limits. Abundance of nitrogen fixing organisms is high in many tropical waters and element ratios in biomass are often suggestive of nitrogen deficiency (Lewis, 1995). However, actual measurements in many Indonesian lakes show that this is obviously not the usual case in most of the Indonesian lakes (Lehmusluoto et al., 1995a,1997). In lakes with a


A 4

5

pH 7

B 8

9

Temperature [°C] 24 25 26

23

4

10

27

0 50

100

150

200

250 300 350 400

450

500

550

0

1

0

2 3 4 5 6 7 8 9 Dissolved Oxygen - DO [mg/l] 200

400 600 800 Conductivity [µS/cm]

C 4

5

6

pH 7

6

24

8

9

pH

7

8

9

Temperature [°C] 25 26

10

10

0

1000

0

1



10

4

26

23

5

6

pH 7

8

27

0

50

100

150

200 250 300 350 400

450

500

550

D


23

5

23

Depth [m]

Depth [m]

6

105

9


10

1000

10

26

A B C D

Lake Toba: South Basin Lake Toba: North Basin Rawa Pening Lake Bratan pH Temperature Dissolved Oxygen (DO) Conductivity

0

0

5

Depth [m]

Depth [m]

5

10

10

15

20

15

25

20

30

0

1

0

FIGURE 7.7.



10

0

1000

0

1



10

1000

Temperature, pH, dissolved oxygen and conductivity profile in Lake Toba (Northern Sumatra), Lake Rawa Pening (Central Java) and Lake Bratan (Bali) (after Lehmusluoto, 1995a).

very low hardness most probably also calcium and other elements can be limiting factors. For example, molluscs like clams need at least 20 mg calcium per liter to build their shells. The pH values and oxygen concentration, as well as the concentrations of certain nutrients largely depends on the biological activities and the mixture of the water, forming by this means for each body of

water a rather complex system of mutual dependencies. Living cells contain a great variety of substances, many of them in solution. A few of them are also found in lakes but almost always in concentrations differing from those within living cells. Because the salt concentrations is the fluids of bodies and cells are mostly far higher than in the surrounding water the organisms have developed

Aquatic Ecosystems

106


effective mechanisms to excrete water which entered, by osmotic processes their bodies and cells. Generally speaking, tolerance to changes in the concentration of solutes in their environment is low in animals with a relatively permeable integument, such as protozoans and cnidarians. Animals with less permeable integument, such as fish, have a greater tolerance. Because animal and plant species

FIGURE 7.8.

Characteristic watershed area and catchment basin on a volcanic tropical island showing major abiotic and biotic factors. 1 2 3 4 5 6 7 8

LAKES

vary in their abilities to cope with differing environments, the distribution of the less tolerant species can be restricted to one, or a few lakes of a particular feature. By this means some species can form an endemic community over time, a feature found in many bodies of waters throughout Indonesia from fish to plankton organisms.

Bacteria and blue green algae Phytoplankton community Zooplankton community with Cyclopidae and their nauplius larva and Daphnidae Macroinvertebrate community with molluscs Vertebrate community with fish Submerged water plants Emergent water plants Tropical lowland evergreen rainforest


FIGURE 7.9.

107

Influence of biotic and abiotic factors on a zooplankton organism; Daphnia similis.

COMMUNITIES, ECOSYSTEM FUNCTIONS AND BIODIVERSITY Biological diversity is more than just the sum of species numbers. It encompasses the variety, variability and uniqueness of genes, species and ecosystems. With its wide range of lake habitats, Indonesia is also on the level lake ecosystems recognized as a major world center for biodiversity. Because the organisms in a lake, like in any other natural habitat, are not easily arranged by order of the taxonomy, ecological classifications are in use. As well as having a functional structure, aquatic communities also have a well defined threedimensional spatial structure owing to the support water can impart to organisms (Payne, 1986). A considerable number of organisms live suspended in

the water body. These mostly microscopic organisms, with only limited powers of locomotion, constitute the plankton. Most of them live in the euphotic or trophogenic zone with sufficient light for algal photosynthesis. In addition to the plankton, freeswimming types of organisms occur, which have sufficiently well-developed powers of locomotion to determine their own distribution within the lake (Fig. 7.13). The organisms of lakes can be classified according to their place in the energy and food chains, webs or cycles (Fig. 7.14). Another possibility used to classify the organisms of a lake is according to the location in the lake where they live or are most abundant. Five major categories are used for this classification:

Aquatic Ecosystems

108


FIGURE 7.10.

Schematic drawing of stratification in a lake.

25

Oxygen [mg/l] Nitrogen [mg/l] Carbon dioxide [mg/l]

20

15

10

5

FIGURE 7.11.

LAKES

Saturation concentrations of water soluble gases under standard conditions of 1013 hP (after Lampert and Sommer, 1993).

0 0°C

10°C

20°C

30°C


FIGURE 7.12.

Daily variation of dissolved oxygen (D.O.) (__ ), carbon dioxide (CO2) ( ), concentrations in the shallow lake Rawa Pening in Central Java.

Benthic organisms - Organisms living on or in the sediment of the bottom of lakes (Fig. 7.15). Periphyton organisms - Animals or plants sitting on the submerged parts of plants or other matter, so-called aufwuchs (Fig. 7.16). Plankton organisms - Drifting or slow moving plant and animal species in the water. Necton organisms - Organisms with the ability to swim actively. Neustic organisms - Organisms living on the water surface or directly underneath the water surface (Fig. 7.17). A third method is basing the classification on the appearance of the organism in a certain zone of the lake. Three major organism groups are distinguished: Littoral organisms - Organisms living in the shallow parts of the lake or those parts receiving light down to the bottom. Pelagic organisms - Organisms living in the free water of the lake down to the depth of 1% light intensity (light compensation zone) compared to the surface intensity. Profundal organisms - Organisms living in the deep water region without light.

109

Producers Four major types of producers can be found in tropical lakes: A. Benthic macrophytic plants in the shallow parts of the littoral e.g. Rhynchospora corymbosa (Fam. Cyperaceae). This zone of emergent vegetation uses the carbon dioxide from the atmosphere for photosynthesis and nutrients from the sediment of the lake. They therefore act as nutrient pump for the ecosystem. These plants form, together with the plants on the wet parts of the lake shoreline, a very important link between the water- and landbound areas. This transition area is called an ecotone. The importance of this area can also be seen by the biomass density found on water’s edge as in Lake Tempe in South Sulawesi (after Whitten et al., 1988; Fig. 7.18). B. Submerged macrophytic plants in the shallow parts of the lake e.g. Hydrilla verticillata (Fam. Hydrocharitaceae), Ceratophyllum submersum (Fam.Ceratophyllaceae). The plants of this zone are adapted to their environment by having mostly thin, filamentous leaves to facilitate the exchange and uptake processes for nutrients coming from the water. C.1 Floating macrophytic plants e.g. Utricularia minor (Fam. Utriculariaceae): This plant has a mass of floating rhizoid that support the erect flower stalk above the water. Absorption of water and nutrients is conducted through the finely divided leaves. This modified leaves bear numerous bladders, the function of which is to catch small animals and so supplement the conventional means of obtaining nutrients. Each bladder has a single opening in which sits a tightly-fitting hinged door. In their relaxed state the bladders are rounded

Aquatic Ecosystems

110


FIGURE 7.13.

Trophic interrelationship in a tropical lake ecosystem.

Phytoplankton : (1) Closterium cornu var. javanicum ; (2) Staurastrum playfairi Zooplankton : (3) Cyclops sp.; (4) Nauplius larva of Cyclops sp.; (5) Brachionus caudatus; (6) Daphnia cephalata FISHES Planktivores : (7) Hypothalmychthyes molitrix Predators : (8) Clarias batrachus Demersal fish : (9) Trichogaster pectoralis

LAKES

BACTERIA + FUNGI + INVERTEBRATES Bacteria : (10) Pseudomonas fluorescens Fungi : (11) Blastadia pringsheimii Invertebrate : (12) Sphaerodema sp.; (13) Chironomus larva; (14) Zygoptera larva Bacteria : (15) Bacilus subtilis; (16) Spirillus volutans; (17) Sarcinia methanica


111

4

3

6

1

2 8

5

9 7

FIGURE 7.14.

Trophic categories of bodies of freshwater cycling energy and nutrients. FIGURE 7.15.

Producers

- Cyanophyta : (1) Oscillatoria sp. - Green algae : (2) Scenedesmus sp. Consumers - Harpacticoid copepoda (Fam. Cyclopidae): (3) Canthocamptus staphilimus - Cladocera : (4) Lynceus brachyurus - Fam. Palaemonidae: (5) Macrobrachium lamarrei - Fam. Cyprinidae : (6) Puntius goniotus Decomposers - Bacteria : (7) various genera - Protozoa, Ciliata : (8) Paramecium sp.; (9) Bursaria sp.

Some macroinvertebrate members of the benthic community in the Central Javanese Lake Rawa Pening.

Mollusca: Gastropoda - (1) Pila polita (Fam. Ampullariidae) - (2) Egg cluster of Pila polita - (3) Bellamya javanica (Fam. Viviparidae) Bivalvia - (4) Anodonta woodiana (Fam. Unionidae) Crustacea: - (5) Macrobrachium rosenbergii (Fam. Palaemonidae) Macrophyta: - (6) Rhynchospora corymbosa (Fam. Cyperaceae)

Aquatic Ecosystems

112


FIGURE 7.16.

CYANOBACTERIA

2

RADIOLARIA

3

CILIATA

4

DIATOMEA

5

RHIZOPODA

6

DESMIDIACEAE

Aufwuchs community on submerged plants in lake water.

but are usually seen with slightly concave sides because the cells of the bladder have actively passed water to the outside. If the door or the hairs around it are disturbed, it swings inwards because of the reduced pressure, sucking in with it whatever small animal caused the disturbance. The animal dies and decomposes within the nowrounded bladder and the process of passing

LAKES

1

water to the outside and setting the trap begins again (Whitten et al., 1988). C.2 Pistia stratiotes (Fam.Araceae), Eichhornia crassipes (Fam. Pontederiaceae), Salvinia cucculata, S. molesta (Fam.Salviniaceae): The majority of these plants, floating on more than 90% of all Indonesian lakes, are species introduced to Indonesia. The most prominent and hazardous one is

113


EPINEUSTIC ORGANISMS ARE: 1 Culex sp. (FAM. CULICIDAE) IMAGO 2 Ptilomera sp. (FAM. GERRIDAE) JUVENILE SUBNEUSTIC ORGANISMS ARE: 3 Culex sp. (FAM. CULICIDAE) LARVA 4 Culex sp. (FAM. CULICIDAE) PUPA 5 Anopheles sp. (FAM. CULICIDAE) LARVA 6 Acella sp. (FAM. RHIZOPODA)

Members of the epineustic and subneustic surface community of a tropical lowland lake.

Eichhornia crassipes (Mart.) Solms, a native of South America, introduced as an ornamental plant in 1894 to Indonesia. Its major negative effects are: 1. Reduction of water by an evapotranspiration rate 2.6 times higher than the free water surface. 2. Blockage of irrigation and shipping channels. 3. Depletion of oxygen exchange between water and the atmosphere. 4. Breeding and hiding site for a variety of pest species like mosquitoes and rats. 5. Contribution to eutrophication processes by providing huge amounts of sediment. The decomposition half-time at 26-32°C is 11.5 days only. As part of the present ecosystem it plays also a significant role as: 1. Breeding and protection site for Crustacea

1000 800 BIOMASS (g/m2)

FIGURE 7.17.

600 400

200 0 1

2

3

4

5

6

DISTANCE (m)

FIGURE 7.18.

Biomass density of plants along a transect from swamp land to 6 m from the water's edge in Lake Tempe, South Sulawesi (after Whitten et al., 1988).

1) 12 m inland 2) 8 m inland 3) 5 m inland

4) Water's edge 5) 3 m from shore with 0.15 m depth 6) 6 m from shore with 0.7 m depth

Aquatic Ecosystems

114


FIGURE 7.19.

Estimations of primary production in Lake Toba (after Kartamiharja, 1987). North basin, August 1985 South basin, March 1986

2. Protection site for fish fry 3. Site for water snails, for depositing their eggclusters on the stalks of the plants 4. Preying sites for frogs and dragonflies. D. Phytoplankton. Two of the most abundant species are for example Lyngbya sp. (Fam. Cyanobacteriaceae) and Staurastrum sp.(Fam. Desmidiaceae). While the macrophytic plant community is relatively diverse compared to those of temperate lakes, the phytoplankton communities are less diverse than temperate ones (Lewis, 1995; Lehmusluoto et al., 1995b, 1997). Most lakes in Indonesia contain about 20-30 species in their respective phytoplankton communities that become sufficiently abundant to be tabulated in routine counts on an annual basis. This number can easily be increased if special attention is given to rare species and endemic species. The detection of rare species often depends only on

LAKES

collecting intensity. Diversity contains two components, namely: number of species and equitability or the even distribution of the individuals in a given area (Lampert and Sommer, 1993). A first attempt to explain differences in diversity was made by Professor Thienemann, member of the Sunda Limnological Expedition, back in 1931. He formulated his so-called biocoenotic laws: 1. The more diverse the environmental conditions are, the more species can live under almost optimal conditions, the higher the number of species, but with low individual numbers. 2. The more specific the environmental conditions are, that is, the greater the distance from the optimum for most species, the lower the species number and the higher the number of individuals. The actual findings of studies performed during the 1980’s found that both the number of species and individuals were relatively low (Lehmusluoto et al., 1995a,1997). The productivity of lakes is often limited by nutrient availability. Therefore, oligotrophic lakesthose with low concentrations of nutrients-have lower productivity than nutrient-rich or eutrophic lakes. The measurement of the chlorophyll-a concentration form the basis for estimating primary productivities. Measurement in Lake Toba - an oligotrophic lake - revealed a chlorophyll- a concentration of 1.21-1.93 mg.m-3 (Lehmusluoto et al., 1995a,1997). The calculated productivity between 0.053-1.039 g C m-2·day-1 (Ratulangi, 1995) or 1.35 25.9 mg C m-3·day-1 shows the great variation in such a uniform lake (Fig. 7.19). In the eutrophic Lake Limboto in Sulawesi chlorophyll-a concentrations of 5.24 mg·m-3 were measured (Lehmusluoto et al., 1995a). Another aspect of importance is the succession clock of the phytoplankton community. This succession clock starts to run when a mixing water column begins to stabilize. The episodic thickening


of the mixed layer that occurs in many tropical lakes affects the phytoplankton by renewing nutrients and increasing turbulence and transparency thus resetting the succession clock. A clear succession pattern can be found with reference to mixing events (Lewis, 1995). While the succession sequence is fundamentally the same in tropical lakes as in temperate lakes, there is an important contrast in the number of succession episodes per year. Very shallow tropical lakes are usually arrested in a single succession stage. They show a greater simplicity and lower degree of seasonality in their respective phytoplankton community. The given nutrient pulse due to mixing events triggers a succession of phytoplankton communities. The first dominant groups are diatoms, e.g. Synedra sp., and cryptomonads, followed by green algae. The greens are replaced by blue-green algae, e.g. Lyngbya sp., and finally by dinoflagellates as the trend continues towards the extremes of nutrient depletion to less than 1 µg.liter-1 NO3-N. The replacement of other phytoplankton by Lyngbya sp. is an indication of eutrophication (Green et al., 1995) (Table 7.4).

TABLE 7.4.

115

Consumers The littoral usually houses much more individuals and a more diverse community of animals as all the other zones of a lake. Besides herbivorous primary consumers like snails (Pila polita, Pila scutata, Bellamya javanica, Melanoides tuberculata, Limnaea rubiginosa), sediment feeders like larva of Chironomus sp. (Fam.Chironomidae), secondary consumers like carnivorous larva of dragonflies (Zygoptera) can be found. Crustaceans like Caridina sp. and Macrobrachium sp. are also abundant in this zone besides clams like Corbicula javanica and the introduced Anodonta woodiana. Deeper in the sediment annelids usually can be found. The nekton of the littoral is usually very diverse with beetle larvae (e.g. dytiscid beetles) and adult hemipterans like Bellostoma indica. An important impact on the smaller marginal fauna is found by the introduced guppy (Poecilia reticulata) which is gradually occupying the food niches of local fish species like Aplocheilus panchax. The zooplankton of the littoral is characterized by bigger and slower swimming crustaceans. Most important groups of the littoral zooplankton community

Dominant phytoplankton species in nine Indonesian lakes in 1928-1929 and 1974 (after Green et al., 1995).

Lake

1928-29 Ruttner, 1952

1974 Green et al., 1995/Eyamer et al., 1980

Pakis/East Java Lamongan/East Java Bedali/East java Klindungan/East Java Pasir/Central Java

Dactylococcopsis Dactylococcopsis Dactylococcopsis Dactylococcopsis Dactylococcopsis

Cigombong/West Java Bratan/Bali Batur/Bali Toba/Sumatra

Peridinium Staurastrum Nitzschia Denticula

Lyngbya Synedra Lyngbya Lyngbya Spiral Cyanobactericeae Peridinium Lyngbya Lyngbya Anabaena

Aquatic Ecosystems

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3

1

4

2

5

6

are the Copepoda, Rotifera and Cladocera (Table 7.5). For Lake Toba in Northern Sumatra an endemic zooplankton species is recorded: Diaphanosoma modigliani (Cladocera). In general endemism is higher in zooplankton species, particularly calanoid copepods, than among phytoplankton species. Important taxa like Keratella tropica and Mesocyclops crassus are pantropically distributed. The genus Brachiosus is with more species represented in tropical than in temperate lakes (Fernando, 1980). Further, species of epineustic organisms like in the families Gyrinidae, Gerridae and Culicidae need to be mentioned as well as the subneustic community like culicid-larvae and Rhizopoda, the latter belonging to the microfauna. Only a relatively small number of primary consumers in a lake feed directly on the living plants of the benthal (e.g. larvae of the introduced beetle Neochitina eichhornia). The vast majority uses the detritus food chain situation in the profundal and benthal areas of lakes (Fig. 7.20).

MACROPHYTIC PRODUCER Utricularia minor (Fam. Utriculariaceae) PRIMARY CONSUMERS: 1. Insect larva 2. Macrobrachium sp. (Fam. Palaemonidae) 3. Melanoides tuberculata (Gastropoda; Fam. Thiaridae) 4. Hippeutis thienemanii (Gastropoda; Fam. Planorbidae) SECONDARY CONSUMERS: 5. Larva Fam. Discidae 6. Larva Fam. Libellulidae

FIGURE 7.20.

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Food chain in the profundal and benthal of a tropical lake in South East Asia.

TERTIARY CONSUMER:

Trichogaster pectoralis (Fam. Belontiidae)

END CONSUMER:

Clarias batrachus (Fam. Clariidae)


The suspended detritus material is eaten by herbivorous organisms which in turn fall prey to carnivorous organisms, both invertebrates and vertebrates. The primary producers in the pelagic area of the lakes are mostly green algae like Desmidiaceae. They belong to the microfauna. The pelagic zooplankton community is usually composed of not too many species but those in relatively high numbers of individuals per liter. Calanoid copepods with their characteristically long antenna are relatively rare (e.g. Eudiaptomus gracilis). The most frequent pair of copepod species in Indonesian lakes consists of Mesocyclops thermocyclopoides and Thermocyclops decipiens (Green et al., 1995). Also cladocera species are rare in tropical lakes. Cladocerans most frequently found are Ceriodaphnia cornuta, Diaphanosoma excisum and Moina micrura. Others which have been recorded for Indonesian lakes are Daphnia lumholzi, Daphnia similis and Daphnia cephalata. The most abundant plankton rotifers are Keratella tropica and Brachionus caudatus. The food chains found are classical chains starting with the producers (P) and running via primary (C1), secondary (C2), tertiary (C3) consumers to the end consumers (C4) (Fig. 7.21).

TABLE 7.5.

117

The information at hand suggests that both topdown and bottom-up control mechanisms are very important in the tropical lakes (Lewis, 1995). While the top-down control, also called “trophic cascade” (Carpenter et al., 1985), says that “where there are many predators, only little prey is left” the traditional bottom-up hypothesis explains “much prey can feed many predators”. According to the bottom-up hypothesis the biomasses of all trophic levels should to correlate positively and be dependent on the fertility of the respective habitat as limiting factor according to the following sequence: more nutrients available more algae more zooplankton more planktivorous fish more carnivorous predator fish. According to the top-down hypothesis the biomasses of neighboring trophic levels correlate negatively the following succession: more predatory fish less planktivorous fish more zooplankton less algae more free nutrients. A synthesis of both hypotheses was proposed by McQueen et al. (1989) by explaining that on the phytoplankton level mainly bottom-up effects are measurable while on all higher levels mainly topdown effects are visible.

Most important zooplankton groups in eight Indonesian lakes (after Green et. al., 1995).

Lake

Changkuang/West Java Pakis/East Java Lamongan/East Java Bedali/East Java Klindungan/East Java Pasir/Central Java Bratan/Bali Batur/Bali

Cladocera Species No./ Litre 4 4 0 2 0 1 1 0

67 29 0 5 0 2 2 0

Copepoda Species No./ Litre 2 2 2 2 2 2 3 1

60 85 233 343 87 210 14 57

Rotifera Species No./ Litre 7 10 7 4 7 4 3 2

1 30 40 67 1 172 4 45

Aquatic Ecosystems

118


1 2 P

3 C1

4 C2 5

C3

6

C4

FIGURE 7.21.

Food chain in the pelagic of lake Rawa Pening in Central Java.

P - Producer

: (1) Scenedesmus sp.; (2) Cosmarium bioculatum : (3) Daphnia lumholzi : (4) Cyclops sp. : (5) Trichogaster trichopterus : (6) Anabas testudineus

C1 C2 C3 C4

Primary Consumer Secondary Consumer Tertiary Consumer End Consumer

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The phantom midge Chaoborus sp. is of exceptional importance. Because of its growth over three orders of magnitude through four instars, Chaoborus sp. takes essentially the entire spectrum of tropical zooplankton herbivores as its food. The potential effects of Chaoborus sp. are twofold: 1. In great abundance it may suppress herbivory by holding herbivores at abundance that are too low to allow efficient harvesting of phytoplankton production. 2. Herbivore production consumed by Chaborus sp. must pass to fish in order to contribute to harvestable yield. Vertical movements of the pelagic zooplankton are also found in Indonesian lakes. For instance Chaoborus larvae is moving during daytime to the bottom region of the lakes and during night-time up to the surface. In addition, plankton ostracodes are well known examples. The ostracodes are usually found at the front-line of the oxygen-free hypolimnic layer of water during daytime moving to the surface during night-time. Pelagic fish can be important herbivore predators in tropical lakes while zooplanktivorous fish are usually rare (Fernando, 1991). The comparison of three important lakes in Indonesia concerning their biological components is given in Table 7.6. Populations in a given ecosystem do interact. The most important type of interactions is trophic, that is “to eat and to be eaten”. Food chains are the most simple kinds of links of interactions (Fig. 7.22). More often we have to deal with rather complex food webs. A more general picture of a pelagic food web can be given by focusing on functional categories (Fig. 7.23). Only two lines inside the foodweb of the pelagic of most lakes are of importance. 1. The four step sequence of: Nano plankton herbivorous crustacean herbivorous fish carnivorous fish.


2. The five step sequence of: Picoplankton Nano-plankton herbivorous crustacean herbivorous fish carnivorous fish. If populations in a food web are connected by interactions then they do not only influence their direct neighbors, but indirectly also those populations which interact with these respective organisms. Species with a far reaching influence are therefore called keystone predators. This is of great importance if biomanipulation or manipulation of the food chain is used as a tool to regulate the eutrophication process in a given body of water. The underlying idea is that the reduction of planktivorous fish would increase the zooplankton population, increase the grazing and finally will lead to clear water. Until today experiences with biomanipulation are contradictory. Fish species are very often keynote predators and therefore of great importance in lakes. In general, South East Asia has some 105 families of marine and freshwater fish. Ninety-nine families have recently been recorded for the Western part of Indonesia (Kottelat et al., 1993b). The Eastern part of Indonesia is very poorly researched with respect of freshwater fishes. This is a relatively high number of families compared with the 60 families recorded for South America and the 74 families for Africa. TABLE 7.6.

119

In contrast the number of fish species which live permanently or temporarily in fresh water is lower with about 950 in Indonesia than for example 2,400 in the Amazon. There is also a striking difference between the islands belonging to the former Sunda Land Area consisting of Sumatra, Java, Kalimantan and Sulawesi, the latter island not belonging to the Sunda shelf area. In Sulawesi no primary division species or fish species who are strictly intolerant of salt water, have been found yet (Fig. 7.24). Secondary division fishes belong to those families whose members now live in freshwater but are able to tolerate seawater for a short period (Kottelat et al., 1993b) (Fig. 7.25). Diadromous species are species which migrate between fresh and salt water and vicarious species are strictly freshwater species of primarily marine groups (Kottelat et al., 1993b) (Fig. 7. 26). All of the indigenous fish of Sulawesi are of marine origin, but are now adapted to freshwater life. Endemism in the five lakes of the Malili region in Central Sulawesi has shown to be very unusual (Fig. 7.27). The entire Malili region system is connected with rivers and contains three large lakes, Matano, Mahalona and Towuti, each downriver of the other, and two much smaller lakes, Masapi and Wawantoa. Of the 60 species of copepods, prawns, molluscs, and fish endemic to Sulawesi found in the system,

Comparison of three outstanding Indonesian lakes concerning their biological components (after Green et al., 1995).

Dominant Phytoplankton

Lake Toba

Lake Batur

Lake Bratan

Diatome algae Denticula sp.

Lyngbya sp.

Lyngbya sp.

Dominant Zooplankton

Copepoda

Copepoda

Copepoda

Main component of marginal fauna

Corbicula tobae

Melanoides granifera

Poecelia reticulata, Ferrissia sp.

Fish species recorded

18 species 7 families



Aquatic Ecosystems

120


FIGURE 7.22.

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Simplified food web of the lake Rawa Pening, Central Java (after Göltenboth and Kristyanto, 1994).


FIGURE 7.23.

121

Simplified food web based on functional groups in the pelagic of a lake (after Lampert and Sommer, 1993).

Aquatic Ecosystems

122


FIGURE 7.24.

Comparison of number of primary division fish species in Western Indonesia (after Kottelat et al., 1993b).

only one prawn is shared by all five lakes (Whitten et al., 1988). This has lead to speculations of species arising within lakes and rivers due to isolation resulting from waterfalls in connecting rivers or to physiographic obstacles not evident today (Whitten et al., 1988). From Lake Poso and Lake Lindu in Central Sulawesi an entirely new reproductive guild for fishes was discovered. The female of Xenopoecilius sp. carries her eggs in a cluster supported by the pelvic fins with each egg attached to the belly by 10 20 filaments. The belly at this point is distinctly concave in order to accommodate the egg mass (Balon, 1975). The name “pelvic brooders” has been proposed for this guild (Kottelat, 1990). In Lake Sentani in Irian Jaya another unique fish species can be found: The 5-meter long smalltoothed sawfish (Pristiopsis leichhardti). This sawfish feeds on the dead and dying fish it has mauled with its jaws. Since the beginning of the 1990’s, the fish has not any more been reported.

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FIGURE 7.25.

Comparison of the number of secondary division fish species in Western Indonesia (after Kottelat et al., 1993b).

FIGURE 7.26.

Comparison of the number of diadromous fish species in Western Indonesia (after Kottelat et al., 1993b).


FIGURE 7.27.

123

Endemic fish species from the Malili Lakes area in Central Sulawesi (after Whitten et al., 1988). Lake Matano : 1 Tamanka sarasinorum; 2 Oryzias matanensis; 3 Dermogenys weberi Lake Mahalona : 4 Telmatherina bonti; 5 Telmatherina celebensis Lake Wawantoa : 6 Paratherina labiosa

The effect of introductions of fish into Indonesian waters have not been studied in depth but it is known that they have had a negative effect on indigenous fish communities. For example, some of the indigenous fish species in both Lake Lindu and Lake Poso in Central Sulawesi may have been lost because of the introductions of snakeheads (Channa striata) and tilapia (Oreochromis sp.) (Whitten et al., 1987). The mechanisms by which the population of the endemic fishes of Lake Poso, known as “buntingi” and “bungu” have declined are probably disease and parasites, transported to the lake via introduced fish, most probably Clarias sp.

Decomposers Little is known about decomposition in Indonesian lakes. In general, the utilization of organic matter as a respiratory substrate of bacteria and fungi in the water, with the consequent reduction of this to its inorganic components, is of importance in sustaining primary production. It is well known that bacteria play a major role in any decomposition process. In recent years the phenomenon of the so-called microbial loop, that is the role of bacteria in the detritus chain of recycling and breakdown of matter, has received more and more attention. It can be shown that bacteria are true detritus feeders because they live on dead organic substances from all

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124


organisms and from their excreta. Due to the fact that bacteria in a lake are food for some protozoa and some herbivorous zooplankton a cyclic component is placed in any food web of lakes. The importance of micro-organisms and particulate organic matter and their relative contribution to the energy supply of other trophic levels is probably one of the biggest unsolved problems in tropical limnology. However, the relatively high temperatures contribute certainly and substantially to the rapid rate of bacterial decomposition in tropical lakes. This decomposition rate was found to be four to nine times faster than in temperate waters (Ruttner, 1940). NUTRIENT CYCLING AND ENERGY FLOW By their activities organisms trigger nutrient and energy flows. These activities have a very profound influence on the quality of their abiotic environment. From a thermodynamically point of view both, organisms and ecosystems, e.g. a lake, are open systems. They can only be sustained by a steady flow of energy through the system. The primary source of energy is light or any available energy from exergonic chemical reactions. Only phototrophic and chemolithotrophic organisms are independent of the synthetic processes performed by other organisms. By far sun is the most important external energy source and photosynthesis the most important starter process of biological energy flows. Organic material is therefore the universal matter of potential energy in any ecosystem. This potential energy is distributed to living matter or the biomass, particulate organic matter (POM) or detritus and dissolved organic matter (DOM). Organic substances which are not available for the majority of organisms as energy source, because they are not digestible, are called refraction substances. For describing energy flow we need to distinguish between pool volume and transfer rate. The volume of the pool (biomes, detritus, POM and DOM) has the dimension energy (= labor = force x way) while

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rates of transfer have the dimension energy / time (= performance). If we do divert the volume of the pool either by the sum of all inputs to a given ecosystem or the sum of all outflows of the system we do get the turnover time of the given system. In principle, all forms of energy can be transferred into other forms of energy with the exception of heat. However, during each transformation, energy is lost in form of heat according to the second law of thermodynamics. This is important if we want to measure the efficiency of energy transfer in a given ecosystem. The ecological efficiency can be seen as the quotient of predator production to prey production. It gives us the value, how much energy is transferred from one member of a food chain to the next one. Most calculated ecological efficiency values, so far measured, show values of 0.05 to 0.2; that is 80-95% of the available energy are lost during transfer in a food chain from one to the next trophic level. Closed energy cycles in ecosystems are rare, if not non existent. The steady-flow system in one direction is the system in existence concerning the energy flow. This is in contrast to the nutrient flow system which mainly consists of cyclic systems inside an ecosystem. The usually employed concept of trophic pyramids to visualize the various trophic levels and energy flow in a lake is based on the food chain (Fig. 7.28). Compared to terrestrial systems, aquatic systems seem to be built of usually 4 trophic levels and energy flow in a given community is balanced by the decreasing turnover rate of the bigger organisms of higher trophic levels (McQueen et al., 1989). With the help of stomach content investigations the major interactions in a given food chain or food web can be revealed. For example, 66% of the stomach contents of Anabas testudineus from Lake Rawa Pening in Central Java consisted of remains of animals and 15% was plant fiber, mainly Eichhornia crassipes roots, most probably accidentally taken during the in take of organisms living in the root balls of the water hyacinth. In Trichogaster trichopterus, 25% of the stomach volume consisted of Peridinium sp.


125

END CONSUMER LEVEL: Man

END CONSUMER

13

12

CONSUMER LEVEL 3 AND 4

(C3 + C4):

Secondary Carnivores and

Omnivores:

12) Anabas testudineus;

13) Trichogaster trichopterus

C3 + C4 8 CONSUMER LEVEL 1 AND 2

(C1 + C2):

11

Herbivores and Primary Carnivores:

8) Macrobrachium rosenbergii; 9)

Caridina laevis;

10) Daphnia similis;

11) Macrocyclops albidus

9 10 C1 + C2 3

2

PRODUCER LEVEL (P):

1

Phytoplankton: 1) Lyngbya sp.; 2) Micrasterias radiata; 3) Pleurotaenium ehrenbergi; 4) Pediastrum gracillimum; 5) Diatomea;

4

FIGURE 7.28.

5

6

7

Macrophyta: 6) Ceratophyllum submersum; 7) Hydrilla verticillata

Simplified trophic pyramid for lake Rawa Pening, Central Java (after Göltenboth and Timotius, 1994).

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126


Although for a number of Indonesian lakes food chains and food webs are known, virtually no Indonesian lake has been studied in a way to allow the construction of an energy flow diagram. It would be of interest to have such energy flow diagrams, because the energy flow approach allows comparisons between whole systems. However, energy-flow diagrams are purely descriptive devices. They do not tell us what causes more energy to go down one pathway than another or how partition of energy between the components of the community is regulated (Payne, 1986). Transfer of energy in an ecosystem is always combined with the transfer of nutrients. All organisms need to feed, that is, they need to get energy and substances from their environment. Many aquatic organisms depend on allochthonous material for their existence, for they fed directly or indirectly on dead leaves and other vegetable matters reaching rivers and rivulets from forests in the respective catchment area. The sum of all consumables from the environment are called resources. The rate by which organisms consume their resources is dependent on the availability of the resource and the ability of the organisms to use it. For organisms living in a lake three models of the so-called functional response, that is, the dependency of the intake of food by a predator from the density of prey, have been developed (Holling, 1959) (Fig. 7.29). While some resources can be substituted by others some can not. Those resources are called essential resources. For example, some vitamins are such essential resources for a great number of organisms. THE CARBON CYCLE Inorganic carbon in the form of dissolved inorganic carbon or DIC, is available in water in three forms: CO2, HCO3-, CO3 2-. Their availability depends on the pH values of the water. If all CO2 would be used up the pH would be 9. If all HCO3- would have been used up by those plants possessing the enzyme

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Carbonhylase, the pH would be 11. Water plants have developed different strategies to take up DIC: 1) Formation of leaves. 2) Use of CO2 in the water of the sediment. 3) Formation of a C4 - metabolism enabling them to fix CO2 during night time, e.g. Hydrilla sp. 4) Use of HCO3-. The most essential pools for carbon in an aquatic environment like a lake include the following: 1) Dissolved inorganic carbon or DIC. 2) Dissolved organic carbon or DOC. 3) Particulate organic carbon or POC. The most essential input for the DIC is the solution of atmospheric CO2, underground pool, inorganic carbon bound in sediments, chemical and biological processes in the hypolimnion. The biological input is the respiration of organisms, while photosynthesis and chemosynthesis are the biological outputs. The DOC (dissolved organic carbon) pool is a mixture of substances. Besides allochthonous inputs, secretion and excretion and autolysis of the detritus are the main sources for DOC. The uptake by bacteria is the most important output. The POC, or particulate organic carbon is mainly composed of the substances bound in organism and the detritus. The main source for POC is the primary production. POC is transformed by respiration into DIC and by secretion, excretion and autolysis into DOC (Fig. 7.30). Sedimentation leads to a depletion of pelagic POC and an import of POC to the benthal. Other mineral elements of importance besides those needed for photosynthesis are: 1) Macro elements: N, S, P, K, Mg, Ca, Na, Cl; 2) Trace elements: Fe, Mn, Cu, Zn, B, Si, Mo, V, Co. Next to carbon the most important elements are nitrogen and phosphorus usually circulating in the environment.


1

2

3

FIGURE 7.29

Models for the functional response between predators and the density of prey (after Holling, 1959). 1) 2) 3)

The handling time to consume the prey is very short, e.g., a fish swallowing entire prey items; Model showing most of the relations in a lake, e.g., Chaoborus sp. consuming small zooplanktons; The predator is selectively feeding on a specific prey easily available.

127

THE NITROGEN CYCLE Quantitatively nitrogen in the form of dissolved N2 is the most essential form in water. Unfortunately, only prokaryotes have the needed enzyme nitrogenase to fix this N2. For the autotrophic organisms, having no enzyme nitrogenase, dissolved nitrate (NO3 2-), nitrite (NO2 2) and ammonium (NH4 +) are the most important sources for nitrogen. Microbial activity may transform these into each other. The respective reactions depend on the availability of oxygen. In an anaerobic situation nitrate is transformed into either ammonium (nitroammonification) or into nitrogen (denitrification). Under aerobic conditions ammonium is transformed via nitrite into nitrate (nitrification). The dissolved organic nitrogen or DON derives from the excretion of organisms and the lysis of detritus (Fig. 7.31). DON consists mainly of ammonium compounds with polypeptides as the major compounds. THE PHOSPHORUS CYCLE In contrast to nitrogen, phosphorus is only available in one form in the aquatic environment as orthophosphate or PO4 3-. The most important sink for soluble reactive phosphate (SRP) is the up-take by algae and bacteria. In the epilimnion the SRP is rapidly decreasing during growth periods of the phytoplankton. The hypolimnion is usually much richer in phosphorus than the epilimnion. By mixing events phosphorus is recharged to the epilimnion. In extreme cases this can lead to accelerated eutrophication processes. The sediment usually serves as phosphorus trap as long as its surface is oxidized. It is a phosphorus source if the surface is in a state of reduction processes (Fig. 7.32). There is evidence that phosphorus may be a limiting factor in tropical lakes. Periodic nutrient limitations are indicated by tight nutrient cycles, fast turnover rates, low labile P content in algae and a

Aquatic Ecosystems

128

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FIGURE 7.30.

General diagram of the general patterns of the carbon cycle in a lake (after Lampert and Sommer, 1993).

Allochth. - Allochthonous; DIC - Dissolved inorganic carbon; DOC - Dissolved organic carbon; POC - Particulate organic carbon

Nitrogen cycle in a lake with anaerobic hypolimnion, e.g. Lake Singkarak in Sumatra (after Lampert and Sommer, 1993).

PON - Particulated organic nitrogen

129

DON - Dissolved organic nitrogen;


Aquatic Ecosystems

FIGURE 7.31.

130


diurnal cycle of phosphatase activity (Schiemer, 1995). HUMAN INFLUENCE AND ECOLOGICAL STATUS Natural lakes in Indonesia comprise approximately 0.52% of the total land area or 1.85 Mio ha. All forms of water resources like lotic water, groundwater and lentic water are combined in a hydrological cycle starting with the precipitation given in a certain area. Despite adequate rainfall over most of Indonesia with average values between 2,000-3,000 mm. year 1 (lowest 600 mm. year-1 in Palu Bay, Sulawesi, highest with 6,000 mm .year-1 in Irian Jaya) some islands, like Java, face water shortages, particularly in relative dry years. Particularly two phenomena, eutrophication and acidification, are of great concern in relation to the ecology of lakes. Disturbances leading to impacts on lakes can occur in various ways: 1) Pollution from organic substances in household wastes and garbage is one of the principal contributors to water pollution. Only around 15% of households in 1980 in Indonesia have sanitation facilities in form of septic tanks (Annonymous, 1980). Around lake Rawa Pening about 60% of the population of more than 30,000 people discharges directly into the lake or the inflowing rivers around the lake (Göltenboth et al., 1994); 2) Pollution from industry with pathogens, toxins, deoxygenerators and nutrient enrichers often discharged directly into the environment and entering the lakes mostly via inflowing rivers. Likewise, the threat of acid rain with pH ranges of less than 5 caused by gaseous nitrogen and sulfur oxides which form nitric and sulfuric acids, are steadily increasing particularly in the highly industrialized zones around Jakarta, Bandung and Surabaya on the island of Java. These

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3)

4)

5)

6)

7)

gases are waste products from the combustion of oil and coal, from metal smelting and a great variety of other industrial processes. Introduction of exotic fish species can cause the demise of indigenous species. More than 75% of all Indonesian lakes have been stocked with exotic fish species the most common one being (Oreochromis sp.) from East Africa. Introduction of exotic water plants contributing to accelerated eutrophication. The most noxious plant is Eichhornia crassipes, a native of South America. Indiscriminate fishing practices like fish poisoning and dynamite fishing causing devastating effects on all living organisms inside a lake. Forest clearing causing changes in temperature, insulation, water input, sedimentation rates and water turbidity and thereby altering the habitat of many species. Mines flushing their tailings into rivers and lakes like the nickel mine near Lake Towuti, and the zinc mine near Lake Matano in Sulawesi or the gold and copper mines in Irian Jaya.

EUTROPHICATION Eutrophication is not, in itself, a major problem for aquatic ecosystems. In the geological history of a lake this is a long and slow natural process (Fig. 7.33). Naturally eutrophic systems are usually wellbalanced, but the artificial addition of nutrients can upset this balance and cause devastating results. Throughout Indonesia eutrophication in 1996 was not yet a big problem for most of the natural lakes. Out of 24 major lakes only two were categorized as being in a eutrophic state, namely the two floodplain Lakes Limboto and Tempe in Sulawesi. However, these lakes do not receive excess amounts of nutrients

Schematic diagram of the phosphate cycle in a stratified lake (after Lampert and Sommer, 1993).

131

P coll. - colloidal phosphorus; P part. - particulated phosphorus; SRP - soluble reactive phosphorus; TDP - total dissolved phosphorus


Aquatic Ecosystems

FIGURE 7.32.

132


but a lot of allochthonous material. Ten lakes were categorized as being oligotrophic, e.g. Lake Toba in North Sumatra, and four as being mesotrophic, e.g. Lake Rawa Pening in Central Java (Lehmusluoto et al., 1995a, 1997) (Table 7.7). Algal blooms are the most spectacular of the eutrophication effects and the combination of high nutrient levels, favorable temperature and light stimulate rapid algal growth. These blooms are a natural response of algae to the environment, but when the environment changes and can no longer support such high algae populations, the algae that accumulate during this bloom later die and decay. The ensuing rapid decomposition of organic debris by bacteria deprives the water of its oxygen, sometimes to the extent that fish and other aquatic organisms suffocate. In Indonesian lakes this is a rather seldom reason for fish kills, but upwelling may be a more important source for such catastrophic events. Balanced eutrophic habitats are excellent for fisheries because of their high productivity. Therefore the lakes with high productivity, like Lake Tempe in Sulawesi, have been called “the fishbowl of Indonesia” (Suwignyo, 1979). After the introduction of Puntius gonionotus and Trichogaster pectoralis in 1937, two years later only these two species accounted for 20% and 70%, respectively, of the lake’s harvest of 25,000 t ·year-1 (Whitten et al., 1988). At present it is about 12,000 t ·year-1 or 600 kg · ha-1, still a high annual production compared to the 288 kg · ha-1 in the mesothrophic Aopa Swamp also in Sulawesi. In Lake Limboto, the other eutrophic lake in Sulawesi, a five - fold decrease in fish harvest is blamed to the steady increasing shallowness of this lake due to siltation. This lake is to a great extent covered with abundant vegetation, including the four most noxious aquatic weeds and submerged plants. These four most common and widely distributed aquatic weeds are:

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FIGURE 7.33.

Natural transition of an eutrophic lake area.


TABLE 7.7.

133

Characteristic features of oligotrophic and eutrophic lakes.

Character

Oligotrophic

Eutrophic

Basin shape Lake substrate Lake shoreline Water transparency Water color Dissolved solids Suspended solids Oxygen Phytoplantkon Macrophytes water Zooplankton Zoobenthos Fish

Narrow and deep Stones and inorganic silt Stony High Green or bluish Low; poor in N and P Low High Many species; low numbers Few species; some in deep waters

Broad and shallow Fine organic silt Weedy Low Yellow or greenish High; N and P high High High in epilimnion; Low in hypolimnion Few species; high numbers Many species; abundant in shallow

Many species; low numbers Many species; low numbers Few species

Few species; high numbers Few species; high numbers Many species

1) Eichhornia crassipes introduced to Indonesia in 1884 as ornamental plant coming from South America. It is observed in 77% of all Indonesian lakes. 2) Salvinia molesta and Salvinia cucculata also originating from South America. They are a major part of carpet like floating mats. 3) The submerged plant Hydrilla verticillata growing only in shallow waters, is often harvested as chicken and pig feed. All these macrophytes have potential advantages and disadvantages with respect to human uses of freshwater and to balance these, efficient management is necessary. This management can be divided into three components (Soerjani, 1985): 1) Preventative measures. 2) Control measures. 3) Utilization. The first requires steady monitoring while control measures can be subdivided into mechanical, chemical and biological measures. All of these can have serious side effects. For example, mechanical control can disperse small bits of stem that are swept away and then grow in new areas. As already

mentioned above the weevil Neochitina eichhorniae can control water hyacinths but it also feeds on arrow roots of Canna edulis and even worse on ginger, Zingiber sp. (Soerjani, 1985). Chemical control with herbicides is the most radical and quick control measure but there are well-known dangers such as unpredicted toxicological effects on non-target organisms and even on cytogenetical structures. During 72 hours any of the usually recommended herbicides for waterplant control reduces the mitotic activity of root tip cells by more than 50% (Fig. 7.34). In Lake Rawa Pening in Central Java a direct correlation between hyacinth control measures and fish yield was found (Fig. 7.35). The utilization of macrophytes like Eichhornia crassipes is in steady progress. The dried stalks can be used for weaving mats which is a raw material for a variety of handicrafts. The semidried plant can be used for mushroom culture. It has some potential as the raw material for paper pulp and as mulch. Hydrilla is an excellent feed for pigs and the grasscarp Ctenopharyngodon idella if this fish is bred under controlled conditions in floating net cages or karambas (Fig. 7.36).

Aquatic Ecosystems

134


By far the best approach is integrated lake management and a clear understanding of the perceived problems, a clear definition of the desired goals, the study of the response of the key species to possible changes, consideration of the economic and ecological costs and benefits, and attention to local socio-economics, particularly potentials for locallyorganized resource management (Whitten et al., 1988). Forest clearance is by far the most serious threat to natural lake ecosystems. Moreover, the rapid silting up of lakes is highly supported by forest clearance. For example, around Lake Tondano in Northern Sulawesi virtually no forest is left and due to agricultural activities this lake is silting up at a rate of 20 cm per year. For most of Indonesia no systematic explanation of the effect of forest clearance on the aquatic ecosystems appears to have been published, but data from Malaysia (Johnson, 1973) strongly indicate very far-reaching and destructive impact of such forest clearances on aquatic environments.

IMPLICATIONS FOR EIA STUDIES Since 1987 Environmental Impact Assessment studies (EIA or AMDAL) are required for all development projects. However, the effect of those studies on the developmental process may be doubted. First of all, there are too many government agencies involved in the lake management. For example, not less than 9 institutions of the government, including the armed forces are responsible for the management of Lake Rawa Pening in Central Java. Therefore, necessary decisions can be watered and delayed nearly indefinitely. Consequently, no one feels actually responsible, particularly if a budget is needed to prevent environmental destruction or if the political will is not advisable to counter certain developments. Therefore, the most needed change to improve lake management in Indonesia is to create one authority as lake management authority. Secondly, in most cases baseline data for most of the lake areas are very scarce, sometimes even misleading or wrong. Even rainfall and temperature

100

MITOTIC INDEX REDUCTION (%)

Diquat 1.5 ppm 80

Glyphosate 1.6 ppm Paraquat 1.5 ppm

60

2.4-D / Glyphosate (1+1) ppm 2.4 D / Ametryn (1+1) ppm

40

Ametryn 1.6 ppm 2.4 D / Paraquat (1+0.5) ppm

20

2.4 D / Diquat (1+0.5) ppm

0

1

2 24

3 48

4 72

5 96

TIME (HOURS)

FIGURE 7.34.

LAKES

The effect of various herbicides and herbicide-mixtures used to control waterplants, on the root tip mitosis of water hyacinth (after Göltenboth, 1979).

135


t • yr1 x 102

kg • ha-1 • yr-1 x 102 6

9

5

4

6

3

3

2

1

AQUATIC WEED CONTROL 1930

FIGURE 7.35.

34

38

42

46

50

54

58

62

66

70

74

78

82

86

90

Negative correlation between water hyacinth removal campaigns and fish yield in Rawa Pening, Central Java (after Göltenboth and Timotius, 1994). Fish yield

data are often not collected on a daily basis and over a longer period. More sophisticated data are often unreliable due to lack of experience and facilities faced by the official institutions in-charge. Thirdly, the distribution and availability of the collected information is not organized in an efficient way, because much of the research already carried out, or information accumulated by one of the existing institutions is not available for everybody or one specific place, e.g. the National Library. Only by chance sometimes highly relevant information can be received. This is particularly true for any kind of map with more information than a tourist map offers. Fourth, there is not yet an agreement between researchers doing an Environmental Impact Assessment (EIA) concerning the standardization

Water hyacinth removal campaigns

of research methodology. Therefore, comparability of individual studies is low. To assess the tropical status of a waterbody like a lake, at least the following groups of primary data need to be collected and measured (Table 7.8): 1)Morphometric data. 2)Hydrodynamic data. 3)In-lake nutrient data. 4)In-lake eutrophication response parameters. For Indonesian lakes, only preliminary data concerning their trophic status and their physical and chemical environment are at present available (Table 7.9).

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136


FIGURE 7.36.

Schematic drawing of the set up of one floating net cage unit with eleven cages, covering about 441 m2 (after Göltenboth et al., 1994). Nine cages of 7 x 7 x 3 m are used for the rearing of Oreochromis niloticus and two cages are used for multiple purposes. The entire unit floats on old petrol drums. The hut has usually a living and a sleeping room plus a storage room. The walks are made of bamboo.

SUMMARY Only a small number of the 526 recorded lakes throughout the Indonesian archipelago have been studied to date. Even the data from those lakes having been studied to some extent are not easily available and data sometimes go back to the very beginning of limnological research in 1928-29 by Ruttner and Thienemann (Göltenboth et al., 1996). In the 1990’s extensive studies were performed by the socalled Expedition Indodanau (Lehmusluoto et al., 1995,1997). The ecological health of the larger natural lakes is still quite good. The circulation and mixing patterns of the lakes are generally aseasonal and mixing

LAKES

tends to be incomplete. Due to the nature of the islands the drainage areas of the lakes are generally small. In contrast to the plankton level, endemism is relatively high on the fish level, particularly on the island of Sulawesi making Indonesian lakes one of the most outstanding areas on the globe in terms of biodiversity. More than 77% of all lakes are dominated by exotic water plants like Eichhornia crassipes, Salvinia molesta and Hydrilla verticillata. More than 90% of the major lakes have been stocked with exotic fish species like Oreochromis sp. Lake management should be based on multipleobjective and integrated planning with more emphasis on non-economic objectives. It is necessary to identify


TABLE 7.8.

137

Primary data for assessing the eutrophication status of a waterbody (after Ryding and Rast, 1989).

Parameter

Units1

Morphometric parameters Lake surface area km2 2 Lake volume (average condition) 106 m3 Mean and maximum depth m Location of inflows and outflows _ Hydrodynamic parameters Volume of total inflow (including ground water) and outflow for different months m3 .d-1 Theoretical mean residence time of the water (renewal time, retention time) y Thermal stratification (vertical profiles along longitudinal axis, including the deepest points) _ Flowthrough conditions (surface overflow or deep release, and possibility of bypass flow) _ In-lake nutrient parameters Dissolved reactive phosphorus; total dissolved phosphorus; and total phosphorus µg P .l-1 Nitrate nitrogen; nitrite nitrogen; ammonia nitrogen; and total nitrogen mg N.l-1 Silicate (if diatoms constitute a large proportion of phytoplankton population) mg SiO2 .l-1 In-lake eutrophication response parameters Chlorophyll a; pheophytin a mg.l-1 Transparency (Secchi depth) m Hypolimnetic oxygen depletion rate (during period of thermal stratification) g O2. d-1 Primary production3 g C.m3.d-1 3 Diurnal variation in dissolved oxygen mg .l-1 3 Dissolved and suspended solids mg.l-1 3 Major taxonomic groups and dominant species of phytoplankton, zooplankton and bottom fauna _ Extent of attached algal and macrophyte growth in littoral zone3 _ 1The terminology and units proposed by the International Organization of Standardization is recommended for expressing the

parameters.

2A bathymetric map and hypsographic curve is necessary in many cases.

3Can provide additional information on the trophic conditions of a waterbody; recommended if resources are adequate or if special situations requrie more detailed information.

and prioritize information and research needs, to monitor freshwaters, to establish ways to assess the quality of the lakes and to compile the existing information in data base. The sustainability of freshwater bodies as an important resource and as an integral part of the earth’s ecosystem should be considered in any management strategy.

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138


TABLE 7.9.

Lake/Island

Parameters and combinations of parameters describing the physical and chemical environments and trophic status of four different lakes in Indonesia (after Lehmusluoto et al., 1995b).

EC µS/cm

LM

Toba, Sumatra North Basin

180

0.90

65 NA 529

South Basin

195

0.98

Rawa Pening Java

260/ 500

Tempe Sulawesi Sentani Irian Jaya

CD EC

TC Zzo Zmax

Zh

SD min

CD

MT

P

pH max

TS

N

NS

NA

L

L

8.2

15.0

0

6.2

I

160 NA 433

NA

L

L

8.2

13.5

0

6.7

I

0.56

NA 5 11

NA

H

L

7.5

0.7

M

43.1

II

220

0.01

NA NA 5

NA

H

M

7.4

0.6

E

38.0

III

250

0.44

4 30 42

40

L

L

8.3

2.6

M

2.2

I

Concentration of accumulated carbon dioxide (mg/l) in the hypolimnion as an indication of the potentiality of a lake being hazardous Electrical conductivity depicts the mineral salt concentration; in the case of two values the first is for the epilimnion and the second for the hypolimnion LM Likelihood of complete mixing defined as the ratio of maximum depth (Zmax) : Area (A) MT Mixing type : I Monomictic; II Oligomictic; III Polymictic N Total nitrogen : L = 0-0.25 mg .l -1; M = 0.251 - 0.500 mg.l -1; H = > 0.500 mg.l -1 NA Not applicable NS Nutrient status of the epilimnion P Total phosphorus : L = 0-0.025 mg.l -1; M = 0.026-0.050 mg.l -1; H = > 0.050 mg.l -1 pH Maximum pH of epilimnion SD Minimum transparency (m) TC Maximum observed depth of thermocline (m) TS Trophic status : O Oligorthrophic; M Mesotrophic; E Eutrophic Zhs Detectable hydrogen sulfide depth (m) indicating the depth at which hydrogen sulfide was first detected Zmax Maximum depth (m) ZZO Zero oxygen depth (m) indicating the depth at which anoxia began

LAKES


THESIS Some limnologists doubt whether rivers can be called ecosystems because the fixation of the quantitatively largest part of the needed energy for the system is not taking place inside the river but in the catchment area of the river. The allochthonous material is only used-up in the river. Therefore, energy fixing processes and energy consuming processes are not part of the same system, as postulated for any real self-regulating ecosystem (Lampert and Sommer,1993). Others say only the study of catchment areas of rivers gives a real picture of the factors involved in an aquatic water ecosystem (Bretschko, 1991). Therefore, streams and rivers are the focus of catchment or drainage-basin processes. Land-water interactions play a fundamental role in shaping the ecology of running waters and any assumption that tropical streams and rivers are nothing more than warmer versions of their temperate analog, needs to be avoided (Dudgeon and Bretschko, 1995). Stream ecology, management and conservation must take into account the drainage basin as a whole rather than the lotic environment in isolation (Boon et al.,1992). The extent of land-water interactions constitutes an integral part of stream ecosystem dynamics as made explicit in the River Continuum Concept (RCC) (Vannote et al., 1980). Of major importance is therefore the allochthonous and autochthonous transported organic load, its origin, nature and magnitude and its effects on the biology and productivity of benthic invertebrates and fishes. The extensive use of river resources for development purposes underscores the importance of ecological functions of the watershed area for those who formulate conservation and management strategies.

139

8

RIVERS

Friedhelm Göltenboth and Pasi Lehmusluoto

OVERVIEW Rivers usually arise in the headwater areas of mountains. They increase in volume and width as they flow downhill, joining other rivers to form a main

Aquatic Ecosystems

140


river that drains a watershed which may be thousands of hectares in area (Whitten et al.,1988) (Fig. 8.1). The hydraulic conditions of a river essentially depend on the morphology of the body of water. These conditions change along the river and its contributors and a hierarchy of tributaries is formed. This hierarchy has been used to number the respective bodies of water and characterize them in a system of assigning river “orders” in the following way (Hynes, 1970): 1st order rivers : rivulet originating from a well 2nd order rivers : Two 1st order rivers form the 2nd order river etc. (Fig. 8.2) Geology and topography determine drainage patterns and in Indonesia mainly three types can be found (Fig. 8.3):

FIGURE 8.1.

RIVERS

Watershed area of a pristine river and water cycle.

1. Dendritic radial drainage patterns like the river Lawo in Sulawesi 2. Dendritic drainage patterns like the river Jeneberang in Sulawesi 3. Trellis dendritic patterns like the river Tumpah in Sulawesi Rivers may also originate from other water sources such as lakes like the Tuntang river from lake Rawa Pening in Central Java or from limestone caves like the Balangajir river in the Maros area of South Sulawesi or from swamps like some rivers in Kalimantan. Rivers are much more dependent on their catchment area than lakes. The allochthonous input of energy is often much higher than the autochthonous


141

input from primary production. Therefore rivers are in general communities of consuments and destruents. Contrary to lakes, rivers are not vertically stratified. Therefore, rivers can only be divided into areas of flowing water, the river bed or benthal, and the deeper areas of the sediment or hyphoreal . More conspicuous are the changes along the river from its source to the mouth and therefore the habitats have been organized as follows (Illies, 1961)(Fig. 8.4): Crenal - Zone around the spring of the river, including cascade and montane zone Rithral - The upper part of the river, including ephemeral and colline zone Potomal - The lower part of the river or riverine zone. When the Sunda region, consisting in Indonesia of Sumatra, Kalimantan, Java and Bali, were connected by dry land most of the present rivers in Sumatra, Java and Kalimantan were tributaries of the same much larger river system that flowed

FIGURE 8.2.

Hypothetical river basin showing the system of assigning river “ orders”: 1+1 = 2; 2+2 = 3 etc; but 2+1 = 2; 3+2 = 3 (after Strahler, 1957)

Figure 8.3.

Types of drainage patterns (after Whitten et al.,1988).

Aquatic Ecosystems

142


towards the east. The present rivers were therefore only the head-waters of a previously rather large catchment area (Fig. 8.5). This fact is still reflected in similarities and differences in the river fauna of the region. Unfortunately the information about most rivers in Indonesia is not easy available, even when compared to the lakes. The Musi river in South Sumatra (Thienemann,1957), the Brantas river and Blawi river (Trihardiningrum et al.,1995) in East Java, some of the West Javanese rivers, the small mountain river Awu (Leichtfried and Kristyanto, 1995) in Central Java, River Ayung (Suryadiputra

FIGURE 8.4.

RIVERS

and Suyasa, 1995) in Bali, the Barito (Hortle, 1995), Kelian (Yule, 1995) and Kapuas river in Kalimantan have been studied to various extent. Most of the rivers in Sumatra, Sulawesi and Irian Jaya are virtually unknown or that information is not available for the scientific community. ECOSYSTEM FUNCTION Abiosis Variation exists across a river as well as down its length. The current or velocity of flow is the determining factor for the profound differences

Schematic drawing of the zonations of a river from the sea to the cascade area forming a river continuum system.


between lentic and lotic waters. The flowing water mixes all the time. Except for the light, layering is not easy to demonstrate. Due to the usually one-directional current, specific features are of major importance for any organism in the river: • Transport of small organisms is always downstream. • Plankton organisms are only able to exist in stagnant parts of a river.

FIGURE 8.5.

143

• In small streams, for example, shallow sections with fast water alternate with deeper pools and stagnant pools with very sluggish water flows. Therefore, a relatively wide variety of microhabitats is formed (Fig. 8.6-8.7). • Resources like nutrients are lost for a sessile organism if not immediately used. • With the same rate as resources are moved downstream new resources can be brought into a given place from upstream.

River system during the pleistocene period in the region of present South East Asia showing the drainage system of the rivers in the Sunda-Area (I) and the pleistocene shoreline of the Sunda-, Transition- (II) and Sahul - Area (III). Wallace’ s Line,

Leydekker’s Line, Sunda Area, Sahul Area

(1) Mekong, (2) Asahan, (3) Musi, (4) Kapuas, (5) Barito, (6) Kelian, (7) Mahakam, (8) Brantas, (9) Ciliwung, (10) Mamberamo

Aquatic Ecosystems

144


LOW GRADIENT RIFFLE BACKWATER POOL

DAMMED POOL

PLUNGE POOL

TRENCH POOL

FIGURE 8.6.

RIVERS

Microhabitats according to the variable features of small streams as seen at the Awu stream on Mt. Slamet, Central Java.


FIGURE 8.7.

145

Microhabitats in connection with a waterfall of a first grade stream into a second grade stream at Mt. Slamet, Central Java.

Aquatic Ecosystems

146


• Current is a very big selective factor for all organisms. • Organism adapt to catastrophic drift events during floods. • River bed composition depends on the surrounding material and the current (Lampert and Sommer,1993) (Table 8.1): • Current velocity is often faster in lowlands than in the headwaters because velocity depends on steepness, river bed composition and cross-sectional area: Discharge (Q) (m3·sec -1) = Mean Velocity (V) x Crosssectional Area (A). TABLE 8.1.

Comparison of current velocity and major river bed particles.

Velocity (cm·sec -1)

Major River Bed Particles

3 - 20 20 - 40 40 - 60 60 - 120 120-200

Mud ( < 0.004 mm) Fine sands ( < 2 mm) Larger sized sand grains - gravel Small pebbles - fist-sized rocks Medium to large-sized boulders

The current velocity decreases in a logarithmic manner from water surface to the river bed. The average velocity of the whole column of water is equivalent to that occurring at about 60% depth (Townsend, 1980). While this parameter is of importance for plankton and nekton, for the animals living on the river bed the shear stress (to) on the river bed is the most important factor. Shear stress is calculated as follows: to= Specific weight of water (y) x depth (d) x slope (s)

The shear stress not only affects animals and plants but also inorganic particles which can be dislodged. Smaller and lighter particles are carried away as suspended load, larger and heavier particles roll along the bottom as bed load.

RIVERS

The lotic body of water does not have a sharp boundary. In the bottom sediment is a system of gaps with flowing water. This continues to the ground water system where the water flows parallel to the river. Depending on the morphology of the river bed, this so-called hyporheal is only some centimeters or up to one meter thick. This hyporheal is for many organisms, particularly in their larval stages, a protective hideout. In small streams in forested areas the forest cover along the riparian zone along the stream banks filters much of the incoming light. Typically only 2 15% of visible light reaches the water surface. The transparency of water is critical for aquatic producers like algae and other submerged plants. Even in completely clear water, light intensity is reduced to about 60% at 40 cm below the surface. In heavily silt-loaded rivers light penetrates only about 5 cm below the surface. On average, the temperature regime is more moderate than that of the air, cooler by day and warmer by night. While water chemistry is predominantly a consequence of local lithology, allochthonous inputs do influence the hydrology. High levels of organic input can override the water chemistry expected due to lithology. Lack of calcium usually results in more acidic water and if soils are highly leached the water is stained brown like tea due to the effect of leachates from mainly allochthonous leaf litter and peat (Fig. 8.8). The concentrations of salts are characteristically low in forest streams and in many cases precipitation represents the most important input (Table 8.2). High sulfate concentrations are mostly due to leaching from the soil and decaying organic matter; the relative concentrations of cations reflect the soil chemistry. Scarcity of dissolved calcium affects particularly animals that need large amounts of calcium like molluscs and crustaceans. Silica is a major solute in freshwater while phosphorus is usually very scarce. Nitrogen is typically higher than phosphorus with organic and ammonium-nitrogen dominating.


FIGURE 8.8.

147

Blackwater of the Sekanir River in Kalimantan. A lentic zone of the river running through a peat swamp forest. The river is fringed with screwpines (Pandanus sp.)(1) and by the long blade leaves of Hanguana malayana (2).

Dissolved oxygen content reaches usually only few mg per liter, even in fully saturated waters. Total dissolved carbon dioxide shows great variation with a pronounced diurnal cycle: high in the early hours of the day due to overnight respiration and diminishing during daylight as a consequence of uptake during photosynthesis by aquatic plants. Biodiversity In general, species diversity in tropical waters is usually high, but the abundance and density of any particular species is usually small.

Producers The importance of land-water interactions in streams depends upon the relative magnitude of allochthonous inputs and autochthonous primary production. While data on lotic primary production concerns only phytoplankton, which is confined to large rivers and floodplains, little is known about smaller streams. The available data indicate that phytoplankton productivity in large tropical rivers is low and periphyton production in small rivers considerably higher. Shading is a major factor influencing the primary productivity as is the current velocity. In general, the magnitude of autochthonous production

Aquatic Ecosystems

148


TABLE 8.2.

Comparison of pH and conductivity of water from some rivers with rain water (after Leichtfried and Kristyanto, 1995; Suryadipura and Suyasa, 1995; Yule, 1995).

Awu River

Ayung River

Kelian River

Location

Undisturbed mountain river in Central Java

Disturbed lowland river in Bali

Undisturbed upstream part of Borneo River

Conductivity(µS.cm-1)

80-100

112

42

4.5

pH

8.0

7.2

7.1

5.5

varies considerably over time and space and makes a relatively small contribution to secondary production. The strong influence of discharge regimes tends to induce variations in biomass and net primary production of benthic microphyte communities and phytoplankton biomass and production is influenced strongly by river pollution( Dudgeon et al., 1995). Consumers The term consumers is generally restricted to animals and contrasted with primary producers and decomposers. Organisms belonging to the lotic zoobenthos in streams and rivers comprise the two main groups of benthic consumers: the macro- and meiofauna. Virtually nothing is known about the meiofauna or those small interstitial animals that pass through a 1mm-mesh sieve but are retained by a 0.1 mm mesh. This meiofauna is certainly of importance, because it mediates the transfer of energy from the microbiocoenosis, which derives energy form the lateral inputs from the surrounding soil, to the larger members of the benthic invertebrate community, thereby making it available to higher links in stream food chains. The general composition of the macrobenthic invertebrates includes members of the families and

RIVERS

Rain Water

genera of Tubificidae (Oligochaeta), Simuliidae (Diptera), Hydropsychidae (Trichoptera), Chironomidae (Diptera), Ephemeroptera, Plecoptera, Coleoptera, Heteroptera, Odonata, Gastropoda (Prosobranchia) Bivalvia and Crustacea (Decapoda). Decapod crustaceans are of high significance in all tropical streams, e.g. freshwater crabs of the families Potamidae and Parathelphusidae and freshwater shrimps of the families Atyidae and Palaemonidae. While the majority of the described 8 000 species of crabs is marine several hundred species have colonized freshwater and terrestrial habitats. Unlike marine crabs, freshwater and terrestrial crabs produce few large eggs which undergo direct or abbreviated development. Free living swimming larvae are either absent or have a short life span. Of the two freshwater shrimp families, the Palaemonidae and the Atyidae, the genus Macrobrachium is of main importance. Macrobrachium rosenbergii still migrates to the sea or estuarine areas to breed. Other Macrobrachium species are found mainly above waterfalls.They are largely restricted to torrent water and the low productivity of this species is compensated by direct egg development. With the tuft of brushlike hairs at the tip of the claws on the first pairs of legs the Atyid Caridina sp. is filtering food particles out of the stream water.


This group of widely distributed freshwater crustaceans is restricted to less acid waters. Usually the insect fauna of freshwater, particularly in forested areas, is very distinctive. For example, the different communities of forest stream dragonflies reflect the ecological distinctness of upper, middle and lower level streams, rivers and pools. Many of the insects are aquatic as larvae and terrestrial or aerial as adults. They therefore perform the role in the stream-bound ecology of transferring resources from the water back to the land and from downstream to upper stream parts in case of drift events. Also most animals are adapted to various extents to the current of a stream. Stream organisms eventually move downstream with the current. This phenomenon is called invertebrate drift or organism drift. Under normal conditions it has been shown that about 160 individuals per 100 m3 of discharge can be expected, reaching a peak at night, particularly just after sunset (Bishop, 1973). A possible explanation for this phenomenon is that during daytime many organisms hide between the gravel or in the sediment of the river and feed at the water surface after the light intensity diminishes while others become active around sunset, particularly predatory animals. Due to the fact that the current is monodirectional, it should be expected that the upper part of a stream is emptied of its fauna over time. This is not the case because many organisms are rheotactic that is, they move all the time against the current. Further, the imagos of most insects perform so-called compensation flights upstream to lay their eggs only in the upstream parts of a river. However, most studies so far have shown that upriver movements represent only about 7-10% of the individuals that move downstreams (Williams, 1981). Drifting, although it has certain risks, is an energy-efficient way of moving from an unfavorable to a more favorable patch. Recolonization of empty

149

microhabitats, for example, after catastrophic drift events during foods, is usually very quick. Insects inhabiting streams and rivers as larvae include dragonflies (Odonata), caddisflies (Trichoptera), mayflies (Ephemeroptera), stoneflies (Plecoptera), black flies, midges, brachyceran flies (Diptera) and moths (Lepidoptera). Water beetles (Coleoptera) are mostly aquatic as larvae and as adults, while certain bugs (Hemiptera and Heteroptera), such as the water skaters and water striders, are tied to water but spend their lives exclusively on the water surface, or like the water boatman, below the surface. Due to the relatively great variety of microhabitats in streams and rivers with lotic, semi-lentic and lentic areas, a great variety of adaptations can be found (Fig. 8.9): • Sucker like gills of larvae of stream mayflies (Ephemeroptera). • Building of heavy cases common among caddisfly-larvae (Trichoptera). • Burrowing into the silt like the larvae of Chironomidae (Diptera). • Streamlining body shape like in the case of the larvae of Ephemeroptera. • Structural osmoregulation to remove excessive water from the body like in most of the larvae of aquatic insects. • Respiratorial adaptations like the trailing air bubble under the wings of diving beetles. • Special feeding strategies (Fig. 8.10). • Special attachment mechanisms like the hooks and silk thread of Simuliidae larva. In rivers and streams, separate assemblages occupy different zones characterized by features such as current speed and flow pattern, temperature, sandy bottoms, leaf drifts, root-bank complexes, stones placement in the current, and sunshine. Since these parameters change along the course of the river, longitudinal zonation patterns of the communities should be found in accordance with the changes within these gradients. Producer and

Aquatic Ecosystems

150


FIGURE 8.9.

RIVERS

Some of the organisms adapted to the various habitats of a tropical stream.

Habitat

Microhabitat

Main Group/Family

Behavior

(a) (b) (c) (d) (e) (f) (g) (h) (i) (j)

Water surface Subsurface Under stones On stones Between stones On submerged plants On emergent plants On stones On stones Free water

Gerridae Culicidae Plecoptera Simuliidae Ephemeroptera Odonata Collembola Hydropsychidae Heteroptera Ditiscidae

Skater Floater Sprawler Clinger Sprawler Climber Jumper Net-clinger Clinger Swimmer

Neustic Epineustic Benthic-Littoral Benthic-Littoral Benthic-Littoral Benthic-Littoral Benthic-Littoral Benthic-Littoral Benthic-Littoral Pelagic


consumer communities along the length of the river should reflect the abiotic factors in a continual manner. This hypothesis is called the River Continuum Concept (RCC), formulated by Vannote et al., in 1980 (Fig. 8.11). The river system from the source to the rivers mouth can be seen as a gradient from a mainly heterotrophic energy river over a system of mainly autotrophic activities, varying on a daily and seasonal base, to a system governed essentially by heterotrophic activities . This continuum is only hindered by tributaries of lower order. The size of organic particles diminutes downstreams and therefore organisms capable to feed on fine particles are gaining in importance. We can therefore distinguish four main feeding types, e.g. shredders, collectors, grazers and predatory organisms. Shredders, like stonefly larvae, have as their main food item coarse particulate organic matter (CPOM) including the aufwuchs organisms on the litter. Collectors, like caddisfly larvae, filter fine particulate organic matter (FPOM) or even very fine particulate organic matter (VFPOM) out of the water sometimes with the help of intricately built nets, like the Hydropsychidae or with brush-like appendices, like the larvae of Simuliidae and Ephemeroptera (Fig.8.12). Aufwuchs and microbes are also for this group of a very important food component. Grazers, like snails and some prawns, have scrapping mechanisms to feed on aufwuchs and algae. Due to the fact that in the upper parts of a stream CPOM is prevalent, the majority of species found in the community should be shredders and collectors. Grazers are not abundant. There are indications that in tropical streams, this is not as significant as in temperate streams and shredders are not as abundant as expected. Together with the collector group, the grazers are dominant in the middle stretches of a stream, while shredders disappear. The lower parts of a stream are dominated by collectors. Predators are in

151

all parts present in more or less equal quantities. At any point of the stream there is a biological steady state situation: energy is moving in, is used, stored and as partly transformed or unused material transported further downstream. A general trend can be seen for the macrobenthos species richness to peak at the point where the slope levels off and the stream enters its floodplain. While rather little is known of functional feeding group representation in tropical rivers in South East Asia, some food web studies of zoobenthos indicate a widespread use of allochthonous food by primary consumers, either directly or after microbial transformation, and a relatively high percentage of nominally predatory forms (Fig.8.13). A widely unknown group of living aquatic organisms are spiders and mites (Arachnida). Water mites are either free-living or parasitic on other aquatic animals. Several species of spiders are always found near water. Some of them can move on the water surface and make occasional dives into the water to catch their prey, like the common fishing spider, Thalassius albocinctus (Fam. Pisauridae). This is also true for the forest fishing spider, Dolomedes sp.(Fam. Pisauridae). While a substantial amount of information is available concerning the fish fauna in lakes and those used for freshwater aquaculture, only very little is known about the ecology, particularly autecology and reproductive ecology of most of the riverine fish species. It is therefore not surprising that whenever more remote areas of streams are systematically researched, always new species of fish are detected throughout the Indonesian archipelago. The richness of the Indonesian archipelago is strikingly high with about 950 recorded freshwater fish species belonging to more than 42 families (Kottelat et al., 1993) An important ecological grouping among freshwater fishes is based on tolerance to salt. While some fishes are tolerant to a wide range of salinity,

Aquatic Ecosystems

152


FIGURE 8.10.

Special feeding strategies of various members of the insect community in a stream. A Shredders : 1 2 B Filterers : 3 4 C Predators : 5 6 D Grazer : 7

RIVERS

Larva of moth (Lepidoptera) inside the stem of a water plant Stonefly larva (Plecoptera) Hydropsychidae larva (Trichoptera) Mayfly larva ( Ephemeroptera) Dragonfly larva (Odonata) Belostoma indica (Heteroptera) Mayfly larva (Ephemeroptera)


FIGURE 8.11.

153

Schematic drawing of a river as continuum of abiotic factors and communities (after Vannote et al., 1980). The relative communities CPOM FPOM

proportions of the single feeding types of organisms in the various is given in the circles. Coarse Particulate Organic Matter Fine Particulate Organic Matter

Aquatic Ecosystems

154


FIGURE 8.12.

Invertebrate community in the first order mountain stream Awu in Central Java.

In the relatively strong current on

boulders of volcanic origin larvae, firmly attached to the rock surface with hooks and a silk thread (1) and slipper-like pupae of Simuliidae(2) with their spiracular gills, net-spinning larvae of Hydropsychidae (3) living inside their catchnet, brush-legged larvae of Ephemeroptera (4), filtering food with the leg hairs and larvae of flat-headed Ephemeroptera (5) with their streamlining shape and platelike gills, form the community.

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Simplified spatial community structure in a tropical river system (after Whitten et al., 1984). Seed of Diperocarpus kerii (Fam. Dipterocarpaceae) Sminthurides aquaticus (Collembola) Leaf of Dipterocarpus penangianus (Fam. Dipterocarpaceae) Colurella unicata Vorticella campanulata Cyclotella cornuta Pediastrum duplex Batrachospermum moniliforme Dimorphococcus micropeltes

10 11 12 13 14 15 16 17 18

Stigmatogobius poecilosoma Channa micropeltes Puntius lateristriga Rasbora elegans Nematocheilus selangoricus Hypostomus sp. Ulothrix sp. Fusarium aquaticum Microstomum lineare

19 20 21 22 23 24 25 26 27

Curvularia lunata Spirillium sp. Saprolegnia anisospora Helicomyces sp. Bacillus sp. Epilampra sp. Ephemeroptera Larva Plecoptera Larva Simuliidae larva

155

Aquatic Ecosystems

1 2 3 4 5 6 7 8 9


FIGURE 8.13.

156


like the Gobiidae, others are very sensitive to even low concentrations of salt. In general, the fish families living in rivers are divided into the same categories concerning their ability to survive in different water types than lake fishes. Two aspects of fish ecology in tropical South East Asian rivers can be linked clearly to land-water interactions: diet and reproduction. Allochthonous food, both of animal and vegetarian origin, are important dietary items, particularly for rainforest stream fish species. In general, fish with small mouths tend to be feeders on plankton or on organisms attached to aquatic plants and other submerged structures. Scavengers are likely to be fishes with medium-sized mouths, because such fish generally take in considerably quantities of mud or sand for the small animals and plants they obtain. Many cyprinoid fish have barbels, short and long and these are used to detect food in turbid or dark water. A large mouth generally indicated that the fish is a predator. Further, fish with large eyes tend to live in clear water while fish living in more turbid water tend to have small eyes. Fish can be divided into at least eight feeding guilds (Kottelat et al., 1993): • Herbivorous endogenous species living on plant material growing in the water or autochthonous material. • Herbivorous exogenous species feeding on plant material of allochthonous origin. • Grade 1 endogenous predator species feeding on small aquatic animals such as nematodes, rotifers, suspended plankton, invertebrates ingested as detritus in mud and sand. • Grade 2 endogenous predator species feeding particularly on insect larvae. • Grade 2 exogenous predator species feeding on aquatic animals such as insects falling into the water. • Grade 3 predator species feeding on larger aquatic animals such as shrimp and snails, generally on or near the bottom.

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• Grade 4 predator species feeding on other fish. • Omnivores feeding on both animal and plant material. Generally, herbivores have a gut which is 4-10 times the length of the body, whereas predators’ guts are much straighter and may be only as long as or even shorter than the body. In areas where monsoon rains inundate lowlying land, like in Kalimantan and Irian Jaya, inundation is often associated with the act of breeding. Other species, such as the halfbeak, Hemirhamphodon pogonognathus, are continuously pregnant and are viviparous, giving birth to live young every few days (Kottelat et al., 1993). There is a wide range of levels and types of parental care. Blackfishes, like Ophiocephalus sp., exhibit some degree of parental care while white fishes, like Puntius sp., are egg-scatterers (Welcomme, 1979). The parents may also protect the young by keeping them in their mouth. Western Kalimantan has the most diverse assemblage of oral brooders with eleven species belonging to six different families. Blackfishes can also better tolerate deoxygenation, while whitefishes avoid severe conditions by long-distance migration. Belontiidae and Channidae species have even developed accessory breathing organs allowing them to supplement their intake of dissolved oxygen with atmospheric air. They also produce floating bubble nests to withstand oxygen poor conditions. Usually two distinct ecological groups of fish can be identified: Those species confined almost exclusively to waters below waterfalls and those found mainly above. The latter group consists of species belonging to the Homalopteridae and Gobiidae. In the faster flowing parts of forest streams in Kalimantan gastromyzontins are sometimes very common. They are dorso-ventrally flattened and


their enlarged pelvic fins are fused to form large adhesive pads with which they cling to rocks and maintain their position even in the swiftest of currents. The mouth is located ventrally, well-suited for grazing on cyanobacteria, diatoms and filamentous green algae growing on rocks. In short streams rushing down mountainsides to the sea Gobiid fish species can be the dominant group species, while in longer rivers the Cyprinids and Silurids seem to be dominant. Changes of the physical conditions along a stream also affect distribution of fish species. In general, as river width increases, the number and diversity of fish species increases (Bishop, 1973). At the same time the number of feeding guilds increases. Also the number of bottom-dwelling species increases downstream and there is a concomitant reduction in the breadth of each species' ‘niche’ as well as a decrease in mean life span and adult size of the individual species (Watson and Balon, 1984). In the Barito River in Kalimantan forty-seven fish species belonging to 17 families were found out of which 16 species were Cyprinids and 6 species were Silurids. One species, Wallago leerii, belonging to the Siluridae, was caught with a weight of 300 kg (MacKinnon et al., 1996). The Kapuas River in Kalimantan, Indonesia’s longest river, can boast 310 fish species of which 234 are primary division species. The members of a fish family have different preferences in the layers they occupy in a river (Fig. 8.14). Most forest streams have one or two surface species, one or two living just below the surface, three to five mid-water species, two to four living just above the bottom, and three to ten living on or in the bottom (Inger and Chin, 1962). The structure of the bottom and the current seem to be the determining factors for this kind of distribution and structure of the fish communities in rivers. During the last glacial, the Sunda plate was traversed by three major rivers, the largest of which

157

carried water from Malaya, Sumatra, Borneo and Java and emerged into the South China Sea near what is now Natuna Island. It is not surprising, therefore, that the fishes of those rivers that once formed a single system show considerable similarities. Among other classes of vertebrates the amphibians are members of aquatic ecosystems, moving onto land as adults. Some species like the cascade frog, Staurois natator, are adapted to the rocky environment of the cascade zone (Fig.8.15). Reptiles like soft-shelled turtles are obligatory aquatic and several of these reptiles are to varying degrees dependent on the resources of streams. The transfer to aquatic resources from an otherwise terrestrial life is more marked among birds such as kingfishers like Halycon chloris (Fam. Alcedinidae). They are well adapted to their life with an insulating layer of feathers and large bills sometimes minutely serrated like those of herons. Otters, like the small clawed otter (Aonyx cinerea; Fam. Mustelidae), the mammal most dependent on water, are well adapted with a fold of skin between the digits, water resistant fur and sharp teeth to hold slippery fish. Decomposers In streams, fungi and bacteria make dissolved organic matter and very fine particulate organic matter available to animal consumers and therefore contribute significantly to energy flow especially in cases where the stream community metabolism is heterotrophic. Also, hyphomycete fungi occur widely on submerged, decaying wood and leaf litter, very little is known about them and their importance for the energy flow. And while the microbiocoenosis may be an important regulator of energy flow in heterotrophic streams, data on the magnitude and extent of this phenomenon are lacking almost entirely. The scarce information available indicates that density and species richness of decomposer organisms appear to increase with the duration of

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158


FIGURE 8.14.

Distribution of members of the Cyprinid family in a Kalimantan River (after Inger and Chin, 1962). Surface Layer (S) : Upper 5-20 cm Layer (UL) : Midwater (M) : Lower 30-40 cm Layer (LL): Bottom Layer (BL) :

1 2 4 6 7

Nematobramis borneensis Luciosoma spilopleura; 3 Pectenocypris balaena Labocheilos falcifer; 5 Puntioplites waandersi Cyclocheilichthyes apagon Garra borneensis

the submergence of the substrate and that the decomposition rates are relatively short under tropical conditions and do last throughout the year with little seasonality. NUTRIENT AND ENERGY FLOW The energy base usually is provided by plants converting solar radiation through photosynthesis into high energy organic molecules. This organic matter can be divided into two components: Allochthonous matter originating from outside the

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given ecosystem and autochthonous matter originating from within the system. The available organic matter, both living and dead, is processed by a wide range of organisms including bacteria, fungi, invertebrates and vertebrates like fish. All these interact in a highly complex manner with different pathways depending on the size of the particles (Whitten et al.,1988; Fig. 8.16). The transported organic load of streams reflects the interactions of a variety of factors, including the quality and quantity of autochthonous production


FIGURE 8.15.

159

Cascade frog, Staurois natator, is camouflaging with the dripping rocks and their algal growth. The tadpoles of the cascade frog are known to live in the cascading waters where they attach to the rocks with the help of special organs. They have special mouthparts to filter their prey out of the surface layer of water.

and allochthonous imports, channel “retentiveness”, discharge regime, and in-stream decomposition processes (Dugeon and Bretschko,1995). The organic particles are divided into various categories: • Coarse particulate organic matter (CPOM) of more than 1mm diameter. For example, entire leaves belong to this category. • Fine particulate organic matter (FPOM) with less than 1mm diameter including micro organisms associated with them.

• Very fine particulate organic matter (VFPOM) of < 0.45 to 250 mm diameter. • Dissolved organic matter or (DOM) with < 0.45 mm in diameter (Fig.8.17). DOM is quantitatively the most important form of organic load, and in unpolluted streams, concentrations are relatively stable over time and space with up to 11 mg C·m-3 (Bishop, 1973). FPOM loads are second in magnitude to loads of DOM and CPOM is quantitatively by far the least important form of organic matter transport.

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FIGURE 8.16.

Simplified river food and energy chain including producers, first and second order consumers and decomposers. 1 2 3 4 5

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Autochthonous producers : phytoplankton 1st order consumers: algivorous fish. 2nd order consumers: predators: Kingfisher; predatory fish species Decomposers: crustaceans and molluscs; bacteria and fungi Allochthonous organic matter e.g. aufwuchs on rocks


The path of the energy flow depends to a large extent on land-water interactions and the nature of the energy base. Land-water interactions influencing the nutrient and energy flow in a given river may take many forms and can occur at a range of spatial and temporal scales. Litter fall from tree canopies extending over the stream channel and, to a smaller extent, aerial drift are the only direct pathways of import for allochthonous organic matter, although litter along the stream banks may be blown into the stream (Dudgeon and Bretschko, 1995). Other material is mediated by ecotones, the riparian zone along the stream banks. This material is usually processed to various degrees before entering the stream system. The land-water interaction with the riparian zone is most intimate during periods of unusually high discharge and throughout the duration of river

FIGURE 8.17.

161

floodplain inundation. Floodplains are most important as sites of land-water interactions in high-order streams, while in low-order streams, riparian vegetation and in-stream ecotones, the bed sediments with its interstitial or hyporheic water are the main sites of energy input. Where the bed sediment is well developed, a proportion of the organic load of the ground water is incorporated into the biofilm and becomes immediately available to animal consumers (Findlay et al., 1993). Regardless of the means of entry of organic matter into the stream, for example, whether it passes through in-stream ecotones or those that lie beyond the maximum high water level limits, much more is known about the fate of FPOM and CPOM than either VFPOM or DOM. The magnitude of autochthonous production varies considerably over space and time or season. It seems clear that allochthonous inputs and, hence,

Simplified model of energy flow in a river system (after Townsend, 1980; Dudgeon and Bretschko, 1995). CPOM Coarse particulate organic matter DOM Dissolved organic matter FPOM Fine particulate organic matter 1 Leaching; 2 Mechanical disruption and microbial action; 3 Floculation and microbial action

Aquatic Ecosystems

162


land-water interactions contribute significantly to instream productivity throughout the year in streams shaded by riparian vegetation. Allochthonous carbon sources will constitute the major energy source during the monsoon season when usually the autochthonous production falls. Rather little is known about the decomposition of the allochthonous matter in tropical rivers and streams, but there are indications that de-composition rates are rapid with complete disappearance of leaves within three month (Dudgeon, 1994). This effect may be reflected in the high temperatures and active feeding by shredders on leaf-litter. There are strong indications that microbial activities in leaflitter breakdown are much more important than the action of shredders, because shredder taxa are significantly under-represented in tropical rivers or that the leaves might enter the rivers and streams in an already decomposed and fragmented state so that much of the input is consumed directly by collectors. It seems that the organic load in small rivers and streams consists of a mixture of dissolved organic material (DOM) and variously comminuted detritus derived from allochthonous leaf litter. About 80% of the mean total suspended load is usually in dissolved form and seasonal variations are not pronounced (Bishop, 1973). Further, the total drift load of allochthonous material from the forested parts of the river catchments is rather constant in areas with only a slight seasonal variation in leaf fall. The allochthonous inputs have a dominant influence on the seston loads in low-order streams and the influence wanes downstream. There is some evidence of changes in functional feeding group representation along the length of tropical South East Asian rivers. This matches with the major prediction of the River Continuum Concept (RCC) that community structure in streams will vary predictably according to the inputs of allochthonous material from the surrounding terrestrial environment. The importance of allochthonous food in the diet of many freshwater consumers suggests that a

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heterotrophic community metabolism is the general feature of streams and small rivers which drain forested catchments and lack an extensive floodplain. It is unfortunate that at present there is virtually nothing known of the extent and magnitude of landwater interactions of big rivers and their floodplains in South East Asia. Further, there are only a few large rivers, like the Mamberamo River in Irian Jaya, in a kind of pristine condition. Most other large rivers and their land-water interaction areas are highly influenced by human activities and therefore highly modified and utilized. HUMAN INFLUENCE AND ECOLOGICAL STATUS Usually activities of man started in the middle watershed areas of rivers, because these areas were easily accessible and free of flooding. Over space and time the direction of development went uphill and downstreams (Fig. 8.18). Humans are bound to use water resources. One of the most widely misused bodies of water are rivers which are used as garbage dump, toilet or cheap means to transport liquid waste to the sea. Industrial and domestic pollution reduces the water quality of rivers with consequent effects on the whole biota. Pollutants of water have been divided into four major categories: • Pathogens, causing water borne diseases like cholera (Vibrio cholerae) entering bodies of water with untreated sewage. • Toxins killing indiscriminately all organisms or killing selectively, like pesticides. • Deoxygenators , mostly organic waste, causing deoxygenation during their decay by bacteria and fungi. • Nutrient enrichers mainly in form of phosphates coming from detergents or overfertilization, nitrogen from domestic and agricultural sources.


FIGURE 8.18.

163

Impact in form of land use by man on a watershed area. 1 2 3

Upper watershed area with natural forest, secondary forest or anthropogenic grass lands or tree crops, like cloves, on slopes > 8 degrees. This is the main erosion area with about 6 t .ha-1 soil erosion in still forested areas, 88 t.ha-1 in degraded forestland, and 138 t.ha-1 in cultivated areas (after Repetto, 1989). Middle watershed area with terraced wet rice fields, dry field crops and vegetable crops Lower watershed area with siltation and sedimentation processes

While trophic structures gives an indication of the processes involved in nutrient enrichment, the degree of saproby reflects the activities of purification or elimination of nutrients in a given body of water. If a pulse of allochthonous organic material is given to a body of water at a certain place and time this organic material will be decayed and mineralized. The organic substance is transformed by various organisms during the process. These organisms

interfere with their environment. Therefore, a socalled heterotrophic succession can be observed. The stretch of a river needed to finish the entire process of removal of a certain amount of organic material by mineralization processes is called the self-purification stretch. Along this self-purification stretch we will find the various phases characterizing the heterotrophic succession. In the field of applied river limnology the various phases of the self-

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164

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OLIGOSAPROBIC

/

I

α - MESOSAPROBIC / III

POLYSAPROBIC / IV

β - MESOSAPROBIC / II

OLIGOSAPROBIC / I

Figure 8.19.

Self-purification succession along a river and saprobic classification system. 1n Melanoides tuberculata Plankton Community and Bacteria: 1o Navicula sp. 1p Oedogonium sp. 1q Dynobryon sp. with and without flagellated cells 2 Organisms usually found under α mesosaprobic conditions: Fish community: 2a Clarias batrachus Invertebrate Community: 2b Chironomus sp. larvae 2c Simulus sp. larvae 2d Parathelphusa maculata Plankton community and bacteria 2e Paramecium sp. 2f Begiatoa sp. 2g Stentor sp. 3 Organisms usually found under polysaprobic conditions:

Fish community: None Invertebrate community:

3a Culex sp. larvae

3b Tubifex sp.

3c Eristalinus sp.

Plankton community and bacteria: 3d Streptococus sp. 3e Spirillium sp. 3f Melosira sp. 3g Ulothrix sp. 3h Sherotilus sp. 3I Oscillatoria sp. 4 Organisms usually found under β mesosaprobic conditions: Fish community: 4a Hypostomus sp.

Invertebrate community:

4b Hirudinaria sp.

Plankton community and bacteria: 4c Pandorina sp. 4d Euglena sp. 4e Spirogyra sp.

165

Aquatic Ecosystems


1 Organisms usually confined to oligosaprobic conditions: Fish community: 1a Nandus nebulosus 1b Pangio semicincta 1c Puntius lateristriga 1d Rasbora maculata 1e Betta splendens 1f Esomus metallicus 1g Aplocheilus panchax 1h Dermogenys pusillus 1i Oryzias javanicus Invertebrate Community: 1j Ephemeroptera larvae 1k Trichoptera larvae 1l Caridina temasek 1m Macrobrachium trompii

166


purification process are used to describe the quality of the water. Besides physical and chemical parameters, in recent years biological indicator organisms or populations have been used to characterize the quality of a given part of a river. To be able to use aquatic organisms, communities and populations as biological indicators it is necessary to know how biological communities originate, how they function, change and which factors are influencing their composition. At a location of a river, having not too extreme physical and chemical characteristics an assemblage of species will take a rather definite composition and become a biological community after a period of time. Any changes in the environment, natural or man-made, will bring about changes in individual organisms, their populations and communities. Therefore, the respective inhabitants of a given area can be considered as biological indicator of environmental changes. The saprobic system of classification is based on this kind of knowledge and the originally 3 categories, introduced by Kolkwitz and Marson in 1902, are today supplemented with classes of water quality to form the main four categories (Fig. 8.19): • Oligosaprobic level or grade I quality, characterized by very clean, unpolluted water with only oxidative processes going on. A great variety of life is present but no one species or type is dominant. Natural condition zone. • a-Mesosaprobic level or grade III quality, transition zone between oxidative processes and reduction processes with a rapid decrease in oxygen contents of the water and number of species, while the number of individuals of some species is sometimes explosively increasing, particularly bacteria and saprophytic organisms. Organic pollution zone. • β-Mesosaprobic level or grade II quality, transition zone where reduction processes decrease and oxidative processes increase. Anaerobic organisms diminish and free

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dissolved oxygen demanding organisms reappear. Recovery zone. • Polysaprobic level or grade IV quality, characterized by predominantly reduction processes and low to anoxic oxygen conditions. Number of species heavily reduced with usually no vertebrates. Predominant are bacteria and saprophytic microorganisms. Highly polluted zone. Under normal and natural conditions the processes of enrichment and of removal are in a balance. Due to excessive human pollution inputs most of the Javanese Rivers have already lost their previous ability of self-purification (Fig. 8.20). Nowadays, the saprobic index besides the biological oxygen demand is used to qualify the water standard of a given river. The saprobic index (S), introduced by Pantle and Buck in 1955, is calculated the following way:

S=

S=

∑s×h ∑ h

110 = 3.2 38

s = Degree of saprobity or the indicator value of each species found (Liebmann’s List) (Zelinka et al.,1961) h = Frequency of each species found

For example (Tables 8.3-8.4):

TABLE 8.3.

Example for the calculation of the saprobic index of a body of water.

Frequency (h) Saprobic degree (s) Species A Species B Species C

7 28 3

2 3 4

Ý

38

110

sxh 14 84 12


Sources of Pollution Burden in Java (ton COD per day)

Industries

167

River, Location Cisadane, Tangerang Banjir Kanal, DKI Sunter, Pulogadung Bekasi, Cileungsi Citarum, Jatiluhur Cimanuk, Tomo Citanduy, Cikawung Serayu, Banyumas Progo, Sentolo Solo, Babat Surabaya, Tawangsari Brantas, Mojokerto

Households

-100

-50

0

50

100

FIGURE 8.20.

Source of pollution burden in some Javanese Rivers in tons Chemical Oxygen Demand (COD) per day (after World Bank, 1987)

Table 8.4.

Comparison of the calculated saprobic index with the respective degree of pollution and the quality status of the water.

Saprobic index

Degree of pollution

Status

Symbol

1 - 1.5 1.5-2.5 2.5-3.5 3.5-4.0

very slight moderate heavy very heavy

Oligosaprobic α-mesosaprobic β-mesosaprobic polysaprobic

S=1 S=2 S=3 S=4

Fish are the most sensitive vertebrate group reacting on pollution of a river whether due to heavy siltation, in cases of forest clearance in the catchment area, low pH due to acid rain produced by air pollutants like SO2 and Nox emerging from exhaustion pipes of motors or high Biological Oxygen Demand (BOD) situations due to heavy organic load of the water. The use of fish poison like the one made from the roots of the climber Derris sp. is highly destructive to the fish and invertebrate community. The chemical rotenone of this plant is killing all organisms without regard to size or species. As a result, many rivers have virtually no fish left, particularly those stretches near villages and towns.

Forest clearance, however, is by far the most serious threat to natural river systems. Particularly indigenous species will be lost forever in rivers without any forest fringe left. For example, the introduced gourami (Trichogaster trichopterus) and tilapia (Oreochromis sp.) were the only fish found in the Toraut River on the edge of the DumogaBone National Park in Sulawesi only a few years after opening the river banks (Whitten et al., 1988). IMPLICATIONS FOR ENVIRONMENTAL IMPACT ASSESSMENT STUDIES The sustainable management of freshwater ecosystems requires certain steps to be taken before and after the execution of any program that might affect them (Soerjani, 1985). Those steps are: 1. Determine carefully the aims and needs of any management program. 2. Make an inventory of basic information related to the aims and needs determined. 3. Gather technological knowledge related to management objectives. 4. Analyze available information in form of an Environmental Impact Assessment study. 5. Determine a plan of action, accepting the need to compensate for lost options.

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6. Execute or implement the program. 7. Evaluate the execution and impacts within a system that is sensitive and flexible enough to allow for modifications in the management goals. Environmental Impact Assessment studies concerning developments in or along a river need to include the entire watershed. Forest clearance is by far the most serious threat to natural river ecosystems and causes wide ranging impacts as do industrial and domestic pollutants. Their effects can be acccumulative and long lasting for plants, animals and man. SUMMARY Rivers are flowing ecosystems with a multitude of different microhabitats. Land-water interactions are of great importance. Not only the physical and chemical features change along the river on its way to the sea, but also the biological features. This fact is the base of the River Continuum Concept. Most of the methods to evaluate freshwater bodies have been developed from studies in temperate regions. It is not yet possible to use all the methodologies and technologies developed for tropical regions without major adjustments. Freshwater of rivers and streams is a multiple purpose resource, and can not be seen isolated from its surrounding environment. Any attempt to manage this resource must be therefore embedded in a watershed management approach. The misuse of water to an extent that the rivers loose their naturally self-purification ability and the wasting of this resource by inadequate use is of growing concern for the steady growing number of people dependent on freshwater.

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CHAPTER III


169

Ecotones and Special Ecosystems

I

n recent years areas of transition between two or more different communities became more and more interesting for ecologists, environmentalists and naturalists. Such edge communities are typically species-rich and arise naturally at land-water boundaries like sea shores and mangroves, estuaries and limnic-terrestrial zones. Often human intervention produced such specific ecotones or region of overlap between adjacent ecosystems. The ongoing human intervention produces a steadily increasing fragmentation of habitats resulting in an increase of edge areas and a decrease in the internal areas of ecosystems. This might lead to a loss of species from all affected ecosystems and an increase in special edge species. Special, often island-like ecosystems, are caves. Small island with their specific interrelation and interdependencies are of high importance for the studying of the ecologically-relevant basic rules and interconnections. They are therefore showcases for most of the basic rules and regulation which govern the existence and development of ecosystems. The basis of island biogeography can be studied leading to a better understanding both of plant and animal communities in areas of cultivation and urbanization.


170


SEA SHORES AND TIDAL FLATS


THESIS Most shorelines in Indonesia are teeming with life. One special type, the sandy beaches belongs to the preferred habitat of domestic as well as foreign tourists. Shorelines, whether sandy or rocky, are sometimes regarded as experimental laboratories of life (Figs. 9.1-9.2). In this ecosystem, probably organisms which conquered dry land during the end of the Paleozoic era evolved. Plants and animals have to be well adapted to withstand the extreme abiotic factors like varying water levels, temperatures or salinities. Two major forms of adaptation can be observed: Organisms evolve physiological mechanisms that enable them to deal with the abiotic factors or they are mobile enough to escape them and search for habitats that offer the suitable range of abiotic factors.

171

9 SEA SHORES AND TIDAL FLATS Friedhelm Göltenboth, Sabine Schoppe and Peter Widmann

OVERVIEW The seashore is the meeting place of land and sea. The beach is often regarded as an amalgam of tidal zones and surf and swash zones between the Low Wave breaker line and the High Wave run-up limit (Carter, 1988). The littoral or intertidal zone of the marineterrestrial ecotone can be subdivided in: • Supralittoral (or upper intertidal): Zone that is only reached by spray of saltwater. • Eulittoral (or middle intertidal): Zone that twice a day, on the average, falls dry during low tides and is submerged during high tides. • Infralittoral (or sublittoral or lower intertidal): Zone that is not any more affected by the tides and is permanently submerged. The extent of eulittoral depends on the inclination of the bottom and the difference in water level between low and high tides. The lower the inclination and the larger the difference, the more spacious are the tidal zones. Due to the rapidly changing abiotic factors within the littoral zone, ususally a distinct zonation of organisms can be found with single




Rock pool area on a hard bottom tidal flat. FIGURE 9.1.

Sea urchin Diadema sp. (Fam.Diadematidae)

Bryozoans (Bryozoa)

Ornate sandgoby Istiogobius ornatus (Fam.Gobiidae)

Brown Algae Padina sp. (Fam.Dictyotaceae)

Brittlestar Ophiocomo scolopendrina (Fam. Ophiocomidae)

Tubeworm (Fam.Sabellidae)

Cowri Cypraea sp. (Fam. Cypraeidae)

8 Threefin blenny (Fam.Tripterygiidae)

9 Spaghetti worm Loimia medusa (Fam.Terebellidae)

10 Leaping Blenny Alticus saliens (Fam. Blenniidae)

11 Seagrass Cymodocea rotundata (Fam.Potamogetonaceae)

12 Sea cucumber Euapta sp. (Fam.Synaptidae)

13 Snail Littoraria sp. (Fam.Littorinidae)

14 Sea cucumber Holothuria sp. (Fam.Holothuridae).


173


1 2 3 4 5 6 7



FIGURE 9.2.

Rock bottom shore with small boulders and sandy stretches.

B Soft corals:

21 Fam.Caryophillidae

14 Lobophyton sp. (Fam. Alcyoniidae)

C Mussel: 12 Chama sp. (Fam. Chamidae) D Fishes: 2 3 10 11 15

Damselfish Pomacentrus sp. (Fam. Pomacentridae) Anglerfish Antennarius sp. (Fam. Antennaridae) Indian goatfish Parupeneus indicus (Fam. Mullidae) Sandgoby Fusigobius scapulostigma (Fam. Gobiidae) Fine spotted puffer Canthigaster compressa (Fam. Tetraodontidae)


175


A Hard corals:

1,8-9 Porites sp. (Fam.Poritidae)

4, 18 Tubastrea micrantha (Fam. Dendrophylliidae)

5,16,19,23 Goniopora sp. (Fam. Poritidae)

6 Seriatopora sp. ( Fam. Pocilloporidae)

7 Fungia sp. (Fam. Fungiidae)

13 Montastrea sp. (Fam. Faviidae)

17 Acropora sp.(Fam. Acroporidae)

20, 22 Scleractinia

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species only occupying narrow areas (Tsuchy and Lirwitayapasit, 1986). In most of the Indonesian islands, distinct zones within the eulittoral and infralittoral could be identified which show a typical distribution of tidal organisms. It is possible and important to distinguish the three major types of shorelines: • Rocky shorelines. • Sandy shorelines of volcanic or other terrestrial origin. • Sandy shorelines exclusively built from the biogenetic materials of reefs, the so-called coral cays. The vast majority of the 17,508 islands of the Indonesian archipelago are most likely coral cays or low islands (Tomascik et al., 1997). Among the best known examples of this kind of islands with splendid white shores are the about 120 islands of Kepulauan Seribu Thousand Islands off the Jakarta Bay in the Java Sea. Coral cay sediments are biogenic, originating mainly from the skeletal material of numerous calcifying plants and animals which built and live in the reef. During the early stages of development, most sand cays are rather unstable systems. Once sand cays reach a certain mass, the movements become much less pronounced. Stabilization is greatly enhanced by the colonization of plants whose seeds arrrive by atmospheric transport, water currents or on floatsam, or carried by birds. In addition to the reef sediments, some cays located close to the mainland of large islands (e.g. Java) or active volcanoes (e.g. Banda Neira in the Moluccas) may have non-carbonate sediments incorporated into the cays (Tomascik et al., 1997). The sandy shorelines of the majority of the larger islands are mostly of pure terrestrial origin with often volcanic or jurassic sediments and sands or a mixture of carbonic and non-carbonic sediments.


Rocky shores occur along the coastlines of many Indonesian islands: • The west coast of Sumatra is lined by rocky beaches. • Most of the Lesser Sunda Islands and the Moluccas consist of volcanic or limestone shorelines with little or no beach formation. ECOSYSTEM FUNCTIONS Shorelines absorb the energy of wave action and hence, prevent erosion in coastal areas. Depending on tidal regime, tidal zones can be sinks or sources of nutrients. Like mangroves, they can hold among the most productive soils in the tropics. Shorelines are habitats of a specialized community of organisms, some of them being useful to man like different species of algae, sea cucumbers, and molluscs. Thousands of shorebirds coming from temperate and arctic zones of both hemispheres greatly depend on different types of shorelines as feeding grounds. Species of endangered sea turtles use sandy beaches as nesting ground. Sand bars or rocky shores are breeding grounds for an array of shorebirds. Abiosis The composition of communities of organisms along shorelines is strongly dependent on the type of substrate. Shoreline habitats can range from steep cliffs, over rocky, boulder and gravel shores, sandy beaches, to silty and muddy flats. The different sizes of particles do not only influence the water content of the substrate and the interstitial space between the particles, but also the stability of the surface as a whole. Mud bottoms consist of very fine particles. Space between particles is small so that these substrates usually contain only small amount of water. Silty and clayey bottoms are more stable than most other substrates. Hence, it is possible for the infauna or such animals of the sediment beaches which rarely emerge onto the surface, in contrast to


the epifauna or animals that spend at least some time on the surface, to build permanent burrows. Sandy substrates consist of mineral and calcareous components of larger size. The latter usually are of organic origin. Sand surfaces are highly influenced by water movement and sometimes form characteristic ripple patterns. Interstitial spaces are inhabited by a unique microfauna. Like in the clayey or silty substrates, the infauna is dominant. However, permanent burrrows are rare, because of the instability of the substrate. The type of substrate strongly depends on the current regime of the respective area. Hard-bottom substrates occur in areas with strong erosive forces, soft-bottoms only can form in situations where deposition is stronger than erosion. Low waves with a long wavelength are carrying material to the shore, whereas high waves with short wavelength have erosive effects (Morton and Morton, 1983). Also wind can have a major impact in the forming of seashore landscapes. Sand dunes are a restricted feature in Indonesia. They only occur near Pangumbahan along the south coast of West Java and the north coast of Irian Jaya. The dunes form parallel to the coastline with the younger more mobile ones closer to the beach. As initial stage of the forming of a dune, drifting sand is caught on the leeward of small obstacles, like vegetation or debris. Sand is blown over the ridge off this small obstacle. Subsequently, the sand bakes together and vegetation establishes. Consequently, the older dunes in the hinterlands are less, but still are growing (Siringan and Pataray, 1996). Shorelines are strongly influenced FIGURE 9.3. by the tides. The latter are caused by the rising and falling of the world’s ocean’s

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water body due to the gravitational influence of the moon and the sun upon the earth (Fig. 9.3). Two tidal protrusions of water permanently exist, one facing the moon and one on the opposite site of the globe. These bulges result in two high tides with two low tides in-between during one lunar day lasting 24 hours and 50 minutes. Together with the rotation time of the earth, a cycle of 24 hours and 21 minutes duration results. The impact of the sun on tidal forces is lower than that of the moon. However, it has a modifying influence. Spring tides occur, with considerable differences in water level during low

Forming of hypothetical tidal bulges under the influence of the moon and the sun during: 1 New moon, 2 Last quarter, 3 Full moon, 4 First quarter.


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and high tide, when the moon, the earth and the sun are situated in line (during full or new moon). The sun’s gravity pull diminishes that of the moon, when the position of the sun is on a right angle to that of the moon. Subsequently, neap tides, with only minor changes of water levels between the tides become prevalent. Each constellation occurs twice during a lunar month. In reality, tidal regimes follow a much more complicated pattern, since the world oceans are disrupted by land masses which influence the tidal bulges considerably. This change between marine and terrestrial conditions is the single most important factor that limits the diversity of the community of organisms in this ecosystem. Tidal cycles do not only influence the diurnal activity patterns of virtually all organisms of the tidal zones, but also sometimes function as triggers for their longer term life cycles, for example through determining time of mating or migrating. Like most ecotones, shorelines are subjected to extremely variable abiotic factors. Especially the water bodies in tidal pools can vary considerably regarding temperature and oxygen content. When exposed to the sun, evaporation increases the salinity, while when exposed to rain, it decreases. In the zone where the surf breaks, organisms are exposed to strong physical forces. Action of waves is influenced by the speed of the wind and the distance over which the wind operates (Morton and Morton, 1983). Algae occurring in tidal zones have developed thick cuticulas to avoid desiccation and structures to stand the physical forces of wave action like strong rhizoids and flexible thalloids. Animals adapt to these factors by evolving hard shells like molluscs. Others hide in crevices or the substrate where they can endure when conditions get unfavorable like some echinoderms or annelids. These organisms are usually referred to as ‘cryptofauna’ (Evans, 1949). Other mobile organisms search actively for their fitting surrounding like crustaceans or some blenniid or gobiid fish, which can move over dry land for some distance.


Biodiversity Littorial communities can be divided into two categories: • Free living species including fish, molluscs, crabs, sea urchins, sea stars, and polychaetes. • Sessil species including algae, barnacles, sea anemones, and corals. Producers Main producers in tidal zones are different forms of algae. On soft bottoms diatoms (Fam. Chrysophyceae) form a yellow to green cover during low tide which partly is removed during high tide. Those microalgae are those producers contributing most to the food chain. Some varieties of seagrasses are also able to dwell on tidal zones. On hard bottoms, the pinkish to red calcareous algae Corallina sp. form encrusting covers. Euryoecious macro algae like Padina sp. are capable of growing on hard bottoms in tidal pools. Higher plants are able to establish on beaches.Pioneering species have different tolerance to saltwater exposure following germination, which results in a loose, but discernable zonation ( Tomascik et al.,1997). On coral cay and other limestone beaches, the most tolerant species to salt water exposure is Sporobolus fertilis . Just above the highest inundation line, the creeping Vigna marina and the fast growing Spinifex litoreus can be found. Parts of the shoreline only affected by sea spray are frequently dominated by the grasses Thaurea involuta and Lepturus repens. A typical pioneering species is the Goat’s foot vine Ipomoea pes-caprae that can form dense vegetation mats on sandy substrates. It does not only prevent erosion but also acts as trap for nutrients with its root system. The bright pink flowers are very conspicuous and the common name is derived from the characteristically shape of the leaves which resembles the hoof of a goat (Fig. 9.4). It is often pollinated by Xylocopa sp.( Hymenoptera).They produce , like many others of the beach plants, floating seeds. The


portulacustrum (Fam. Aizoaceae), Euphorbia chaissonis (Fam. Euphorbiaceae), Vigna marina (Fam. Fabaceae), Triumfetta repens (Fam.Tiliaceae), and Vitex trifolia (Fam. Verbenaceae). Different species of grasses and sedges can also settle on barren sand. Common are the sedge Cyperus pedunculatum (Fam. Cyperaceae) and the grass Spinifex littoreus var. longifolius (Fam. Poaceae) which further enhance the stability of the substrate. Eventually this vegetation can be replaced by woody species which may develop into beach forest. On very sandy stretches, pure stands of Casuarina equisetifolia can develop followed by a full Barringtonia community.

A

B

FIGURE 9.4.

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A) Pes-caprae formation on a sandy beach. B) Goat’s foot vine Ipomoea pes-caprae (Fam. Convolvulaceae).

whole plant community with this habit is named after this species as Pes-caprae-formation.This formation is an open community of low, sand-binding herbs, grasses and sedges behind the drift line. Endemics are absent and many species have a pantropical distribution. Often associated with the former species is Canavalia maritima (Fam. Fabaceae). Superficially the vegetative parts resemble that of the goat’s foot vine with fleshy shoots that form a tangle of vegetation. Other associated plants are Wedelia biflora (Fam. Compositae), Sessuvium

Consumers The community of animals inhabiting tidal zones and beaches is dominated by the following guilds: • Sessile or hemisessile planctivores. • Grazing herbivores which feed on the algal turf growing on the rocks and the layer of diatoms on the soft bottoms. • ‘Grazing’ carnivores which feed on benthic invertebrates. • Detritivores which feed on the dead organic matter brought by high tide. • Carnivores and scavengers are particularly abundant in supralittoral beaches. The majority of animals belong to three groups concerning their feeding habit: • They filter plankton from the seawater and are therefore filter feeders. • They suck organic deposits and microorganisms off the sediment surface. • They sort edible particles of sediments and are therefore deposit feeder. In addition, beach organisms are frequently divided into three sediment-size related groups (Carter, 1988): • Attached microfauna • Interstitial meiofauna


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• Borrowing or loosly attached macrofauna. The nearshore waters support usually rich populations of phytoplankton and zooplankton, which derive great benefit from turbulent waters. Diatoms are the most abundant phytoplankton group. The diatom Chaetoceros sp. thrives particularly in the surf zone of high energy beaches, like in Java and Bali, where nutrients are available from land runoff and strong coastal upwelling. They have the ability to attach themselves to bubbles which allow them to remain at the surface in maximum light (Carter, 1988). A study on a tidal reef flat yielded a very high abundance of meiofauna and small macrofauna, the nematodes, harpactoids and polychaetes being the three most important groups. Planctivores like some cnidarians, polychaetes and bryozoans are most abundant in tidal pools that never or rarely become dry. The primitive Chiton Acanthopleura sp. is commonly found attached to rocks splashed with sea water. Oysters (Fam.Ostreidae) have solid shells and are permanently attached to hard substrates and therefore can withstand strong waves, as well as being exposed to the sun during low tide. Barnacles also have developed shell-like structures which can be closed to avoid dessication. Despite superficial resemblence with molluscs, they are highly specialised crustaceans. Their legs have been modified to cirri that function as filtering organs. Common in intertidal zones are Pollicipes mitella, Chthalamalus sp., Tetraclita sp., Tetraclitella sp. (Rosell, 1986). Other species live attached to animals, especially crustaceans, but also on drifting woods and other hard substrates. Higher crustaceans are relatively diverse along shorelines. The most conspicuous crustaceans on mud flats are the Fiddler crabs Uca spp. The males have one enlarged claw with which they signal other males their position and that the respective territory is occupied. Before their burrows get flooded, they cut out round pieces of mud from the surface, retreat


back in their burrows and seal the hollow tight with the piece of mud used as a cover. On sandy beaches, land hermit crabs Coenobita sp., and sand crabs Ocypode sp. are particularly common. They are predominantely nocturnal to avoid predation in a habitat that does not provide much shelter. The soldier crabs Mictyris sp. are closely related to the latter. Like their relatives they live in sand holes. In contrast to the larger sand crabs, they often forage in large aggreggations, possibly as a means to avoid predation. The crabs of the genus Dotilla leave behind very conspicuous signs of feeding. Their holes are surrounded by concentric walls of sand ‘pebbles’. These are formed when the crab is screening the sand for food around its hole. The walls of sand pebbles surrounding the central hole are not completely closed to allow the crab a fast retreat in case of danger.The environmental effects of these burrows lay in the increase of the penetration depth of oxygen and bringing lower sediments to the surface. The deposits of the suspension feeders in form of fecal pellets are food for the deposit feeders, while the deposit feeders resuspend their deposits in the sea water. Members of the genus Grapsus are typical for rocky shores. With their flattened carapaces and their strong legs, they can withstand the waves without being washed away. Insects are becoming increasingly more abundant going from the seaward to the landward side of shorelines. Tidal zones are the only ecosystems strongly influenced by the sea where some insects are able to successfully compete with crustaceans. Water skippers (Fam. Gerridae) dwell on the surfaces of tidal pools and some species of aphids, beetles and ants live in soft bottom tidal flats. To avoid flooding of their burrows, the openings are not made wider than 3mm. This is enough to hold back the air due to adhesive forces, even during high tide (Maitland and Maitland, 1994). Sandy beaches are often inhabited by tiger beetles (Fam. Cicindelidae). Agile predators with


strong mandibles prey on small invertebrates on the barren ground. Large wasps of the families Pompilidae and Sphecidae hunt spiders and caterpillars, respecively, by immobilizing them with their poisonous sting. The still living prey is buried alive in sand holes and serves as food for the wasp larvae. Molluscs are the most common herbivore grazers on tidal flats. Patellid snails even can survive on rocks which are exposed to very strong wave action. They have cone-shaped shells and attach with their sucker-like foot to the rocky surface always returning to the same spot after grazing. Subsequently, a cavity forms which follows the outlines of the shell. Hence, the snail is able to seal of its body from the unfortunate microclimate during low tide. Prosobranch snails like Littoraria sp. can close their shell tight with a calcareous structure at its foot called operculum. The zonation of organisms on rocky shores usually follows a typical pattern with three major zones: Lower intertidal; middle intertidal; and upper intertidal. Each zone is characterized by a key group of orgnisms. Space is a key limiting factor and inter- and intraspecies competition can be intense. Brittle stars (Ophiuroidea) are the most common echinoderms to be encountered on tidal flats. They can be easily spotted by the vivid movements of their arms to filter out detritus from the water surface. However, the whole animal is difficult to see, since it usually hides in a crevice. Most sea urchins that most commonly graze on algae growing on hard bottoms are not adapted to be exposed to the air and have to retreat to rock pools or water-filled crevices during low tide. Predators among the molluscs are some cowries (Fam. Cypraeidae) and cone snails (Fam. Conidae). The latter are killing their prey, with toxins that in some species can even be fatal to humans. Nekton like schools of goatfishes (Fam. Mullidae) or gray mullets (Fam. Mugilidae) enter tidal zones only during high tide to utilize the

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productive feeding grounds. In tidal pools, only few fishes permanently use the open water body like some damselfishes, when still being immature. However, the fish community in the intertidal is dominated by benthic families with the Gobiidae and Blenniidae being the most diverse. Some species are even able to leave the water and live on land for a limited time. The mudskippers Periophtalmus sp. are well known amphibious fishes which commonly live in mangroves. The leaping blenny Alticus saliens is typical for more open tidal zones. Marine turtles are only temporary visitors of sandy beaches where they lay their eggs. Mainly four species are recorded: the largest and rarest is the Leatherback Dermochelys coriacea. It can reach a length of 3 m and weights up to 750 kg. In contrast to its smaller relatives, its upper shell consists of bony plates that are embedded in the skin with seven conspicuous ridges. Its main diet consists of jellyfish and it has been reported that more and more animals die because they swallow discarded plastic bags which they mistake for their prey. The other species all have bony shells that are completely covered with horny scales. With some exercise, the different species can be identified by the distinct scale patterns. The Green turtle Chelonia mydas is mainly vegetarian and is found in seagrass beds and stands of algae in shallow water. The Loggerhead Lepidochelys olivacea feeds on fish and pelagic invertebrates, whereas the smallest species, the Hawksbill Eretmochelys imbricata feeds on benthic invertebrates. Alcala (1980) has conducted a threeyear study on the ecology of this species. It was found to be most common in shallow coral reefs, reef drop offs and channels between islands. The preferred nesting beaches have generally fine gray sand. Laying of eggs presumably occurs year-round. However, the single females do not lay eggs every year, but seem to follow three-year nesting cycles. Clutch sizes are reported to range between 112 to 130 eggs. Each female produces two or even more


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clutches that are laid in three-week intervals in one nesting season. After laying eggs, the turtles are known to return to the beaches where they have been born. However, it is still not fully understood what features make a suitable nesting beach. Depending on the temperature, propagation time is around 60 days. Only very few of the hatchlings survive the first years. Already the eggs are heavily predated by monitor lizards, pigs, dogs, rats and man. Additional predators of the young when they try to reach the sea are crabs and larger seabirds. In the sea, sharks and other predatory fishes and even large jellyfishes are known to decimate the numbers of the young turtles. However, the main threat to turtles is the capture of adult animals by man. Especially in demand are the Hawksbill and the Green turtles, because of their meat, the bones and the shells which are used for handicraft. Now on the brink of extintion, all marine turtles are protected by law in Indonesia and conservation projects are launched also to secure the nesting beaches. One of the most important reserves for marine turtles in the country is Pulau Sangalaki in East Kalimantan where 30-45 turtles dig their nests every night of the year (Tomascik et al., 1997). The main nesting sites for the Green turtle in South East Asia are the islands of Penyu, Lucipara and Aru (Fig.9.5). The skink Emoia atrocostata (Fam. Scincidae) is a relative frequent visitor of the Pes-caprae formation. Resident sea birds like boobies (Fam. Sulidae), frigate birds (Fam. Fregatidae), tobicbirds (Fam. Phaetonidae), and noddies (Fam. Laridae) and migrant shore birds relay heavily on shorelines as feeding grounds. Most of them are winter visitors coming from Siberia or North East Asia. The different species of waders (Charadriiformes) have adapted to different feeding niches to avoid competition. The Sanderling Crocethia alba forages near the water’s edge of sandy beaches on small invertebrates washed ashore by the surf. The Mongolian sandpiper Charadrius mongolus feeds on open sand or mud


flats, whereas the Ruddy turnstone Arenaria interpres is more often encountered on shores with gravels or crushed corals where it preys on animals by turning around the stones under which they hide. The Common sandpiper Actitis hypoleucos is the wader most likely to be encountered in Indonesia feeding on soft bottom, hard bottom and boulder shores alike. It has been recorded that the biomass density of prey for these tactile feeders varies widely between 1-37 g.m-2 around Java. Due to their long beaks the Asian dowitcher Limnodromus semipalmatus and especially the Whimbrel Numenius phaeopus are able to utilize food sources that are hidden so deep in the substrate that most other waders cannot reach them. Several species of herons and egrets (Fam. Ardeidae) can be regularly observed in tidal zones, but only the Reef egret Egretta sacra seems to be restricted to it (Fig. 9.6). The only mammal that usually can be found in tidal zones is the Small-clawed otter Aonyx cinerea which is widespread in Southeast Asia. Decomposers Since particulate organic matter (POM) is brought to the system twice a day, the guild of decomposers is rich in species. Especially the echinoderms like brittle stars and sea cucumbers are abundant, as are different species of crustaceans and annelid worms. As much as 27 species of holothurians have been recorded from intertidal areas (Tan Tiu, 1981). Since POM is a resource with spotty distribution, most detritivores are mobile or hemisessile. One exception is the spaghetti worm Loimia medusa that has tentacles which can cover up to 1m2 around its burrow in search for food (Storch and Rosito, 1981 and Fig. 9.1). NUTRIENT AND ENERGY FLOW Since solar radiation is high and nutrients are usually abundant, shorelines where sedimentation takes place are productive ecosystems. Every high tide brings


183

1

2

3

4

5

FIGURE 9.5.

The most conspicous species of marine turtles recorded from Indonesian waters. 1 Leatherback (Dermochelys coriacea) 2 Green turtle (Chelonia mydas) 3 Loggerhead (Caretta carctta)

4 Hawksbill (Eretmochelys imbricata) 5 Olive or Pacific ridley (Lepidochelys olivacea)


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new nutrients to the system. Losses of nutrients are caused by currents in the first place. Pelagic fishes or terrestrial animals which are exploiting the resources of tidal flats during high or low tide, respectively, are also devoiding the system of nutrients (Fig. 9.7). Most of the nutrients originate from the neritic zone. Primary production is virtually non-existent. For rocky tidal zones with strong waves eroding the stone, the only source of nutrients is the sea water during high tide and possibly terrestrial run-off. During low tide, these nutrients are usually not disposed in form of POM like in the tidal flats, but washed away by the surf.

FIGURE 9.6.

Different species of shore birds feeding on tidal flats. 1 2 3 4 5

Mongolian plover (Charadrius mongolus)

Sanderling (Crocethia alba)

Common sandpiper (Actitis hypoleucos)

Ruddy turnstone (Arenaria interpres)

Asian dowitcher (Limnodromus

semipalmatus) 6 Whimbrel (Numenius phaeopus) 7 Reef egret (Egretta sacra)


HUMAN INFLUENCE AND ECOLOGICAL STATUS Most probably, extensive gleaning represents the most severe human impact on shorelines. However, restriction of access is difficult, since most of the people involved can not afford expensive fishing equipment and therefore, have no other access to marine sources of protein. On small islands, predominately women are involved in gleaning activities. Most important collected organisms are molluscs (41 species), followed by echinoderms (7 species), algae (2-3 species), fish (22 species) and one species each of swimming crab and one sea anemone (Schoppe et al.,1997, Schoppe, 2000). Gathering of sand, gravel or rocks from tidal flats is commonplace. It is not known how these activities affect the biocoenosis of this ecosystem. In tidal flats with soft bottoms, pollutants can easily enrich with the effect of the whole community of organisms being destroyed through poisoning. Even when some organisms can withstand these hazards, they will possibly accumulate the pollutant and probably poison organisms feeding on them. Even man can be affected by this, when collecting intertidal organisms in contaminated areas like the Bay of Jakarta where extremely high concentrations of heavy metals can be found in sediments.


FIGURE 9.7.

185

Simplified model of the nutrient and energy flows on a sandy beach. Most of the nutrients originate from the neritic zone (after Ott, 1988). AM ARM BPP CA DOM

anerobic meiofauna with microbial symbionts anerobic meiofauna benthic pelagic predators chemoautotroph microorganisms dissolved organic matter

Shorelines are sometimes affected by construction of harbors, moles or fishponds. IMPLICATION FOR EIA STUDIES Commercial exploitation of organisms inhabiting tidal zones should be based on data of population dynamics of the respective species to ensure sustainable harvest.

M microorganisms POM particulate organic matter RPD redox potential discontinuity

Contents of toxicants in soft bottom sediments, especially of heavy metals and organo halogenides, should be monitored carefully in the vicinity of larger human settlements, near industrial facilities, or in areas with intensive agriculture. Construction in tidal flats should not cut off the area from the tides, nor change the tidal regimes considerably. The gathering of sand or gravel in


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beach areas should be monitored carefully since it can lead to serious erosion. SUMMARY Shorelines form a marine-terrestrial ecotone. Parameters of some abiotic factors are subjected to extreme variations. Only a limited set of species can survive in this environment by adapting to these fluctuations or by avoiding them through mobility. To avoid competition, the single species have adapted to separate niches which can be quite narrow in space and time. Succession is fast and easy to follow, especially the sessile organisms are easily manipulated, making tidal zones a convenient object for ecological studies (Morton, 1990). Tidal zones are heavily exploited by man for their organisms since they are easily accessible and not many pieces of equipment are required for gleaning.



THESIS Most people think that mangrove swamps are not an attractive place to wander with all the projecting roots to trip off the unwary, the oozing mud and smell of decay, and clouds of mosquitoes and biting sandflies. Others find this habitat fascinating, particularly at low tide, when the exposed mudflats bustle with teeming life. A remarkable animal community occupies this coastal world between the sea and the land, including some creatures, like the mudskippers and the fiddler crabs which are equally at home in or out of the water (MacKinnon, 1992b). Paradoxically, their saline environment is physiologically dry. Mangroves thus, show special adaptations normally characteristic of xerophytes.

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10

MANGROVES

Friedhelm Göltenboth and Sabine Schoppe

OVERVIEW The world distribution of mangrove habitats parallels those of scleractinan corals and tropical seagrasses (McCoy and Heck, 1976). The Indo-Malayan mangrove region is recognized as the current center of diversity with respect to mangrove forests (Chapmann, 1977).Throughout Indonesia there were originally 50,800 km2 of mangrove forests with about 40 major plant species in 20 families occurring in mangrove swamps (Fig. 10.1). In coral reef associated mangrove ecosystems, 38 mangrove trees are recorded for the Indonesian archipelago. By 1990, only 44 % of the original area (about 25,000 km 2) remained (Min. Nat. Dev. Plan, 1993). Low forests between and marginally above the tides are referred to as “mangals”. The term mangrove can also be applied collectively to the many-species assemblage, but is used more familiarly as the vernacular name for the plants themselves. Mangroves are relatively recent and ephemeral coastal features on a geological time scale. The


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FIGURE 10.1.

Distribution of mangrove forests in Indonesia (after Koesoebiono et al., 1982).

mangrove forests in the Beran River Delta of East Kalimantan may be among the oldest mangrove communities in Indonesia (Eong, 1993). Some 63 million years ago during the cretaceous era, Nypa sp. was already existing, while Rhizophora sp. were recorded to be present 30 million years ago as revealed by the fossils found and analyzed. Mangroves are a product of convergent angiosperm evolution where plants from different families have evolved under similar adaptations that enabled them to colonize and reproduce in tropical intertidal environments of the early Thetys Sea between Laurentia and Gondwanaland (King et al.,1990). It is even assumed that angiosperm radiation may have originated from coastal environments (Retllack and Dilcher, 1982). The first established angiosperm vegetation type included Avicennia sp., Rhizophora sp. and Hibiscus sp. in both centers of diversity, the western center with West Africa, Atlantic, and Pacific South America and the eastern center with East Africa to the Western Pacific (Tomlinson, 1986).

MANGROVES

CONDITIONS FOR MANGROVE DEVELOPMENT Though several sorts of mangroves grow upon sheltered and sedimented stretches of reefs and islands, the complex mangal is completely achieved only in estuaries and deltas. The sea has little part in their construction because they are composed of land-derived sediments enriched by organic breakdown. These stretches are part of the widely extended “schorre” or salt-marsh system. Influencing factors for mangrove swamps and plants are: • Physiographical structure of the area under tidal influence. Mangroves grow only on sheltered shores often protected by coral reefs on shallow muddy deposits or on pure corraline or calcerous substrate with minimum water temperatures between 12 oC and 32 oC. • Aggressive or erosive action of the sea: Mangroves are absent in coastal areas with strong wave action and strong tidal currents.


• Tidal inundation (Fig. 10.2). There are five species groups recognized under this factor (Morton, 1990): • Inundated at high tides: Rhizophora mucronata along stream banks and with its main foliage head still above water. • Inundated at medium high tides: Avicennia sp. and Sonneratia sp. or the edge community along rivers, where Rhizophora mucronata predominates. • Inundated by higher than normal tides: the greater part of the mangal is occupied mostly by Rhizophora sp. • Inundated by spring tides: Rhizophora sp. are replaced by Bruguiera sp. • Occasionally inundated by exceptional or equinoctial spring tides: Bruguiera gymnorhiza often thrieve with the mangrove fern Acrostichum sp. • Saline conditions: Mangroves follow accretion or accumulation of land and soil and aid in further accretion.The specific plant species of the mangrove community occur

FIGURE 10.2.

Examples of two mangrove species and average tidal range.

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usually in zonation, according to the increase

in firmness of the soil and decrease in salinity

from the shoreline inland.

Mangrove trees, with probably the exception

of the Rhizophora genus, are no halophytes,

that is, they do not need salt to grow.

Instead, they have developed special adaptation mechanisms to tolerate relatively high salt concentrations with an average of 34.7 ‰ salinity (g salt . 1 kg-1 of water), hence, creating a very specific� niche. • Artificial conditions brought about by exploitation: Removal of mangrove forests is often followed by erosion of the shore, a decline in fish catch, and a siltation of adjacent coral reefs. ADAPTATION MECHANISMS Living under intense light and high temperatures, and on unconsolidated soils which are anaerobic and periodically flooded with saline water, mangroves have acquired several mechanisms of adaptations. The adaptations can be : 1. Morphologically like the rooting system (Fig. 10.3) and succulent leaves with thickend epidermis, waxy cuticle on the upper side of the leaf and sometimes white tormentum on the underside of the leaf, like xerophytes. 2. Anatomically like the pneumatophores, very stout structures in Sonneratia sp. and like thin threads in Avicennia sp. 3. Physiologically like water conservation meachanisms Rhizophora and Sonneratia species, are good examples for the characteristics of the leaves. Some leaves are covered with pubescence, like in some Avicennia species or scales like in Heritiera species. They tend to have reduced leaf areas (Fig. 10.4), sunken stomata like in Rhizophora, Bruguiera, Ceriops, Avicennia, Aegiceras and Lumnitzera



MANGROVES

FIGURE 10.3.

Stand of Rhizopora sp. during high tide . Marine organisms migrate into the mangrove area. Seedlings of Rhizopora sp. can even stand to be completely submerged for hours.

Anchoring stilt roots of Rhizophora sp.

Seedling of Rhizophora sp.

Pneumatophores of Sonneratia sp.

Seaweed Halimeda sp.( Order Chlorophyta)

Seagrass Halodule sp. (Fam. Cymodoceaceae)

Diadema sp.

Holothuria sp.

Anemone

Sea sluge

Littorinidae

Neritidae

Sepia sp., juvenile (Fam. Octopodidae)

Crab

14 15 16 17 18 19 20 21 22 23 24

Gobiid fish Gobiid fish Halichoeres sp. Platax orbicularis, juvenile Triacanthus biaculeatus Apogon amboinensis School of fish fingerlings (Neosthetus villadolidi) School of fish (Pandaka trimakulata) Pomacentrus grammorhynchus Sponge Sea snail


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1 2 3 4 5 6 7 8 9 10 11 12 13

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species, smaller cells with high internal osmotic pressure. Living in soils not only salty but too watery for normal angiosperms, mangroves have also many of the adaptation meachnisms of halophytes: They take in water easily, with high rates of flow and abundant guttation. Relatively high salt concentrations are found in the xylem sap of the plants. They can tolerate greater concentrations of salts in the sap than most land plants. Since water always flows from locations with greater waterpotential (psi,Y), but with lower salt concentration, to areas with lower waterpotential but higher salt concentration, substantial metabolic energy is required for both processes respectively, to transport the water from the site of absorption to the leaves, and for desalination processes.

1 FIGURE 10.4.

2

3

4

5

6

Morphology of leaves of some mangrove species and associated species. 1 Lumnitzera sp. ( Fam. Combretaceae) 2 Avicennia sp. ( Fam. Verbenaceae) 3 Sonneratia sp. ( Fam. Sonneratiaceae)

MANGROVES

The mechanisms used to balance the salt concentrations can be divided into three groups: • Ion accumulation mechanism: In specifically equipped parts of the plant, the salt is actively accumulated until the death of this part or the plant itself. Also, special metabolism is usually established to prevent salt intrusion to those tissue with high metabolism, because salt influences many enzyme activities. The osmotic adjustment in the cytoplasm is connected with proline, choline, and betain accumulation. Bark, roots, and leaves of Rhizophora, Xylocarpus, Bruguiera, Ceriops, Osbornia and Sonneratia species play this part. • Salt secretion mechanism: Special salt excreting glands and as trichoms or outgrowth

4 Rhizophora sp. ( Fam. Rhizophoraceae) 5 Bruguiera sp. (Fam. Rhizophoraceae) 6 Acanthus sp. (Fam. Acanthaceae); associated species


of the epidermis of the leaves secrete sap with salt concentrations up to 20 times higher than the sap of the xylem. About 80-85% of the salt can be excluded by actively removing the respective Na+, K+ and Cl- - ions out of the parenchyma cells. Some Avicennia, Aegiceras and Aegialitis species are using this mechanism. • Salt exclusion mechanism: Using a so-called “passive ultrafiltration process” needing very high sucking tensions, some Rhizophora species, including Sonneratia, Bruguiera, Ceriops, Osbornia and Lumnitzera species actively prevent the penetration of salt into their xylem sap. Some of the salt is deposited in the leaves and shed. Dispersal Adaptations Many of the mangrove plants show vivipary or germination of their seeds while still attached to the mother plant. All species of the family Rhizophoraceae, all species of Avicennia sp. and Aegiceras corniculatum exhibit this phenomenon. Vivipary is simplest in Aegiceras sp. where the small banana-shaped seed germinates within the pericarp, its cotyledons forming a long tube enclosing the plume (Morton, 1990). Avicennia sp. shows further development with thick bright green cotyledons, folded double. In species of Avicennia sp. and Aegiceras corniculatum, the embryo ruptures the testa and fills the pericarp which then starts to enlarge in proportion to the growth of the embryo. The species of Rhizophoraceae are well known for their long torpedo-shaped hypocotyls, hanging in cluster from the mature inflorescence. The hypocotyl pierces the fruit and grows out of it and this embryo seldom falls directly into the mud. Instead it floats horizontally and when anchorage is possible, bends itself up to vertical. In Bruguiera sp., the whole fruit

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falls from the plant with the hypocotyl still attached, and piercing its apex, so that the embryo grows cigar-like out of this base. The cotyledons are connate only at the base and their glandular epidermis takes nutrients from the pericarp to feed the hypocotyl. In Rhizophora mucronata, with a hypocotyl reaching sometimes up to 1 m in length, the hypocotyl falls out of the fruit base which is left attached to the plant. The two cotyledons are completely fused, with the plumule entrenched in them. They suck nutrients from the pericarp for the growth of the hypocotyl. The plumule often protrudes from the fruit and is demarcated by a grove from the hypocotyl. The viable seedling can be water-borne over long distances and can take immediate advantage of opportunities at an advanced stage of development. It can be stated that the embryo development is more or less continuous and the dispersal takes place through seedlings, not seeds. In Aegialitis, Acanthus, Avicennia, and Aegiceras species, the embryo does not rupture the pericarp. This condition is called cryptovivipary. The main advantages of vivipary and cryptovivipary are as follows (King et al,. 1990): 1. Rapid rooting 2. Salt regulation 3. Ionic balance 4. Development of buoyancy 5. Prolonged attainment of nutrients from the parents (= nutritional parasitism) Rooting Adaptations Since mangroves are not visited by strong waves and currents, they develop superficial rooting systems. This rooting system serves first for shallow anchorage, then for absorbing water and oxygen in largely anoxic surroundings. The laterally spreading subsurface cable and anchor roots give mechanical support to the tree, while the nutritive fine roots serve for nutrition and


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for the assimilation of oxygen from the uppermost silt layer. The dense anaerobic mud in which the roots of mangrove plants are embedded and the periodic inundation of the tide cause various adaptations to the rooting system, aiding in respiration and in anchoring the plant. The main roots or cable roots are anchored by vertically descending small lateral roots or anchor roots and the cable roots and pneumatophores (if present) produce an extensive net of very fine nutrition roots in the uppermost mud-stratum. The rooting adaptations of mangroves include surface roots, stilt roots, various types of pneumatophores, and various types of aerial roots (Fig.10.5). Avicennia sp. and Sonneratia sp. have no tap root. They are moored by radiating cable roots, 25 50 cm deep and profusely branched. From the radial roots, smaller anchoring roots are given off, and vertical pneumatophores or breathing roots protrude above the surface. In Avicennia sp. these are slender and flexible, while in Sonneratia sp., strong and woody. In place of a tap root, Rhizophora sp. has only a set of branching prop roots from which a succession of long arched roots, halt-hoops are put out radially. They serve as pneumatophores. Just beneath the surface, each of the prop roots break into a bundle of air -filled anchoring roots. These in turn give rise to nutritive roots. Aerial stilts grow downward from the upper branches to take additional foothold in the mud. Bruguiera sp. and Ceriops sp. have air-filled cable roots, from which knee-like loops arch up from the ground, serving as pneumatophores with patches of air-admitting lenticels. Lumnitzera sp. has clusters of thinner, hoop-like pneumatophores. Xylocarpus sp. has horizontal roots which are periodically compressed into narrow upward flanges which cluster around the trunk base above the soil and function as pneumatophores. The triangular, thin but strong, buttresses of Heritiera sp. are the largest of all flange

MANGROVES

pneumatophores. Mangrove species usually possess numerous lenticels covering the stem and the roots, aiding in respiration. When the lenticels are covered by the tide, root pressure begins to drop. When the tide goes down, air is again sucked into the aerenchym. Reproductive Adaptations The majority of the mangrove plants are hermaphrodites with perfect flowers containing both stamens and carpels.The Rhizophora, Bruguiera and Sonneratia species belong to this group. About 11% are monoecious with male and female flowers on the same plant but seperated from each other, like in Nypa, Heritierea and Xylocarpus. About 4% are dioecious with male and female flowers on different plants, e.g. Laguncularia and Excoercaria species. Mangove plants are almost exclusively pollinated by animals with the exception of Rhizophora species, with a high pollen to ovule ratio, light powdery pollen and absence of odour. All these features are typically signs of wind or selfpollination. Nocturnal and diurnal animal pollination takes place. While Ceriops sp. is pollinated mainly by nocturnal moth species, Sonneratia sp. is pollinated by bats like Macroglossum minimus and Eonycteris spelaea, the latter also responsible for the pollination of Durio zibethinus the commercially valuable Durian fruit. Diurnal pollinators are birds, like the Brown Honeyeater,Lichmera indistincta,or the Copper throated Sunbird, Nectarinia calcostetha.They are both regular visitors of Bruguiera flowers. Insects, like bees, fruit flies, and butterflies are also diurnal pollinators of Nypa, Avicennia, Acanthus, Xylocarpus and Bruguiera species. ZONATION OF MANGROVE COMMUNITIES Classification and zonation of mangrove communities can be based on either structural attributes of mangrove forests (Specht, 1970), physiogeographic characteristics (Lugo and Snedaker, 1974), or coastal geomorphology (Thom, 1982).


FIGURE 10.5.

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Rooting and aeration system of some mangrove trees.

Mangroves can reach far upstream from the sea, wherever a wedge of heavier sea water can creep over the bottom, to raise the salinity of the surface mud. Not all the species of mangrove plants can be found in any one mangrove community. The zonation is controlled by the interaction of tidal flooding, and salinity and drainage of the soil. The zonation varies in different areas and no two areas are exactly the same (Fig.10.6). Mangrove swamps are divided into various zones using dominant tree as a mean of zoning. In general, two types of zonation can be observed: 1. From a sheltered tidal area to the beach

forest area the following zones are

distinguishable:

• The Sonneratia zone: Sonneratia species is one of the pioneering species of a mangrove swamp with Sonneratia alba being the most seaward species thus, inundated daily. • The Rhizophora zone: Rhizophora forests develop behind the pioneering species. R. mucronata being more tolerant of salt water than R. apiculata, occurs behind a seaward fringe. • The Bruguiera zone: Bruguiera forest usually develops behind the Rhizophora species on better drained soils. • The Ceriops zone: Ceriops develop in areas with intermediate rainfall and well drained soils.


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FIGURE 10.6.

Schematic diagram of the zonation of the mangrove forest. 1 Maximum low tide 2 Average tide 3 Average high tide

4 Maximum high tide 5 Maximum tropical storm situation MC Mangrove Channel

• Mixed zone: This is the most variable zone under this category. Different species occur depending on the type of soil present. In this zone Heritiera littoralis, Lumnitzera littorea, Camptostemnon schultzii, Cynometra ramiflora, and other species may occur. • The Nypa zone: Nypa fruticans occupies areas along tidal streams flooded by the highest spring tides. It thrives in brackish water. 2. From the open sea to the beach forest area the following zonation can be observed: • The Avicennia zone: Like the Sonneratia species, the Avicennia species are the pioneers of the mangrove swamp. A. marina colonizes more the fringe of the swamp, while A. alba grows more along the channels. A. eucalyptifolia is found

MANGROVES

mostly in the vicinity of coral reefs or off shore coral islands. • The Rhizophora zone (see above) • The Bruguiera zone (see above) • The mixed zone: In this zone, species like Heritiera littoralis, Excoecaria agallocha, Xylocarpus granatum, and Osbornia octodonta may occur. It should be emphasized that the forest composition and expansion of mangroves differs from place to place depending partly on the physiography of the coast and the presence and absence of streams. Where there are streams and deltas which bring abundant clay and sand to the coastal area a much wider belt of mangrove will develop while in the absence of streams it is mostly rather narrow.


ECOSYSTEM FUNCTIONS Mangroves are stands of emergent plants in the eulittoral of highly sedimented coasts in the tropical and subtropical zones of the globe. Besides a very distinct horizontal zonation pattern, a vertical pattern of layers can also be distinguished: • The sediment with a variety of burrowing invertebrates: the surface is usually covered with cyanobacteria, sometimes with Begiatoa or sulfurbacteria • The always submerged parts of the rooting system of mangrove trees: they are usually covered with thick layers of algae including Halimeda and Caulerpa species while a fauna of cnidarians, ascidians, bryozoans and sponges can be found usually in typically hard rocky soils. • The temporally air exposed parts of the rooting system of mangrove trees: Cirripedia, Bryozoa and Oyster species are commonly found or attached to the roots. Carpet-like algae layers can be found near the average tidal line, including Bostrychia species. • The trunk and big branch area of the mangrove trees: here, a mixture of typically marine organisms like littorinid snails and grapsid crab species, and typical terrestrial organisms like lichenes and many insects can be found. • The canopy of the mangrove trees: this is mainly the domain of terrestrial insects, like the weaver ants and in some specific places the very habitat of eminent endemic monkeys, like the proboscis monkey, Nasalis larvatus, living only in some parts of Kalimantan and feeding particularly on Sonneratia leaves (Fig. 10.7) or the Macaca pagensis or Mentawai Macaque (Fig. 10.8). They search for crabs and whelks in the mangrove areas of Siberut Island off the Western coast of Sumatra.

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Biodiversity While the major floral components of the mangal are restricted to only a few families, the faunal components belong to a large variety of classes. About 75% of the fauna under this zone is not found in any other zone (Fith et al., 1976). The fauna can be divided into three groups: Tree fauna, ground surface fauna, and burrow fauna. Producers In Indonesia, about 115 plant species can be found in mangrove communities which can be sorted out into 75 trees, 10 bushes, 10 lianas, 8 herbs and grasses, 2 ferns, 4 epiphytes and 6 parasites. The most prominent emergent mangrove trees with a height between 15 and 40 m belong to more than a dozen plant families. The most important of these families are the Rhizophoraceae (Rhizophora sp., Ceriops sp., Bruguiera sp.) Avicenniaceae (Avicennia sp.), Sonneratiaceae (Sonneratia sp.), Plumbaginaceae (Aegialitis sp.), Myrsinaceae (Aegiceras sp.), Meliaceae (Xylocarpus sp.), Combretaceae (Lumnitzera sp.), Myrtaceae (Osbornia sp.) and Palmae (Nypa sp.). Common papilionacean vines are Derris trifoliata and Entada phaseoloides, with their heavy strip-like pods. The asclepiad vine Hoya sp. trails amongst mangrove branches. Above high water spring tides grow the common mangrove fern, Acrostichum aureum. The biomass of the plants can reach more than 47 kg·m-2 with more than 50% belonging to the root systems. The leaf biomass is usually not more than 2-8% (Ott, 1988). Around the higher water mark, typical mangrove algae like Caloglossa sp., Catenella sp.,and Gelidium sp., and further up in the shade, Bostrychia sp., may be found.


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FIGURE 10.7. The Proboscis monkey, Nasalis larvatus, feeding on leaves of Sonneratia sp. in the mangrove area of Southern Kalimantan. This endemic species is an excellent swimmer. The male is large, with red nose which is not just a respiratory organ but may act as a sound booster when he gives warning calls and a sexual signal to attract females to join his harem.

MANGROVES


CONSUMERS Not only the sediment, but also the trunks, leaves and roots support a zonation of sessile and mobile animals. Ciliates and foraminifers are numerous, but the meiofauna of the sediment does not contain many species. The peculiar peanut worm, Phascolosoma sp., is able to store oxygen in its coelomic fluid. When the tide is out it lives permanently in the soil of the pioneer zone of the mangal (Brasfield, 1978). The Littorina snails like Littoraria scabra and Littoraria carinifera stay high at foliage. During the day or dry period, they close the operculum, to remain suspended by the lip with dried mucus. The primitive pulmonate snail, Melampus sp.(Fam. Elobiidae), as well as the prosobranchs Nerita sp.(Fam. Neritidae), Heminerita sp., Truncatella sp.(Fam. Potamididae) may be found on more silty sand, while the pointed, ovoid Vittina sp., Cassidula sp., Auriculastra sp.,Terebralia sp. (Fam. Potamididae) are usually found on more muddy parts of the mangal. Altogether, 90 species of molluscs belonging to 32 families are recorded in Indonesian mangrove communities (Kastoro et al., 1991). But only two families of gastropodes are true mangrove molluscs, the Potamididae and the Elobiidae. Branches and roots near high water mark carry small acorn barnacles, Chthamalus sp., and oysters,Crassostrea sp.. At mid-tide level, sometimes a small estuarine mussel, Modiolus sp. may be found. Also present is the bivalve Enigmonia sp. which lives on leaves and trunks of mangroves attached by a stout byssus. The left or upper valve is purple, streamlined and limpet-like, with the functionless right valve below. Amongst the lower roots, a flat bivalve, Isognomon sp., may be found. Dead trunks and roots are usually hollowed by shipworms. Root holes and clefts, amongst mangrove and litter, can shelter amphibious species such as the ellobiid molluscs. They also provide refuge for

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crabs, prawns, and nereid and other polychaete worms. The wood-drilling Sphaeroma sp. is specialized on living roots of Rhizophora. The heteropteran bug Halobates sp. skims actively over the surface of still water. The bivalve Geloina ceylonica lives buried deep in the mud. Besides the snails, the crustaceans are always a prominent and diverse element of the mangrove fauna. About 80 species of crabs are recorded in the mangroves of Indonesia. They have developed adaptations like an impervious exoskeleton, respectively shells, the ability to breath air, the use of microorganisms and/or organic litter as major food stuff, and the specific protection mechanisms like internal fertilization and protection of eggs and developing young. All these features make them the predominant organisms in the mangrove fauna. The fast running Grapsidae are often represented by the red-clawed Sesarma sp. and Metopograpsus sp.. The Grapsids have an important accessory respiratory device with the “cheeks” or outer surfaces of the branchiostegites, reticulated with chitinised grooves lined with fine hairs. A flow of exhalant water passes over these areas to be re-oxygenated, then returns to the inhalant apertures (Morton, 1990). The Xanthidae are represented by the slow moving Epixanthus sp. often living under boulders and in holes between roots. The fiddler crabs (Uca sp.) belonging to the family Ocypodidae, are the most attractive of tropical mudflat shore crabs. The male has one of the cheleae immensely enlarged and, like the carapace, often exquisitely coloured. It may be either claw, the right or the left which becomes enlarged. In females, both claws are small and weak. They have also spatulate fingers used for picking up deposite and algae during low tide. During high tide, they rest in their sediment burrows measuring up to 30 cm long, carved and L-shaped, blocking the entrance with balls of mud and sand to keep out the encroaching waters and retain a bubble of air to allow them to breath beneath the water. The colour



MANGROVES

FIGURE 10.8.

Community of mangrove organisms above the sea surface.

Mudskippers Boleophthalmus sp. Periophthalmus sp. Periophthalmodon sp. Crab-eating frog (Rana cancrivora) Mangrove snake (Boiga denrophila)

6 7 8 9

The kingfisher (Halycon sp.)

Macaque (Macaca sp.)

Butterflies belonging to the families of Papilionidae

Crustaceans like Uca sp.


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1 2 3 4 5

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Sonneratia sp. Rhizophora sp.

MANGROVE OYSTER

Isognomon sp.

PNEUMATOPHORES OF Sonneratia sp. SIGNALING

Uca sp.

Uca sp. IN FRONT OF BURROW

FIGURE 10.9. Mangrove area during low tide with Rhizophora sp. in the background and pneumatophores of Sonneratia sp.in the foreground showing some of the crustacean and mollusc organisms visible during low tide on the surface and the usually submerged roots.

MANGROVES


and action patterns of the enlarged claw are highly distinctive in each species. The enlarged claw is waved vigorously in territorial disputes between males or as a signal to attract a female. At any sign of danger the fiddler crab retreat hastily into their burrows (Fig. 10.9). About 24 species out of 60 world wide are found in Indonesia. The very high diversity of Uca species in Indonesia is due to the mixing -pot features of the archipelago with species from three different biogeographical regions: Indian Ocean, Asia, and Australia. These crabs mainly feed on detritus and benthic microphyta and the rolled small sand pellets form sometimes indricate patterns on the harder beach parts. The soldier crab, Dotilla sp., adopts a different strategy when the tide comes in. It builds an igloo of mudballs around itself, then burrows vertically down into the mud plastering the excavated sand into the roof. The finished burrow protects the crab’s precious bubble of air till it can emerge again when the tide ebbs (Fig.10.10). Hermit crabs are usually very common in the mangal. Two distinct but convergent groups are represented: • Between the tide-marks are numerous individuals of the family Paguridae like Clibanarius sp.

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• Above the high tide mark members of the family Coenobitidae like Coenobita sp., are active. An outstanding crustacean of the mangal is the mud-lobster, Thalassina anomala that can grow from 15 to 20 cm long. It builds conical molds, for example, amongst the knee roots of Bruguiera trees at the end of a U-shaped tunnel system of up to 2-3 m length and down to 1.5 m depth. Its mode of life is still widely unknown. Narrow-bodied and pinkish brown, it has powerful front claws,each being strongly sub-chelate. The pleopods are reduced, clearly incapable of irrigating the long burrow which appears to go down to the water-table. The sub-chelate claws can chop up mangrove leaves. The mouthparts are strongly setose and it would appear that the mud-lobster can strain particulate food from deep in the burrow, near the water table (Fig. 10.11). The most conspicuous of the insect population in mangals are the mosquitos, but only one, Anopheles sundaicus, carries malaria. The larvae of this species can live in water with a salinity of up to 13%. About 125 species of mosquitoes have been recorded from mangrove areas in Sulawesi. Colonies of weaver ants, Oecophylla sp., live in untidy leaf nests made by binding five or six leaves together with fine silk thread (Fig. 10.12). The colony’s green queen lives inside the nest guarded

FIGURE 10.10. Construction of an air-filled burrow by the soldier crab Dotilla sp. protecting him during high tide (after Ripley,1975).


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a

FIGURE 10.11. Burrow system of the mud-lobster Thalassina sp. (after Morton, 1990). b

by big, black soldiers and taken care of by worker ants. Weaver ants are fierce predators. One of the strangest denizens of the mudflats, the king or horseshoe crabs, Carcinoscorpius rotundicauda are not true crabs at all. They are living fossils, ancient marine relatives of the spiders and scorpions not at all changed in their appearance from their ancestors which inhabited the oceans some 200 million years ago. They are surviving members of the ancient lineage of Xiphosura. These “crabs” comes up onto the muddy tidal flats to mate and spawn. The female carries a bundle of two to three thousand eggs between the front legs. She excavates a depression in the mud and the male clinging to her back fertilizes the eggs as they are deposited. The eggs hatch into free-swimming larvae lacking the long tail of the adults. Despite its armor and long, sharp tail, this “crab” is in fact harmless (MacKinnon, 1992b). Like the related arachnids, the body is divided into two parts: cephalothorax or prosoma and abdomen or opisthosoma. The prosoma, the largest part of the body, is convex and rounded like a polished tin helmet, with two pairs of arachnid-type eyes set in its upper surface. The prosoma carries seven pairs

MANGROVES

c

FIGURE 10.12. Building procedure of the nest of weaver ants, Oecophylla sp.. The workers cling to one edge of a leaf and seize the other with their jaws, drawing the two sides together (a-b). Other ants bring ant grub in their jaws and, as the grub is passed back and forth, it secretes a sticky thread that binds the rands (c).


of appendages, of which the first is a small pair of chelicerae, with chelae, corresponding to the fangs of a spider. Five pairs of short jointed legs follow these, corresponding to the pedipalps and four walking legs of a spider. The last pair of appendages (chilaria) are reduced. The abdomen or opithosoma is a nearly rectangular flat shield, movable hinged to the prosoma and strongly serrated at the sides. Jointed to it behind is the long telson spine. The abdomen carries flattened appendages, concealing beneath them the thin plates of the “gill books” through which respiratory water circulates. The “crab” swims through the water by flapping the abdominal appendages. Most time, it is bulldozing or burrowing in the sand and mud, picking up the worms and other soft-bodied organism on which it feeds. At the base of each limb pair are spiny jaws or gnathobases, passing the masticated food along

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the ventral mid-line to the mouth (Morton and Morton,1983; Fig. 10.13). Drainage channels of the mangal are a very important habitat for many littoral fish species, reef fishes, and fishes from rivers. Juveniles of species of the families particularly Mugilidae, Tetradontidae and Gobiidae can be found. The genus Boleophthalmus and Periophthalmus (mudskippers) are bound to the muddy flats of the mangal. These fish can live as much out of the water than in it. They move across the mud between tides by skipping nimbly with the aid of flippers and well-muscled fore-fins, internally strengthened with bony struts. In some species (Periophthalmus chrysopilos), a second pair of fins, further down the body on the underside, has become joined to form a sucktion cup with which the fish can cling to mangrove roots. They have periscopic eyes enabling them to see

FIGURE 10.13. “King or horseshoe crab”, a living fossil belonging to the ancient lineage of Xiphosura, related to the spiders, laying between the stilt roots of Rhizophora.


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above the surface of the water. They keep their gill chambers full of water, though they have no way of circulating it to renew the oxygen, and regularly return to the water’s edge to collect a new refreshing mouthful. In addition they have an absorbent skin surface. Different mudskipper species seek different diets and occupy different niches within the mangrove mud. One of the smallest remains in the water for the longest time and only ventures out of it at low tide. It feeds on tiny worms and crustaceans. Boleophthalmus boddaerti is usually found on soft mud at the seaward edge of the mid-tide area, grazing the algae by moving the head from side to side. Periophthalmodon schlosseri makes its

homeson the firmer mud and is carnivorous, while Periophthalmus chrysophilos feed on both plants and animals. This species occupies the highest part of the swamps. Strong territorial rights are asserted by mudskippers at breeding time. They built circular burrows in the mud to which they attract the female with a series of leaps. Boleophtalmus sp. is strictly territorial and is even patrolling the mud around it. It builds low mud ridges several meters long around its boundary (Fig. 10.14). The low-tide species does not care for its young, while the mid-tide and high level species protect their offspings by providing a kind of small mudpond.

FIGURE 10.14. Different niche occupation by three species of mudskippers from soft mud sea-ward areas to firmer mud areas between the rooting system of the mangrove vegetation. Schematic transsect through habitats of the sea-ward edge of the mangrove swamp with Boleophthalmus boddaerti (1), Periophthalmus chrysopilos (2) and Periophthalmodon schlosseri (3). A Mouth to mouth display confrontation by the strictly territorial Boleophthalmus boddaerti species B Jumping individual of Periophthalmodon chrysopilos C Individual renewing water for respiration at a small pond

MANGROVES


In some areas of mangrove, particularly in Kalimantan, the banded archer fish, Toxotes jaculator, can be observed “shooting down” insects from above the water at high tide (Fig.10.15). Adult species can “shoot down” an insect from 1.5 m. The fish is capable to reduce the refraction of light by positioning itself almost vertically below the prey. The fish will jump and snatch the insect if it is only a few centimeters above the water (O’Toole, 1987). About 53% of all fish species inhabiting the mangrove-nypa zone are actually estuarine species (Erftemeijer et al., 1989). The mangrove frog, Rana cancrivora, is exceptional among amphibians in being able to live and breed in weak saline water. The tadpoles are more resistant to salt than the adults, and metamorphosis only occurs after considerable dilution of the salty water (MacNae,1968). The main staple of this animal is crabs. A variety of reptiles inhabiting the water, the ground floor and the trees can also be found. The biggest one is Varanus salvator. The common skink, Mubaya multifasciata, is also found on the ground and lower root system. The cattle snake, Elaphe radiata, is also a ground snake, while Cerberus rynchops (dog-faced water snake), Homalopsis buccata (puff-faced water snake) and the crab-eating snake, Fordonia leucobalia, are found in shallow water (Supriatna, 1982). Arboreal snakes are the common cat snake, Boiga dendrophila, and the reticulated phyton, Python reticulatus. Mangrove forests are potentially a very attractive bird habitat. Up to 105 bird species are recorded from Segara Anakan mangrove forests. The abundance of particularly small preys is very attractive to kingfishers, Halcyon chloris. The sweet nectar of flowers attracts both nectivorous birds, like the brown-throated sunbird, Anthreptes malacensis, purple throated sunbird, Nectarinia sperata, and insectivorous birds like the mangrove blue fly-catcher, Cyornis rufigastra.

207

FIGURE 10.15. The banded archer fish, Toxotes jaculator shooting down an insect from an overhanging leaf with a jet of water squirted from its mouth.

The different ways which mangroves are used by birds can be listed as follows (Nisbet, 1968; van Balen, 1989): • Residential species confined exclusively to mangroves like Javan coucal, Centropus sinensis. • Migratory species nesting in the mangroves but feeding elsewhere or which move daily or seasonally to and from the mangroves. • Aerial species which feed over mangroves as well as over land, like the Pacific swallow, Hirundo tahitica • Species of rural and urban areas which are also found in mangroves like the White collared kingfisher, Halcyon chloris; Great tit, Parus major, and Pied fantail, Rhipidura javanica.


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The most endangered bird species found in mangrove communities is the Milky Stork or Mycteria cinerea. The only obligate mangrove bird known is the Mangrove blue Flycatcher, Cyornis rufigaster. The mangrove forest shares a variety of species of mammals with riverine habitats, including some species of monkeys like the long-tailed macaque, Macaca fascicularis, living in Java and Kalimantan; the Javan luteng, Semnopithecus auratus; the Bornean silvered langur, Presbytis cristata; and the endmic proboscis monkey, Nasalis larvatus. Young leaves of Rhizophora and Sonneratia are a very important part of the diet of proboscis monkeys in these coastal areas. The lutungs eat about 60% leaves and 40 % fruits while the macaque consumes 50% fruits with lesser amounts of leaves, bark, roots, insects and other animals. Leaves are a poor source of food for most mammals. To break down the cellulose into digestible molecules, the leaf monkeys have a highly sacculated stomach in which special bacteria ferment the material. Further, the pH in the stomach is maintained between 5.0 and 6.7 to cope with the defense compounds in the leaves, like phenols and tannins. While lutengs chew and eat seeds, the macaques spit out seeds bigger than 3-4 mm. The small-clawed otter, Aonyx cinera, and the fishing cat, Felis viverrina are, in some more remote areas, common residents of the mangal. Fruit bats, particularly the flying fox (Fig. 10.16), Pteropus vampyrus, roost also in the mangrove forest canopy. Other bats like the cave fruit bat, Eonycteris spelaea, and the long-tongued fruit bat, Macroglossus sobrinus are very important pollinators of Sonneratia sp.(Start and Marshall, 1975). Decomposers The total production of litter in form of leaves, twigs, branches, flowers and fruits is 7-14 t.ha-1.year-1 (Jimenez et al., 1985) and forms the

MANGROVES

basis of the complex foodweb including invertebrates and vertebrates. Probably less than 10% of the production of mangrove leaves is consumed in the form of living leaves by herbivorous animals (Johnstone, 1981) the remainder entering the ecosystem as detritus. About 90% of the mangrove leaves are either eaten or buried by crabs and enters the system as excreted detritus, enriched by fungi, bacteria and algae growing on and within it (Whitten et al., 1996). It was calculated that about 62 g C .m-2 . year-1 is taken underground. The sesarmid crabs, like Sesarma messa, consume up to 30% of the

b a

c

FIGURE 10.16. The flying fox, Pteropus vampyrus. (a) Resting position; (b) Head; (c) Resting tree during daytime.


annual mangrove litter production and up to 75% of mangrove propagules (Robertson, 1991). The detritus is eaten by a host of small animals such as zooplankton, crustaceans, like penaid prawns and small crabs, and small fish , particularly fingerlings. The most important litter processers after the crustaceans are isopods, like Exosperoma sp., and capitelid polychaeta like Capitelides sp.. NUTRIENT FLOW The mass of the above gound parts of undisturbed mangal appears to be in the range of 100-250 t.ha-1 (Ong et al., 1985). The leaf production ranges between 150-200 g C . m-2 . a-1 and the values for the wooden above-ground parts between 150 and 500 g C. The gross primary production (PG) or the total accumulation of new organic matter in plant tissues in excess of respiratory per unit area per unit time is in the range of 8.4 - 27.1 kg C . ha-1 . day-1 in Ujung Kulon area in West Java (Atmadja and Soerojo, 1991). Characteristically, the net primary production (P N) rate is independent of the community composition, higher at upstream locations subject to regular freshwater influence and higher during rainy season. Mangrove litter fall accounts for about 50-78% of the total net primary production of mangrove forests, while wood production accounts for 22-50%. Avicennia produces highest and Rhizophora lowest rates of litter fall. Detritus food chains are the most important ones inside the mangrove ecosytem (Fig. 10.17.) Relatively dense layers of microorganisms covering the litter attract macroconsumers which form the main stratum of shredder organisms. How much of the production is recycled to the vegetation is very variable, but it is generally assumed that the mangrove areas supply the neretic water with Particulated Organic Matter (POM) and Dissolved Organic Matter (DOM) (Fig. 10.18.). The Fine particulate matter (FPOM) and the DOM also support heterotrophic bacteria in the soil with 2-3 orders of magnitude greater than in water

209

(Mills, 1981). The bacterial productivity has been calculated to be about 1.6 g C.m-2.day-1 (Alongi, 1988). Mangroves with high productivity are characterized by: • High influx of fresh water • Low salinity • Cloudy-humid climate • High nutrient concentrations in the substrate. Mangrove detritus contributes about 16-20% of the energy requirements of the nearshore benthos (Boto et al., 1991). While 30-80% of mangrove litter fall is consumed directly, the provision of nutrients and therefore consumable energy to the open water is certainly true for highly exposed mangrove areas. However, in more protected areas, accumulation processes with neretic material even being accumulated in the mangrove areas, is the rule. HUMAN INFLUENCE AND USES OF MANGROVE COMMUNITIES Because of their high productivity and the shelter they provide, mangrove forests are key habitats in the life cycle of many marine organisms and are vital to the health and productivity of other coastal ecosystems. They are important as nurseries for young fishes and shrimps, as nesting place for birds, and habitat for numerous invertebrates. (Fig.10.19). Mangroves are important for coastal protection, fisheries productivity, timber, and numerous products utilized by local communities (MacKinnon et al., 1996). Nypa fruticans is one of the most useful of the mangrove plants. Its leaves are used for thatching, umbrellas, sun hats, raincoats, baskets, mats and bags. Stalks are used as fuel and arrows. Sugar, alcohol and vinegar can be obtained from the plant. The young seeds are edible (Fig.10.20). Not only the wood in form of trunks and branches is used, but decayed wood is also used medicinally as are bark, leaves, and fruits.


210


Rhizophora sp.

Sonneratia sp.

1 Production of litter , including shredded matter by herbivorous organisms 2 Organic matter washed from mangrove into waters around the mangroves and into estuaries 3 C1 - organisms , like invertebrate, protozoan and microbial activity forming detrital complex 4 Loss from estuary 5 C2-organisms like detritus - feeding fish, shellfish , shrimp 6 Organic by-products and waste 7 C3-organisms like small carnivores 8 C4- organisms like large carnivores 9 Humans

FIGURE 10.17. Pathways of nutrient flow in a mangrove-fringed estuary (after Saenger et al., 1983).

MANGROVES


211

FIGURE 10.18. Energy flow system of a mangrove forest (after Ott, 1988). C Cm Ct

Chemo-analytical microorganisms Marine consumers Terrestrial consumers

The most useful timber are Rhizophora species. The wood is also used to produce high quality charcoal. Tannins are tapped from Rhizophora species and are used as fishing net preservative, as adhesives, and for tanning hides. Decoction of the bark of Rhizophora mucronata is used for haematuria, diarrhea, dysentery and leprosy. Ceriops tagal species are the most durable of all the mangroves and are used as building material.

DOM Nf

Diluted organic matter Nitrogen fixing organisms

The bark is used to produce dyes for batik and matmaking. Bark decoction is said to stop hemorrhages. Leaves of Avicennia are used for boils and the resin from the bark is used in some areas as contraceptive, and for treatment of skin parasites and gangrenous wounds. The bark and seed of Avicennia alba contain fish-poison and is said to relieve as ointment smallpox ulcers.


212


FIGURE 10.19. Schematic diagram of the interrelationship and function of the mangrove swamp-forests as transition between marine coastal waters and estuary-riverine communities (after Margraf et al., 1996b).

MANGROVES


FIGURE 10.20. Structure, fruit stand and seed of Nypa fruticans (after Margraf et al., 1996b). The seed can float for a long time in sea water without being affected. A B C D

Structure of the palm Fruit stand Germinating seed Seed showing the supportive structure to float in sea water

The fruits of Bruguiera species are used as astringent, for diarrhea, and sometimes in cases of malaria. The timber from Heritiera littoralis is used for boat-building and the ground seeds cure diarrhea. Lumnizera sp. is used as timber, for poles, and a decoction of leaves for thrush. Sonneratia alba and Sonneratia caseolaris leaves are a good fodder for cattle and goats. The fruits of S. caseolaris and S. ovata are edible.

213

Rheumatism is eased by rubbing with fruits of Cerbera manghas. The seeds also contain medicinal oil and the bark contains a purgative. Xylocarpus sp. produce highly priced timber and a bark decoction is said to be good to cure cholera. Mangroves are particularly threatened by largescale commercial wood-chips operations, fish and prawn pond constructions called tambaks, residential and industrial developments. Ironically, the supply of young shrimps and larvae of the milkfish (Chanos chanos) for the expanding pond industries come only from mangrove areas. By this means the genetic diversity of the future breeding stock is in danger. Penaeid prawns are the main target species for cultivation and Penaeus monodon is the most economically valuable species. Also, diatoms (Bacillariophyta) which are used for hatchery in raising shrimps and fish are produced in mass cultures. All these tambaks are dependent on the natural productivity of the reclaimed area. Without proper protection, the values of the marketable and more important, non-marketable values provided by the mangrove forests in form of shoreline protection, waste filtration, and fish fingerling protection can not be maintained. IMPLICATIONS FOR EIA STUDIES Overexploitation, conversion and mismanagement of the mangrove forest areas particularly since 1970 have led to significant losses. The precise extent of mangrove losses in many areas of Indoensia remains uncertain (Giesen, 1993). Therefore, the extent of loss varies greatly and insufficient accuracy of estimates is a major handicap for any management purpose. Environmental Impact Assessment is a vital tool for sound management and conservation and should be an indispensible part of any develoment process. It is a constructive, pro-development management tool that improves the success of and lengthens the life of projects (Carpenter and


214


Maragos, 1989). EIA can also stand for three important attributes of sound environmental impact assessment like “Early”, “Integrated” and “Always”. Not only individual and sectoral environmental parameters but also their placement in assessible ecological data banks are needed. Because mangrove forests are of great value, all proposed projects in these areas need to have a critical evaluation in terms of what will be gained versus what may be lost by altering the natural processes and properties of the ecosystem (Dixon, 1989). SUMMARY Not too long ago, mangrove forests were viewed as mosquito - infested, unproductive wasteland without too many redeeming features. Only the very durable wood of some of the mangrove trees was considered to be an important commodity for construction and for charcoal-making purposes. Therefore the area of mangrove was reduced from about 4.25 million ha to a mere 2.5 million ha in 1990 (Giesen, 1993). Today, it is clear that this valuable ecosystem does not only protect the coastline but is crucial for coastal fisheries which depends on the well-being of mangrove areas.

MANGROVES


THESIS In the tropics soft bottom shores intermingle much more with hard substrates, as with the pockets of sediment forming sea-grass beds in the moats and flats of reefs (Morton, 1990). The estuaries are semienclosed coastal bodies of water which have a free connection with the open sea (Monk et al., 1997). The mixing of estuarine and ocean waters is sometimes inhibited by a high salinity plug so that fresh water does not leave the estuary (Alongi, 1990). The ecology of estuaries and mudflats exemplifies the interdependence of terrestrial and marine systems (McKinnon et al., 1996). Coastal upwelling is another feature in tropical oceans influencing the coastal ecology. The distribution of sediment on inner continental shelves reflects the influence of sediment run-off from the continents wherif mud and coral are most abundant in the tropics, whereas sand is globally abundant. There are indications that low water content is a characteristic for most tropical marine sediments (Alongi, 1990). Sandy beaches, mud and sand flats, seagrass beds, salt marshes, mangroves and coral reefs comprise the greatest variety of littoral habitats found along tropical coastlines.

215

11

ESTUARIES AND SOFT BOTTOM SHORES Friedhelm Göltenboth and Sabine Schoppe

OVERVIEW Soft shores are those where sediments are retained and progradation is taking place, either by entrapment within reefs, or from angles of slope so low that wave run-off has too little energy to carry materials away. There is thus a net accumulation of sediments, which includes a majority of species classified as burrowers. The particle size of a given shore is determined not only by the source and nature of the material, but by their degree of shelter from waves and currents. Particles of flats and beaches range from the finest silt and clay to medium and coarse sands.


216


Soft bottom shores fall according to exposure or shelter into three broad types (Morton,1990): • High energy or open shores: Such beaches are generally silt free and coarse grained • Medium to low energy or protected shores: They are of fine sand with significant amount of silt and organic matter. Clay is absent and no high viscosity shown by mud can be recorded. These type of shores are faunistically the richest of soft habitats. • Lowest energy or enclosed protected shores: Mostly lying in estuaries without wave access. They are accumulations of the finest particle grades like silt and clay. The sticky cohesive mud is poorly oxygenated with often a black sulfide layer almost at the surface. Mangroves are characteristic from half-tide to well above tidal reach. Both sorts of protected shore develop seaward sea grass beds below low water neap and can be white or grey according to the origin of the sandy parts either from the marine corals or from terrestrial basaltic volcanic material. It can be said that wide variations in tropical rainfall lead to the formation of many sedimentary facies and habitats. Mudbanks, green and blue anoxic mud regions, mixed terrigenouscarbonate bedforms, hypersaline lagoons, stomatolites and extensive carbonate shelves are characteristic formations of shallow, tropical seas (Alongi, 1990). Estuaries are often closely associated with the other coastal forms such as embayments, deltas, swamp forests and mangrove. They provide the filtering system and settling basin for river silt and exemplify the interdependence of terrestrial and marine systems. Most of the estuaries in Indonesia would be fringed by mangroves in the absence of man’s activities. Both, estuaries and protected soft bottom shores are productive habitats and highest faunal densities generally occur in moderately exposed and sheltered habitats. Seasonally patterns are found concerning the benthic communities

ESTUARIES AND SOFT BOTTOM SHORES

particularly during monsoons with the accompanying relatively high sediment erosion and low salinities in the surface waters (Fig. 11.1). The effects of upwelling, as found on the Indian Ocean side of the Indonesian arc of islands and the El Niño phenomenon on the intertidal assemblages is less known. Via tropical estuaries about 70% of the world’s continental water discharge and about 74% of the world’s sediment discharge reaches the sea. Further, between-year variations are greater than withinyear variations in tropical oceans. Considering the regional variability of precipitation and high solar insolation sharp gradients in temperature, salinity and dissolved nutrients are usually exhibited in the surface water. Equatorial surface waters, as found throughout South East Asia are characterized by 20-28 oC and 34-35 ‰ salinity. These surface waters are greatly influenced by river-run-off and dilution by monsoonal rains particularly on most continental shelves, like the Sunda and Sahul shelf areas. This phenomenon is called “estuarisation” in which the inner portion of continental shelves consist of low salinity waters (Alongi, 1990). Further, sedimentation rates, erosion and the general distribution of oxygen and nutrients is highly influenced by monsoonal rains and cyclones. Due to the findings that warm-water habitats are intrinsically more fragile, any pollution of tropical coastal habitats is likely catastrophic. ECOSYSTEM FUNCTION Estuaries vary by their physical, chemical and biological properties. They are affected by short and long-term changes in river-flow and tides, seasons and occasional extreme weather conditions. The edges along widening estuaries are often marked by nearly vertical banks, instead of a sloping pioneer zone. The top of this banks are usually at or slightly above the mean high water of neap tides. Burrowing species, like various crabs can generally be found here.


In wider parts of estuaries bare saline clay flats can be found which are rarely inundated. They often have white salt crystals on the mud surface and are sparsely vegetated by a very specific type of perennial, succulent herbs, like Arthrocnemum indicum (Fam. Chenopodiaceae) and Suaeda maritima (Fam. Chenopodiaceae) or seablite. Abiosis The various influencing conditions have a wide range of impact on the water characteristics like salinity, temperature, nutrients level and sediment loads. The interaction of the volume of freshwater flowing to the sea, factors produced by wind and current and tidal mixing determine the rate of change from the freshwater riverine environment to the marine environment. Three classes of stratification in estuaries can be generally described (Levington, 1982) (Fig. 11. 2.): • Highly stratified estuaries where freshwater flows for a considerable stretch over a layer of saline water with little mixing. This type is found where river flow is large compared with tidal flow. • Moderate stratified estuaries where tidal and river flow are more equal and therefore the salinity increases gradually with depth. • Vertically mixed estuaries where vigorous tidal mixing leads to a vertically homogenous column of water, varied with time according to the tidal state. In shallow areas, particularly during dry season, vertical gradients of buoyancy develop, inhibiting vertical mixing and resulting in the formation of a fluid mud layer or lutocline, separating clear surface water from sediment-laden bottom waters. Subtidal mud generally shows less than 50% water, contains more silt than clay and undergoes desiccation with corresponding increases in porewater salinity (Alongi, 1990).

217

Biosis Response and adaptation to changing salinity gradients of an estuary determines the pattern of zonation of species. A change from freshwater to marine organisms can be detected along the length of an estuary. At about 5-6 ‰ salinity there is a distinct dearth of species. This point represents the threshold above which ion regulation is necessary for freshwater animals, but not for marine organisms (Khlebovitch, 1968) (Fig. 11.3). The size to which a particular species will grow is also affected by water salinity. For example, the size of certain bivalves decreases with decreasing salinity (Barnes and Hughes, 1982). Effects of flooding by monsoons and cyclones are a function of the duration and intensity of the disturbance, river geomorphology and faunal composition. Oxygen levels are unlikely to be responsible for any decrease in faunal abundance, because minimum levels are usually associated with post-monsoon periods. The most dominant community of macrofauna on more sandy soft-bottom intertidal shores are the gastropods with averages of up to 5600 individuals per m2 (Alongi, 1990), while on mudflats an average of 305 individuals per m2 have been recorded. In moderately exposed and sheltered habitats usually highest faunal densities are found. The meiofauna in mudflats of mainly Nematoda show density averages of up to 2420 individuals per 10 cm2. The monsoonal regime and torrential rains have detrimental effects on benthic communities whether benthic microbes, meiofauna or macrofauna due to increased sediment erosion and low salinities. Recovery does not necessarily equate with the return of all taxa and species to pre-monsoon community structure. Only crustaceans and oligochaetes are found to be well adapted to withstand fluctuating environmental conditions, while the diversity of copepods decreases at all sites during the rainy season, while polychates are relatively rare in intertidal mudflats.




Estuarine and soft-bottom ecosystem. FIGURE 11.1.

Pinna sp. Scopimera sp. Ocypode sp. Euridicid isopoda Pteriophthalmus sp. Ariciidae

7 8 9 10 11 12

Clypeaster sp. Archaster typicus Eunice sp. Uca sp . Lingula sp. Balanoglossus sp.

13 14 15 16 17 18

Crocodylus porosus Tapes sp. Chelonia mydas Egretta sp. Limicola falcinellus Branchiostoma sp.

19 20 21 22

Scatophagus argus Siganus verticulatus Lathrinus ornatus Leptoptilus javanicus


219


1 2 3 4 5 6

220


FIGURE 11.2.

Stratification classes of estuaries (after Levington, 1982). Numbers express salinity in part per thousand. a Highly stratified estuary

b Moderately stratified estuary

c Vertically mixed estuary



221

• A supralittorial fringe is dominated by ghost or ocypodid crabs, like Ocypode sp. and talitrid amphipods. • An upper midlittoral fringe is dominated by clams, like Pinna sp. (Fam. Pinnidae) and eurydicid isopods. • The lower midlittoral and infralittoral fringes are dominated by crabs and echinoderms. • A mobile fauna can also be recognized consisting of those species which migrate across tidal zones like hippidide crabs and a number of molluscs, including Stenothyra glabrata.

FIGURE 11.3.

Effect of different salinities on the number of freshwater, brackish-water and marine water species (after Barnes, 1984).

The seasonality on mudflats is also expressed in the increased reproductive output of species with planktonic larval stages, like in the case of bivalves. Breeding and reproductive activity is not continuous for most tropical benthic species but triggered by clues. Several breeding habits can be noted: • Continuous breeding throughout the year, irrespective of season. • Continuous breeding with higher activity periods occurring in particular seasons. • Breeding only at a definite time of the year. • Discontinuous breeding throughout the year, often occurring irregularly in response to cues such as wet or dry season, or lunar cycles like in the case of the Nyale or Palolo worm (Polychaeta), found in East Indonesia. In more muddy sandflats a certain zonation can be observed corresponding roughly to the low-, midand high-intertidal zones:

Biodiversity Many marine organisms use estuaries as nursery grounds and spend part of their life cycle in both fresh and saline waters. Estuaries are also used as pathways during their migration. In this variable and dynamic environment, plants and animals must be tolerant of widely fluctuating conditions. The influence of the estuaries on plankton organisms, for example in the Java Sea, is shown by the decrease in number with distance from an estuary (Hahude et al., 1979). In the more saline locations of the Malangke estuary in Sulawesi diatoms (Navicula sp.) dominate while the more freshwater locations are dominated by blue green algae (Anabaena sp.). Estuaries and adjacent soft bottom shores, including mudflats, provide spawning and nursery grounds for many marine fish, crustaceans and other invertebrates. The infauna of the sediment shows considerable variation across the mudflats showing two characteristics: poor in numbers of species , but rich in gastropod molluscs (Fig. 11.4). Species richness as number of species and diversity is similar worldwide in the respective intertidal habitats, but tropical intertidal communities are, on average, subject to greater environmental stress than temperate organisms. A variety of physiological and behavioral mechanisms including


222


FIGURE 11.4.

Records of major animal groups on different shore habitats (after Berry , 1972)

horizontal and vertical migration, aestivation and habitat modifications have been developed to avoid stress. The soft-bodied invertebrates with often worm like forms are either tube-building, sedentary or freely mobile, errant polychates. The errant families of Ariciidae with dull red bodies and the carnivorous Glyceridae and Nephthyidae can be found in more sandy stretches of soft bottom shores. Commonest tubicolous worms belong to the families of Euniciidae and Maldanidae. The echinoderms of protected soft bottom flats include the starfish Archaster typicus and the spatangoid and cypeastroid urchins. Common are also synaptid holothurians and sand-burrowing ophiuroids (Morton, 1990) (Fig.11.5). Usually crustaceans are rich and varied with the burrowing ocupodids Uca sp. being one of the dominant genera. Other burrowing crustaceans generally encountered are Alpheidae or Pistol shrimps. The various trophic types like deposit feeders, scavengers, suspension-feeders, algae grazers and predators are all represented. Shell-crushing predation of intertidal gastropods is relatively abundant.


Burrowing rates of the infaunal brachiopod Lingula sp. are greatly influenced by salinity changes and physical disturbances, like erosion. Coil sand castings crumbling into conical molds betray the presence of hemichordates or early worm like chordate associates. They are deposit feeders on the surface mud, but can also filter particles by the passage of water through gill slits. The nutrient rich waters support a diverse fish fauna. The most abundant fish species are those that have a broad niche, exploiting a wide range of foods and habitats. More than 222 species of fish were recorded from the estuary of the largest Indonesian river, the Kapuas in West Kalimantan (Hardenberg, 1937). In general, about 16 fish families can be regularly recorded in estuaries and soft bottom shores (Whitten et al., 1988) (Table11.1). The great majority of fishes found in tropical estuaries are juveniles. And usually a maximum standing stock of amphipodes and worms correspond closely with the influx of juvenile demersal fishes. Demersal fishes can be subdivided into three groups based on their diet: • Ichthyophagous fishes • Active epifauna and fish-eaters • Sedentary infauna and epifauna-eaters.


TABLE 11.1.

223

Ecological status of some of major fish species living in estuaries and in soft bottom grounds (after Whitten et al.,1988).

Family

Common name

Scientific name

Ecological information

Apogonidae Belonidae

Cardinal fish Needle Fish

Apogon hyalosoma Stongylura urvilli

Carangidae

Jacks and Scads

Gerridae Gobiidae

Silverbellies Gobies

Haemulidae Hemiramphidae Latidae Leiognalthidae

Grunts Halfbeaks Barramundi Ponyfish

Lethrinidae Mugilidae

Emperor Bream Mullets

Sillaginidae

Whitings

Selaraoides leptolepis, Chorinemus tala Gerres nacracanthus Glossogobius celebius, Etenogobius suluensis, Eleotris macrolepis Podadasys maculatus Zenarrchopterus buffonis, Ambasis macracanthus Leiognathus equula, Leiognathus splendens, Secutor ruconis Lethrinus ornatus Liza dussumeiri, Liza vaigiensis Silago sihama

Small nocturnal carnivorous fish Schooling surface dweller; fast swimmer; often jumping; predator of smaller fish Schooling or solitary predator of benthic fauna and plankton

Scatophagidae Siganidae Theraponidae

Scats Rabbit Fish Sea Perch

Toxotidae

Archer Fish

Scatophagus argus Siganus vermiculatus Eutherapon theraps, Mesopristes argenteus Taxotes jaculator

In some parts of Indonesia the estuarine crocodile, Crocodylus porosus, can still be found with a total body length of up to 5.5 m. This animal is able of entering both saline and freshwater. It has developed physiological adaptations which allows it to control the osmotic pressure of its plasma by water reabsorbtion mechanisms in their kidneys and guts. Through nasal glands and glands in the corner of their eyes sodium chlorine can be excreted. Female crocodiles build dome-shaped nests of leaves, grass and peat for their up to 50 eggs. The heat generated by the decomposition of the vegetable matter helps to incubate the eggs. It is assumed that incubation temperatures of up to 30 oC produces all females, while 34 oC and above produces all males, as shown in other groups of crocodiles. Before the eggs hatch, the young crocodiles make high-pitched croaks while still inside the eggs soft shell.

Schooling fish on sandy shores; plankton feeder Benthic carnivorous or omnivorous fish living in groups or solitary in a wide range of habitats Nocturnal predator of benthic invertebrates on sandy beaches Schooling in brackish water; omnivorous; elongated lower jaw Medium sized , commercially valuable carnivorous fish Schooling carnivorous fish feeding on small benthic animals Commercially valuable predator Commercially valuable schooling fish; Benthic diatoms and algae feeder Preferable on sandy shores and in estuaries; digging for worms and crustaceans Algae and bottom detritus feeder Schooling herbivorous fish in muddy brackish water and reefs Medium sized carnivorous fish in brackish water Group-living carnivorous estuarine and mangrove fish; famous for the ability to shoot insect prey with jets of water

The mother then scratches away the hardened surface of the nest material, picks the young up gently in her mouth and carries them away to a secluded nursery in a swampy bank. Both parents guard them there for about a month. The main food of the young crocodiles are insects and small fish and amphibians (Whitten et al., 1988). Areas of mud exposed at low tide offer a rich feeding ground to migratory shore-birds which feed by the thousands on the invertebrate communities (Medway, 1967). Also other waterbirds are frequently found in this ecosystem. For example, in the Mahakam River delta in East Kalimantan a total of 146 species was recorded, including Chinese egrets, Egretta eulophotes and Leptoptilus javanicus or Lesser Adjutant Stork (Eve and Guigue, 1989).




Insight into a soft bottom area. FIGURE 11.5.

7 8 9 10 11 12

Mantis shrimp (Fam. Squillidae)

Blue star fish Linckia laevigata (Fam. Ophidiasteridae)

Sea urchin Diadema sp. (Fam. Diatematidae)

Nudibranch Dolabella auricularia (Fam. Aplysiidae)

Nudibranch Pleurobranchus forskali (Fam. Pleurobranchidae)

Branded pipefish Corythoichtys intestinalis (Fam. Syngnathidae)


225


1 Dugong seagrass Thallassia hemprichii (Fam. Hydrocharitaceae)

2 Fiber strand grass Halodule sp. (Fam. Cymodoceaceae)

3 Brown algae Padina sp. (Order Phaeophyta)

4 Brown algae Sargassum crassifolium (Order Phaeophyta)

5 Holothurian Synapta maculata (Fam. Synaptidae)

6 Horned star fish Protoreaster nodosus (Fam. Oreasteridae)

226


FIGURE 11.6.

Large-scale distribution of soft-bottom benthic biomass in South East Asian Waters (g WW/m2) (after Alongi, 1990).

Dolphins and dugongs are often found in estuaries where they come to mate and give birth. NUTRIENT FLOW The large scale distribution of soft bottom benthic biomass shows relatively high values with more than 100 g WW( wet weight). m-2 for most of the Java and Sulawesi Seas (Fig. 11.6). Mudbank deposits are generally high in particulate nutrients like C, N and P while carbohydrate and plant phaeopigment values are low, indicating a nutritionally poor situation. Carbon


concentrations greater than 5% , nitrogen levels greater than 1% and total phosphorus concentrations of more than 1 mg.g-1(dry weight) of mud are not unusual. However, the ratio of C/N and N/P can vary greatly in tropical sediments. A C/N ratio less than 8 indicates a marine origin, whereas higher values suggest more terrestrial input. Ammonium and silicate concentrations are usually greatest in tropical sediments and one characteristic is the frequent presence of nitrite in the pore waters, an indication of moderate anaerobic conditions.


The productivity of an estuary is highly influenced by the tidal and riverine flows, because they facilitate the mixing and distribution of nutrients. These effects stimulate high rates of primary and secondary productivity. Particularly, the rivers bring nutrients and minerals which replenish the raw materials required for sustaining high productivity. Nutrients are received from three major sources: river inputs, marine inputs and bottom sediments. Regeneration of nutrients across the sediment-water interface is relatively low, despite a sharp gradient in nutrient concentrations between the overlying waters and the sediment. This phenomenon could be caused by the following reasons: • Low rates of plankton production and sedimentation of dead phytoplankton cells • High rates of bacterial growth. In these areas usually a two-layered water environment is created with the salt “wedge” retreating and advancing with the tides. Concentrations of phosphorus, for example, can be more than twice those in the open sea (Soegiarto and Polunin, 1980). In lagoons and estuaries a strong trophic link can be observed between the benthos and species of demersal fisheries. The gross productivity in shallow lagoons can reach rates above 1 g C·m-2·day-1 (Alongi, 1990). Microbial standing stocks, measured as chlorophyll a, are generally low in tropical sediments with 0.3 m girth on 1 ha is around 240 (Schulte and Ruhiyat, 1998). The high diversity and high rate of rare species in Tropical Lowland Evergreen Rainforests makes it necessary to consider also different reproductive strategies (Flenley, 1980). Two categories can be decribed:


• R-selected strategies: Many offsprings are produced with minimal parental investment in each offspring as found in rats, pigs, fish and insects and pioneer plants. • K-selected strategies: Few offsprings, but each receiving a great deal of care like ob served in hornbills, elephants, bats, cows and monkeys. The Shannon-Wiener function gives the mathematical base for the calculation of the richness (H) or the number of species in an area of vegetation: s

H = Σ ( pi)(log2 pi)

i=1

S = number of species pi = proportion of the ith species log 2pi = log 10 pi - log 102 = log 10 pi - 0.3010

The way individuals are distributed between the species is called eveness (E): E = H - H max H max = Log 2 S

S = Number of species

However, the usefulness of calculating diversity is questionable because its biological meaning is unclear (Stocker et al., 1985). The observed high diversity in the tropical rain forests reflects certainly the great structural diversity and the enormous range of potential niches available. Two broad approaches to the problem of the species richness exist: • The resource partitioning hypothesis states that a species will ultimately be eliminated from the community unless it is competitively superior for some resources at least some of the time. • The local history hypothesis stresses the chance processes in determining the compo-

305

sition of tropical plant communities. The competion among species is seen as of minor importance. The inventory of the flora and fauna of Indonesia is still an ongoing process, so that exact quantitative figures for most taxa, in particular invertebrates, can not be presented yet. Utilization of biodiversity in the past was more or less restricted to timber extraction, hunting and collection of so-called minor or secondary forest products. The potential of gathering of other products, as it was done in the past in form of dyes, resins, oils, medical drugs, food, is still not fully appreciated and economical prospecting for these resources has just begun recently. Abiosis The environment of the forest ecosystem consists of (Schulte, 1996): • The atmosphere respectively the local microclimate; • The ion pool bound in the interior of soil minerals, characterized by the parental ma terial for soil formation. This is part of the input vector; • The seepage water leaving the rooted soil. This is the main carrier of output of bioelements in natural forest ecosystems; • Neighboring ecosystems; Originally, the lowlands and submontanous areas were covered by lowland evergreen rainforest. However, distribution of different types of lowland evergreen rainforest is subjected to the gross climatic conditions in the archipelago. Walsh (1996) defines tropical rainforest climate ‘as one with monthly mean temperatures of at least 18°C throughout the year, an annual rainfall of at least 1,700 mm (usually above 2,000 mm), and either no dry season or a short one of fewer than four consecutive months with less than 100 mm rainfall’. Temperature is only limiting the distribution of lowland evergreen rainforest in higher altitudes. However, amount and annual

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306


distribution of rainfalls vary considerably from place to place, depending on the prevailing wind systems and the distribution of land masses. Generally, it can be stated that forests become more seasonal in the eastern part of Indonesia where there are pronounced wet and dry seasons. Two different means of physiological adaptations to water stress can be found: drought-tolerance and drought-avoidance. Trees belonging to the first type have adapted to stand varying water contents within their cells resulting in differences of osmotic pressures, without being harmed. Species belonging to the second type avoid water shortages by developing deep-reaching root systems, small leaves called microphylls, minimizing absorption of radiation by changing leaf inclination or by partial or complete shedding of leaves during dry periods to minimize water losses due to transpiration. Timing of flowering or fruiting can be triggered by temperature, rainfall and amount of radiation, which in turn is influenced by cloud cover. Sunlight, the sole energy source of photosynthesis, is very unevenly distributed in the different strata of the forest. Whereas emergent trees and canopy trees are exposed to full radiation, as little as 1% can reach the forest floor. Therefore, the bulk of biomass is located in the canopy and consequently the major part of primary production takes place here. Richards (1996) compared the upper strata of the forest with the ocean’s photic or euphotic zone, whereas the forest floor equals the oligophotic or aphotic zone being dependent on a steady flow of organic matter from above for the maintenance of this subsystem. This comparison does not hold true entirely, since frequently patches of bright sunlight, so-called sunflecks, can even be observed on the forest floor which appear to have a significant impact on the primary production in this stratum. The unequal distribution of light resulted in different adaptations of plants depending where they are growing, not only depending on their lifeform, whether they are trees, epiphytes or herbs.

TROPICAL LOWLAND EVERGREEN RAINFOREST

Even within the same species, the amount of sunlight that is required or can be tolerated can change during the individual development. An emergent dipterocarp has a crown that receives full sunlight during the whole day, whereas as seedling, it would not only be tolerant to shade, but even would die when subjected to the conditions mentioned above. This fact has to be considered when planning reforestation measures. The comparison of gap plants and understorey plants concerning their adaptation meachnisms to the pattern of sunlight availability showed that all seedlings in a gap have high rates of net photosynthesis, particularly the seedlings of pioneer species. The gap seedlings have significantly less leaf area than that of the plant of the same species growing in the shade, and the stomata density was about 40% greater. The understory seedlings, however, tend to be photosynthetically more efficient than gap plants (Cranbrook and Edwards, 1994). It can be said that there are very important local gradients in micro-climatic factors including light availability, relative humidity, air temperature and air movements. Near the floor, the prevailing conditions are most constant, with low light intensities, moderate temperature, and high humidity. The soil is another important feature determining the type of forest growing on a certain site. The main processes which form soil are the weathering of the parental rocks and the decomposition of organic matter in the form of surface litter layer of dead leaves and twigs, fallen boughs and trunks. Soluble constitutents are removed in solution by a process called leaching. Leached soils are predominantly composed of clay minerals, which are the insoluble products of weathering. In the presence of iron oxides, yellow, orange or red soils are formed. Soils can be classified on the basis of the size of mineral particles. Particles of 0-0.002 mm diameter are clay, particles of 0.002-0.02 mm diameter are silts and particles > 0.02 mm are sands. Fine textured soils, like silty clays, are relatively impenetrable to water. Only via macropores, cracks, animal burrows, and


root channels can water penetrate to deeper soil layers. The total C and N content diminishes usually sharply in the top 15-20 cm, while P decreases markedly. The pH of the soil increases normally from upper to lower slopes. The vertical section through the soil reveals the soil profile developing generally in four steps (Fig. 16.8): 1. Decomposition in the leaf litter layer re leases organic acids which percolate into the surface mineral soil. 2. The chemical weathering of rock minerals and the release of basic cations like potas sium, calcium and magnesium, and silicon is speed up. These minerals are leached. 3. Iron and aluminium oxides accumulate in the soil. The Al saturation percentage in East Kalimantan soils is generally higher than 70%. 4. Kaolinite, the most resistant clay mineral, accumulates in the soil. It dominates in East Kalimantan soils, followed by vermiculite and gibbsite. The resultant soil material is high in iron and aluminium oxides and kaolinite, but extremely low in plant nutrients such as nitrogen and phosphorus, which are rapidly recycled in the litter layers and also low in the basic nutrients such as calcium and magnesium. Soils in the vast areas in the lowland evergreen rainforest covered alluvial plains of Kalimantan are highly weathered, iron-rich soils, relatively poor in basic chemicals with a clay-enriched B-horizon. They are called orthic acrisols (FAO classification or udult ultisols in the US Dep. of Agricult. Classification). These ultisols are the most abundant soils in South East Asia occurring in association with non-basic, geological formations. Further, typic paleudults and typic hapludults (US Dep.of Agric. Calssification) are major soils under tropical lowland evergreen rainforests. They are as acid, vulnerable to soil erosion and infertile as the ultisols.Their morphological and physical

307

characteristics such as mottle formation, soil structure and cutan development, vertical distribution, and porosity are governed primarily by clay content. Soil texture is the primary factor determining the vertical distribution pattern and storage of C, N, and P in typic paleudults. The cation exchange capacity, exchangeable Mg, K, Al, and C, N and P are also closely related with the total clay content. Therefore, soil texture is the most important factor affecting the nutrient status and productivity of typic paleudults and typic hapludults and can change over relatively short distances, independently of the terrain. Its contents of nutrients and grain size, and waterretaining ability are strongly related to the nature of the underlying rock formations. Forests stocking on limestone areas exhibit a more seasonal behavior compared to those on volcanic soils, because of the limited water retention capability of the former. The hydrological cycle of a forested area includes, in general, eight processes (Fig. 16.9): 1. Interception 2. Evapotranspiration 3. Throughfall 4. Stemflow 5. Infiltration 6. Overland flow or runoff 7. Throughflow and 8. Deep percolation. Any condition which enhances water runoff, particularly on hilltops, will cause soil erosion. Tree canopies intercept raindrops while the tree roots stabilise the surface of the soil. A 20-fold increase in soil erosion can be caused by removal of the forest floor litter layer only. Differences in relief can also result in differences in floral composition. Microphyllic trees and shrubs seem to be more abundant growing on the drier ridges and upper slopes, compared to the more humid lower slopes (Cranbrook and Edwards, 1994). Unpredictable and catastrophic natural events may also influence structure and species composition of forests considerably. Events like eruption of

Forest Ecosystems

Profile

Processes

Above ground level

Precipitation Breakdown of plant material by decomposers

Runoff stemflow ... rainfall O Topsoil A Horizon

Start of decomposition

Organic acids H+ Breakdown of clay minerals

Fermentation layer; ....... layer

usually sharp boundary between A & B

Accumulation of Fe, Al Subsoil B Horizon

Losses of Si Transition rather than boundary between B & C

Formation of Kaolinite Parental material C Horizon

Losses of Si, N, Na+, Ca++, Mg++ K+ Weathered material

Drainage of water

1 O - horizon or fertile forest floor with fragmented organic matter and root matter. The cover with loose leaf litter averaging 20 cm depth. Often covered by a very fine mesh of roots ramifying through the litter. 2 A - horizon, topsoil layer or epipedon and mineral horizon with very fine crumb structure with tiny fragments of leaf litter. Often a silty clay texture with visible pores. Color often dark reddish to brown. Very few tiny stones at soil surface. Sharp boundary to O horizon and diffuse boundary to B horizon.

B - horizon or sub-surface and mineral horizon. Mostly a medium angular blocky structure and a silty clay texture. Color often yellowish brown with few visible pores. Medium sized roots throughout the horizon. Diffuse boundary to C horizon.This horizon is sometimes referred

FIGURE 16.8.

to as E horizon and shows the lower limit of major root penetra tion and animal activity C - horizon of weathered and weathering parental material. Stones and weathered shale fragments are found frequently. The soil matrix is often yellowish red or multicolored. Usually no roots visible. Decomposer fungi: 1) Leucocoprinus caepistipes; 2) Phallus indusiatus. Decomposer invertebrates: a) Woodlice (Order Isopoda): (a1) Creeping woodlice, (a2) Jumping woodlice, (a3) Rolling woodlice (Oniscomorpha sp.); b) Milliped (Thyropygus sp., Family Harpagophoridae); c) Termites

Natural soil layers and major processes in a rainforest area (after Cranbrook and Edwards, 1994; Göltenboth, 1990).


Biomass

308


Desscription


1 Huge surface roots ramify over the soil 2 Bark of Dryobalanopsis sp. with large coars flakes

FIGURE 16.9.

309

3 Emergent tree (Koompassia excelsa) 4 Clump of bamboo (Schizostachyum sp.)

The hydrological cycle in a tropical lowland evergreen rainforest (after Cranbrook and Edwards, 1994).

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310


volcanoes lead to the complete destruction of forest over vast areas and to the extinction of endemic species on the slopes of the respective mountain. Earthquakes or heavy rainfalls can cause landslides which bring more restricted forest tracts back to early successional stages. No genetically fixed adaptations to storm damage are known so far. However, some forest formations give the impression of having adapted modificatorily to frequent storms by stunned growth without protruding branches. This sort of forest can be found in constantly exposed areas. Though wildfires are not a common feature in tropical lowland evergreen rainforests, especially during ENSO years (El Niño Southern Oscillation),

they can endanger forests, especially on ridges that are drained well and with trees exposed to lightning (Fig. 16.10). Biodiversity Indonesia’s species-rich forests harbour the world’s greatest diversity of palms with 477 species of which 225 occur nowhere else. Besides these, the dipterocarps are prominent due to their highly priced timber called “meranti” and “keruing”, to mention only two of the most important trade names for a great variety of different plant species. Altogether, an estimated 25,000 species of flowering plants grow throughout the archipelago. This fact makes

FIGURE 16.10. Abiotic factors influencing Tropical Lowland Evergreen Rainforest (after Ashton, 1983).


311


Indonesia the seventh most diversed region in the world when it comes to flowering plant richness. The composition of trees in tropical lowland evergreen rainforests has been calculated with up to 550 tree species of more than 10 cm dbh on a 1 ha plot (Cranbrook and Edwards, 1994) and the larger the plots are made the more different species are recorded. Further, an average of 7-20 giant trees can be found per ha. This high diversity involves large numbers of rare species with up to 62% of the species recorded, represented by a single specimen. For mammals with 515 species, 36% endemic, and swallow-tail butterflies with 121 species, 44% endemic, the Indonesian archipelago is ranking first in the world (Tables 16.1-16.2).

TABLE 16.1.

Group

Comparative estimated total number of major taxa (after McNeely et al., 1990).

Indonesia

World

% of Total

Fungi 12,000 Mosses and Liverworts 1,500 Ferns 1,250 Flowering Plants 25,000 Insects 250,000 Molluscs 20,000

47,000 16,000 13,000 250,000 750,000 50,000

25 9 9 10 33 40

TABLE 16.2.

Island Sumatra Java Borneo Sulawesi Nusatengara Maluku Irian Jaya

Numbers of invertebrates, particularly of insects, are highly speculative, but probably range in the magnitude of 250,000. The original habitat of the vast majority of these organisms is forests. Some species were able to adapt to conditions created by man, but some are dependent of forests as habitats. Consequently, their number dropped sharply with the destruction of forest ecosystems all over the country. Species richness or alpha diversity seems primarily determined by physical resources of the environment, but there is still no final explanation for species richness in tropical forests. Many species got extinct unnoticed, many more are on the brink of extinction.

Group Fish Amphibians Reptiles Birds Mammals

Indonesia

World

% of Total

8,500 1,800 2,000 1,500 500

19,000 4,200 6,300 9,200 4,170

44 42 31 16 11

Comparison of species diversity of some groups of organisms in Indonesian Islands (after MacKinnon, 1981). % end. = Percentage of endemics

Birds spp. % end. 465 362 420 289 242 210 602

2 7 6 32 30 33 52

Mammals spp. % end. 194 133 201 114 41 69 125

10 12 48 60 12 17 58

Reptiles spp. % end. 217 173 254 117 77 98 223

11 8 24 26 22 18 35

Flowering

Plants spp. %end.

820 630 900 520 150 380 1030

11 5 33 7 3 6 55

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312


Biodiversity, however, is more than only species richness. Biodiversity needs also to be defined in terms of genetic diversity, species diversity, and ecosystem diversity (Groombridge, 1992). While genetic diversity refers to the heritable variations within and between populations and organisms and has therefore, a striking impact on the changes of the frequency of genes within a pool, the species diversity is of great ecological importance. The ecological importance of a species is very different and can have a direct effect on overall biological diversity. For example, a dipterocarp species which supports an endemic invertebrate fauna of hundreds of species makes a greater contribution to the maintenance of global biological diversity than an European alpine plant hardly supporting any other organism (Schulte, 1996). Ecosystem diversity is one of the most complex approaches and seems to be only possible to assess on a local or regional basis (Fig. 16.11). Producers Terrestrial ecosystems have, in the steady state, the property of keeping the internal cycle more or less closed. That is the forward reaction by primary producers is balanced by the backward reaction caused by secondary producers. Primary producers in contrast act as sink for ions, secondary producers as source and both produce organic matter with the soil as the corresponding source or sink, respectively. Therefore, organisms have the property to change the chemical state of their environment (Schulte, 1996). The state variables in a dynamic system, like a forest, are the organisms and those variables in their environment which depend upon their activity. Therefore, the following major factors are involved in the ecosystem of a forest: • Producers : Trees, herbs, epiphytes; • Consumers: Herbivores, carnivores, omnivores; • Decomposers: microorganisms; • Dead organic matter;


• Soil solution with its dissolved ion pool; • Mobilizable ion or material pool bound on surfaces of the solid soil phase and in soil organic matter. All state variables vary in space and time and therefore, tropical forest ecosystems are practically defined by the floristic composition, structure and physignomy. Dipterocarp Trees The major forest formation owes its name to the plant family Dipterocarpaceae. They are a quite old group of angiosperm plant which came into existence during the late Cretaceous era, possibly even before the southern continent Gondwana broke into several pieces that drifted apart. This may be the reason why we can find dipterocarps in Africa as well as in South and South East Asia. Quite recently, one genus has even been discovered in South America. Obviously, dipterocarps are rare or inconspicuous in the Neotropics and Afrotropics. Only in the Indomalayan region they are the dominant trees in most Tropical Lowland Evergreen Rainforest types. The greatest diversity recorded for dipterocarps is in Borneo with 267 species consisting of members of the following genera (Table 16.3). Earliest evidence of the existence of dipterocarps in Borneo is from fossil pollen dating back more than 30 million years (Mueller, 1970). Dominating dipterocarps can grow up to 60m high with branchless boles of 40 to 50 m length. Dipterocarps show a high degree of endemism, at least in the non-seasonal forests. This may be due to their inefficient dispersal mechanism which results in the isolation even through minor barriers like small rivers (Ashton, 1983). Most dipterocarps are easily recognized by their cauliflower-shaped crown. The winged fruits also look very characteristically, actually the translation of dipterocarp is ‘two-winged fruit’ (Fig. 16.12). After flowering, some or all sepals enlarge in the mature fruit, becoming wing-like. The different


TABLE 16.3.

Genera

Diversity of dipterocarp genera in Borneo Evergreen Lowland Rainforests (after Cranbrook and Edwards, 1994).

Number of Species

Anisoptera Cotylelobium Dipterocarpus Dryobalanops Hopea Parashorea Shorea Upuna Vatica

5 3 1 7 42 6 127 1 35

Total

267

genera can be sorted into different categories due to the number of wings of their seeds: • No sepals are found in some Vatica. • Two dominant sepals are found in Anisoptera, Dipterocarpus, Vatica, Cotylelobium and Hopea. • Three sepals are found in Shorea. • Five sepals are found in Dryobalanops and Parashorea. However, fruits are not found frequently. Most species are not flowering yearly, but only if conditions are suitable. Flowering can be highly synchronized between individuals of one species. In some parts of the Indomalayan region, mass-flowering can sometimes be observed with also non-dipterocarps being involved (Appanah, 1985). The trigger for the development of flowers is not definitely known yet, but there seems to be a broad correlation between flowering events and the occurrence of droughts. Another possible trigger could be the difference of temperature between day and night during cloudless periods when solar radiation during daytime and back radiation from the surface during nighttime are usually high. Rainless periods over longer times are typical for El Niño years and flowering of dipterocarps

313

seem to be connected to the occurrence of this climatic event (Ashton, 1989). In the Malay Peninsula, thrips, tiny insects belonging to the order Thysanoptera, have proven to play an important role in the pollination of dipterocarps. They comprised 95% of all flower visitors (Chan and Appanah, 1980 cit. in Ashton, 1989). Female thrips lay their eggs in the bud, and their young feed on the growing petals. One female can produce up to 4,000 decendants by the time the flowers are mature. The petals are arranged that the juvenile thrips population is largely trapped within the chamber into which the anthers open. The winged seeds are subject to a high predation, since they contain large amounts of nutrients. Most common are boring beetles of the family Scolytidae which feed on immature and mature fruits alike. After the seeds drop to the ground, squirrels, other rodents and wild pigs are commonly foraging on the fruits. In dry lowland evergreen rainforest in continental Southeast Asia, it was observed that ground squirrels carry away fruits from the mother trees and hide them in the ground. They may therefore play a role in the dispersal of these trees. Most of the dipterocarps have two or more wings which sometimes give them a helicopter-like appearance. Yet, dispersal through wind is only possible, when it is quite strong. Most seeds end up in the close vicinity of their mother tree. It is difficult to imagine, how a plant family with an apparently inefficient dispersal mechanism could be so successful in Southeast Asia. As in many other tropical forest trees, seeds of dipterocarps are viable only for a short period. Further, successful establishment also depends on the presence of appropriate mycorrhizae. However, after germinating the small trees can endure with only very few light for longer periods in order to get a chance to reach the canopy when a gap is created through the dying of a larger tree (Fig. 16.13). Trees die and fall from disease or old age, from windblow or landslides, and cause gaps of varying

Forest Ecosystems



FIGURE 16.11. Idealized insight into a Sumatran Lowland Evergreen Rainforest.

315


C11 P1

C14

C8

P10

P11

P3

P2 P13

C7

C5 P6 P9

P2

C6

C9 P4

C4 C2 P12 C13

D3 P5

P8

P14 D2

P15

P12

C15

C1

D1

C3

C12 C16

C17

Some members of the producers group: P 1 Smooth barked Vatica oblongifolia (Fam. Dipterocarpaceae) P 2 Shallow fission barked Shorea gibbosa (Fam. Dipterocarpaceae) P 3 Cauliflorous Ficus variegata (Fam. Moraceae) P 4 Strangling fig Ficus sumatrana (Fam. Moraceae) P 5 Palmtree Licuala sp. (Fam. Palmae) P 6 Climbing rattan palm tree Korthalsia sp. (Fam. Palmae) P 7 Bush-like palmtree Gronophyllum sp. (Fam. Palmae) P 8 Seedlings of various tree species P 9 Creepers P 1 0 Ant-plant Hydnophytum sp. P 1 1 Tree-fern Asplenium nidus P 1 2 Pitcher plant Nepenthes sp. P 1 3 Liana Gnetum sp. P 1 4 Root parasite on the vine Tetrastigma, Rafflesia arnoldi (Fam. Rafflesiaceae) P 1 5 Zingiberaceae leaves P 1 6 Leaves of an aroid P 1 7 Aroid Amorphophallus sp.

C10

P16

Some members of the consumer community: C1 Sumatran tiger, Pantera tigris sondaicus C2 Sun bear, Ursus malayanus C3 Asian Tapir, Tapirus indicus C4 Sumatran Rhinoceros, Dicerorhinus sumatrensis C5 Sumatran elephant, Elephas maximas C6 Lar Gibbon, Hylobates lar C7 Orang utan, Pongo pygmaeus C8 Slow loris, Loris tardigradus C9 Great red flying squirrl, Petaurista elegans C10 Monitor lizard, Varanus salvator C11 Brahminy kite, Haliastur indus C12 Great argus pheasant, Argusianus argus C13 Stork billed kingfisher, Pelargopsis capensis C14 Hornbill, Rhyticeros undulatus C15 Red jungle fowl, Gallus gallus C16 Birdwing butterfly “ Radja Brooke”, Trogonoptera brookiana mollumar (Fam. Papillionidae) C17 Black scorpion Some members of the decomposer community: D1 Fungus D2 Termites D3 Milliped

Forest Ecosystems

316


Dipterocarpus validus (warburgii)

Dipterocarpus grandiflora

FIGURE 16.12. Selection of dipterocarp fruits.

size in the forest. A gap of at least 20 m2 is the start of a new forest growth cycle. The forest growth cycle can be divided, generally into 3 phases: • Gap Phase: A large mature tree falling over in a closed canopy forest. • Building Phase : the gap is filling with a suc cession of plants. • Mature Phase: Large mature trees fill the space and eventually one falls over. The same change over time in the occurrence of species or succession is to be expected after landsides or fire. The formation of a mature forest from a gap is called secondary succession.


Basic ecological principles for primary and secondary succession are: • Succession proceeds in only one direction with fast growing species, pioneers or colonizers first, replaced by slow-growing species with more specific requirements and great competitive abilities. • New species alter the environment by their very presence. • New conditions are less suitable for the “old stock” of seedlings but more for other spe cies, a situation observable particularly in land slide areas. In principle, trees have adopted three ways to propagate: • From shoots growing out of roots, stumps or fallen trunks. • Establishing seedlings. • From seeds. The reservoir of young trees waiting for their chance is called seedling bank (Fig. 16.14). Pioneer species, on the other hand, commonly endure as seeds in the soil forming so-called seed banks. Vigorous light-tolerant and shade-intolerant species grow up first in the gap creating favorouble conditions for seeds and seedlings of shade-tolerant tree species. Then, the seedlings of shade-tolerant, but not necessarily light-tolerant species, grow up and eventually superscale the pioneer species. In general, pioneer species produce large numbers of small seeds often easily dispersed by wind, squirrels or birds. They do have therefore a wide geographical distribution, show mostly high viability, and the seedlings can grow under favorable conditions very rapidly. The plants, usually forming the building phase, are often trees whose seeds are dispersed by frugivore animals, like the seeds of Dracontomelon dao, being dispersed by macaques and birds. This phase of a forest cycle is characterized by a relatively high density of animals. Mature phase trees are shade-bearers, that is, they tolerate growing in shade, but if more light is available, they grow much faster.


317

FIGURE 16.13. Life cycle of a Dipterocarpus validus tree.

They have often large seeds with a very restricted range of dispersal and therefore, also a restricted geographical distribution can be observed. Each lowland evergreen rainforest comprises a mosaic of gap, building and mature areas and to form a stable and dynamic system it may need up to 500 years under conditions as we do find them in Kalimantan, with one of the largest still existing portions of lowland evergreen rainforest (Fig. 16.15). Identification of dipterocarp species only relying on the leaves requires more experience than the identification with the help of fruits. Dipterocarps

FIGURE 16.14. Seedling of Dipterocarpus gracilis.

Forest Ecosystems

318


have simple, penninerved leaves with articulated stalks. However, even leaves of a single individual can differ considerably in size and shape, mainly depending on their exposure to sunlight. Diagnostic features are the number of nerves, the stipules that surround the buds, and the general form of the blade. However, leaves of tropical trees growing in the same environment often look alike superficially (Vareschi, 1980) (Fig.16.16). A typical feature of leaves of many lowland rainforest species is the drip-tip at the apical end of the leave. At least in some cases, this tip helps to draw off rainwater from the leave’s surface more quickly. Watercloaked leaves are easily settled by lichens, liverworts and

algae, called epiphylles which hamper its photosynthesis and compete for nutrients dissolved in the rainwater. Similarity of leaves between tree families and the unavailability of flowers make characters like sap, bark type, buttress size, leaf-veine arrangements, seedlings, and seeds very important for the identification of the respective plant. Many of the dipterocarps exude a rich scent when flowering. Some produce copious resin or damar. Damar exudes as a result of injury to the bark. Fresh damar is clear but old one is hard and opaque. It was once an important product and chief constituent of varnishes. Fresh damar is collected by

FIGURE 16.15. Composition, biomass and age expectancy of trees after the creation of a large gap in tropical lowland evergreen rainforest (after Riswan et al., 1985).



Dipterocarpus validus (warburgii)

Anisoptera laevis

Shorea ovalis

Hopea rudiformis

319

Vatica javanica

FIGURE 16.16. Some examples of leaves of dipterocarp trees. The drip-trip in most species is a prominant feature.

stingless bees of the family Meloponinae and utilised to form the nest entrance tube. ‘Non-Dipterocarp’ Trees Members of the Dipterocarpaceae are clearly the dominating trees in most undisturbed lowland and submontane forests in terms of grande individuals. However, trees of other families are more numerous in species, though they received only little attention until recently, since the timber of most of them is not as highly in demand as that of dipterocarps. In Kalimantan alone, more than 100 non-dipterocarp tree families of about 360 genera of almost 2,000

species can be found. Besides important pioneer species like, Anthocephalus chinensis and Pertusadina eurhyncha, both belonging to the family of Rubiaceae, a great variety of other families with numerous genera is part of the tropical lowland evergreen rainforest forming the bulk of the understorey layer. The most important groups belong to six families (Table 16.4). Borneo is the center of diversity for the Sapotaceae including five important fruit trees (Table16.5). Two trees of very special features found in the lowland evergreen rainforests are:

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• Eusideroxylon zwageri (Fam. Lauraceae), the ironwood tree growing up to a height of 40m in the forests of Kalimantan • Aquilaria malaccensis (Fam. Thymelaeaceae), a tree held in high esteem due to its incense wood (gaharu) probably caused by fungus attack. Aquilaria malaccensis (Fam. Thymelaeceae), Goniothalmus sp. (Fam. Annonaceae), and Hydnocarpus polypetala (Fam. Flacourtiaceae) are used as medicinal plants. Some of the major features are summarized for the various non-dipterocarp tree families in Table 16.6. About 20 genera of non-dipterocarp trees play an important role in the international timber trade particularly Alstonia sp. (Fam. Apocynaceae). Also Heritiera sp.(Fam. Sterculiaceae) is playing a more and more important role as an attractive veneer. About 4,000 woody species grow in Indonesia’s lowland evergreen rainforests and about 400 play a role in the timber industry. About 260 of them are at present on the market classified into 120 commercial timber “species”. Presently, in most Tropical Lowland Evergreen Rainforests near rivers or in coastal areas, it is not easy to find a mature member of these families, since most of the stands have been overlogged. When standing in an Indonesian forest, it is difficult to distinguish more than a handful species at TABLE 16.4.

TABLE 16.5.

Scientific name

Important fruit trees from their center of diversity, Borneo (after Kessler,1996).

Family

Recorded number of

species Mangifera sp. Durio sp. Baccaurea sp. Garcinia sp. Bouea sp.

Anacardiaceae Bombaceae Euphorbiaceae Guttiferae Anacardiaceae

34 19 25 n.r. n.r.

the first look. Most trees in a similar habitat exhibit a striking resemblance, as was already mentioned for the leaves. Buttresses are another feature that commonly occur in lowland forests. Richards (1996) defines them as”... more or less flat triangular plates of wood subtended by the angle between a tree-trunk and a lateral root running at or little below the surface of the soil”. Though quite widespread, the adaptive value of this structure is still not fully understood. Sometimes buttresses occur together with a shallow root system that prevail in areas were nutrient concentrations are largest near the soil surface, but also in watercloaked areas where deeper soil strata only contain little oxygen. However, there are frequent exceptions from that rule. For example, Dao, Dracontomelon dao, a mango-related species with some of the most conspicuous buttresses that can be encountered, usually has a deep-reaching

Some important non-dipterocarp tree families in lowland evergreen rainforests of Kalimantan (after Kessler, 1996).

Families

Number of genera /species Special features

Rubiaceae Euphorbiaceae Myristicaceae Sapotaceae Guttiferae

about 500 species about 71 genera about 100 species about 100 species about 60 species


Important pioneer plants Important component of strata up to 30 m Important for frugivorous animals tree species growing from the coastal plains up to the montane rain forest


TABLE 16.6.

Major feature

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Major features of the non dipterocarp tree families in lowland evergreen rainforests (after Kessler, 1996).

Families/Genera

Major component of the understorey layer Annonaceae, Euphorbiaceae, Lauraceae, Meliaceae, Myristicaceae, Myrtaceae, Rubiaceae Commercial use as fruit trees Anacardiaceae, Bombaceae, Euphorbiaceae, Guttiferae, Lauraceae, Mimosaceae, Moraceae, Polygalaceae, Sapindaceae Used as commercial timber Agathis, Alstonia, Anthocephalus, Calophyllum, Cratoxylum, Dialium, Eusideroxylon, Gonstylus, Heritiera, Koompassia, Lophopetalum,Palaquium, Poyena, Peronema, Pometria, Pterocarpus,Scaphium, Sindora, Tetramerista Used as timber on a local scale Buchanania ,Dracontomelon, Gluta, Parishia, Mezzettia, Durio, Canarium, Dacryodes, Santiria, Triomma, Octomeles, Elmerillia, Artocarpus, Rhodamnia, Tristianiopsis, Ochanostachys, Scorodocarpus, Schima, Giromiera.

root system (Richards, 1996). In general the buttress formation hypothesis gives the following view (after Whitten et al., 1988): • Buttresses are not increasing the tree’s re sistance to mechanical stress, like trunk snap ping, or reduction of pulling strain on the roots. Another feature of importance for species determination is the structure and coloration of the bark. Even more important information can be obtained by the ‘slash’ which means to remove a chip of the bark with a knife. Coloration of the inner parts, and exudation of sap or resins give hints on the identity of a tree. Typically the bark is quite smooth and thin. One example is the smooth, orange-brown to pinkish-grey bark of the Pelawan tree (Tristania sp.) of the family Myrtaceae. It peels off its bark in large, scroll-like pieces which fall and piles up around the base of the trunk. However, also in this case many exceptions exist. The deeply fissured barks of Diospyros sp. or Koordersiodendron pinnatum more closely resemble those of temperate forest trees like oaks or pines (Fig. 16.17). The most important features for tree identification, besides general growth form, leaves and bark are the generative organs, notably the flowers and fruits. Since they are situated in the upper strata of the forest in most cases, the access

to these sources is somewhat restricted. Generally, trees in tropical rain forest rely more on pollination and seed-dispersal through animals than those of temperate high forest which are commonly pollinated and dispersed by wind. This leads to the development of conspicuous coloration and smells of flowers and fruits and to exposed insertions of inflorescences and fruit stands. This is particularly true for species which specialized in the pollination or seed dispersal through vertebrates. A peculiarity of this symbiosis between vertebrates and trees is the development of cauliflory. Inflorescences directly develop on thick branches and trunks where they are more accessible to larger pollinators, like birds and especially fruit bats. The different species of durian Durio sp. (Fam. Bombacaceae) are among the best known examples and are confined to tropical Asia. The center of distribution is Borneo, where 19 of the 27 known species occur. The large white flowers directly insert at the trunk of the tree and emit a distinctive odor during nighttimes which attracts fruit bats, in particular the Common cave fruit bat Eonycteris spelaea. The durian fruits are big and spiny, splitting segmentally when ripe, to expose the fleshy aril which encloses the large seeds, one to half a dozen in each compartment or locule. The fruits are very heavy, so that another advantage of this

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1

2

3

4

5

FIGURE 16.17. Bark features of some Dipterocarp trees. 1 Scaly bark of Dipterocarpus sublamellatus 2 Deep fissured bark of Hopea beccariana 3 Shallow fissured bark of Shorea gibbosa


4 Laminated bark of Anisoptera curtisii 5 Smooth bark of Vatica oblongifolia


insertion could be the higher stability compared with fruiting on twigs. In other parts of Southeast Asia, durian fruits are commonly eaten by large mammals, like elephants, rhinos, orang-utans, and probably even tigers. These are also attracted by the stench of the ripe fruits and subsequently, disperse the large seeds through gut passage. Maybe, the original dispersers of durian were pleistocene megaherbivores, like the long-extinct elephant-related Stegodon (Janzen and Martin, 1982). Another means of exposing inflorescences out of the surrounding vegetation is by penduliflory. Long inflorescences are developed which are suspended in the relatively open space of the subcanopy. Not only trees have developed this form of flowering, but also certain lianas, like Mucuna longipedunculata whose white boat-shaped blossoms are visited by the Dagger-toothed flower bat Macroglossus minimus, one of the smallest of the flower-visiting bats occurring in South East Asia (Widmann, 1995). Other bat-pollinated plants develop inflorescences which reach over the canopy, like those of Oroxylum indicum, a small tree that can be frequently found in old landslides or river banks (Fig. 16.18). One of the tallest trees found in lowland evergreen rainforests belongs to the family Leguminosae. Koompassia excelsa which can reach a height of 80 m, with a spreading crown of compound leaves with small leaflets. It also shows enormous buttresses, and a columnar trunk with smooth, greyish-green or olive bark. Combs of giant bees (Apis dorsata) often hang under the branches. The timber is hard and heavy but not durable. The straight trunks of many of the emergent trees are often found with rotten inner parts. These empty cores of large trees are important habitats for bats and rats, hornbills and finches, but also for a big number of invertebrates. All these organisms supply the tree with valuable mineral nutrients, particularly in the form of feces (Janzen, 1981).

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One of the largest genera of flowering plants of any description in this region with a remarkable abundance of individuals and number of species is the genus Eugenia (Fam. Myrtaceae). Eugenias are evergreen and shed their leaves generally throughout the year. Flowering is in irregular intervals with species flowering once per year another three times per year. The genus Ficus (Fam. Moraceae) composes of large and small trees, scrambling climbers, creepers or epiphytes. A very remakable fig-tree-form is the strangler which begins life as epiphyte ending up as a gigantic tree composed of different strands of thick trunks (Fig. 16.19). Theory of niche differentiation predicts that individuals of different species only can coexist when they differ at least in one parameter that defines their respective ecological niche. It is still not understood how diversity of tree species in lowland evergreen rainforests has evolved and is maintained. It is difficult to imagine how several hundred species can grow on one forest patch of only few hectares in size without outcompeting themselves (Fig. 16.20). Shrubs Shrubs are woody plants which branch near the ground and do not have a leading shoot in contrast to trees that develop solitary trunks. Main advantage of this life-form is their greater tolerance to mechanical disturbances. In case one shoot is destroyed, there are many others which can replace it. In closed lowland evergreen rainforests shrubs are scarce since they are usually outcompeted by the trees in the race towards the light. They are more frequently found in early successional stages, as landslides or in situations where sunlight can reach the understorey along rivers or on very steep slopes. Because of reduced wind speed in the interior of the forest most of the shrubs have only little chances to get their seeds dispersed by wind. Consequently, the overwhelming majority depend on animals as seed dispersal vectors.

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Cauliflory in Durio zibethinus

Penduliflory in Mucuna longipedunculata

a

b

a) Erect florescence above the canopy approached by the Dagger-toothed flower bat Macroglossas ninimus b) Single flower showing scratches of bats

a) Cauliflory in Oroxylum indicum b) Single flower

a

b

FIGURE 16.18. Different possibilities to facilitate access of larger pollinators (in this case fruit bats) to inflorescences.



325

FIGURE 16.19. Structure of the lower part of a mature strangler fig (Ficus balete) and its surrounding major vegetation, indicating a secondary forest situation. A B

Tree fern species Cyathea sp. Macaranga shrub

One of the most noticable woody shrubs is the Strait rhododendron (Melostoma malabathricum) which flourishes at the forest edge, in clearings or landslips, along the riverside and in open scrubs. The flowers with their bright pinkish colour bloom all the year round but each lasting only for one day. The sweet fruits are very attractive to birds and small mammals hence, the seeds are widely dispersed. A well known shrub throughout South East Asia is Medinilla magnifica. It is most common in open situations in dipterocarp montane forest or near

C Various saplings

D Zingiberaceae species

lakes. It exhibits spectacular pinkish flowers that insert in large inflorescences and is therefore, a much sought for ornamental. Epiphytes and Hemiepiphytes Epiphytes and hemiepiphytes found a mode to avoid the race for light with the much more competitive trees. Instead of starting their life in the dark understorey, they have evolved features that allow them to grow on other plants. They are using the branches and trunks of their host trees as anchorage.

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FIGURE 16.20. Profile diagram of a lowland evergreen rainforest in Borneo dominated by Dipterocarpaceae in an area measuring 60 x 7.5 m (after Ashon, 1982).

For they are not connected to the soil they have to cope with difficult nutrient conditions. Because they can tie up nutrients which would otherwise have fallen through to the soil they are called "nutritional pirates". Most of the epiphytic community relys upon nutrients dissolved in rain, in litter fall, and occasional mineral input from animals. Different ways to cope with the nutrient poor conditions can be observed: • Low nutrient concentration in the own tissue.


• Prolonged juvenile stages. • Reduced size of vegetative parts. • Tapping of unconventional nutrient sources in form of symbiotic arrangements like with ants. • Long lasting leaves. • Construction of nutrient traps in form of leaf containers to trap litter and water. Further, this plants are characterized by pollination of flowers primarily by animals. On the upper boles and branches, light demanding epiphytes abound,


among which aroids (Fam. Araceae), orchids (Fam. Orchidaceae), Gesneriaceae, Melastomaceae, Rubiaceae, Asclepidiaceae and ferns (Fam. Polypodiaceae) are notable. In addition to these are numerous epiphytic lichens and bryophytes, inlcuding mosses and liverworts. However, some mistletoes (Fam.Loranthaceae), although they are autotroph, utilize nutrients and metabolites transported or produced by the trees they are growing on. Therefore, these plants are tree parasites. Major problems epiphytes have to solve are to control their water balance, to gather nutrients, and to disperse their offspring to other trees. For practical reasons we can distinguish macroepiphytes, comprising flowering plants and ferns, and the microepiphytes with algae, lichens, liverworts and mosses. By far, the largest family of macroepiphytes are the orchids, with more than 2000 species occurring in Kalimantan alone, almost all of them being epiphytes. The largest orchid on earth is Gramatophyllum speciosum which has inflorescences about three meters long and with more than one hundred flowers inserted on each. Single plants can weigh more than one ton and were recorded to be chosen as nest site even by birds of prey. However, most other species are quite inconspicuous, some with flowers slightly exceeding the size of pinheads. Typically, orchids exhibit fleshy organs called bulbs or pseudobulbs which serve as storage for water. Another common feature observed in some orchid species is the reduction of vegetative parts. Some species do not develop leaves any more but have green shoots and roots which are able to photosynthesize, like Taeniophyllumsp.(Fig. 16.21). An explanation brought forward for this morphological peculiarity is that nutrients are saved by not investing too much into the vegetative parts, but to concentrate on the production of generative organs, especially pollen and fruits (Benzing and Ott, 1981 cit. in Whitten, 1984). Pollination often takes place by insects which in

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some cases, actively transport the pollinarium firmly fixed onto their back while visiting the flower (Fig. 16.22). Most orchids produce thousands of tiny seeds which are light enough to be dispersed by wind. However, there is not enough space left for storage of nutrients to allow growth after germination. This could only be achieved with the help of symbiotic fungi that help the seedling to utilize the nutrients already available at the site of germination. The next larger group, regarding number of species, is the ferns. Like the orchids, most are small and difficult to spot in the canopy. Exceptions are the bird-nest fern Asplenium nidus that exhibits large and shiny leaves and the stag’s horn fern (Platycerium sp., Fam. Polypodiaceae) with its pendulous fertile fronds and upright fronds forming the ‘nest’. In both forms, older leaves that are dying are not shed off but form a sort of ‘flower pot’ in which nutrients in the form of dead organic matter are trapped. These pteridophytes are vascular plants and exhibit an alternation of generations, with the sporophyte being the dominant generation, which produces sporangia containing spores. Ferns can be recognised by the groups of sporangia, called sori. The sori can be very varied, like elongated along the veins in Aspleniaceae or covering the whole lower surface like in Polypodiaceae. The spores germinate to form a diminutive free-living gametophyte, the socalled prothallium, which bears the male and female sex organs. The sperm swim through a film of water to reach the ovule. After fertilization, the zygote develops into a new sporophyte. As varied as the leaves are the shoots. There are creeping to upright forms, like the tree fern (Cyathea sp.) bearing a crown of large fronds on an upright trunk as much as 4 m high. While many species are epiphytes, particularly the families Polypodiaceae and Hymenophyllaceae or filmy ferns, others are terrestrial, growing on the forest floor like the families Thelypteridaceae, Dryopteridaceae and

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FIGURE 16.21. Leafless orchid Taeniophyllum sp.(after Whitten et al., 1988).

Woodsiaceae. The ‘nest’-forming plants form own so-called ecotopes with unique animal community living in there ‘nests’, sometimes filled with water. Species of arboreal scincid lizards (Fam. Scincidae) living in these restricted habitats are found as well as tree frogs of the family Racophoridae depositing their egg clutches within the water-filled leave axils. Another group of ferns which are growing in their own ‘flower pot’ is the stag’s horn fern Platycerium sp. which exhibits a markedly leaf dimorphism. The photosynthetic active leaves are deeply serrated, whereas basal leaves which collect and hold the nutrients are broader and shaped like oak leaves. In some of the humus aggregated by larger epiphytes, ants build their nests and accumulate the nutrient content of the substrate by bringing food to their nests.


FIGURE 16.22. Drawing of the hypothetical possibility that an insect (Carpenter Bee Xylocopa sp.) visits the flower of the orchid (Phalaenopsis sp.) (A) and leaves the flower with the pollinarium firmly attached on the back of the insect (B). This pollinarium will be inserted into the respective place at the next flower and pollination will take place.

Epiphytes of the genus Myrmecodia have evolved a symbiosis with ants that goes even one step further. The shoots of the plants contain tunnels and cavities in which ants can easily establish their nests. These so-called dormatia provide shelter for the ants and sometimes even food is provided by the plant. It is said that in return the ants are protecting the plant from herbivores. Material collected by the ants in form of prey or feces can be directly absorbed by the plants (Fig. 16.23).


It is well known that epiphytic ant-plants or myrmecophytes are best developed in forests growing on nutrient-poor soils like peat swamp forests. However, they can be found in all forest types with representatives of several different plant families including fern (Lecanopteris sp., Fam. Polypodiaceae), Dischidia sp.(Fam. Asclepiadaceae), Hydnophytum sp. and Myrmecodia sp. (Fam. Rubiaceae). Terrestrial ant-plants include Macaranga sp., known as the world’s largest genus of pioneer plants, some rattans including Korthalsia sp., the rheophyte Mymeconauclea sp., having swollen internodes which are inhabited by small black ants, and even at least one pitcher plant, Nepenthes sp.(Fam. Nepenthaceae). Macaranga species, belonging to the family of Euphorbiaceae, show a substantial radiation of myrmecophytes with at least 23 known myrmecophytic species( Fiala, 1996). These mutualistic effects between plants and animals are of special ecological importance concerning pollination and seed dispersal opportunities. It is therefore an important factor for the high biodiversity in tropical forests. Some Macaranga species, whose center of distribution is in South East Asia, are associated with ants of the genus Crematogaster (Subfam. Myrmicinae). These ants nest inside the stem. The nesting space or dormatia provided by the plant is inside the naturally hollowed internodes. Colonization usually starts at about 10 cm height of the plant. The queen actively bites her way into the interior of the stem and starts laying eggs at the base of the hollowed stem. The emerging brood of workers make many small holes along the stem which serve as nest entrances and exits. The plant provides the ants with small nutrient rich lipoprotein balls called Beccarian bodies. These bodies are characteristically located on the undersurface of young leaves and in some species under recurved stipules. It is generally accepted that the ants protect actively the plant from

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herbivores and from being overgrown by vines by their so-called pruning behaviour. It could be shown experimentally that if ants are removed from their host plant the plant is strongly attacked by gallforming wasps. Seventeen obligate myrmecophytic Macaranga species are recorded. Specific antMacaranga associations do exist: For example: Macaranga pruinosa associates with Decarema sp., Macaranga puncticulata associates with Camptonotus sp., Macaranga lamellata associates with Colobopsis sp. Besides these obligate myrmecophytes, two more types of associations are recorded for the genus Macaranga:

FIGURE 16.23. Cross section through the stem part of Myrmecodia sp. It is an epiphyte which hosts ants in the chambered shoots that provide the plant with additional nutrients derived from feces and the prey the ants store in their nests.

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• Non-myrmecophytic but myrmecophilic spe cies which are visited but not colonized by ants, like Macaranga gigantea • Incipient myrmecophytes which are transitional species between myrmecophilic and obligate myrmecophytes, e.g. Macaranga pearsonii and Macaranga hosei. Among the micro-epiphytes, lichens, bryophytes and algae are most abundant in lowland evergreen rainforests. Mosses and liverworts presumably occur in more humid situations in midmountain localities or in riverine forests. However, they do occupy a wide range of micro-habitats from the upper branches of tall trees, the bark of the trunk, the base of large trees, rotting trunks, termite moulds and even on rocks and stones. Some fig species like the strangling fig Ficus balete are hemi-epiphytes which start their life as epiphytes as well. The fruit of a fig, called syconium contains several tiny seeds.It is a flower-head, turned ouside in, formed from the expanded inflorecene base which curves over and inwards. By this means the true flower lines the inside. Figs may be borne in the leaf axils, on the twigs just behind the leaves, on the branches or the trunk, where they may be arranged in clusters on woody knobs or on short, pendant leafless twigs. Within the fig the minute flowers are of three kinds: male flowers with stamen, female flowers that produce seeds, and gall flowers which are sterile female flowers. The fig flowers are pollinated by tiny wasps of the genus Blastophaga. There are many species of fig-wasps, each restricted to one of a few allied species of fig. The wasp larvae develop inside gall-flowers. The males, being wingless, emerge first and live as adults for a few hours during which they seek out their female companions and inseminate them as they lie curled within the gall flowers. The female later push their way out past the male flowers, picking up pollen on the way, and fly to another younger fig of the same species. Here they attempt to lay egg in the ovaries of morphologically female flowers, by passing the


ovipositor down the style. The relative shapes of ovipositor and style are such that laying can only be achieved in gall-flowers and not in fertile female flowers which are, however, pollinated in the attempt. The microcosmos of interdependent insect life inside a fig is one example of the very fine tuned relations between a plant and its pollinators (Fig. 16.24). The pulp of the fruits is attractive to many frugivore animals, among them potential seed dispersers like birds, bats, and mammals. Hornbills gather to feed on ripe figs and Hose’s leaf monkeys (Presbytis hosei) and gibbons (Hylobates sp.) join in. Giant squirrels (Petaurista sp.) can be found in the canopy and pigs (Sus sp.), mouse-deer (Tragulus sp.) and porcupines relish the fallen figs on the forest floor. The tiny seeds pass through the guts of these animals and some, like the birds, are defecating them on upper branches of trees that are reaching the canopy. The young seedling first tries to accumulate nutrients by developing a dense root systems. Subsequently, it sends down one large aerial root to the soil surface. If it manages to tap the source of nutrients from below it can grow very fast sending down more roots which can subsequently cover the host tree entirely. Additionally the crown of the strangling fig competes for light with the one of the host trees. Subsequently, the host tree may die. It leaves behind a cavity after decaying, surrounded by the trunk of the fig which is formed by the interwoven aerial roots that are now strong enough to support the weight of the strangler (Fig. 16.25). Climbers Climbers are life-forms that are not able to develop a trunk which is firm enough to reach the sunlight in the canopy. They are plants rooted in the ground, with aerial parts supported by other plants. To achieve access to the sunlight, climbers rely on trees on which they attach to grow upwards. However, despite these handicaps climbers are usually abound in lowland evergreen rainforests with up to 40 % of trees with a trunk dimater of more than 15 cm dbh


331

WINGLESS MALE

THE WASP LARVAE INSIDE THE FEMALE FLOWERS. THE WINGLESS MALE EMERGE FIRST, FERTILIZE THE FEMALE PUPAE AND THEN TUNNEL THEIR WAY OUT. THE REDUCTION OF

CO2 INSIDE THE FIG STIMULATES THE

EMERGENCE OF THE FEMALE WASPS.

CAULIFLOROUS FIG TREE

FIG WITH THREE KINDS OF

FLOWERS: MALE, SHORT-STYLED

FEMALE AND LONG-STYLED

FEMALE

MALE FLOWER

WITH TWO

STAMENS NEAR

THE MOUTH

WASP DEVELOPMENT

WINGED FEMALE FIG

WASP WITH EGG

LAYING TUBE, THE

OVIPOSITOR

SEED DEVELOPMENT

SHORT-STYLED FLOWER

IT IS GETTING POLLEN ON ITS BODY

ON ITS WAY CRAWLING OUT OF THE

MOUTH OF THE FIG AFTER HAVING

MATE INSIDE THE FIG. IT THEN

FLIES TO A YOUNG FIG ATTRACTED

BY THE SCENT.

LONG-STYLED FLOWER

YOUNG FIG

GALL FLOWER USED TO LAY INSIDE A WASP EGG

FEMALE FLOWER WILL EVENTUALLY BE POLLINATED

FIGURE 16.24. Plant-animal interrelationship in the pollination cycle of a fig (after MacKinnon, 1962).

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carrying climbers (Whitten et al., 1988). Different groups consisting of species which are not necessarily related coming from at least 24 families evolved different climbing strategies. In general, the climbers belonging to the family of Leguminosae show coiled or convoluted forms with flattened stem, while the Gnetum species (Fam. Gnetaceae) are characterized by regular hoops around the stem of the host plant. The woody stem of the climbers, commonly known as lianas, are prominent in the forest and are looped and festooned at all levels (Cranbrook and Edwards, 1994). The climbing bamboos Schizostachyum sp. is one example of this form of liana which often forms high walls of vegetation which are almost impossible to penetrate, particularly in transition areas between primary and secondary forest. The rattans, one of the climber groups relatively well studied, with genera including Calamus sp., Korthalsia sp., Ceratobolus sp., Daemonorops sp., and Plectocomiopsis sp., also have developed sharp thorns on their stems nobody will forget who got in closer contact with them. The ones at the apical end of the leaf, the so-called rachis, are even recurved and serve as ‘boarding hook’. This enables the palms to overgrow more than one tree even when they have reached the canopy already. Calamus has even hooked inflorescenes, both fertile and sterile, growing from the stem. These climbers belong to the longest terrestrial plants. A rattan measured in Java was 240 m long (Burkill, 1966 cit. in Richards, 1996). Climbers like the camel’s foot (Bauhinia sp., Fam. Leguminosae) can spread horizontally across the canopies of several trees. The brilliant orange colour of their blossoms form showy masses. The climbers from the Family Gnetaceae bear their flowers on raised rings throughout the length of the sturdy stem. All climbers compete with trees for light, nutrients, water and can even mechanically damage trees.


Twiners are able to attach safely to their substrate by winding round it. However, the diameter of the trunks on which they can establish is restricted. They are exceptionally abundant along waterflows and in clearings and can hamper the regrowth considerably. The introduced vine Mikania cordata can kill saplings by just overgrowing them and has therefore to be regarded as a serious weed in reforestation schemes. In gaps, young climbers can attach to fast growing pioneer species giving them an advantage in reaching the canopy layer. Different species of Piper and some Araceae affix to tree trunks with their roots and are accordingly termed root-climbers. The roots of the latter exhibit a root dimorphism with some of them specialized in adhesion and some in nutrient and water uptake (Richards, 1996). Even woody lianas develop only a stem with low diameter compared to their length. Since mechanical stress can be considerable, structural elements have to be developed which sometimes make lianas resemble ropes. Water transport in small stems over long distances may be a limiting factor for the growth of lianas. The longer the “pipe”, the stronger the resistance of the water column. This can only partly be avoided by increasing the diameter of the vessel which lianas frequently do, since the effectivity of the capillary forces diminishes and the danger of vessel collapsing increases with growing diameter. Creepers Only trees with flaking bark, like Tristiana sp. (Fam. Myrtaceae), and Eucalyptus deglupta (Fam. Myrtaceae) do not have creepers. Herbs Only a limited set of herbs can deal with the dim light in the understorey of tropical lowland evergreen rainforest. In this type of forest, this life-form is partially replaced by tree seedlings. Herbs are typically lacking secondary growth and are usually not woody. Herbs in the tropical rainforest are


1

2

3

4

333

FIGURE 16.25. Development of a strangling fig like Ficus sp. (Fam. Moraceae). 1 A fig seed dispersed by a frugivore animal germinates and grows as a hemi-epiphyte on a host tree 2 The fig develops a denser crown and encircling roots after aerial roots have anchored themselves on the ground 3 The host tree eventuallly dies due to the shading out of his crown by the fig tree 4 In some cases the hollow core of the standing fig tree shows still the morphological features of the host tree. These hollow cores are important resting and nesting sites for bats, tarsiers, birds and snakes.

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mostly perennial and therefore some species become rather woody at the base with age but still remain herbaceous towards the apex. The most important plant families contributing to the ground herb layer are: Monocotyledonous herbs: gingers (Fam. Zingiberaceae), aroids (Fam. Araceae), bananas (Fam. Musaceae) and sedges (Fam.Cyperaceae). Dicotyledonous herbs: Gesneriaceae, begonias (Fam. Begoniaceae), and orchids (Fam. Orchidaceae). Large herbs can gain several meters in height. The best known are the bananas (Fam. Musaceae). They are not typical for closed dipterocarp stands, but frequently occur in gaps and along river flows. Usually three species of wild bananas are recorded in Kalimantan: • Musa campestris , which shows the greatest drought tolerance and occurs most frequently in large openings • Musa borneensis, a large species up to 7 m high which has a hanging inflorescence with uniserate flowers, frequently visited by birds, like the Long-billed spiderhunter Arachnothera sp. • Musa textilis, also up to 7 m high with a reddish-purple imbricate male bud. Bananas are a favorite food plant for wild elephants thoughout Sumatra. The same habitat as for the bananas is also preferred by other species often from the aroid family (Fam. Araceae). Their huge leaves, like in Alocasia sp.with up to 4 m height are as characteristic as the spike shaped inflorescence, consisting of very small flowers, enclosed by a spathe. Many Araceae produce a nasty irritant sap. The Araceae family consists of ground-dwelling species, climbers and epiphytes. On some climbing aroids, like Amydrium medium, there is a progressive change in leaf shape as the plants ascend the trees. They germinate on the forest floor and will grow towards darkness with an almost leafless shoot. This behaviour raises the chance of finding a tree trunk to climb. As the plant


grows up the trunk, bigger leaves and eventually flowers are produced. The peculiar Amorphophallus sp. produces a single leaf at a time and after this leaf has died back, the conspicuous flower appears. There are several species of this aroid plants which are common in many forested areas throughout the archipelago. The most impresive is the rare Amorphophallus titanum of Sumatra whose giant flowering spike grows rapidly to a height of 2 m (Fig. 16.26). Several species of the pantropical ginger family (Fam. Zingiberaceae) also belong to the larger herbs in dipterocarp forest. The ginger plants are perennial and grow best in damp and humid shady places. In some of the terrestrial species, flowers are borne directly on underground rhizomes. About 1,300 herbaceous ginger species are presently known from 49 genera. At least 152 species belonging to 19 genera can be found in Kalimantan. The flowers of some ginger species, like Alpina glabra, are spectacular. Pollination is in many cases performed by bees and butterflies. Ginger species occur in various habitats, from dump riversbanks, sunny gaps, and a few species, like Burbidgea stenantha or Hedychium sp.occur even as epiphytes. The gingers are both, attractive ornamentals and famous as spices, dyes, medicine or as food plants. Out of the many plant families considered as a constituent of the herb layer of forests, single species have been domesticated and some became most important crops. Maybe, the most common cultivated aroid, taro (Collocasia esculenta) is not native in the archipelago, although it can be found along all major river flows, even inside closed forest. Most other herbs in tropical lowland evergreen rainforests are much more inconspicuous. Relatively well represented are two dicotyledonous herb families: the Gesneriaceae and the Begoniaceae. Gesners like Cytandra and Didymocarpus are large terrestrial genera, while Aschynanthus is a representative of the epiphytic genera of gesners.


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are pollinated by insects (Richards, 1996) which is unique for this plant family. However, grasses (Fam. Poaceae) are not prominent members of the rainforest flora. An exception from this rule are the bamboos. Usually, only three species of grasses occur naturally in the true forest environment: Sedges (Fam. Cyperaceae) are better represented with about 10 species . One of them is the sometimes very abundant Mapania monostachya. It flourishes particularly on steep slopes with bare soil surfaces.

FIGURE 16.26. The flower of Amorphophallus titanum (Fam. Araceae), a native of Sumatras forested areas. It flowers every few years and is pollinated by flies attracted by its smell like rotting meat.

The family of Begoniaceae has some unique features: • Almost all of the more than thousand species belong to one genus - Begonia. • All begonias show asymmetrical leaves. • They have separate male and female flowers. • Leaf characteristics, rather than flowers, are more striking and diagnostic. Typical features of rainforest herbs are large leaves to catch a maximum of the penetrating lights. Their coloration is usually dark green, sometimes the lower surface is dark red or purplish to reflect the radiation that otherwise would have passed through the leaves. At least in the Neotropics, some grasses

Parasitic Flowering Plants Only two families of root and stem parasites are found in the tropical lowland evergreen rainforest: Rafflesiaceae and Balanophoraceae. Both are characterised by: • Body of the plant exists as a ramifying net work in the tissue of the host. • No leaves or other external orgns are formed apart from the inflorencence and flowers. While not much is known about the Balanophoraceae, the Rafflesiaceae are better studied. This is most probably due to the fact that in this plant family, the world’s largest flower is recorded with a diameter up to 90cm. The scientific name, Rafflesia arnoldi, honours the two persons who first described in 1818 this parasitic flower: Sir Stamford Raffles, the founder of Singapore and Dr. Arnold, a British botanist. The flower they found near Benkulu in Sumatra had a weight of 7 kg and an estimated amount of smelly nektar of 6.8 liter inside the flower. The reddish or purplish-brown flower is flecked with white sports. Like all the other four known Rafflesia species from Sumatra and those from Kalimantan, the brightly colored blooms smell of rotten flesh or carrion. This smell attracts flies which presumably effect pollination (Fig. 16.27). In order that the filaments of the germinating seed may infiltrate a Tetrastigma vine successfully, the vine must be damaged in some way. The way by which this is accomplished is not yet known but it

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seems feasible, that pigs, squirrels, rats and tree shrews may get Rafflesia fruits stuck in their feet while searching foor food. If they disturb the ground around a Tetrastigma vine , the seeds may be rubbed off onto the bark and eventually enter the tissue where they can germinate (Whitten et al., 1984). Vertical Distribution of Major Plants Many researchers state that rain forests consist of three layers of trees with different sizes (Brown, 1919 in Richards, 1996). In the actual mixed dipterocarp, this stratification is hardly discernible. But for descriptive purposes, it has been proven useful to distinguish between different strata. The A-stratum is formed by the largest emergent trees whose crowns are fully exposed to sunlight.This topmost layer is in Borneo composed mostly of Dipterocarpaceae and Leguminosae (MacKinnon et al., 1996). The tallest emergent of all is Kompassia excelsa (Fam. Leguminosae) with up to 80 m height. These high trees are often the sites of extensive honey bee accumulations because these wild bees choose the open, lofty boughs to hang their honeycombs. The B-stratum comprises trees that build the closed canopy. Burseraceae and Sapotaceae are well represented as well as Euphorbiaceae, Rubiaceae, Annonaceae, Lauraceae and Myristicaceae. The C-stratum consists of shrubs, trees of the understorey and subcanopy and immature individuals of the A and B strata. The shape of the tree crowns changes as the trees grow. Young trees tend to have a single main stem or monopodial stem while mature trees tend to be sympodial, meaning without a single main stem at the canopy level (Whitten et al., 1984). The forest floor herbs and the few grasses build their own stratum, together with seedlings of trees. Epiphytes can show up almost anywhere but are most abundant in the B-stratum. Lianas and hemi epiphytes can only be assigned to a distinct strata with some difficulties (Fig. 16.28).


FLOWER, FRUIT AND LEAF PRODUCTION Canopy trees show a wide variation between and even within species in the pattern of flower, fruit and leaf production. At any time of the year, some trees are in flower, some are fruiting and some are developing new leaves. Some species flower and fruit at consistent but non-annual intervals. The dipterocarps, for example, tend to fruit together at long but irregular intervals of 5-7 years. In general, flowering peaks after the driest time and fruiting peaks just before the wettest time, while leaf production peaks just after the driest time. But it has to be stressed again that variations are big from place to place and from year to year. It is further interesting to notice that also fruiting times may be synchronized between species, flowering time is not. This disparity may be caused because pollinating insects are shared between species. There are trees that produce sometimes only sterile seeds after localized climatic events triggered flowering (Whitten et al., 1984). The evidences visible for a kind of seasonal cycle at least in some forest species can be correlated with changes in either the water supply, the hours of available sunshine or the monsoon seasons. Like with the famous Merpati orchid (Dendrobium crumentatum), blooming in an entire area at the same day, triggered by a marked drop in temperature during a thunderstorm about 10 days before this blooming day, most of these flowering and fruiting events are triggered by a certain natural event. It is striking that the 14 wild species of Durio zibethinus recorded for Borneo, the wild rambutan (Nephelium sp.), and wild mangosteen (Garcinia sp.) are fruting in irregular intervals in the forests, but very regular and annually when cultivated. Simultaneous mass fruiting recorded for Dipterocarpaceae has the effect of swamping predators and ensuring that at least some fruits and seedlings escape predation. This is a strategy needed for a species which produces large and energy-rich seeds which are poorly protected chemically.


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FIGURE 16.27. Development of the flowering parasite Rafflesia pricei (Fam. Rafflesiaceae). The Bornean plant parasites on the vine Tetrastigma (Fam. Vitaceae) (1). It grows for about 19-21

months before they open as flower (2). Inside the red cabbage-like buds the male and female flowers

are separate (3). In comparison with the bloom of the Rafflesia arnoldi from Sumatra, this Bornean

species shows more white flecks and has an diameter of the bloom up to 30cm (4).

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FIGURE 16.28. Schematic diagram of a Bornean lowland evergreen dipterocarp forest (after Ashton, 1982). BPA Building phase area after a larger gap 1 Shorea laevis 2 Shorea glaucescens

However, this strategy contradicts the k-selected strategy hypothesis. It can be summarized that mast flowering and fruiting correlates with: • Peak in abundance of certain insect species needed as pollinator, e.g. thrips. • Breeding behaviour of insectivorous birds related to insect abundance. • Breeding of insect-feeding bats. • Breeding pattern of fruit and seed eating rats.


MPA Mature phase area 3 Shorea parvifolia

4 Hopea sp.

• Ranging and migratory patterns of wild pigs like Sus barbatus (Borneo), Sus celebensis (Sulawesi), and Sus scrofa vittatus (Sumatra). • Patterns in ranges of orang utans, hornbills, parrots and pigeons. • Patterns in diet of frugivores with fixed home range such as orang utans and long-tailed macaques.


During those times when there is no flowering or fruiting of the majority of species, the so-called "keystone" species, or other plant species which are fruting at times of low general fruiting play a very important role in maintaining sedentary populations of arboreal frugivores (Howe, 1984). Consumers Plants as Sources of Food Most plant eating animals need to employ certain bacteria, protozoans or fungi to conduct the first stage of digestion, the breakdown of the complex sugar molecule called cellulose which makes up the cell walls of plants. More than 50% of the leaf biomass consist of cellulose. Only with the help of these microorganisms does the widely distributed and abundant food source become accessible to the majority of animals. The bacteria and protozoans can also synthesize essential nutrients like vitamins, except for vitamin A and D and are itself an very important source of protein for the host organisms. In vertebrates, there are two major forms of bacteria-assisted digestions: • Foregut fermentation as found in deer, cattle and leaf eating monkeys • Hindgut fermentation as found in rabbits, horses, rodents and flying lemurs. Herbivores Animal-plant interactions have recently received much scientific attention, particularly in tropical forests. Feeding on leaves was long considered as the simplest form of interaction. However, the plant is not a simple victim to animal predation. Almost all species have developed mechanisms to defend themselves against extensive folivory through the development of poisons, crystals that function like glass splinters, internal spicules like in Araceae, and protective siliceous hairs, like in bamboos. In their subsequent evolution, animals were able to overcome these defense mechanisms, only to face new ones.

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To an animal which depends on leaves as a food souce, the various leaves of a tropicl lowland evergreen rainforest, the phenolic and alkaloid compounds like tannin, lecitin, strychnine, cannabiol, sterculic acid, cannavanine, lignin or nicotine are a “horrible” mix (Janzen,1981). Some seedlings are even able to increase the amount of phenolic compounds in their remaining leaves if heavily damaged. Some animals may be able to eat specific leaves because they have co-evolved with the plant- that is, changes in the plant’s chemical defence will be met by changes in the animals’s digestive capability (Whitten at al.,1984). This coevolutionary arms race makes sure that neither the plant nor the animal wins in the long run. Caterpillars of some species are even known to be able to incorporate the poisons of their host plants and use them for their own defense. A very striking example of this kind of ecological setting is found in the relationship between the milkweed (Asclepias currasavica) and monarch butterflies. The plant produces substances called cardiac glycosides which have a strong effect on the vertebrate heart. Larvae of the butterfly assimilate the substances, which are retained via the pupal stage by adult butterflies, so that the adult butterfly is unpalatable to birds. Folivory poses some challenges to the respective animal species, since common leaves do not contain large amounts of nutrients. Generally, amino acids are rare. In order to cover the demand for these components, large amounts of leaf materials have to be devoured in a relatively short time. Green plant matter is difficult to digest. Some folivores have evolved symbioses with microorganisms that live in their digestive system and have enzymes to break down the long chain carbohydrates. No wonder that larvae of insects, particularly the butterflies, beetles and certain hymenopterans, which comprise a large fraction of the folivore biomass, are merely more than moving digestive systems. Among the largest are the caterpillars of hawk moths (Fam. Sphingidae)

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that are able to devour a leaf within minutes. Attacks on dipterocarps are reported from Kalimantan. The hawk moth is also an example for a Lepidoptera capable to produce sounds, although these are less strident. The animal passes air through the mouth region to produce a squeak. Males of Psilogramma menephron produce a sound by rubbing patches of stiff scales at the apex of the abdomen and on the genitalia to produce a hissing noise. The sounds produced by night-flying moths seems designed for defensive purposes, to confuse predatory bats because these sounds are of high frequency (Cranbrook and Edwards, 1994). The tusock moth caterpillars (Fam. Hymantridae) can defoliate entire stands of Shorea sp.( Anderson, 1961). The stick insects belonging to the order Phasmida are predominantly tropical and include one of the longest insects in the world with up to 30 cm body length. About 300 species are recorded for Borneo alone. Most of these insects are nocturnal and during daytime relay for concealment largely on stillness and the cryptic colours and outline of their elongated, twig-like bodies. Some members of the subfamily Lonchodinae drop their eggs to the ground and tend to live near the ground. Members of the subfamily Heteropteryginae even lay their eggs in the soil. They are heavily built creatures. Members of the subfamily Necrosciinae includes most of the winged phasmids and the majority of this group seems to live in the canopy. They glue their eggs to the trees or push them into cracks in the trees. When some of these insects take a flight, a sudden flash of bright colour ensues.This bright colour dissapears just as suddenly when the insects settle down again. Such “flash colouration” is confusing to a searching predator and is an effective protective device (Bernard, 1991). The leaf insect (Phyllium sp.) resembles a different part of the plant with great perfection. The body shape is leaf-like and like the leaf-like legs greenish or yellowish. A nearly perfect camouflage.


The grasshoppers and crickets belonging to the order Orthoptera and most of them are primary herbivorous consumers in the forest. Most are winged and in some the wings are elaborate modifications that disguise the form of the animals, often as leaf. The grasshopers with their greatly enlarged hind legs can jump to escape predation. The male species have the ability to produce sounds by stridulation for communication and courtship. Bush crickets (Fam. Tettigonidae) process greatly enlarged hind legs and long, thred-like antennae. Some of the members of the bush crickets are perfect mimics of leaves. Crickets (Fam. Gryllidae) sing at night. Their sounds are produced by rubbing together specialised areas at the base of their wings, called plectrum. These insects are generally grounddwellers and omnivorous. The beetle family of Chrysomelidae is a very species rich and mostly brilliantly coloured group of insects chewing leaves. All these animals are part of various food chains or food webs inside the forest (Fig. 16.29). Large body sizes are a characteristic of some vertebrate folivores. There is probably no plant whose defence preclude attack by all herbivores, and there is certainly no animal which can eat all types of leaves. Leaves are eaten by a wide range of larval and adult insects and of mammals. It has been estimated that about 7 12.5% of the leaf production is eaten by insects (Wint, 1983) and only 2.4% by vertebrates (Leigh, 1975). A typical food chain develops in form of a unquantifiable pyramid of species deriving from one big producer, like a dipterocarp tree. A very big number of invertebrates, particularly insects belonging to different families and groups, are usually associated with such a tree, often growing ”like an island” in a green sea as an emergent tree. Birds and other second grade consumers like spiders or reptiles are dependent on these invertebrates, while the top predators occupy the top of the pyramid whether they are air-borne like the hawk or bound to the


ground, like the Marbled cat (Neofelis marmorata) ((Fig. 16.30). Not a single herbivore is known among the amphibians except a fruit-eating frog from Brazil. Among the reptiles, the sailfin lizard Hydrosaurus amboinensis feeds on leaves as adults and on seeds as juveniles, but also on some insects (Visser, 1984,Gaulke, 1989). It is a large agamid lizard with a length of slightly more than one meter. It can be found in or near forest streams, often basking in the sun on exposed rocks or branches. Surprisingly, herbivorous lizards are most commonly found in deserts and on mountains, and least common in tropical rain forests. Whether this is due to availability of basking sites, difficulties of resource partitioning, or some other factor is not known (Rand, 1978). Density of large folivore mammals is low in rain forests (Fig. 16.31). Large herbivores occurring in the Indonesian archipelago include: • Elephants (Elephas maximus), which have a matriarchial or female - dominated society. The calves stay with their mother until about eight years old. The lone bulls live peripheral to the mother-family groups. In open grounds these relatively small animals with about 3 meter height and 5 tonnes weight, may congregate in larger groups, like in some parts of Sumatra, but in forests they travel in small groups only. These animals are browsers, feeding mainly on monocotyledones like palms, grasses, bamboos and wild bananas. Shrubs, leaves and bark supplement their diet. Elephants travel great distances along tradi tional pathways between favorite feeding areas, drinking pools and mineral licks (Oliver, 1978). • The Sumatran rhinoceros (Dicerorhinus sumatrensis) with its two small horns, is the smallest living rhinoceros and the hairiest. It shares its ancestery with the prehistoric wooly rhinoceros (Coelodonta sp.). These animals

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are about 100-135 cm tall, 250-280 cm long, and weigh around 800-1000 kg. They wan der singly or in pairs over wide ranges, brows ing on saplings. They prefer areas with salt sources because as all the other large herbiv ores, they do experience a shortage of so dium in their diet of more than 100 different plant species. Pregnancies about Sumatran rhinoceros are thought to occur only once every four years and result in one calf. The One-horned Javan rhinoceros (Rhinoceros sondaicus) within Indonesia can only be found in Ujung Kulon National Park in Western Java. The average height at the animal’s shoulders is about 140-170 cm and its body is 300-320 cm long. The thick, dark grey skin is deeply folded and hairless. Unlike the Sumatran species, it has scent glands on its feet. It browses on about 190 different plant species. It is also a solitary wanderer and communi cation among the individuals is like in the case of the Sumatran rhinoceros olfactory, particularly through urine squirts on vegeta tion. A pregnacy is estimated to last about 16 months, and the cow-calf relationship about 2 years. Both animals need up to 100 km2 per individual to survive. They visit favourite mud wallows regularly. This might be the rea son why they unlikely will survive. More than US$ 12,000.- was paid in 1995 for a kilo of rhino horn, for sale as an aphrodisiac and cureall in Chinese traditional medicine. Also, all other parts command good prices on traditional medicinal Chinese markets. Ironi cally, the protuberance is nothing else than a huge fingernail, with absolutely no proven pharmaceutical properties. • Tapirs (Tapirus indicus), which are very se lective feeders mainly on saplings of some plants, and dipterocarp seeds, can today only be found on rare occasions in Sumatra. They are extinct from Borneo since 1850. The adults

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Araphium antiphates itamputi

Shorea leprosula

CATERPILLAR OF A BUTTERFLY

Gasteracantha arenata

Tricondyla

aperta

TWIG, LEAVES AND FRUITS OF Shorea leprosula

LEAVES USED BY Lumbricus terrestris

INSECTOVOROUS BIRD Merops viridis

Tupaia gracilis Hylomys suillus

FIGURE 16.29. Simplified food web relationships in a dipterocarp forest.


Acipter sp. SPARROW HAWK

Neofelis marmorata MARBLED CAT

D

Angiope sp. FAM. ARANACIDAE

C

ASIAN PIED STARLING Sturnus contra

BLACK-CRESTED BULBUL Pycnonotus

CHESTNUT-RUMPED

WHITE PHASE ASIAN PARADISE FLYCATCHER Terpsiphone paradisea

FLYING LIZARD Draco volans

BABBLER

melanicterus

Stachyris maculata

B THYSANOPTERA Acaraius grandis FAM. PASSALIDAE

Megaloxantha nigricontis FAM. CANTHARIDAE

Allotropus rosebergi FAM. LUCANIDAE

Chalcosoma moellencampi FAM. ELATERIDAE Paracalais sp. FAM. CANTHARIDAE

Duliticola sp. FAM. CANTHARIDAE

Mormolyce sp. FAM. CARABIDAE Anisolema sp. FAM. COCCINELLIDAE

Diastocera wallchi FAM. CERAMBICIDAE

Camptonotus sp. FAM. MYMICIDAE

Attacus atlas FAM. SATURIIDAE

Dipterocarpus sp.

FAM. DIPTEROCARPACEAE

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FIGURE 16.30. Food web in form of a not quantifiable pyramid of numbers. This type of food chain characterizes such relations which start with one huge producer. The various organisms are not necessarily the very food item of the respective bird or animal but rather represent the large variety of invertebrates living in connection with a lage tree in a tropical forest.


A

Macrochirus praetor FAM. CURCULIONIDAE

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7

8

10

1 9 5

11

2 12

4 3

6

FIGURE 16.31. Some of the most outstanding members of the community of large herbivores in the Indonesian archipelago. 1 2 3 4 5 6 7 8 9 10 11 12

The Asian elephant Elephas maximus (juvenile) The Asian tapir, Tapirus indicus The Asian two-horned or hairy rhinoceros, Dicerorhynus sumatrensis Javan one-horned rhinoceros, Rhinoceros sondaicus Barking Deer, Muntiacus muntjak Banteng, Bos javanicus Anoa, Bubalus depressicornis Sulawesi Black Monkey, Macaca nigra Babirusa, Babyroussa babyrussa Tree kangeroo, Dendrolagus goodfellowi Sugar glider, Petaurus brevis Rusa, Cervus timorensis



•

•

• •

•

•

fur markings are very striking with a black head and front part and a white belly and backpart. This coloration offers an excellent camouflage at night. They live usually in solitary, are mainly nocturnal, and stay usually in their respective area. The Anoa (Bubalus depressicornis) is a dwarf buffalo and an endemic to Sulawesi. Its short sharp horns are dagger-like. It’s the world’s smallest buffalo. It moves singly or in small groups and grazes on grasses, ferns, leaves of ginger, pandanus, figs and even mosses. They do need mineral salt to supplement their diet. These animals do need undisturbed, deep forest as their habitat. The lack of adaptability makes the anoa’s survival very fragile. The Rusa deer (Cervus timorensis) is still a relatively common sight in the the remaining forested areas of Java particularly if they are fringing with grasslands. The Sambar deer (Cervus unicolor) is still common on Java, Sumatra and Borneo. The Wild cattle (Bos javanicus) may stand tall as 1.7 m and weigh around 800 kg. The bulls are dark brown to black, while the cows are orange-brown. Interbreeding with domestic cattle threatens their genetic survival. The Lesser mouse deer (Tragulus javanicus) is not closely related to the true deer. This 20 cm tall animal can still be found in Sumatra, Java and Kalimantan. The male mouse deer does not carry antlers, but has large tusk-like canine teeth on his upper jaw, which it can use for self-defence. It is specialized in forest-floor feeding and usually solitary. It is only the size of a large cat and still widespread in Southeast Asia. The Barking deer or Muntiacus muntjak is a “link” between the mouse deer and the true deer. It has both the canine tusks and the

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stag’s antlers. It is a native of Kalimantan, Sumatra, Java and Bali. • The Black tree kangaroo (Dendrolagus ursinus) is only found in the Bird’s Head Pe ninsula area of Irian Jaya (West Papua). These animals have found their niche by living in trees and brousing on leaves, creepers, and fruits. They are able to jump from tree to tree as wide apart as 6 m. Like all the other marsupials the newborn, very small, blind and na ked kangaroo climbs through the mother’s fur to a pouch on the mother’s belly where it attaches itself to a teat and begins to suck milk. The young kangaroos are carried in the pouch until they are able to feed for themselves. Due to the mentioned weight problem connected with folivory, this type of diet is almost non-existent among the two groups of flying vertebrates, the birds and the bats. However, the Flying lemur Cynocephalus variegatus is a highly specialized folivore. The flying lemurs form an own order of mammals, consisting of only two species. They are not capable of true flight, but with the help of the patagium between their fore- and hindlimbs, they are able to glide considerable distances from tree to tree. High lowland evergreen rainforest with a well developed subcanopy free of obstacles is the optimal habitat and the decline of this habitat is at the same time the main reason for the decline of this amazing mammal. Sap and Exudate Feeders Several groups of animals feed on saps and exudates of trees. The term gumivory has been proposed for this kind of foraging, but not found a wide application. Especially insects of the order Hemiptera are known to tap plants for their sap. Among the insects, the orders Hemiptera and Heteroptera have developed proboscises that are suitable for attacking plants for their sap.

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One of the most oddly shaped bugs living in the tropical lowland evergreen rainforest is the lantern bug (Fam. Fulgoridae). The cicadas (Fam. Cicadidae) spend most of their life of several years underground, as a wingless larva sucking the sap of roots. Ultimately the larva extends its underground tunnel above the ground and emerges. It climbs a stem of a small tree or shrub and takes firm hold with its clawed feet. The brown larval skin splits open and the glittering colourful winged adult emerges. Most cicadas have transparent wings like the one of the Giant empress cicada (Pomponia imperatoria) which has a wingspan of some 20 cm. The cicadas are the most accomplished insect singers. Their very loud songs are produced by tymbals situated at both sides of the first abdominal segments. The stiff cuticular tymbal membrane is drawn inward by a strong muscle and flips back by its own elasticity, thus producing a click. The sounds are amplified by an airsac which can occupy a large part of the abdomen. Only male cicadas possess sound-producing abilities. Some membracid cicadas exhibit unusual thoracal appendices whose function are still subject of speculations among the scientific community (Fig. 16.32). Members of the staghorn and longhorn beetle families (Lucanidae and Cerambycidae) have mandibles strong enough to penetrate the bark of many trees to reach the phloem which transports the metabolic products of the tree. Feeding on saps and exudates from trees among vertebrates is not well documented, but squirrels of the genus Sundasciurus have been observed to show this feeding behavior in Kalimantan (Borneo) (MacKinnon et al., 1996). Bark Feeders In general, bark is only eaten as a sort of supplematary food. It has been recorded as a constituent of the diet of Orang utans (Pongo pygmaeus; Fam. Pongidae), gibbons (Fam. Hylobatidae), elephants (Elephas maximus; Fam. Elephantidae), Sumatran rhino (Dicerorhinus sumatrensis; Fam. Rhinocerotidae)


and squirrels (Fam. Sciuridae). It has been suggested that certain compounds may be actively sought for specific purposes (Janzen, 1978). Tannin-rich material, for example, may be eaten to combat heavy parasite loads or upset stomachs. Mining Feeders Food supply and protection from predators are neatly and economically combined in those animals that mine their food. For miners and tunnellers in living plants or wood, feeding and excavating are the same exercise. Leaf-miners are protected from physical damage and climatic extremes. They are often the larvae of small flies and their body is flattended in shape with mostly pointed heads and their mouthparts are directed forward rather than down. They defecate within their mine and lead a completely self-contained existence until they emerge from their shelter as imago. Nectarivory and Pollination Some animal-plant interactions are also advantageous for the plant partner. One of these is in most cases nectarivory. Animals visit flowers to feed on nectar or pollen and in most cases, contribute to the reproduction success of the plant by pollinating it. Flying animals have proven to be particularly efficient pollinators. The most diverse group are the insects. The morphology of the flower allows some speculations on the potential visitors. These socalled ‘syndromes’ have been summarized by van der Pijl (1960). Disk shaped, fragrant flowers with easily accessible nectar and pollen can be visited by unspecialized forms like beetles or flies. More sophisticated flowers only allow more adapted insects to feed. This limits the number of potential visitors, but at the same time enhances the chance that flowers of the same species are visited in a row which then can be pollinated. Bees are strongly attracted to blue and yellow flowers. Some groups of


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a b

c

d

FIGURE 16.32. Possible functional morphology of small cicadas of the family Membracidae. a b c d

The The The The

animal looks like the feces of a caterpillar animal looks like an old twig spike might protect the animal from being taken by birds animal has a ram-like shape

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butterflies are highly specialized flower visitors. The large proboscis, in particular the one of the nocturnal hawkmoths, make them to be the sole pollinators of some long-tubed flowers that regularly occur in the families of Rubiaceae, Apocynaceae or Orchidaceae. The relatively large night-flying hawk moths are common in rainforests and visit white, heavily-scented flowers. The day-flying butterflies visit preferrably brightly coloured, less-scented flowers, often trumpet-shaped. Flying vertebrates as pollinators are a typical phenomenon of the tropics and do also occur in Indonesia. Among the birds, the most specialized are the sunbirds (Fam. Nectarinidae). They usually exhibit large saber-like beaks and large tongues to reach the nectar source. Although they are able to hover in front of flowers, they are far less perfect than the convergent hummingbirds in the New World which they resemble superficially. However, both families are not closely related. Typical plant species that are pollinated by birds are colorful ,often bright red, but not fragrant. Typical species occurring in lowland evergreen rainforest are for example Clerodendron sp. or the epiphytic Aeschynanthus sp. Fruit-bats are known to pollinate flowers. At least two species, the Common cave flower bat Eonycteris spelaea and the Dagger-toothed flower bat Macroglossus minimus totally depend on nectar and pollen as diet, whereas most other species also feed on fruits. Flowers pollinated by bats open at night and are typically robust and highly fragrant (Table 16.7). FRUGIVORES AND SEED DISPERSAL MECHANISMS Density of single tree species is usually low and individual trees of the same species are often widely scattered over a given area. A prerequisite to this distribution is an efficient dispersal mechanism of their seeds because mere fertilisation of the seed is not enough to ensure survival. Only few species,


among them the dipterocarps, rely on wind as dispersal agent. Most winged dipterocarp fruits fall within 20 m of the parent tree. The majority of fruits of forest trees in Indonesian evergreen lowland rainforest are designed to be consumed by animals by developing a more or less fleshy pulp which covers the seed. Animals feeding on fruits are called frugivores. However, not all animals are also dispersing the fruits and seeds they consume. Besides the ‘fair’ dispersers, there are also animals that destroy the seed and are consequently called seed predators. The boring weevils which infest large percentages of dipterocarp fruits are destroying seeds, so do parrots, rodents and pigs. However, there is always the slight chance that fruits are removed intact from the mother tree and dropped later accidentally. In temperate zones, mice, squirrels and jays which usually consume the seeds are known to store some seeds and therefore contribute to their dispersal. In the tropics, there is no evident necessity for storing food, since fruits are usually available year-round. However, the porcupines Thecurus crassispinis (Fam. Hystricidae) were observed also to hide food in captivity and might therefore also be a candidate as seed disperser.These animals are mixed vegetarians, feeding on fallen fruits, but also on shoots, bark and even tree sap. Birds are also important seed dispersers. They can be divided into two categories (Fig. 16.33): • Fruit specialists, e.g. the hornbills; the impe rial pigeons (Ducula spp.) feeding on ripe nutmegs. The fruits are generally large, with large seeds and are highly nutritious. Major tree families of this kind of fruits are Lauraceae and Myristicaceae. The seeds are usually voided intact, either by regurgitation or defecation. • Opportunists or nonspecialists, e.g. the ma jority of birds are feeding on relatively small fruits, less nutritious and many-seeded. Some birds are feeding extensively on the pulp of fruits, while dropping the seeds directly under the


TABLE 16.7.

349

Generalized comparison of flower type and type of pollinators (adapted from Deshmukh, 1986, in: MacKinnon et al., 1996).

Flower charcteristics bees

Type of primary pollinator Insects butterfly moth beetles

bird

Vertebrates bat

Size and shape

bilateral symmetry

tubular, small

deeply, lobed simple, open

tubular, long large, strong

Colour

yellow, white, blue

red, blue, white

white, drab

red with drab contrast white

Perfume

fresh,weak

fresh,weak

sweet, strong fragrant

absent

strong

Nectar hidden

yes

yes

yes

-

yes

no

Nectar production

day

day

night

day

day

night

Plant example

Orchids

Mussaenda

Ceriops

Rafflesia

Hibiscus

Durian

mother tree, where chances of survival and establishment are somehow limited. Most parrots belong to these so-called pulp predators. They exploit the reward offered by the tree but do not fulfill the service of dispersing their seeds widely. The large flightless cassowaries of the Irian Jaya (West Papua) tropical lowland evergreen rainforest like the Double-wattled cassowary (Casuarius casuarius; Fam. Casuariidae) feed on fruits on the forest floor. These spectacular birds, standing 1.5m high and weighing between 30 and 55 kg, have bristle-like feathers and bony helmets or casques. The female lays three to six greenish eggs on a nest of leaves. The male does the incubating for about seven weeks and cares for the chicks. He is an aggressive defender of the chicks and the innermost of the three toes is armed with a long, sharp claw, a deadly weapon in combat when the bird leaps feet first at its adversary. Most frugivore invertebrates, like wasps, beetles or butterflies are much too small to transport seeds. However, ants have been observed to carry away seeds of figs attached to the pulp which they are

white, red

interested in. Some plant species are adapted to seed dispersal by ants. They have developed elaisomes, fleshy appendices of seeds that usually are rich in fat. These seeds are carried away unless the elaisom is removed from the seed. The latter then is eventually dropped. However, most fair seed dispersers are vertebrates, in particular birds and mammals because their larger body size enable them to transport seeds over some distances. There are no frugivores known among the Indonesian amphibians (and only one frog species in Brasil is known to feed on berries) and only relatively few among the reptiles. The Asian leaf turtle Cyclemys dentata is known to leave its riverine habitat from time to time to feed on fallen fruits. Among the birds the most specialized frugivores are the fruit and imperial pigeons, some parrots, the hornbills, and the flowerpeckers. Fruit and imperial pigeons are relatively large and clumsy birds which feed silently in the upper canopy of the forest. Their coloration is mostly green with some colorful markings. They can feed on

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A OPPORTUNISTS

B SPECIALISTS

Megalaima lineata LINEATED BARBET

Nectarina jugularis OLIVE-BACKED SUNBIRD

CATERPILLAR

APHID

LEAF BUG

BEETLE LARVA

FIGURE 16.33. Interactions of opportunist feeders and specialist feeders with their environment.

remarkably large fruits since they have extendible gapes. After they devoured the fleshy pulp, the seed is regurgitated again. The large Blue crowned pigeon Goura cristata, a native of Irian Jaya (West Papua) feeds mainly on fallen fruits on the forest floor.


Hornbills exhibit spectacular beaks which, despite their appearance, are very lightly built and delicate instruments to pluck even small fruits from exposed twigs which otherwise could not be reached by the heavy birds. The nesting behavior of hornbills is unique (Fig. 16.34). The females is sealed into a tree cavity by closing the tree hole with feces and wooddust and sticky fruits or other food. Finally, only a vertical slit is left open, just large enough to allow the male to feed its mate throughout the nesting period. In Bornean forests, the heavily protected fruits of Meliaceae appear to be dispersed exclusively by hornbills, as only these birds possess sufficiently strong bills to open the thick husk and extract the large seeds (Leighton, 1982). Thirteen species of hornbills are recorded from Indonesia (MacKinnon, 1992b). Twelve species are found in Sumatra, eight in Kalimantan, two species in Sulawesi, and one species in Irian Jaya (West Papua). As already mentioned, parrots are predominantly seed predators. With their strong beaks, they can break even strong seeds. Usually they are noisy feeders and it is no problem to spot trees which are visited by parrots. The smallest avian frugivores are the flowerpeckers. These tiny birds were said to specialize on the fruits of mistletoes. However, at least some species feed on a variety of fruits and also on nectar. Other birds, like the bulbuls, orioles, leafbirds, trushes and starlings also feed on fruits and can play a major role as seed dispersers because of their abundance. The most specialized frugivores among the mammals are the fruit bats. Different species of figs form the staple diet for most of the species, although other fruits are taken as well. Most fruit bats also visit flowers and feed on pollen and nectar. Only limited information is available on frugivory of other mammals. At least the arboreal tree shrews (Tupaia sp.), reaching their greatest diversity in


Borneo with ten of the fourteen species occuring in Indonesia, some of the Bandicotes (Fam. Peroryctidae) found only in Irian Jaya (West Papua), the Long-tailed macaque Macaca fascicularis, and the Black monkey Macaca nigra (Fam. Cercopithecidae), some rodents (Fam. Sciuridae), civets (Fam. Viverridae), like the fruit specialist Arctictis binturong, deer (Fam. Cervidae) and pigs (Fam. Suidae) are known to consume fruits. Their role as seed dispersers, however, remains obscure. Primate fruits include mangosteen, rambutan and durian, notably many of the fruits that people also prize and have domesticated. It has been brought forward by Corner (1949) that bright and contrasting colours, and edible, fleshy and sometimes strongsmelling arils are attractants to animal dispersers. Under these aspects, the spiky fruits of the durian is a very ancient or primitive form of fruit which only splits open when ripe. Plants, paticularly those producing big heavy fruits must be economical and prevent waste. They offer to their animal dispersers tasty, rich, strong-smelling seed coverings. For such large seeds, animal dispersal is obviously necessary. This, the rainforest can provide, e.g.in form of orang utans, elephants and pigs. “Modern fruits”, show the tendency to be less dependent on animal dispersal for their seeds by decreasing size, by a progressive drying up and the aril and the capsule, towards ever more portable, even wind-blown seeds, or towards the succulence of berries. This so-called “Durian Theory”, suggested by Corner (1949) places the durian tree with its heavy, spiky fruit and big seeds at the evolutionary beginning in the development of modern trees. Feeding niches of various animals can also be found regulated by substances in the layers around a seed. For example: • A toxic and distasteful resin in the thick peel of Garcinia is deterring squirrels chewing through the rind but is no deterrent to a monkey, which remove the peel easily, eat the

351

FIGURE 16.34. Nesting behaviour of the great hornbill (Buceros bicornis). The tree hole is partly cut open. This hornbill is native to Sumatra.

It is the largest hornbill in the world with about 1.5 m length from

head to tail.

The female remains walled up until the young has been hatched.

Than the partition is removed and the female helps in feeding the

chicks.

The chicks are re-sealed into the hole until they are big enough

to emerge.

jucy pulp, and swallows the seeds which pass undamaged through the digestive tract. • The orang utan has a real competitive advan tage over other frugivores like gibbons and monkeys due to his tolerance of bitter and sour young fruits (MacKinnon, 1974). • The extremely toxic seed of Antiaris toxicaria, which contains glucosides, are eaten by macaques and dispersed with their feces (Janzen, 1983).

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INSECTIVORES AND OTHER INVERTEBRATE-FEEDERS Most insect-eating organisms in Indonesian tropical lowland evergreen rainforest are other insects. Carabid (Fam. Carabidae) and cicindelid beetles (Fam. Cicindelidae) and ants (Fam. Formicidae) forage on the ground. Especially the latter have undergone a massive adaptive radiation in tropical forests and are virtually omnipresent. Ants have very varied diets: some are predators, some specialist feeders on fungi or plant material. All ants form colonies, in which there is usually one, sometimes more, egg-laying female and many smaller, non reproductive workers. In an established colony, large numbers of winged males and females are periodically produced, leaving the nest in swarms and mating in flight. After mating, the male die and the female seek a suitable nest site to found a new colony. One of the more conspicuous ant species is the Giant ant (Camponotus gigas). It usually wanders singly on forest paths, measuring about 3 cm. While this giant species is normally not aggressive at all, the Weaver ant (Oecophylla smaragdina) which lives in colonies inside a leaf ”castle” of joined together leaves, are extremely aggressive. Because of the aggressiveness of some of the predator ant species, they are often spared by other insectivores. Some more defenseless insects have evolved ant-like body shapes which shun away potential predators. This kind of imitation is called Batesian mimicry. Groups of poisonous or otherwise dangerous organisms which are not necessarily closely related, sometimes exhibit strikingly similar coloration patterns or body shapes. This kind of mimicry is called Müllerian mimicry (Fig. 16.35). This redundancy of signals make the learning process to avoid this prey easier for predators. The tiger beetle (Fam. Cicindelidae) is not completely defenseless, since it has strong mandibles and maybe this form of mimicry is rather Müllerian than Batesian.These beetles are fierce predators themselves and their larvae are also carnivores.


Different groups of wasps, including the quite dangerous Banded Hornet (Vespa tropica) and the Lesser Banded Hornet (Vespa affinis), mantispid neuropterans, asilid flies and dragonflies belong to the most effective aerial insectivores. The latter can sometimes be observed hovering above the canopy, well away from any bodies of water to which most species are restricted. About 300 species of Odonata occur in the vicinity and aquatic habitats of the rainforest areas of Borneo. The aquatic larva and the flying imagos of the two suborders, the Anisoptera (dragonflies) and the Zygoptera (damselflies), are preying mainly on insects. Anisopteras hold their wings outstretched when they rest, the Zygoptera hold their wings close while resting. The territories of Calopterigidae and Euphanidae, both Zygoptera, are always in the vicinity of fallen logs near or inside of rivers and rivulets, but the different species choose areas with waters of different current velocities. Wasps are represented by solitary and social forms. Solitary wasps, particularly, capture small creatures, like spiders, caterpillars and other insects and store these in their nests as food for their developing young. They construct nests, usually of mud, in cavities or on open surfaces. Potter wasps (Eumenes sp.) make urn-shaped nests with a neat funnel-shaped opening. The mantises (Mantodea) are medium to large sized predaceous insects with front legs which they dart out to catch their prey. Sexual cannibalism is common among mantises. The male is often consumed during mating and even when the head and thorax of a male are consumed, mating can successfully be completed. Many mantis species are cryptically cloured and excellently camouflaged. The Flower mantis or Orchid mantis (Hymenopus coronatus) has the middle joints of the two hind legs widely expanded and resemble the petals of flowers. It resembles a large four-petalled flower. This camouflage serves a double purpose: it protects the mantis against predators, like birds, and serves to


lure prey, such as bees and butterflies which visit the flower for nectar. Spiders (Fam. Araneae) are predatory arachnids represented in the forest by a very large number of species. Most spiders hunt on the ground or the vegetation. The web spiders are able to tap the source of flying insects by building webs in potential flight corridors with the help of silk threads produced in their spinnerets. Spiders are abundant in the forest, mostly active by night, occupying varied niches, from streams to the tree-tops. While one of the largest nets are set by the silk spiders Nephila sp., the most numerous group of spiders are the

ANT FAM. FORMICIDAE

353

jumping spiders (Fam. Salticidae).The comb-footed spiders (Fam. Theridiidae) are usually very abundent on low vegetation, while in the litter layer, the family Oonopidae has its main niche. Some spiders are beautifully marked with patterns of metallic hairs, while others particularly, the genus Myrmarachne mimic species of ants in appearance and behaviour. A very interesting spider according to its trapping behaviour is Liphistus sp.. It lives in burrows provid with a hinged trap-door and several communication lines to inform the occupant of the landing of an insect prey.

TIGER BEETLE FAM. CICINDELIDAE

PREDATORY BUG

FAM. NABIDAE

PARASITIC WASP FAM. ICHNEUMONIDAE

FIGURE 16.35. Ant and ant mimicry. The overwhelming abundance of ants in the rainforest and their ability to defend themselves effectively led to a number of imitations which shun away potential predators from otherwise harmless arthropods.

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Almost all forest amphibians feed on insects, forest arthropods, and other invertebrates when they become adults. From Borneo about 183 amphibians have been collected, about half of them arboreal, while on Sulawesi only about 30 are so far known. Many of the amphibians are endemic and many more can be detected. This is also true for Irian Jaya (West Papua) were 176 amphibians have been recorded so far (Petrocz and Raspado, 1984a). Frogs and toads are conspicuous components of the ground community and they feed on termites, ants, small flies and other invertebrates. The majority of amphibians produce large-yolked eggs and lay them generally in water or wet places. The young hatch as larva, called tadpoles. These tadpoles are entirely adapted to life in water, respiring by means of feathery external gills. During their growth the larva undergo changes in a process called metamorphosis. First, the external gills become covered, than the limbs grow from bud-like origins and the tail progessively degenerates. The imagos are semiaquatic or terrestrial, even aboreal and are mostly adapted for locomotion on land and in water. While adult frogs typically feed on living prey, tadpoles generally feed on macrophytes, algae and sometimes carrion within the water column.One toad, found in the lowlands of Sulawesi (Oreophryne celebensis) is renown for the fact that the eggs develop directly into miniature toads without going through a tadpole stage. Among the true forest species, the genera Rana, Bufo, and Megophrys are the dominant ground dwellers, whereas the Rhacophoridae prevail in the vegetation (Fig. 16.36). Many toads and frogs can be identified by their calls. This is very needed for the identifiction of the tree and bush frogs which is the most diverse group of forest amphibians. Many tree living frogs spawn on tree branches overhanging pools and streams and lay their eggs in a foam nest. The emerging tadpoles drop directly into the water below. Most stunning of the canopy frog dwellers is the Wallace’s flying frog (Rhacophorus


nigropalmatus). The webbed feet, expanding during the jump, are presumed to give some degree of uplift, carrying the frog long distances among the tree tops. In principle the amphibian community can be divided ecologically into aquatic or riparian, terrestrial and/or fossorial or arboreal species. The riparian community has usually the largest species of both frogs and toads. Generally, almost all frogs are nocturnal and show a very variable niche occupation and sometimes bizarre morphological features and behaviours. Some of them are polymorphic in coloration like the day and night active Smooth guardian frog (Rana palavanensis). The male of this frog species guard the eggs after they have been laid by the females on the forest floor until they hatch, and then carry the tadpoles on their backs to the water. Others exude sticky secretions from glands to repel soldier ants, like the Red-sided sticky frog Kalophrynus pleurostigma. The Bornean horned frog, Megophrys nasuta, is a leaf-mimic, staying motionless on the forest floor, preying on large insects and snails. The poisonous rock frog, Rana hosei, derived its name from its toxic skin secretion. Among the order of Apoda, the caecilians (Fam. Ichthyophiliidae) show a worm-like body with short tails and no limb or limbgirdles. They live a burrowing mode of life. The left half of their lungs is degenerated and with their up to 135 cm bodylength they easily can be taken as snakes. They live in damp soil and live on invertebrate prey. Among the reptiles, most of the lizards (Suborder Sauria), in particular the Agamidae, Gekkonidae and Scincidae are insectivorous. The latter family is predominantly ground-dwelling and forages in the leaf litter. In several genera, a reduction of the foreand hindlimbs occurred as an adaptation to locomotion in microhabitats with narrow crevices (Brown and Alcala, 1980). The ribs of all sauria species are movabale and in one case extensions of the ribs form the gliding


membranes of the flying lizards (Draco sp.) (Fam. Agamidae). They glide rather than fly with the aid of the expanded patagium on each side of the body. These agamids are specialized ant eaters. Males are agressively territorial, extending and lowering their brightly coloured throat flaps in display. The Gliding gecko, Ptychozoon horsfieldii, is thought to steer with its wide tail as it decends through the air. This animal has flaps of skin on the sides of the body and broad webs between the fingers and toes. To cast off the end of the tail in cases of emergency, a property known as autotomy, is a remarkable ability of some lizards. The tail does not snap between two vertebrae, but fractures across the weak central part of a vertebra. The tail regenerates but never attains the original length.

355

The Agamidae, which include the relatively abundant skinny long-legged, long-tailed Green crested lizard, Bronchocela cristatellus, do also occupy various niches from the seashore to the primary tropical evergreen rainforest (Fig. 16.37). Tropical lowland evergreen rainforests often give the impression that they do not contain birds at all. But all of a sudden one can be surrounded by a large noisy flock that moves quickly through the vegetation. These so-called “bird waves” are a typical feature of all tropical forests. They contain different insectivorous species which congregate outside of their breeding seasons.Such flocks comprise the core species which are almost always present, like warblers, flycatchers, whistlers, whiteeyes, frequent participants, like flyeater, fantails,

FIGURE 16.36. Niche occupation by various amphibia in Kalimantan forests (after Denzer, 1994, pers.comm.). 1 2 3 4 5 6 7 8 9 10

Rana cancrivora : Rana erythrea : Bufo melanosticus : Rana chalconota : Rana blythi : Occidozyga laevis : Megophrys nasuta : Anolopos jaboa : Rhacophorus micropalmatus Staurois natator :

Mangrove forests Open areas near rivers and rivulets Open transition areas Secondary forest floor in leaf litter Banks of rivulets in forested areas Near sidepools or backwaters of rivulets in forested areas In leaf litter of primary evergreen lowland forests Banks of rivulets in primary forests : In high trees of primary evergreen lowland forests In crevices in the ever moist rocks behind waterfalls

Forest Ecosystems

356


and occasional participants, like greybirds, cuckooshrike, monachs, tailorbirds,and starlings. Also, larger birds are regularly present, as drongos, orioles and sometimes even cuckoos or woodpeckers. Drongos are also following the diurnal migratory pathes of macaques from their resting trees to the food trees. These mixed flocks have been interpreted as a means to increase food supply during times of food shortage by increasing the catch advantages for the members of the flock. Squirrels, like Sundasciurus sp., were observed to accompany mixed species flocks. Avoidance of predation and more effective foraging have been proposed as adaptive value of such aggregations. Other birds feed solitary like the forest kingfishers or the pittas, and are rarely or never encountered in mixed species flocks. The largest group of insectivores among the mammals are definitely the microbats. They are strictly nocturnal and have developed an ultrasonic location system for their prey. The design of this system and the overall morphology reflect the mode of feeding. Strictly aerial feeders which hunt above the canopy, have far-carrying ultrasonic calls and long, narrow wings which allow a fast flight. Species that glean insects within the vegetation, have highfrequency calls that permit a high accoustic resolution of their environment but do not carry very far. Their wings are usually short and broad which make them slow, but highly maneuverable. Other insectivorous mammals comprise shrews, tree shrews and some rodents. However, research results on the diet for most species are not available yet. A specialized insectivore is the Scaly ant-eater Manis javanica (Fam. Manidae). Its body is completely covered with scales which are hair derivates. With its strong claws, it digs out nests of ants and termites that are ingested with the help of a 40 cm long and sticky tongue. The curved claws are so large in proportion that the the sole of the foot cannot be placed flat on the ground: in effect, a pangolin walks on the sides of its feet. If attacked


they roll up into scaly ball in order to protect the nonscaly underparts. Palaeontological finds have shown that a giant pangolin lived in the middle Pleistocene on Java and Borneo. This animals was about two and a half the size of the existing pangolin or about 3 m body length. A very strange specialist of the AustraloMelanesian region, feeding mainly on insects and earthworms is the Short-beaked echidna (Tachyglossus aculeatus). This egg-laying Monotremata lives in the lowlands of Irian Jaya (West Papua). The female lays one egg a year and carries it around in a pouch on her belly. After about 11 days the baby breaks out and suckes inside the pouch on milk secreted from slits in the mother’s abdomen. The youngster stays in the pouch until its spines interspersed in the fur become uncomfortable for the mother. The youngster is than parked in a burrow and fed every second day until it is weaned (Petrocz and Raspado, 1984a). Other specialists are the tarsiers. Three species are found, all of which are strictly arboreal and nocturnal: the western Tarsius (Tarsius bancanus) on Sumatra and Borneo, the Sulawesi Tarsier( Tarsius spectrum), and the Philippine Tarsier (Tarsius syrichta). They represent one of the smallest members of the primates with a head-and body length just 10 cm, a tail 20 cm long and an overall weight up to 120 g. In contrast to all other members of this order, tarsiers seem not to feed on any plant matter (Niemitz, 1988). Besides insects, their diet also comprises small vertebrates. Tarsiers are strictly nocturnal. Their eyes in relation to the size of the skull belong to the largest of all mammals. They can turn there heads 180 degrees in any direction without changing the position of the body. The animals locomote with frog-like leaps of up to 2m from one tree trunk to another.With their long legs they attain a firm grip on the tree branches, supported by enlarged finger parts in form of terminal sucking pads. Their mostly naked tail is used as an additional tool for holding


1

5

357

4

2

3

6

FIGURE 16.37. Spatial distribution of Agamidae (after Denzer, 1994, pers. comm.). 1 2 3 4 5 6

Brochocela cristatella Draco volans Gonocephalus liogaster Aphaniotis fusca Draco melanopogon Gonocephalus grandis

: : : : : :

Stems and bushes of transition area and secondary forests Stems of trees in transition areas and secondary forest Smaller trees in secondary and primary forests Bushes and smaller trees in primary forest Trees in secondary and primary forest Shrubs along rivulets and rivers in primary forest

onto the tree trunk. Their social unit is formed by two adults, with long-termed monogamous relationship, and one or two immature offsprings. Their monogamous territorial life has some advantage, like: • Minimizing reproductive wastages and a kselected strategy for the care of the one young born at a time;

• Minimizing time spent in conflict with

neighbours;

• Minimizing time spent competing for mates.

The territory of the Sulawesi tarsier (Tarsius

spectrum) is defended from other tarsiers by songs.

Every morning, during dawn, the entire family returns to their nest hole and do sing a complicated territorial song comprising of squeaks and series of sequals.

Forest Ecosystems

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The Western tarsier (Tarsius bancanus) does not show this behaviour. At dusk, the tarsier family leaves their nest, often in hollowed trees, which can be found in a wide range of habitat types from urban areas, secondary growth, mangrove, lowland forest, riverine forest and mountain forest with densities ranging from 3-10 individuals·ha-1 (MacKinnon, 1981). Most hunting occurs in the lower parts of the surrounding up to 10 m above the forest floor. The home range is about 1 ha and during hunting they use regularly the same routes. There is some overlap of home ranges of different families but the sleeping sites are generally the exclusive area of one family. There are similarities between gibbons and Sulawesi tarsiers, like territorial calls, specialized form of locomotion, longevity (up to 25 years), specialized diet, and the stable nature of their environment. The niche they occupy is sometimes compared to the niche occupied elsewhere by a small owl, which is, however, not able to move in the dense undergrowth (Fig. 16.38). Like owls, the tarsiers have large eyes, the ability to rotate the head, a completely noiceless locomotion, and a similar range of prey species. Carnivores Carnivores are defined as organisms that prey on vertebrates. Though ants may be able to overwhelm small vertebrates, most carnivores are vertebrates themselves. Besides the carnivorous reptiles, and birds, like the birds of prey, there are two important groups of mammal carnivores: the canoid which includes the dogs, martens and the bears and the feloid which comprises cats and civets. Reptiles are diverse and abundant in tropical regions. They are found in many niches from the sea to the primary forests. In the tropical lowland evergreen rainforest they exploit the full range of habitats from the tree-tops to the soil, and water of streams and rivers (Fig.16.39).


Among the birds of prey the Indonesian national bird, the garuda or Javan hawk-eagle (Spizaetus bartelsi; Fam. Accipitridae) is one of the flying top predators. This bird is mainly feeding on large birds and medium-sized mammals and needs an estimated 20-30 km2 of forest and forest edge to support it. Despite the fact that it has been declared the national bird of Indonesia in 1993 it is one of the most endagered birds with only 50-60 pairs remaining in 1995 (Soezer and Nijman, 1995). In Indonesia, the place of the top predator is held by the Sumatran tiger (Panthera tigris sondaicus). Diversity of carnivorous mammals in Indonesia is generally high with recorded 20 species of carnivores, including cats, bears, civets, weasels, otters, badgers, and mongooses. The tiger (Pantera tigris sondaicus) is the largest and one of the most endangered carnivores still found at some places in Sumatra. Adults can measure two and a half meters and weigh over 200 kg. The Clouded leopard (Neofelis nebulosa) is entirely arboreal and is the largest cat found in Borneo. It is too, highly endargered, while the leopard or panther (Panthera pardus) is still found on Java, as it has adapted well to man-induced environments. The Leopard cat (Felis bengalensis) is the smallest and due to its astonishing adaptability they are even seen in villages. The Fishing cat (Prionailurus viverrinus) gets much of its prey by wading through rivers and mangrove forest in Sumatra and Java. The most frequent encountered carnivores are the Common palm civet (Paradoxurus hermaphroditus) and the Masked palm civet (Paguma larvata). Also, the Small mongoose (Herpestes javanicus) is still common. These primarily nocturnal species can be found in plantations, orchards and suburbs and they are even entering roof spaces in houses. Mongoose, like the Small Asian mongoose (Herpestes javanicus), were originally found only in the western part of Indonesia. Today, these mongoose, together with the Sunda civet (Viverra


tangalunga), the Small civet (Vivericula indica), and the Common palm civet (Paradoxurus hermaphroditus) are also found on some islands east of Sulawesi for reasons not yet fully understood. Weasels and martens are the least known carnivores. While the Mountain weasel (Mustela lutreolina) is bound to areas above 1 500m, the Malay weasel (Mustela nudipes) is recorded for a wide range of altitudes. The Yellow-throated marten (Martes flavigula) is widely distributed in western Indonesia. The martens are opportunistic hunters and prey on small mammals, birds, amphibians,and insects. They do eat fruits occasionally. Near rivers and lakes, one of the three otter species is occasionally found. The Small-clawed otter (Aonyx cinerea) can also be encountered in mangroves and ricefield areas. It seems to feed exclusively on crabs. As other otters (Lutra sumatrana, Lutra perspicillata) it is an excellent swimmer and diver. The otters are usually catching a wide range of aquatic prey. In villages located near the forests in Sumatra, the most fearsome occasional visitor is the Sun bear (Helarctos malayanus). This smallest bear in the world has enourmous hooked claws, making them accomplished climbers and very dangerous, when they are accompanied by their offsprings. This plodding, short-sighted, shiny-coated animal eats entire bees nests, termites and also the nucleus of the sprouting part or “heart “ of the coconut palms. Considering the still ongoing destruction of habitat, the extinction of most of these large predators in the wild seems to be inevitable. Omnivores Some animals can not be categorized in a special feeding guild as ‘herbivore, ‘insectivore’ or ‘carnivore’, since they forage on food belonging to all or a combination of these categories. Selection of forage can be a function of habitat, seasonality, age, previous experience, just to mention a few.

359

Reptiles (Reptilia)

Monitor lizards Varanus salvator occur in very

different ecosystems, they are excellent swimmers

and juveniles and semiadults are also good climbers.

Monitors feed on crabs, fish, mammals and carrion,

juveniles seem also to prey on arthropods (Gaulke,

1989).

Birds (Aves) A very spectacular group of birds, the birds’s of paradise (Fam. Paradisaeidae), feed on fruits and insects from the 42 known species 26 are known from Irian Jaya (West Papua) and two from the Moluccas. They do live in the tropical lowland evergreen rainforest and in the mountain forest. All the species belonging to this family of Paradisaeidae show gorgeous accoutrements in form of coloured brest shields, like the Magnificent riflebird Ptiloris magnificus, elongated wiry tail feathers, like the Raggiana Bird of Pradise, Paradisaea raggiana or flank plumes, like the King Bird of Paradise Cicinnurus regius. These brilliantly ornamented males engage themselves in sometimes very elaborate ritual dances on special trees or dancing grounds to attract a mate. After mating the female alone builds the nest and tends the young. The bowerbirds are another fruit and insect eating bird group known for a very specific behaviour in courting rituals. The males attract their mating partners with highly decorated bowers built on the forest ground. Species groups build bowers according to one of the three basically different plans: simple platforms, avenue bowers, and maypole bowers. When decorating the bowers, males choose their ornaments according to colour. The platform building catbirds tend to select greenish objects, avenue builders prefer black and blue berries and green and blue fruits, while maypole builders take red and yellows. As soon as a female enters the bower the male starts to dance and displays colorful objects, like

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1 Strangling fig tree used as nesting place for the tarsier family 2 Single tarsier feeding on a grasshopper 3 Pangolin (Manis javanica) digging up the nest of termites 4 Mantis sitting on a flower (Hymenopus coronatus) 5 Web of a silk spider (Nephila sp.) 6 Moon rat Echinosorex gymnurus, filling during nighttime the niche occupied during daytime by the Common tree shrew (Tupaia gracilis) 7 Tarsier in their nest 8 Leaping tarsier

FIGURE 16.38. Territories of tarsier families in a lowland evergreen rainforest (after MacKinnon and MacKinnon, 1980).



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FIGURE 16.39. Niche occupation of some snake species from the sea to the primary forests in Insular South East Asia (after Denzer, 1994, pers. comm.). 1 2 3 4 5 6 7 8 9 10 11

Half-banded laticauda, Laticauda semifasciata : Seashores with tidal flats and seagrass beds Mangove blunt-headed tree snake, Boiga dendrophila: Mangrove trees Common cobra, Naja naja : Inhabited areas Common bronze-backed snake, Dendrelaphis pictus : Inhabited transition areas Elongate-headed tree snake, Ahaetulla prasina : Inhabited areas on shrubs Reticulated phython, Python reticulatus : Transition areas between plantations and forested areas Arboreal rat snake, Gonyosoma oxycephala : River banks Rhabdophis sp. : River and creek areas Worm snake, Calmaria sp. : Leaf-litter area of primary forests Paradise snake, Chrysopelea paradisi : Canopy of primary forest Wagler’s pit viper, Tropidolaemnus wagleri : Overhanging twigs along creeks and rivers in primary forest areas 1 2 King cobra, Ophiophagus hannah : Forest Floor

berries, to the female. As soon as the male has succeded in luring the female into the bower mating takes place. The female lays their eggs in a potshaped nest built in a tree some distance away. Marsupials The marsupial of the family Peroryctidae found only in Irian Jaya (West Papua) has some members, like the Spiny echymipera (Echymipera kalubu), taking fruits, insect larva, and molluscs. The same is true for the Cape York rat (Rattus leucopus).

Monkeys (Primates)

The long-tailed macaques (Macaca fascicularis)

occur in closed forests as well as in mangroves and

feed on fruits, leaves, bark, arthropods (including

crabs) and molluscs. Other Mammals Wild pigs are somewhat more restricted to forest ecosystems. However, all six species recorded from Indonesia feed on a variety of plant and animal matter. Two of these pig species, the endemic Bornean Sus barbatus barbatus and the only non-

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endemic pig species in South East Asia, the Sumatran Sus scrofa vittatus are not endangered. All these pig species pile up a nest when due to give birth. It is usually made of stems, often from saplings of dicotyledones, ginger and palms. This dome of plant material offers shelter for the piglets during their first vulnerable hours and days. The nest site is defended by the sow. Faunal Parasites Parasites are organisms that are extracting metabolics from their host organisms in order to accomplish their own life cycle. Parasites can be reasons and vectors for epidemic diseases. Classical parasitology only considers eucaryotic animals as subjects of research. However, viruses, bacteria and fungi can occupy a comparable ecological niche. Among the animal parasites members of the protozoa (single-celled animals), plathelminthes (tape worms) and nemathelminthes (round worms) are the most important ones which live inside the body cavity of their hosts and are called endoparasites accordingly. Several arthropods, in particular mites, chiggers and ticks (suborder Metastigmata or Ixodiodea), as well as fleas, lice and different types of flies (Diptera) are the most common ectoparasites. The mammalian ectoparasites are charcterised by the following parameters: • They are subject to little predation or parasitation while on the host. • The chemical composition of blood varies very little between species of mammals. • Movement of parasites between hosts assisted by the movement of the host. • They spend most of their life on the host. The parasitic fleas forest rats are carrying, belong all to the family of Pygiopsyllidae, while the fleas carried by commensal rats belong all to the family of Pulicidae (Durden, 1986). Mites can be locally abundant particularly during dry conditions


and in a handful of leaf litter hundreds of mites from many species and many parasitic can be found. In well-balanced (that is: evolutionary old) parasite-host relationships the former does not kill the latter, since this would also cause its individual death. Co-evolution has therefore lead to a state where the two live in balance. Parasitism in the animal kingdom is the rule and by no means the exception. It is next to impossible to find a wild living bird or mammal which is not infested with parasites. For example, one Musschenbroek’s rat from Sulawesi was infested with 129 mesostigmatid mites, 7 astigmatid mites, 4 ticks, 79 sucking lice, and 3 pseudoscorpions (Durden, 1986). Sometimes parasites can even evolve to symbionts as is the case with some gut-inhabiting microorganisms of herbivores which enable the breakdown of the cellulose in the plant matter which otherwise would be unavailable for the host. The parasites, a human visitor in tropical lowland evergreen rainforest is most likely to come across, are mosquitoes. Particularly abundant are the diurnal tiger mosquitoes Aedes sp. which can easily be recognized by their black-and-white color pattern. In dense populated areas they are important vectors for dengue fever. Different species of Culex and Anopheles are mainly crepuscular and nocturnal. The latter is vector of malaria. Land leeches Haemadipsa sp. are abundant in tropical lowland evergreen rainforest throughout Southeast Asia. However, in upland forests they can even become a nuisance to all warm-blooded animals, and humans. These blood-sucking leeches loop over the fallen leaves or hang from the vegetation, waving sinuous bodies in the air to sense the appraoch of any animal that will provide them with a meal. Attached by its sucking mouth piece it rides on its host until after feeding. A single meal may provide sufficient sustenance for three to eight month (Fogden and Proctor, 1985).


Decomposers Decomposers break down dead organic material to water, carbon dioxide, minerals and other simple chemicals which can again be consumed by green plants. Dead organic material occurs in form of leaf litter, dead wood, animal carcasses and feces. Most decomposition processes take place in and on the forest floor, since most organic matter accumulates there. Although decomposition is an integral process in any ecosystem, only few studies have been conducted on that topic in tropical rainforests. Swift and Anderson (1989) have identified the main factors influencing decomposition in tropical rainforest ecosystems: • Climate • Evapotranspiration • Micro-environmental effects (at the actual site of decomposition, e.g. canopy, soil surface, soil) • Moisture • Temperature • Seasonality • Litterfall • Leaching from leaves • Edaphic factors: Physical and chemical • Resource quality • Degree of lignification • Macro- and micro-nutrients • Soluble organic molecules • Presence of stimulatory or allelopathic molecules • Decomposer community. The decomposer community plays an essential role in maintaining the high productivity of the forest. They regulate the flow of energy and nutrients within this ecosystem (Fig. 16.40). Three methods are frequently applied to measure rate of decomposition: 1.The annual input of organic matter to the decomposer community (F) and the mean

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annual standing crop (nett accumulation of plant litter at the soil surface) (X) are meas ured. The ratio is expressed in the turnover coefficient k: k = F/X 2.Net bags with organic matter are exposed and their weight is measured after defined time intervals. Due to decomposition the weight decreases as a function of time. 3.Measurement of soil respiration. Data for decomposition within Insular South east Asia are only available for Sarawak (Swift and Anderson, 1989). Weight of leaf litter exposed to net bags decreased 7-30% after the first month, 25-52% after three, and 30-90% after nine month. Duration of decom position is also strongly correlated to the quality of the resource. Woody branches for exam ple were not decomposed faster, than in temperate forest. Generally the perception of quick nutrient cycles therefore holds not true for all tropical rainforest conditions. Most important decomposers are bacteria, fungi, protozoa, annelid worms and arthropods. Again quantitative data at least for the overall soil and litter macrofauna (not all taxa play a role in decomposition) are only available for Sarawak, Borneo (Collins 1980; Anderson et al., 1983 cit. in Swift and Anderson, 1989) (Table 16.8). In the process of decomposition there seems to be a certain succession of decomposers. Microorganisms, fungi in particular are the first settlers on dead organic material, breaking down the macromolecules as polysaccharides and lignin. Superficially the fungi look plant like. Their most observable manifestation is the fruiting body. However, these are short-lived extensions of the main mass of tissue, the ramifying thread-like underground mycelium. Actually they are nothing else than densly interwoven thread-like parts of the mycelium called hyphae. The fruit bodies produce spores which germinate into new mycelium. All

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fungi lack the pigment chlorophyll found in green plants and therefore can not utilise light energy. Fungi therefore live either as parasites or as saprophytes drawing nutrients from dead remains. The absorption of nutrients takes place via the mycelium consisting of hyphae which spread in soil, or within the tissue of other organisms or their dead matter. Particularly saprophytic fungi play an important role in the decomposition processes by breaking down dead organic matter. They produce enzymes that can degrade the tough plant tissue. The nutrients like nitrogen, potassium and magnesium are than available for other organisms. Therefore, fungi and microrganisms are resposible for the mineralisation wherby organic matter is converted to inorganic forms. These inorganic compounds are essential for the growth of vascular plants and the roots of many plants, including many trees, have mycorrhizal associations with fungi. As a result, almost all mineral nutrients are reabsorbed and very little is lost. Fungi can be microscopic small or large. The larger fungi are divided into two main groups, the ascomycetes with many forms of fruit-bodies and the basidomycetes. The latter family is for example associated with orchids. While the fruit-bodies of the harder bracket fungi are often perennial, those of many other fungi appear only at certain times of the year. Wet situations stimulate the formation of fruit-bodies. Animals feed partly on the microbial aufwuchs, so that it is difficult to decide, whether they really belong to the decomposer guild or should be termed as grazers. Annelid worms (Order Annelida) are much rarer in tropical soils than in temperate ones. The role of other soft-bodied invertebrates like the landturbellarians living in damp forest floor areas is not yet fully understood. This is also true for most of the roundworms or nematodes. These free-living roundworms, ranging in length between 0.2-6 mm, can be plant-root and microbe-feeders or predators


on protozoa and small mites. They are sometimes very abundant in the topsoil layer with more than an estimated 7 million individuals per cubic meter. The role of the woodlice (Order Isopoda) in the decompoition processes of the forest floor is also a wide field for research. At least four eco morphological groups can be recorded (Cranbrook and Edwards, 1994): • Runners; they have smooth, elongated bod ies and long, strong legs.

FIGURE 16.40. Simplified diagram of main pathways of non volatile nutrients in the decomposition processes in a tropical lowland evergreen rainforest. Herbivores and predators are excluded (after Jones, 1996).


TABLE 16.8.

Soil and litter macrofauna in Sarawak (after Collins 1980; Anderson et al., 1983 cit. in Swift and Anderson, 1989). The decapoda are not part of the soil or leaf litter community, but may play a role in decomposition.

Animal biomass (mg wet weight per m2) evergreen rainforest ANNELIDA Hirudinea (Fam.Gnathobdellida) Oligochaeta (Fam.Megascolecidae, Fam. Moniligastridae) MOLLUSCA Pulmonata CRUSTACEA Isopoda 31 (Decapoda) Myriapoda Diplopoda Chiliopoda Symphyla ARACHNIDA (mainly Fam. Araneae) INSECTA Diplura 43 Blattodea Isoptera 522 Coleoptera Formicidae Orthoptera Others 64 Total

365

2739

• Creepers; they have broad, flattened bodies with short legs and a reinforced dorsal ex oskeleton. • Jumpers; they respond to sudden disturbances with high somersaulting jumps. • Rollers; they have a very thick dorsal exoskel eton and roll into a ball if disturbed. The millipeds, particularly the large glossy milliped Thyropygus sp.(Fam. Harpagophoridae) feeds on any kind of vegetable detritus. The body segments are fused in pairs so that each apparent segment bears two pairs of legs. The legs move in synchronized waves.

Alluvial forest

Tropical lowland

12 1003

1 645

19

0

31 (710)

(0)

110 79 10 128

11 370 10 171

48 162 1818 361 134 61 244

121 494 527 29

4520

Termites (Order Isoptera) are among the bestknown decomposers, since they are known to attack timber and can cause considerable economic damage. It is far less well known that besides the dry woodfeeder some species do also break down leaf litter, the majority is feeding on rotten wood (rotten wood feeder), a small group is specialized to feed on mosses and lichenes, and some even feed on humus as soil-feeders. In tropical lowland evergreen rainforests on Borneo 59 species have been collected, showing the richness of this locality. Termites can represent 60% of the soil- and litter macro-invertebrate

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individuals in the tropical lowland evergreen rainforest, accounting for 42% of its biomass. Termites live in colonies in highly organized societies. One, occasionally more fertile females, the queen is accompanied througout her life by a fertile male and produces hundreds, in some cases thousands of eggs daily. The larvae develop into adults of three casts: • Workers, responsible for construction and maintenance of the nest, gathering of food, tending the eggs and larvae, feeding the queen and the king and the soldiers. • Soldiers, responsibel to defend the nest. Their mouth-parts are so modified for defence pur poses that they are unble to feed themselves. • Reproductives, called alates who develop wings and swarm at certain times of the year, flying from the nest to seek a partner of the opposite sex. The new pair will shed their wings and mate at a new nest site and estab lish a new colony. Termites can built their nest in the soil or above ground. Nests can be found on trunks, in butresses, in tree stumps, hanging from climbers or on leaves. The most numerous termites found on the forest floor are members of the fungus-cultivating macrotermitine subfamily. They are responsible for most of the consumption of organic matter. They lack micro-organisms in their gut helping them to break down cellulose. Instead, they cultivate the fungus Termitomyces which breaks down for them celluose. The leaf-litter feeding termite of the subfamily Nasutitermitinae are also common and characterised by a long snout or nasus. With the help of symbiotic micro-oranisms in their gut the termites are able to break down celluose, the main constitutent of any plant litter. It has been calculated that the termite number per hectare tropical lowland evergreen rainforest exceeds 15 million (Cranbrook and


Edwards,1994). Termites play an important role in forest dynamics by three major factors: • They consume large quantities of dead or ganic matter which they transform during this process. • They translocate organic matter. • They are an important food resource for other animals. The larva of a very special guild of flies feed on decaying plant material. These flies have stalked eyes as adults. In the family of Tephritidae the males have much longer eyestalks, while in the family of Diopsidae, both sexes have stalked eyes. They are usually found near small creeks in the forest and the eyspan in some males may reach 20 mm, compared with a body lenth of only 8 mm. The males are frequently engaged in highly ritualised flights to win a harem. Coprophages are feeding on feces of other animals, still able to utilize organic matter that was left over by the digestive processes. Scavengers feed on animal carcasses (Fig. 16.41). Among these are also some vertebrate species like the Monitor lizard Varanus salvator or the wild pigs. SPATIAL DISTRIBUTION OF ANIMALS IN TIME AND SPACE Theory of niche separation predicts that different species can not exploit exactly the same set of resources at the same place and time. According to the principle of competition exclusion sooner or later one species would displace the other. There may be many constellations in the forest where exactly that happens, but it is a process which is extremely difficult to observe under the complex interrelationships of a tropical forest. The manner in which simlar species are able to co-exist in the same area is termed niche differentiation. This can be effected by spatial seperation, dietary seperation, temporal seperation, or a combination of all of these factors.


Segregation in Space Just as the trees and vegetation can be zoned horizontally so can the animals. Unfortunately, very little quantitative data on the topic are available for Indonesia, although qualitative observations offer good opportunities for further research. Animals can move between zones, but, in general, each forest layer tends to have its own characteristic complement of animals. The most important determinant for the respective niche occupation is the availability of food and therefore, the feeding habits of the respective animals. Certain animals are well represented in a large variety of ecosystems, others are only found in the forest but there from the ground floor to the canopy level, and others are striktly bound to one certain niche whether on the ground floor, the middle layer of trees or in the canopy of large emergent trees only. One example for the occupation of a large variety of niches in various ecosystems is found in scincid lizard species occuring syntop in low secondary and primary forest, in cultivated areas and areas down to the seashore (Fig. 16.42). One species, Tropidophorus beccari, is restricted to the vicinity of creeks, others forage on the ground under fallen logs or in the leaf litter, whereas some are arboreal (Denzer, 1994). A good example for the representation of one group of animals, in all layers of the forest, all being opportunistic daytime feeders living on both insects and vegetarian matters, are the squirrels. • In the canopy two species of large squirrels (Ratufa affinis and Ratufa bicolor) are found in Sumatra, one in Java (Ratufa bicolor) and one in Borneo (Ratufa affinis). • In the middle layer of the canopy live smaller squirrels like the Common plantain and slender squirrels (Collosciurus notatus) and the small est squirrel of the world, the tiny pygmy squirrel (Exilisciurus exilis) with only 11 cm bodysize.

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• On the ground several squirrels can be found, the most common being the three-striped ground squirrel (Lariscus insignis). In Borneo it was shown that during nighttime the respective niches are occupied by various flying squirrels (MacKinnon et al., 1996): • Canopy by Petaurista petaurista • Middle Layer by Iomys horsfieldi • Ground and shrub layer by Petaurillus hosei. There is no doubt that life at the various levels of a forest requires different lifestyles, different methods of travel, and choices of sleeping and breeding sites. To be successful an animal has to find its appropriate niche for each of these requirements. The Forest Floor Community The understorey is a relatively cool, moist and windless area, compared with the conditions above in the canopy. In contrast to the productive forest canopy the number and diversity of larger animal consumers on the forest floor is poor. The abundant seedlings and saplings are consumed by mostly large herbivoures, like elephant, rhinozeros and tapirs. The Lesser mouse deer (Tragulus javanicus) not bigger than a hare and having instead of antlers, curved canine teeth for defence and the common Barking deer (Muntiacus muntjak) having both, antlers and long canins, feed on insects and other small invertebrates as well as fruit. Fruits are a rich source of nutrients but they are extremely patchy in time and space. Therefore, only during mass fruiting soil dwellers like pigs get a good supply of this valuable source of nutrients and they have to compete with the large number of frugivores capable to reach the fruits before they fall down to the forest floor, although cauliflore trees can bear their flowers and fruits on the lower trunk. Although there are few large mammals, including the top predator the tiger, a myriad of small

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FIGURE 16.41. Possible detritus food-chain in a Tropical Lowland Evergreen Rainforest. 1 Twig of a dipterocarp tree 2 Catoxantha opulenta (Fam. Buprestidae) 3 Tupaia glis 4 Leaf of a Dipterocarp as part of the leaf litter on the forest floor

organisms function as decomposers. Some of these decomposers in turn support a diverse set of mammals. The pangolin (Manis javanica) lives mainly on ants and termites, the sunbear (Helarctos malayanus) is very attracted by beetle grubs and wild bees honey. For the arthropode community in an Indonesian rainforest on Ceram the following distribution of the biomass was estimated (Stork , N.E., cit.in: Cranbrook and Edwards , 1994):


5 Dead Catoxantha opulenta beetle (Fam. Buprestidae) 6 Dead Tupaia glis and feces of the animal 7 Earthworm Lumbricus sp. 8 Catharsius molossus (Fam. Scarabaeidae) 9 Diamesus osculans (Fam. Staphylinidae)

• Soil - 56% • Litter - 14% • Ground vegetation - 0.2% • Tree trunks - 1.2% • Canopy - 28% Dead wood on the ground-floor is a habitat in itself where fungi, ants and termites, stag beetles and rhinoceros beetles, longhorns and scorpions aggregate. The flat fiddle beetle, a carnivorous carabid lives among the platelike bracken fungi


369

FIGURE 16.42. Schematic diagram of the spatial organization among seven scincid lizards from Borneo (after Denzer, 1994). 1 Apterygodon vittata 2 Emoia atrocostata 3 Mabuya multifasciata 4 Mabuya rudis 5 Dasia grizea 6 Shenomorphus cyanolaemus 7 Tropidophorus beccari

: : : : : : :

Arboreal in beach forests Semiaquatic in coastal areas Terrestrial from the coast to secondary forest areas Terrestrial from secondary forest to pimary forest areas Arboreal in secondary forest Arboreal in primary forest Semiaquatic in secondary and primary forest

which grow on rotten wood. All these animals are seperated by dietary preferences, time of activity or space preferences. Canopy Community In a reported case from Borneo, where insectidal fogging was used to bring down the arthropod community of 10 trees, 23 874 arthropods were collected with more than 3000 different species (Cranbrook and Edwards, 1994).

It is safe to say that the richest arthropod fauna is that of the upper canopy followed by the near ground area. The multitude of provided niches by the combination of different tree species and structures, climatic conditions, and plentiful of food resources are reasons for the concentration of forest dwelling orgnisms in the canopy. The sunlit surface of the outer layer of foliage is where many animals find most of their food in form of tender new leaves, pollen and nectar of flowers,

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pulp and seeds of fruit. Diet specialisations has evolved in many canopy animals. Besides specialised folivores and frugivores, like the possums, a marsupial of the superfamily Phalangeroidea of Easten Indonesia, specialists are found here like woodpeckers feeding mainly on wood-boring insect larva or the squirrel Callosciurus melanogaster on the Island of Siberut feeding on fruits, bark, and mainly on invertebrates. Only during midday the conditions in the very tops of the emergent trees is hot and dry and most animals find refuge from this conditions by sheltering within the canopy. A web of sometimes very fragile links and interactions charcterises the ecological complexity of the life in the canopy of the rainforest: • Specific pollinators are needed for specific flowers. • Specific animals are needed to disperse the seeds. • Specific conditions are needed to keep seeds vital. • A specific set of conditions is needed to get seedlings grow into a new generation of trees. The most spectacular tree canopy dwellers are the apes and monkeys. While the three apes found in Borneo and Sumatra are the Orang utan (Pongo pygmaeus) and two species of gibbons, the monkeys are represented by langures, macaques, tarsiers and slow lories. The latter two are nocturnal, while all the others are diurnal. About six to eight diurnal primates can live together in the same rainforest by different use of forest space and foods. There is spatial seperation, dietary seperation and temporal seperation visible (Fig. 16.43): 1. Spatial separation: The Pig-tailed macaque (Macaca nemestrina), for example, is more terrestrial while the Long-tailed macaque (Macaca fascicularis) is more arboreal.


2. Dietary separation: • the gibbons are primarily fruit-feeders; • the macaques are opportunities-feeders with insects, fruits and leaves as their main staple food items; • the langurs are young leaf-feeders, a food item available in unlimited supply; the Orang utans feed on leaves and fruits; 3. Temporal separation: • the different primates performe their territaorial calls at different times of the day; e.g. Thomas Leaf monkey calls in the early hours of the day and late afternoon, White -handed gibbon calls only during the morning, while orang utans call mainly during late afternoon and night; • the tarsiers are nocturnal and feed mainly on insects; • the slow lories are nocturnal and feed on insects and smaller vertebrata. The majority of diurnal primates relay on fruits particularly on figs and some of them follow regular “fig routes” which take them to all major fig trees in their area. This is also true for other fruit trees, including durians, a favourite fruit for Orang utans. Segregation in Time There are groups of animals only active during daytime or nighttime, at dawn or dusk. The time-partitioning of the environmental resources by related animals can be on a daily base but also on a long-term base. These long-term cycles are sometimes related to seasonal breeding. Therefore, time-sharing is also one aspect of the niche including questions of alpha diversity or richness of species and beta diversity or species turnover. The variation in species composition at different places and at different times is a consequence of species distributions due to two main causes:


• Spatial changes in the environment; e.g. tem perature limitations to growth, food availabil ity, availability of breeding sites. • The existence of barriers of dispersal; e.g. a very characteristic of species found on iso lated mountain tops, islands or very isolated habitats. This geographical isolation eventu ally might lead to the formation of new spe cies. A prediction is therefore, that sites separated by a greater distance will have a greater beta diversity. The magnitude and determinants of species turnover are cucial to our understanding of biological diversity. And as shown in the case of moth diversity in a habitat, the respective diversity reflects the surrounding botanical diversity. Those groups that show a high species turnover are likely to contain species more susceptible to extinction from loss of habitat. Nocturnal Organisms Night fall in a tropical forest is like the scene change in a short period of time. Photosynthesis ceases and the daytime animals of the forest floor and the canopy withdraw to find safe refuges. As the daytime animals retire a complete new suit moves out from their daytime refuges and very often fill in the niches left by the daytime organisms. While more than 90% of the birds are diurnal, about 80% of the mammals are either crepuscular or active at dawn and dusk, or nocturnal. True nocturnal species have developed several specialised features that enable them to make optimal use of the darkness: • Eyes must be constructed in such a way that they are capable to receive any available light; e.g. owls, slow loris (Nycticebus sp.), tarsier (Tarsius sp.) and forest cats (Panthera tigris, Panthera pardus) have developed large eyes, or can change the pupils size. • Hearing is very essential and navigating by sound is one mean to avoid obstacles and to

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locate food; e.g. bats, said to be the most suc cessful group of night creatures with mem bers belonging to a wide range of dietary niches including fish-eating bats, insect-eat ing bats, nectivorous bats and fruit-eating bats. • Sensory organs able to locate by smelling a mate or food items; e.g. moths, able to lo cate a mate over more than a kilometer dis tance with the help of pheromones, bats smelling fruits and flowers in the dark. • Communication by sound; e.g. grasshoppers, crickets, cicada and frogs, the latter two making the short time of dusk to one of the noisiest parts of the daily cycle in a forest. • Flashing of a phosphorescent light; e.g. male fireflies signal their presence by an intermitted rhythmic flashing, the sequence of which is unique to each species. Geckos emerge from cracks. This is one of the rare reptile groups being able to call, and have followed the settlers and are one of the most successfully established former forest organisms in inhabited areas. Snakes find their prey with the help of temperature receptors on the front of the head. Owls fly absolutely noiseless through forest gaps and along forest edges in search of prey. The different nocturnal mammals have developed very different means of locomotion: • The folivour flying squirrels (e.g. Petaurista petaurista) emerge from their daytime hide outs. So do the vegetarian Flying lemur (Cy nocephalus varigatus) both able to glide rather than to fly from tree to tree. By this means they both are able to range widely to exploit large food sources. • The carnivorous Palm civets, e.g. Hemigalus derbyanus range widely by decending to the ground. • The omnivorous Slow lories move very slowly and carefully in the understory level, cover ing a small home range of only 5-10 ha (Barrett, 1984).

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Tree

Height [m]

50 40 30

A. SPATIAL SEPARATION 20

10 0

: 50% OF ALL OBSERVATIONS 100%

a b c

B. DIETARY

SEPARATION

e

d

a insects

b bark

c leaves

d fruit

0%

e flowers

hours 20

16 C. TEMPORAL

SEPARATION

12

6 20-6 40 20 1

0

20

0 2

20 3

0

20 4

0

% OF CALLS

5

FIGURE 16.43. Examples of spatial, dietary and temporal separation in some primates (after Rijiksen, 1978; MacKinnon and MacKinnon, 1980). A B C 1 2 3 4 5

Spatial separation expressed in form of the vertical use of the canopy

Dietary separation expressed as proportions of typical diets

Temporal separation expressed as percentage of calls occuring through the day

Orang - Utan (Pongo pygmaeus)

Siamang (Hylobates syndactylus)

White-handed gibbon (Hylobates lar)

Long-tailed macaque (Macaca fascicularis)

Thomas’ leaf monkey (Presbytis thomasi)



• The prosimian mainly insectivorous tarsiers (Tarsius spectrum, Tarsius bancanus) leap from trunk to trunk. • The porcupine, Thecurus crassispinis, is nois ily searching for starchy roots fearing no predator due to its ability to charge backwards sharp spines. • The bats leave their daytime resting sites and fly long distances in search of either fruits or prey. The ecology of the forest at night is as complex as by day. Only the larger mammals roam the forest by day and night but the arboreal community is more clearly divided into diurnal and nocturnal groups (MacKinnon et al.,1996). The Malay pangolins, Manis javanica, exploits during its nocturnal life a dietary niche which is mainly vaccant during daytime. Most others, particularly the bats and the moonrat (Echinosorex gymnurus), an evil-smelling large insectivore in Borneo and Sumatra, share resources that are exploited by other forest residents during the daytime. In the case of the moonrat this is the tree shrew feeding on beetle grubs, earthworms and insects. NUTRIENT AND ENERGY FLOW Four paradigms dominate the discussion on nutrient flows in tropical rain forests: 1. Tropical forest soils are poor in nutrients. 2. Biomass is the major pool for nutrients, not the soil as in many temperate forest eco systems. 3. Nutrient cycles are short-cut. Decomposi tion and nutrient uptake are fast. 4. Organic contents of tropical soils is low, a humus component is almost non-existent. This might be true for parts of Kalimantan and the Amazon basin on aged and deeply weathered soils, where the original data were gathered. With ongoing research in Southeast Asian tropical forest ecosystems all these paradigms are more and

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more questioned and subsequently replaced by more detailed statements (MacKinnon et al., 1996). It now seems, that there is an important distinction between rainforests with deep soils, which receive nutrients solely in rainfall, and forests with soil parental material within the rooting zone (Whitmore, 1990). Nutrient cycles are almost closed in areas with sedimentary soils, where the parental material is very low in nutrients, like in most parts of Central and West Kalimantan while in young shallow soils high concentrations of essential nutrients can be found in the soil. Further, lowland rainforest cycle little phosphorus through their litterfall, while mountain forests cycle little nitrogen. Indonesia is a geologically young archipelago where in higher altitudes natural erosion sets free nutrients from the bed rock. In the lowlands these nutrients accumulate. Through limited erosion forces, natural forest cover makes sure that the ‘right’ amount of nutrients is mobilized. The most important function of trees may be therefore not so much lie in the retention of nutrients in closed cycles and in the biomass, but in the prevention of extensive erosion. These considerations may influence the discussion on the reasons for the high biodiversity, since poor soils were stated to have a major influence on tree speciation in the tropics in order to utilize rare resources as efficient as possible. It is well known that tropical rainforest plants are highly successful at scavenging chemical nutrients from all sources: rainfall, throughfall, soil and decaying litter. The plant biomass, that is the total dry weight of the forest community, including leaves, branches, trunks and roots is the result of the ability of plants to do photosynthesis and by this process transform carbon from the atmosphere into organic matter. The rate at which this occurs is the gross primary productivity. The net primary productivity is the rate of production of new plant matter per unit area over time, while the primary production is the gross primary production reduced by the losses during

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respiration. By estimating productivity of the standing crop and litterfall, the energy flow through a ecosystem can be estimated. The above ground biomass for lowland evergreen rainforests in South East Asia has been estimated to be 400 t .ha-1 (Whitmore, 1990). This figure varies, according to forest type between 210-650 t ·ha-1. The above biomass of single nutrients in kg ·ha-1 has been estimated to be (Brandes, 1991): for N: 7,000, for Ca: 1,000-2,000, for K: 1,000-1,500, and for Mg: 250 500. To obtain the total biomass it is necessary to add the root or below ground biomass. This is extremely difficult to measure. About 4,000 kg·ha-1 of living fine roots and about 1,000 kg of dead fine roots have been measured for a Bornean forest (Schulte and Ruyat, 1998). The only attempt to estimate the net primary production comes from a site in Malaysia. There 30 t·ha-1·yr-1 were calculated as net primary production and 80 t·ha-1·yr-1 for the gross primary production (Whitmore, 1984). Net primary production is lowest in the gap phase of the forest life cycle and greatest during the building phase (MacKinnon et al., 1996). Nutrients enter the system through weathering of bedrock, soil erosion and through the air in form of aerosols. The latter can originate from marine aerosols, wind erosion, and volcanic eruptions. Atmospheric nitrogen may also be converted into a form available to plants life by electrical discharges in form of lightenings during thunderstorms and eventually be carried in solution during rain. Other nutrients are cycling within the system. Rain penetrating the canopy leaches nutrients from leaves and tree trunks. Leaf litter and other particulate organic matter eventually reaches the forest floor and is decomposed. The leaf litter decomposes slowly over 4 to 12 month on average. The nutrients are partly consumed by plants, partly they are fixed in the soil within the humus or clay minerals. A certain amount leaves the system through erosion, leaching or export of organic matter in form of e.g.,


organic debris, pollen, seed dispersal, migrating or drifting animals (Fig. 16.44). Although nutrients may not be limiting factors in a number of Indonesian tropical lowland evergreen rainforest, deeply weathered soils like in most parts of Kalimantan and forests on limestone and ultrabasic rock areas may be exceptions, there are sure mechanisms of nutrient conservation. Strategies can be storage of nutrients in the biomass or control of movement between components (Golley, 1983). About 90% of the essential plant nutrients with exception of N and P are stored in the vegetation of the tropical lowland evergreen rainforest ecosystem (Jordan, 1985). In the Lowland Dipterocarp Forest of Kalimantan the bioelement storage fixed in vegeation is: 65-80% of K, 70-80% of Mg, about 95% of Ca, 10-20% of N. Further, a rich community of decomposers break down the litter, taking up nutrients into their own structures, a process called immobilisation. Simultaneously, these decomposer organisms release nutrients for root uptake, a process called mobilisation. The mineral soil surface is completely enmeshed in a feeding root mat which grows into and through the litter layer as it decays. Through decomposition processes the available nutrients are therefore immediately taken up again. Leaching of nutrients out of leaves maybe is avoided by the development of leaf surfaces which are water repellent, like hairs or waxy cuticulas. Trunks and branches can be significant sinks, especially for elements which are otherwise very mobile like potassium and phosphorus. About 5-10% of the rain water reaches the forest floor as stem flow. Leaching of nutrients is likely to occur in this process. However, probability of quick uptake is high, since the water reaches the ground directly at the bottom of trees, where the root system is best developed. By biological associations , including mycorrhiza, nutrient usage is maximised. This system is particularly enhanced by the association with mycorrhiza, fungi or mycobionts that live in symbiosis


with most of tropical tree species or phytobionts through increasing the actual root surface. These symbiosis can be ectosymbiotic, where the fungus penetrates the tissue of the roots and forms chacteristic vesicles within the cells or endosymbiotic. Generally, the fungus receives carbohydrates from the trees and channels minerals into the root tissue of the trees. In tropical forests the endosymbiotic vesicular-arbuscolar type is the most common. In this form the fungus surrounds the root but does not penetrate the living cells. Ectomycorrhizae are specialised and very often host specific and mostly formed with basidomycetes, sometimes with ascomycetes. The uptake of nutrients becomes more efficient since the mycorrhiza establishes a direct connection between roots and litter. Mycorrhiza also plays a significant role in the uptake of phosphorus, and the absoption of nitrogen, elements which can be easily leached out or can be fixed chemically in the soil in a form unavailable for plants. Ectomycorrhizae is probably characteristic of all Dipterocarpaceae, most Myrtaceae, and many tropical members of the Leguminosae. Pioneer species do not have in general mycorrhizas because they still have to grow fast up and can not depend on a fungus infection cycle first before they are able to grow. Others, like the Dipterocarpaceae can not grow without mycorrhiza. These trees have often large seeds to provide enough reserves of food upon which the seedling can draw before infection with the fungus occurs. The adult trees show often a reduced root hair system due to the mycorrhiza association. Nitrogen is an important element for the metabolism of proteins. Although air consists to 71% of nitrogen in form of N2, it is not available for plants. Through photochemical reaction triggered by UV radiation or lightning, ammonia and nitrogen oxides are synthesized which can be leached out of the atmosphere by rain. Some bacteria and blue green algae are also able to fix nitrogen. Some plants, in particular the Fabaceae have evolved a symbiosis

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with N-fixing bacteria and therefore can also thrive in soils extremely poor in this nutrient. The majority of nitrogen, however, originates from decomposition processes of organic matter (Fig. 16.45). A genetic change in an organism leading to an increase of entropy production of the ecosystem may result in storage losses and decreases the elasticity of the system. For example, the development of a species causing large scale destabilization of ecosystems is man. Man has however the cabability to realize, what he is doing and to embark on adequate consequences by changing his behaviour (Schulte, 1996). HUMAN INFLUENCE AND ECOLOGICAL STATUS On a natural and global perspective the decrease in the extent of original forest cover was in the geological past associated with the advance and retreat of ice and climatic change. Forests can disappear and reappear gradually as a result of such climatic changes. They can also disappear abruptly as a result of some catastrophic event such as fire, vocanic eruptions, typhoons or major landslides. Man became an agent of forest destruction when he learned to use fire as a means of clearing vegetation for purposes like: • To herd game for hunting. • To extend his pasture. • To clear forest for shifting cultivation. To fire was later added the other tools that were used for forest felling from the primitive stone axes of the Neolithic man to the chain saw of modern man. The human impact on the forests in Indonesia can roughly be divided into three periods: • Pre-colonial periods with some deforestation in the areas of some major kingdoms in Sumatra and Java. • The colonial period of about 400 years with clearings for plantations, for mining and road and railway constructions.

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C2

C1

FIGURE 16.44. Nutrient and energy flow in a tropical lowland evergreen rainforests. Producers First order consumers (C1) Second order consumers (C2) Decomposers


: : : :

Photosynthetic active plants Herbivores like caterpillars of insects, bats, nectivorous birds, hornbills Predators like birds of prey, snakes Bacteria, yeasts, fungi, termites, ants, ground beetles, eathworms, and centipeds


• The decades since independence with dra matic deforestations due to timber trading and resettlement schemes on all major islands, particularly Sumatra, Kalimantan and Irian Jaya (West Papua). Today the main reasons for forest degradation and deforestation in Indonesia are logging and shifting cultivation. While degradation of the forest through logging, fuelwood gathering, forest fires, landslides and other natural or anthropogenic causes will result in a modified forest structure and composition and an impoverishment in timber species, deforestation, by definition is the complete clearing of natural forest formation and its replacement by some other use of land. Infrastructure development as road construction, mining, hydroelectric dams, power plants, power lines and agricultural schemes locally can also play an important impact on the remaining forested areas. All these problems are strongly interwoven. Logging roads and infrastructure lead to easier accessibility to forest areas by squatters. Although there are regulations which should be effective to conserve the remaining forest, their enforcement is hampered by political interference, lack of funding and manpower, lack of training or willingness in the authorities in charge to do the needed, or simple ignorance. About 55% of the twelve types of forests recorded in Indonesia is Tropical Lowland Evergreen Rainforest. Today the forest cover of this type of forest is still greatest in Kalimantan, the Moluccas and in Irian Jaya (West Papua). In 1995 about 60% of the land surface of Borneo was still under natural forest with about 34,000,000 ha. In 1968 it was calculated with 77% or 41,470,000 ha, at that time about 34% of the total forest cover of Indonesia. Therefore, inbetween 27 years more than 8 million hectares of forest were lost in Borneo alone and there mainly in Kalimantan. In 1990 on Java only 7% of the original forest cover was left, in Sumatra 49 %, Sulawesi 56%

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and in Irian Jaya (West Papua) 82% (FAO, 1990) (Fig. 16.46). Particularly the tropical lowland evergreen rainforest with its valuable stands of Dipterocarpaceae has been heavily logged and replaced for agricultural and other purposes due to the relatively good assessability of this type of forest. Virtually all lowland rainforest have been replaced on Java by farms or plantation forest. Sumatra continues to lose its natural vegetation faster than any other part of Indonesia due to large resettlement schemes for mainly Javanese transmigrants and a steadily increasing plantation industry. In Kalimantan much of the land officially classified as forest is seriously degraded by scrupulous logging methods and huge areas of Imperata cylindrica grasslands have developed. Fires, fueled by the underlaying peat and brown coal, have during the eigthies and ninethies destroyed vast areas of forest. In Irian Jaya (West Papua) extensive logging concessions and large scale transmigration schemes are reducing since the nineties the existing lowland forest areas. The services and benefits man might receive from the forest can be summarized as follows (after Poore and Sayer,1988): • Protection of the full range of animal and plant species and their genetic variability for generations to come: Ecological diversity. • Sustainable yield of wood products: Provision of timber. • Sustainable harvest of many secondary for est products including rattan, resins, pharma ceutical compounds, fruits, nuts: Secondary forest products. • Protects watersheds and ensure an adequate quality and flow of water: Water and soil con servation. • Moderate the climate both locally and globally: Regulation of climate. • Support fish and wildlife: Provision of wildlife.

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FIGURE 16.45. Simplified diagram of inorganic nutrient flow in a montane rainforest (after Edwards, 1982 cit. in MacKinnon et al., 1996) (Figures in kg .ha-1). 1 2 3 4 5 6 7

Rain input: N 6.5; P 0.5; K 7.3; Ca 3.6; Mg 1.3. Canopy leaching Throughfall: N 30; P 2.5; K 71; Ca 19; Mg 11. Fine litterfall (dry weight) : Total 7 550 N 91; P 5.1; K 28; Ca 95; Mg 19 Forest floor fine litter (dry weight) : Total 6 500 N 91; P 5; K 11; Ca 96; Mg 15 Rock Weathering


8

Mineral soil organic matter : Total 410 000 N 19 000; P 16; K 400; Ca 3 700; Mg 6 800. 9 Streamflow 1 0 Uptake 1 1 Roots (dry weight): Total 40 000 N 140; P 6.4; K 190; Ca 330; Mg 61. 1 2 Canopy (dry weight): Total 310 000 N 680; P 37; K 660; Ca 1 900; Mg 190.


379

BALI 1900

BALI 1980 SUMATRA 1932

SUMATRA 1985

FIGURE 16.46. Reduction of forest of all types in Sumatra and Bali (after Whitten et al., 1988; Whitten et al., 1996).

• Support the integrated development of rural lands: Opportunities for integrated rural development. • Provide opportunities for formal and informal education and research: Education and re search. • Are part of the cultural and national heritage: Cultural heritage. • Retains natural processes and ensures open options for the future: Options for the future. In such cases were clearing or deforestation is used there is an extremely high loss of biodiversity to expect. But also the practice of selective logging has a multitude of negative impacts on the forest: • The focus on less than 100 economically valu able tree species out of about 3000 as performed in Kalimantan leaves the popula tion of these species highly depauverated. • The gene pool is highly affected because only huge mature trees are usually taken.

• About 50% of the residual trees are heavily damaged due to recless mechanical logging practises. • The soil is heavily compacted by the big machinery used resulting in reduced infiltration properties and therefore, higher risk of erosion. • Soil erosion is accelerated by the network of logging and skidding roads. • Large gaps are cut into the forest in form of roads, campsites and log yards. These unnatu rally large gaps are colonized by secondary species only if left alone. • The impacts on the climate particularly the microclimate, the humidity and wind flow is dramatical and brings many members of the ground floor and soil community to the verge of extinction (Table 16.9). • The opening up of the forest by the logging roads invites squatters, illegal hunters and wildlife collectors.

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TABLE 16.9.

Effects of tropical deforestation on the hydrological cycle of the environment (after German Bundestag, 1990).

Direct effects: • Reduction in transpiration • Less local rainfall • Reduction in field capacity • Increased runoff Indirect effects • Increase in albedo:

• Reduced surface roughness:

• Direct effects:

• • • Indirect effects: • •

Reduction in the amount of solar radiation absorbed by the earth’s surface. Reduction in the net inflow of solar radiation at the earth’s outer atmosphere. Weakend atmospheric circulation Further reduction in the net inflow of solar radiation at he earth’s outer atmosphere and in the amount of solar radiation absorbed by the earth’s surface as a result of: 1) Warming of the earth’s surface- increase in infrared radiation into outer space; 2) Reduction in atmospheric water vapor concentration- loss absorption of heat radiation in the atmosphere; 3) Further drying out of soil- increase in albedo. • Reduction in the degree of cloud cover- reduction in albedo. • Raised lower limit for cloud formation - warming of the lower layer of air

• Reduced convergence in tropical low-pressure areas - reduction in rainfall • Modified turbulent exchange of air mass between layer of air close to the ground and higher air layers - change in evaporation behaviour

• The hydrological cycles are heavily disturbed, water ways highly polluted and with enormous sediment laods affecting even the coastal areas with their fishing grounds and coral reefs. • Destruction of the seedlings bank by the log ging operations. • Reduction of the germination rate of seeds due to the compaction of the soil. • Pushing myriads of organisms out of their habitat. • Affecting the life of indigenous people on all levels like, availability of clean water, hunting opportunities, collection of secondary forest products like resins for torches, honey, fibers and medicinal plants. It is well documented that selective logging of trees with more than 50 cm dbh and a given rotation cycle of less than 30 years is not sustainable. It is


further becoming more and more evident that after the second round of logging the removal of the parent stock of Dipterocarpaceae is completed, because many Dipterocarpaceae with over 50 cm dbh may have never fruited. Therefore, this kind of logging practise is neither sustainable, nor ecologically sound, but a form of mining the forest with the risk to loose an entire characteristic forest tree population inbetween 50-60 years. As forest disappear so do such valuable natural products like rattan, resin, fish, game, honey, wild fruits, pharmaceutical and cosmetic compounds and asthetical values of the landscape. Any alteration of a natural habitat results in changes in plant and animal communities and many species are eliminated, while a much smaller number, mostly weeds or pest species benefit by increasing their populations. If the rate of forest destruction is allowed to proceed 81% of the rainforest mammals are


threatend with extinction (Stevens, 1968). If selective logging is done with care many rainforest mammals and birds can survive if the forest is left to regenerate naturally. However, forests that have been selectively logged once exhibit a similar species diversity to primary forest but a different species composition. If habitat corridors are left between logged over forests and remaining natural forests than the “ island effect” observed for remaining pockets of forest within cleared land can be avoided. These “islands” certainly will lose many of their species over time. Reforestation, Afforestation and Enrichment Planting Replanting trees on open land is called reforestation. If trees are planted on areas that have been without forest for a long time the term afforestation is used. If in still existing but highly disturbed forest after logging trees are planted than this activity is called enrichment planting. While in each country laws exist to regulate the restoration of logged over areas, unfortunately the enforcement of these rules and regulations is very weak. In addition, the trees used for this activities are very often not indigenous species but fast growing exotic trees like Eucalyptus, Pinus or Acacia are used for re- and afforestation. It is one of the most saddening chapters of the ongoing destruction of the tropical rainforest that even the small efforts to prevent further losses on biodiversity and carrying capacity of the respective ecosystem are completely neglected. Future generations will have to live with the fact that they most probably will not be able to enjoy the luchness of a primary tropical lowland evergreen rainforest but have to refer to history books and filmes to get an idea of this type of forest.

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Forest Fires Forest fires are natural events occuring during longer dry spells induced by climatic events like El Niño. Between 1830 and 1953 about 93% of all droughts in Indonesia occured during ENSO events (Berlage, 1957). Abundant charcoal in forest soils give evidence of prehistoric and historic natural and anthropogenic wildfires in prehumid lowland and in seasonal dipterocarp forest types (Goldammer et al., 1996). In 1982-83 and 1997-98 such events gutted millions of hectars of forest in Kalimantan, Sumatra and Sulawesi. Unfortunately most of these fires were started by man, either companies supplying the pulp and paper market with plantation timber who wanted to extend their plantation area or by small holder settlers trying to extend their farms of pepper and vanilla. Burning out of control due to the dry conditions, the entire region of South East Asia was sometimes engulfed in haze and smoke for months. Main reasons for the cause of the uncontrolled fires was a combination of severe drought, destructive logging practices and slash-and-burn agriculture. During protracted dry seasons drought stress particularly in logged over areas causes evergreen trees to shed their leaves. In general, if the precipitation falls below 100 mm/month and periods with two or more weeks without rain occur, the forest vegetation sheds its leaves progressively with increasing drought stress. Together with dead wood left after felling this accumulated dry litter lead to a rapid spread of an uncontrolled fire. Aerial fuels such as desicccated climbers and lianas become fire ladders potentially resulting in crown fires or torching a single tree. Dipterocarps are very suceptile to fire and are replaced by pioneer and fire-tolerant species. In burned areas 99% of the trees below 4 cm dbh are usually dead. 50% of trees with 20-25 cm dbh died and 20-35% of trees above 25 cm dbh (Lennaertz and Panzer, 1984). Fire resistant trees belong to four families: • Ironwood (Eusideroxylon zwageri, Family Lauraceae).

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• Families of Caesalpinaceae, Ebenaceae, and Palmae. Seriously affected by fire are the following sites: • Sites with low water retention capacity, peat swamp forests, forests on limestone, forests on shallow soils, logged over forests and forests near settlements. The fire in Kalimantan spread also through both the underlaying peat and underground coal seams and continued there to smolder even after the onset of the rainy season. These smoldering organic material is reactivated as an ignition source in the next dry spell (Goldammer and Seibert, 1989). It could clearly be shown that the fires killed more trees in secondary forest than in pristine forests (Riswan and Yusuf, 1986). The major effects of burning on ecological processes can be summarized as follows (after Ovington, 1984): • Effects on ecological processes: • Creation of bare areas facilitating invasion of weeds. • Natural successions are curtailed. • Left vegetation mosaics containing different successional stages. • Breakdown of local ecological balance. • Reduction of species diversity. • Increase in uniformity with fewer niches. • Concentration of herbivores in areas with a flush of new vegetation. • Promotion of light demanding pioneer species like Euphorbiaceae, Sonneratiaceae and Verbenaceae. • Supression of climax species like Dipterocarpaceae, Annonaceae, Fagaceae, Myristicaceae. • Effects on organic production and decompo sition processes: • Loss of biomass. • Reduced primary production. • Reduced secondary production.


• Reduction of organic turnover by decompo sition. • Effects on nutrient circulation: • Nutrients and minerals loss about 1-4 billion tons of carbon are released annually into the atmosphere by forest fires globally (Andreae and Goldammer, 1992). • Destruction and interruption of nutrient cycles. • Reduced retention of nutrient capital in organic matter. • Excessive loss of elements by surface runoff and leaching. • Change in the rate of nitrogen fixation. • Effects on water circulation: • Increase in throughfall and water discharge. • Decrease in rainfall interception, transpiration and top soil moisture. • Effects on soil development: • Increase in pH and soil erosion. • Loss of organic matter. • Formation of base-rich soil surface layer. • Increase in soil temperature. • Increase in nutrient loss by leaching and salinity. • Progressive long-term decline in soil nutrient capital. • Death and decomposition of plant roots. IMPLICATIONS FOR EIA STUDIES As long as forests are left undisturbed or are harvested sustainably in a ecological sound manner, the option for future land uses are left open. As in the cases of hydroelectrical power plants and dam construction also for large scale logging and plantation concessions an environmental impact assessment should be applied. Once forests are damaged and cleared their ecological diversity declines, species are lost and irreversible ecological and environmental changes occur. The many roles forests play, like providing soil stability and protection, enhancing soil fertility, regulating the quantity and quality of water flow, affecting local and global


climates, providing a livelihood for many local communities, and improving the quality of life by providing opportunities for recreation, should not be placed at the mercy of some concessioners. It is imperative that the extent of protected forest areas should be increased and that protection and management of existing national parks and reserves should be improved as part of the efforts to conserve the rich national and international heritage in form of tropical lowland evergreen rainforests in the Indonesian archipelago.

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the degradation and desertification of entire landscapes mainly due to human stubidity. If we are not concerned about what happens now and if we do not insist on consequences without any compromise then the introductory sentences of the Environmental law of Indonesia, laid down in the 4th Act of 1982 is meaningless.

SUMMARY The tropial lowland evergreen rainforest being one type of the 12 types of forest still found in the Indonesian archipelago plays a central role under many aspects. For example: • Aspects concerned with biodiversity and their conservation. • Aspects of economical development of tropical countries. • Aspects of global climate changes. • Aspects of stewardship of man for all creation. • Aspects of renewable resources and their sustainable use. • Aspects of existing rights for all organisms on this globe. • Aspects of carrying capacity of a given environment. While the establishment of the very fine tuned relationships inside a tropical forst needed in some cases millions of years, this valuable ecosystem is plundered in recent decades mainly under only one aspect: unsatifiable greed and gross neglect and ignorance of the laws of nature by man. There is, in fact, no method or technique for exploitation of tropical rainforest which provides for the retention of all species ad infinitum within the context of cash economy. One can view the destruction of an entire and unique ecosystem including the extinction of scores of organisms and

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SPECIAL FOREST ECOSYSTEMS


THESIS The more specific adaptation are needed to live in a given special environment the more unique communities of plants and animals can be found. This fact makes ecological studies in such environments like swamps, areas with characteristic soil composition and climatic specialities highly interesting research sites for both adaptation mechanisms and evolutionary survival strategies. OVERVIEW The types of forests which are dealt with in this chapter never have been much a topic for research. This is true for forestry, because only few trees can be found that yield comparable prices to the highly sought dipterocarps. Also the costs for reaching the commercially interesting trees prevented extraction activities in these types of forest ecosystems. But also researchers involved in ecology or taxonomy neglected these ecosystems.

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17


Friedhelm Göltenboth, Gerhard Langenberger and Peter Widmann

SWAMP FORESTS Swamp forests are vegetation forms which are restricted to flood plains. Extensive plains exist on the Malay Peninsula, in Sumatra, Borneo and in Irian Jaya (West Papua) and here are the centers of swamp forest distribution in South East Asia (Vijarnsorn, 1996). They are rather commonly found landward of mangrove forests on alluvial soils. Ninety-five per cent of the original area of swamp forests in Indonesia are found on Sumatra, Kalimantan and Irian Jaya (West Papua). About 14% of the total forest cover of Kalimantan is swamp forest. Two major categories can be distinguished: 1. Freshwater swamp forests: They are a very diverse assemblage of forest types with usually a soil pH of about 6.0. Four distinct types can be observed: Mixed swamp forest; Melaleuca sp.(Fam. Myrticacea) swamp forest; Terminalia sp. (Fam. Combretaceae)

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swamp forest; Campnosperma sp. (Fam. Anacardiaceae) swamp forest. 2. Peat swamp forest. Since sea level rose at the end of the last glacial maximum, the rivers have deposited silt as levees and on flood plains. Swamps developed and sometimes mangroves became replaced by inland species whose litter failed to decay in the still salty, high sulphide, waterlogged conditions. The litter turned into peat which continued to form up until today. The domed center of the peat swamp is usually the oldest part and in a concentrical manner up to six distinguishable forest types may be formed. This type of forest is only found in parts of Sumatra, Kalimantan and Irian Jaya (West Papua) and not in Sulawesi and the Nusa Tenggara Islands. Since the smaller islands of the outer arc of the Indonesian archipelago are very young, the reliefs of their islands are very rugged and there are only relatively narrow flood plains along the coast. Only on the larger islands larger valleys could form with more extensive swamp formations. Ecology Rieley et al. (1996) summarize the following criteria to characterize tropical peatlands; • Fiber content of the peat. This reflects particle size and the state of decomposition. • Depth of peat layer. Shallow: 50-100 cm; Moderate: 100-150 cm; Deep: 150-300 cm; Very deep: >300 cm. • Trophic status: eutrophic, oligotrophic and mesotrophic. • Topographical location, mode of formation and age. Different types of peatland have developed in different environments. The major types are: Coastal peatlands of the maritime fringe and deltas; Basin or valley peatlands of river valleys; High peats of low altitude watersheds between major rivers.


Two totally different types of swamp forest are frequently distinguished, depending on the drainage pattern of the landscape and their nutrient status: • Freshwater swamp forests usually develop along river flows, lakes or in areas with high water table. Nutrients are provided by the water flow and the forest is flooded seasonally. • Peat swamp forests stock in soils which are supplied by precipitation exclusively. Only under ever wet conditions on flat terrain and on substrate poor in nutrients this kind of forest can develop (Jacobs, 1988). This kind of peat-soil loses more than 65% of its dry mass when burned and is deposited as ombrogenous peat or peat with the surface above the surrounding land. It is characterized by the fact that due to this circumstances no bigger quantities of nutrients are entering the system from the mineral soil below or from runoff of the surrounding area . It is very poor in nutrients and therefore oligotrophic and can form layers up to 20m thick. The second form of peat deposition is called topogenous peat usually only occurring in depressions where the respective plants can get nutrients also from the mineral subsoil, an entering river, and runoff water, plant remains and rain. This type of peat swamp is found generally behind coastal sand bars and other sites where free drainage is hindered. The peat layer is usually thin with less than 4 m thickness, slightly acidic with a pH around 5 and in a mesotrophic status due to a greater availability of nutrients. An example for such a swamp is the Aopa Swamp in Sulawesi, which is at the same time a good example for a former lake area in its final natural stage. However, the main criteria to distinguish both forest types are the source of water, since also in


freshwater swamp forest peat can form to a certain degree. As this layer of peat grows thicker, freshwater swamp forests may eventually be cut off from the groundwater table or from periodical floods. They then may develop into true peat swamp forests. Corner (1978) observed a succession of vegetation types in the Malayan Peninsula and Singapore, starting with mangroves, to nipa and eventually to four different types of swamp forests. The climax vegetation could be either ‘dry land’ rain forest or peat swamp forest. In the succession from freshwater to peat swamp forests, the conditions are getting more and more dystrophic. pH in peat swamp forests in Kalimantan are usually below 4, in freshwater swamp forests above 6 (MacKinnon et al., 1996). Those parts of the soil in freshwater swamps which are not submerged all the year round undergo a specific process. This gleying process turns the soil into a greyish-yellowish color. Iron compounds are reduced to their ferrous forms during inundated periods, and then partially are reoxidized and precipitated during dry periods. Also, manganese is oxidized in this type of soils. Nutrients, in particular calcium, are deficient in peat swamp

SONNERATIA SP.

NYPA FRUTICANS

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forests. The draining water usually is tea-colored because of the persistent humic acids which are a result of the imperfect decomposition under anaerobic conditions. The humic acids are chelating agents for inorganic ions, binding them into larger molecules, thus preventing their uptake by plants. They are phenolic compounds which are one of the many groups of plant defence compounds and have been found to be very important in plant- animal interactions. Phenolic compounds are generally toxic to animals and decomposers because they bind protein and are difficult to degrade. Only some litter microorganisms are able to degrade phenolic compounds, but they need for this process a welloxygenated substrate. This is not easily available in a swamp area and therefore litter from peatswamp forest will probably lie on the ground for many months, unattacked by decomposers, until most of the defence compounds have leached out by rain water. The entire process of using defence compounds on a relative bigger scale particularly by plants in swamp forests must also be seen as a consequence of the low nutrient level. The loss of a leaf to a herbivore is proportionately more serious

BARRINGTONIA SP.

HERITIERA SP.

RHIZOPHORA SP.

FIGURE 17.1.

Hypothetical succession of mangroves to peat swamp forest. Black soil layer indicates deposits of peat.

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for a plant growing in a peat swamp than for one growing on more fertile soil. The productivity is also relatively low and therefore protective measures or seedling strategies involving anti-predator measures is a necessary ecological consequence. Other defence compounds besides the phenolic compounds are latex, resins, tannins and oils. The aquatic community that lives in blackwater rivers is poor. Cladocera, annelid worms, rotifers, nematodes and protozoans are rare as are algae. Most of the fish species found are air-breathers. This also holds true for the insect population. The main reason found is the high level of phenolic compounds in the water (Whitten et al., 1984). Another ‘wet’ forest type occurs in Indonesia: Riverine forest. It may only be flooded during very short periods of the year, but it is characterized by a highly fluctuating water table and soils rich in nutrients. It may be found along rivers particularly in big meanders. This type of forest ecosystem is under the threat of becoming extinct because it occupies an area easily accessible by the waterway. Producers Generally) swamp forests seem to be poor in tree species. On elevated areas are usually found Casuarina sp. and sedges such as Scleria sp. (Fam. Cyperaceae). Further Eugenia sp. (Fam. Myrtaceae), Sago palms of the species Metroxylon sagu or larger tree palms like Pholidocarfus sp. can be found. Epiphytic ant ferns like Lecantopteris sp. are also not unusual. On floating mats Cyperus sp. and on drier portions Saccharum spontaneum will be recorded (Susanto, 1984). Climbers are common as are creepers and the herb layer is very varied. With the exception of the families of Combreataceae, Lythraceae, Proteaceae and Styraceae most of the tree families of the tropical lowland evergreen rainforest are found in swamp forests, including such high valued trees like Gonystylus bancanus and Shorea albida (Fam. Dipterocarpaceae). Peat swamp forests are often dominated by one or two


tree species like Stemonurus secundiflorus (Fam. Icacinaceae) or Radermachera gigantea (Fam. Bignoniaceae) in the topogenous swamps of the Island Siberut off the Western coast of Sumatra. Also, palms are not very common the Salacca conferta, a stemless palm, is more or less confined to Sumatran peat swamp areas. Riverine forests are characterized by Eucalyptus deglupta, (Fam. Myrtaceae), the only native species found even in rainforests of this predominantly Australian genus. This tree can grow up to 45 m with a straight bole. Its seeds are very light and are dispersed by wind and water. Altogether 47 species of trees can be found in this ecosystem belonging to 38 genera and 28 families. Most outstanding species are Duabanga mollucana (Fam. Sonneratiaceae), Dracontomelon dao (Fam. Anacardiaceae). Of special interest is a small tree Saurania oligalepis (Fam. Actinidiaceae) because of its geocarpy. The inflorescences grow from the base of the tree but descend into the soil and the white flowers are finally seen up to 2 m away from the tree. The inflorescence is actually pushing the fruit into the soil (van Balgooy and Tantra, 1986). Geocarpy is relatively common in riverine tree species. In many remnants of freshwater swamp forests Barringtonia racemosa often is the only occurring tree species. Like with its relative Barringtonia asiatica which thrives in beach forest, its flowers are pollinated by fruit bats and its fruits are designed to be dispersed by water currents. Near-shore swamp forest usually also hold species which are typical for beach forests or back mangroves, like Heritiera littoralis or screwpines Pandanus sp. Trees in swamp forests are waterlogged for extended periods and face similar problems regarding the aeration of their root systems as do mangroves. Some species have therefore evolved almost identical pneumatophores which enable gas exchange above the soil.


Vegetation varies in freshwater swamps according to the wide variations in its soils and the proximity to free water. Submerged macrophytes are rare in swamp forests. The freshwater swamps usually only contain typical rice field weeds like Hydrilla verticillata. In more open situations, for example after removing the forest cover, grassy species, like sedges or cat tails Typha sp. take over. The plant community then is very similar to those of an eutrophic lake shore. In nutrient poor swamp forests submerged macrophytes are usually absent, because of the lack of nutrients. One exception is the carnivorous Utricularia minor which gains additional nutrients by trapping small animals. Pitcher plants of the genus Nepenthes sp. are not an unusual sight in freshwater swamps and peat swamps. Consumers The invertebrate fauna of swamp forests may partly resemble those of lakes or other freshwater ecosystems regarding the water body and lowland forests for the terrestrial portion. However, specific research on this topic seems to lack. Densities of mammals in peatswamps are generally lower than in most dryland lowland forests. In some cases as in the Aopa Swamp Area in Sulawesi, even higher or similar densities are reported with sightings of Anoa, Babalus depressicornis, and an abundant bird community. In Kalimantan, the long-tailed macaques, Macaca fascicularis, and the silvered langurs, Presbytis cristata, do occur in higher numbers in the swamp forests than in the lowland dipterocarp forest. During the day the macaques move away from the river to forage in spread-out groups, searching out fruits, leaves and flowers. The usually large troops of animals have a complex social behavior and clear hierachies. The males do migrate into other groups and by this means the genetic exchange is guaranteed. This monkey species can adapt to disturbed forest

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and even achieve higher numbers there than in unlogged forest. Reptiles found and observed in some of the more remnant swamps are Sailfin lizard, Hydrosaurus amboinensis, Crocodylus porosus and Python reticulatus. Two widespread fish species, the Striated mudfish Channa striatus and a catfish Clarias sp., have been recorded in this type of habitat. Both are able to breath atmospheric oxygen. This is important, since the dark brown water can heat up very quickly in the sunlight which results in a minimal capacity for storage of oxygen. Although the list may be far from complete and aside from the fact that there may be a major influence from cultivated lands it is obvious that these habitats are very important for wetland species which are also dependent on trees for roosting, breeding or as perches. Aggregations of herons and egrets can be observed roosting in swamp forests in the evening. Herons and egrets also breed in colonies in trees, the Grey-headed fish eagle Ichthyophaga ichthyaetus nests solitary in larger patches of forest. Wandering whistling ducks Dendrocygna arcuata breed in hollow trees. All kingfisher species recorded use trees as perches for foraging (Table 17.1). Among the mammals the Dagger toothed flower bat Macroglossus minimus may play a significant role, since it pollinates the flowers of the dominating Barringtonia racemosa (Widmann, 1997). Ecological status Many smaller areas of swamps have stepwise been cleared for agricultural purposes, although most peatlands are of limited value for aqua- and agriculture, because of the high acidity and the low nutrient contents of the substrate (Rieley et al., 1996). However, freshwater swamps are generally very fertile and therefore mostly reclaimed for agriculture. The alluvial plains of Southeast Asia once carried extensive swamp forests but now little

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TABLE 17.1.

Example of vertebrate species observed from remnants of freshwater swamp forests.

Common Name

Scientific Name

Family

Channa striatus Clarias sp.

Channidae Clariidae

Bufo asper Polypedates leucomystax

Bufonidae Racophoridae

Gekko gecko Varanus salvator Cuora amboinensis

Gekkonidae Varanidae Emydidae

Ardea purpurea Bubulcus ibis Egretta garzetta Nycticorax sp. Alcedo atthis Milvus migrans Haliastur indus

Ardeidae Ardeidae Ardeidae Ardeidae Alcedinidae Accipitridae Accipitridae

Macroglossus minimus Aonyx cinerea

Pteropodidae Mustelidae

Fish Striated mudfish Catfish Amphibia Toad Common tree-frog Reptilia Tokay Common monitor lizard Box turtle Birds Purple heron Cattle egret Little egret Night-heron Common kingfisher Black kite Brahminy kite Mammals Dagger-toothed flower bat Small clawed otter

remains in the more populated areas, as these have mostly been cleared for wetland rice cultivation. This process is even today accelerated by transmigration projects particularly in Southern Sumatra and Kalimantan. Some of the original freshwater swamp forests have been converted into single-species stands of Melaleuca cajuputih in south and southeast Kalimantan. After repeated burning this fire-adapted tree becomes gregarious. The planned burning of peat to generate electricity would even be more disastrous for this special ecosystem. FORESTS OVER LIMESTONE Limestone areas throughout the Indonesian archipelago originate from jurassic, cretaceous,


tertiary and quarternary times. Forests over limestone are usually a mosaic of rich and poor growth due to free-draining, steep slopes, water stress, high concentrations of calcium and magnesium, richer soils between jagged peaks and pinnacles. The tree species diversity is usually less prominent, but the herb flora can be rich with many endemics. This type of forest is most commonly found in coastal areas, in situations where limestone of marine origin was lifted above the sea level by tectonic processes. Limestone areas in higher altitudes do exist, particularly in Eastern Java, the Nusa Timur Region and in Irian Jaya (West Papua). The landscape resulting from weathering and the processes of dissolving of calcium by slightly acidic waters is called karst. The surface of the limestone


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often riddled with caves, separated by flat depressions. Examples of this landscape can be found in Sumatra and in the most strikingly area of the Eocene and Miocene coral limestone areas of Moros and Tona in Sulawesi (Fig. 17.2).

NORTH BONE AREA

MOROS AREA

FIGURE 17.2. Diagrams of conical hill Karst and tower karst from Sulawesi (after Sunartadiradja and Lehmann, 1960).

may be either rocky or covered with intricately sculptured, sharp pinnacles. The karst landscapes are generally in two forms: • The conical hill karst or cockpit karst is characterized by series of conical hills and hollows with moderately steep sides up to 40°. Examples of this landscape can be found in North Aceh and in the Bone district of Sulawesi. • The tower karst consisting of low isolated hills with relatively steep sides up to 90° and

Ecology Limestone consists of calcium carbonate (CaCO3). It was formed by the activity of hermatypic (reef building) marine organisms, in particular calcareous algae, foraminiferans, sponges, corals or molluscs. After being lifted up above the surface, chemical and physical erosion relatively quickly form characteristic landscapes. Dissolved carbon dioxide in rain water can dissolve calcium dioxide. This can result in the forming of caves, but also of rugged surface formations. Limestone landscapes can undergo typical stages of geological succession depending on the intensity and duration of erosive forces (Fig. 17.3). Usually, soils on limestone are rich in calcium and magnesium and their cation-exchange capacity is higher than in other lowland forest soils (Procter et al., 1983c in MacKinnon et al., 1996). Other nutrients are generally scarce. Soils are usually thin and because of the usually porous substrate, water drainage is fast. This can lead to recurrent water stress for the vegetation. Producers Forests on limestone generally have few trees and tree species (Crowther, 1982). Density of large trees in forests is low, the intervening spaces are occupied by smaller trees or by bamboos. The indicator species in the very large limestone areas in Nusa Tenggara are Flemingea lineata (Fam. Leguminosae) and Gymnostemma hederifolia (Fam. Cucurbitaceae) an endemic liana only found on three places in the world, namely: West Timor, Senan and Kangean in East Java in limestone area. Another tree of importance found in limestone

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INITIATION PHASE STARTED MILLION YEARS AGO OR AFTER UPLIFTING OF THE AREA FROM THE SEA

YOUTH STAGE WITH CAVE FORMATION

OLD AGE STAGE WITH ISOLATED PINNACLES

MATURE STAGE WITH DISTURBED SURFACE AREA

SCHEMATIC REPRESENTATIVE OF ONE PINNACLE

FIGURE 17.3.

Succession of a limestone landscape (above, jagged limestone area and single pinnacle.



TABLE 17.2.

Dominating tree species in forests over limestone.

Scientific Name

Family

Afzelia rhomboidea Albizzia acle Cassia javanica Intsia bijuga Pterocarpus indicus Vitex parvilora Pterospermum sp.

Leguminosae

Leguminosae

Leguminosae

Leguminosae

Leguminosae

Verbenaceae

Sterculiaceae

areas of Nusa Tenggara is the sandelwood tree Santalum album (Fam. Santalaceae). Common trees found throughout limestone areas of Indonesia are Ficus sp. (Fam. Moraceae) and Artocarpus sp. (Fam. Moraceae). There is a number of dominating tree species found in limestone areas throughout South East Asia (Table 17.2). Most of the species are deciduous as adaptation to the seasonal water shortages. In areas with a perhumid microclimate, limestone forests also can consist of dipterocarp species. Often, a distinctive herbaceous flora occurs. According to Madulid (1997) the degree of endemism among tree species in forests over limestone is high. This is also true for the other components of this special ecosystem and a percentage of up to 21% endemics is not unusual. Also epiphytes, like the fern Drynaria ridigula (Fam. Polypodiaceae) and lithophytes, like pandans, orchids and wild figs contribute to the endemism. As a kind of adaptation to the relatively often occurring water stress situation for the vegetation many plants with an annuality of their life cycle can be found. The completion of the entire life cycle in between the rainy season and the survival of the dry season in form of seeds is one of the more common adaptations while fleshy plant structure, for example Euphorbia sp. (Fam. Euphorbiaceae) and Kalanchoe pinnata (Fam. Crassulaceae) is another form to overcome dry spells. Kalanchoe sp. avoids severe water stress by closing the stomata during daytime

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and performing essential part of the photosynthetic processes during nighttime, a process called crassulacean acid metabolism (Chin, 1986). Dioscorea sp. or yams can stand long dry spells and revive on rewetting. This phenomenon is called poikilohydry (Whitmore, 1984). Other herbs, like Amorphophallus sp. (Fam. Araceae) with its hooded spatix up to 120 cm tall, sitting on a stem of the same or even greater height, has large deep tubers and becomes dormant during the dry season. Consumers No specific vertebrate fauna is known so far from forests over limestone. It is, however, reported that the serow Capricornis sumatraensis, a goatantelope, is specifically found in such areas. Typical bird species in these forest and bamboo include Rufous coucal Centropus unirufus, Azurebreasted pitta, Pitta steerii and Mangrove blue flycatcher, Cyornis rufigastra. The only fauna restricted to certain limestone habitats are some molluscs (Weedie, 1961). Another example known is the butterfly Graphium androcles (Fam. Papilionidae). This butterfly is found mainly in the limestone areas of Sulawesi because its food plant is bound to this kind of ecosystem. Ecological Status There are two major threats for forests over limestone: logging and quarrying of limestone for construction, as fertilizer (e.g. to prevent acidification in fish ponds) or for cement. However, because of difficult accessibility, forests on very rugged limestone are relatively safe from logging as yet. Large cement plants are in operation already, like in East Java, Nusa Penida (Bali), North Sumatra, Sulawesi and Nusa Tenggara. Forests on limestone appear to be particularly susceptible to fire damage, probably because of the generally drier conditions imposed by rapid drainage (Lennartz and Panzer, 1983). After fire the ground may remain bare for several years, prone to

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accelerated weathering and erosion, before slow succession of bryophytes and ferns reestablishes, and shrubs begin to grow in pockets of soil and litter (Anderson, 1965). FORESTS OVER ULTRABASIC ROCKS Tropical forests over ultrabasic rock seem only to be known from Malaya, Borneo, Palawan, Sulawesi, New Guinea, Solomon Islands and New Caledonia (MacKinnon et al., 1996, Richards, 1996). The most extensive areas of the world are found in the east of Central and South Sulawesi with about 8,000 km2. This ecosystem does not exist in tropical Africa or America. Ultrabasic or ultramafic rocks come into existence in trenches, fault lines or other areas that exude heavy metals. Ecology Serpentines, named after their green color, and peridotite are the most important minerals besides iron, magnesium, aluminum and heavy metals in ultrabasic rocks. They are dense and of igneous origin. The ratio sesquioxide: silica is low (Richards, 1996). Silica does not amount for more than 45% (MacKinnon et al., 1996). Conditions for plant growth are not very favorable. They are notorious infertile due to: • High levels of exchangeable magnesium. • Deficiencies in Ca, N, P, K, Mo, Zn. • Toxic concentrations of heavy metals such as Ni, Co, Cr. Producers The vegetation, generally, is low and scrubby. Most tree species belong to Ficus sp. Fam. Moraceae) or are members of the families of Sapotaceae, Guttiferaceae, Burseraceae and Myraceae. On flat ground Rhamnaceae can be found as a kind of pioneer species. Also the local ironwood species Metrosideros sp. (Fam. Myrtaceae) is found in Sulawesi.


Foliar analyses of tree species growing over ultrabasic rocks in New Caledonia indicated that 21% of the investigated species showed increased levels of manganese (more than 1 mg•g-1) and 5% high contents of nickel (MacKinnon et al., 1996). In the forest over ultrabasic rocks of Gunung Silam, Sabah, Borneo, this was only the case for five (Mg) and one (Ni) species respectively. This study also showed that rates of growth, herbivory and decomposition are well within the range of other forest types (Proctor et al., 1989 in MacKinnon et al., 1996). This indicates the existence of mechanisms to neutralize the potential negative effects of heavy metals in plants, decomposers and producers alike. On steeper ground stiff grass, Miscanthus sinensis (Fam. Graminaceae) and the yellowflowered Scoevola oppositifolia (Fam. Goodenicaea) can be found. As an endemic of this kind of areas in Sulawesi the Gardenia celebica (Fam. Rubiaceae) is recorded. Consumers The density of vertebrate animals is generally very low. Whether this is due to low productivity, high level of defence compounds in the plants, low concentrations of major nutrients in the provided plant material or toxic concentrations of metals in many plant parts is not yet known (Jaffre, 1976, Whitten et al., 1988). In Sulawesi, five endemic bird species are only found in these areas and some fly catchers and starlings seem to have a preference for ultrabasic soil areas (Holmes and Wood, 1980). It is remarkable that a significant lower number of fruitflies do occupy these areas, but that there are much more ants found in this areas. The latter phenomenon might be due to the relatively large number of plants processing mutualistic associations with ants (Whitten et al., 1988). Otherwise, no information on a special fauna in forests over ultrabasic rocks is available.


395

HEATH FOREST

ULTRABASIC FOREST BANDAR SERI BEGAWAN

SANDAKAN

LIMESTONE FOREST

PONTIANAK SAMARINDA

PALANGKARAYA BANJARMASIN

FIGURE 17.4.

Distribution of various special forest formations in Borneo (after MacKinnon et al., 1996).

Ecological Status Experiences from Borneo have shown that conditions for sustainable agriculture are very unfavorable, and are deteriorating very quickly with ongoing erosion (MacKinnon et al., 1996). Further mining activities and the leading of a wide spectrum of heavy metals into the environment is highly dangerous for the actual locality but usually has also a far-reaching effect along the rivers draining the area. The study of this ecosystem could give very valuable information concerning the regreening

necessities of industrial sites, including mining areas and hydropower plants on ultrabasic soils. HEATH FOREST This kind of forest ecosystem is not known from volcanic soils in Indonesia. It occurs usually on spodosols or podzols, strongly weathered siliceous soils developed on quarz-sand terraces, sandstones or rocky summits (Whitmore, 1984). These soils are poorly buffered and pH of less than 4.0 is common. The soils are frequently of coarse texture and freely drained. The streams draining heath

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forests are dark brown or tea-colored, due to the presence of humic acids (Whitmore, 1990). These areas correspond with those areas in Kalimantan which the Dyak tribe of the Ibadan call "kerangas" or "forested land that if cleared will not grow rice" (Whitten and Whitten, 1992). The greater extend of heath forest in Southeast Asia is found in Borneo. Of the originally 66,000 km2 in the mid 80's 48% was remaining at the end of the 90's (MacKinnon and MacKinnon, 1986) (Fig. 17.4).

A

Ecosystem Functions Producers Heath forest has distinctive structural and vegetation characteristics and is strikingly different from lowland dipterocarp forest in structure, texture and color (Whitmore, 1984). Most of the trees are xeromorphic, smallstemmed and often microphylled. The leaves are often thick and leathery or sclerophyllous. The canopy is usually low, uniform and single-layered. Trees are often densely packed with up to 750 trees of 10 cm dbh per hectare (Riswan, 1982). Two possible explanations have been discussed to describe the special structure and xeromorphic character of heath forest. They may be caused by nutrient deficiencies or they are adaptations to minimize water losses and reduce heat load during periods of drought (Brünig, 1971). Major plants genera found are Syzgium sp. (Fam. Myrtaceae), Ilex sp. (Fam. Acquifoliaceae), Planchonella sp. (Fam. Sapotaceae), Acronychia sp. (Fam. Ruttaceae), Diospyros sp. (Fam. Ebenaceae), Garcinia sp. (Fam. Guttiferae) and Glochidon sp. (Euphorbiaceae) (van Balgooy and Nooteboom, 1995). All the plants are specialized in minimizing water losses and heat load by holding the foliage obliquely or vertically and are often equipped with highly reflective leaf surfaces. Other commonly found trees species are Eugenia palembanica (Fam. Myrtaceae), Dactyloglodus sp., Dacrydium sp. and


S

B

FIGURE 17.5. Structure of a pitcher plant showing the dimorphism of the upper and lower pitchers (after Kurata, 1976). a Morphology of the dimorph pitcher plant b Cut open pitcher showing some of the life cycle inside the pitcher filled with digestive liquid S Thomasiid Spider


Casuarina sp.. The absence of genera of Australian affinity is noteworthy. Lowland heath forests have many features in common with peat swamp forests (Brünig, 1973). Plants with supplementary means of obtaining minerals are common. Casuarina nobilis has root nodules which contain nitrogen fixing bacteria. Myrmecophytes of the family Rubiaceae produce thick, hollow tubers to host ants, bringing both organic and inorganic compounds into the chambers to be also absorbed by the plant (Wallace, 1989). Under the convex leaves of the creeper Dischidia ants can live. And while the ants receive shelter the plant receives nutrients in form of waste food, feces and ant corpse. Scoop-shaped leaves of the orchid Bulbophyllum becarii can catch plant litter and a special group of roots from the pseudobulb base grow into the trapped litter. Due to the nutritional status of the soils, epiphytes, myrmecophytes, ground bryophytes and insectivorous plants, like the pitcher plants (Nepenthes sp., Fam. Nepenthaceae) (Fig. 17.5) are well represented (Whitmore, 1984). While swampy areas and the so-called mossy forests hold most of the species Nepenthes can not be considered to be a rainforest plant preferring shade, but in fact exhibits a preference for more exposed places, such as mountain ridges, forest edges, rock faces, swamps and crown of tall trees. They can even be found in limestone areas, sandfields and partly submerged places. The pitcher is in fact a modified leaf with a shape like a jug or funnel with a slippery inner surface and an incurved pallisade at the mouth. It acts in the first stage as a trap for insects and in the second stage digests its prey with digestive fluid. In the third stage the dissolved protein is absorbed by the same glands to make up for the deficiencies of normal nutrients in a poor soil habitat (Kurata, 1976). The center of evolution for the genus of Nepenthes is considered to be Southeast Asia. While this genus can be found all over Southeast Asia the

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only other places are Madagascar, Sri Lanka, Northern India, Southern China and New Guinea. Neither in mainland Africa nor in South America these pitcher plants can be found. The total number of species worldwide recorded is 71. In the Indonesian archipelago 51 species are found, 30 for Borneo alone followed by 21 for Sumatra. Nepenthes is a dioecious plant. The marginal nectar glands are placed mostly in a conical pit located at the base of each tooth usually placed on the inner rim of the mouth. Inside the pitcher, the inner surface of the lower parts are densely occupied by digestive glands, secreting the enzyme endopeptidae, able to dissolve protein into peptides which can not be absorbed by the plant. Another enzyme, aminopeptidae, is needed to dissolve the peptide into aminoacids which can be absorbed by the glands of the plant. This enzyme is provided by bacteria living in the fluid of the pitcher. Also a surface-active-agent akin to alkohol is responsible that trapped insects quickly drown. However, more than 55 insect species have been recorded as inhabitants, two-thirds of them living and breeding in there. Also a species of freshwater crab can be found in pitcher plants in Borneo. Consumers The animal community faces similar problems as in peat swamp forests due to the fact that plants defend themselves with toxic or unpalatable compounds. High levels of phenols and tannins can be recorded in plant parts of many heath forest species. The mammal density was estimated with only 1 per 2 ha and the bird density at 1 per 0.4 ha in Borneo, a figure about less than a half of the surrounding lowland dipterocarp forest. This trend is also true for amphibians and reptiles, even cicadas, which are so characteristic of other lowland forest formations are virtually absent. Also the streams draining heath forests are considerably less divers than comparable rivers in other forest formations, because they are 'black rivers' full of humic acid.

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Termites are the major detrivore besides beetles such as saprophages like the Oxytelinae and predators like the Staphylinidae. Ecological Status The soils are poor in bases, highly acidic, commonly coarsely textured and free-draining. They are often covered in a superficial layer of peat or humus which is quickly lost once the natural vegetation is cleared. IRON WOOD FOREST Ironwood forest is a characteristic forest type in the lowlands of Sumatra, Borneo and Southern Philippines. The formation can vary in composition and from site to site and from island to island. In East Kalimantan this tree (Eusideroxylon zwageri, Fam. Lauraceae) is rather common within lowland dipterocarp forest. Ecosystem Functions Ironwood trees can form a distinctive, monodominant forest like in Sumatra or as scattered individuals and small stands as found in East Kalimantan. These trees are usually a part of the main canopy of about 30-35 m height and grow on sandy or alluvial soils along river terraces or in poor to moderately well-drained soils of undulating hilly terrains (MacKinnon et al., 1996). It can occur in mixture with Intsia palembanica, Eugenia sp. and Palaquium sp. Ironwood has a irregular flowering season which peaks around the middle or end of the dry season (Koopmann and Verhoef, 1938). The seed is about 14 cm long, weight 230 g and is ovoid like a rugby ball. It is the largest of all recorded dicotyledon seeds (Fig. 17.6). As most large seeds high humidity is needed to remain viable, but this viability is retained only briefly. Dispersal by transport through animals is not easy and therefore monodominant stands can occur.


A

B C

FIGURE 17.6. Structure of an ironwood tree, Eusideroxylon zwageri, and its seed A Structure of the tree B Fruit C Seed morphology


Ironwood trees are slow growing with a kstrategy lifestyle, characterized by the production of relative few offsprings, but with a large investment in each seed to ensure its successful germination and survival (Jacobs, 1988). Only about 10 cm thick trunks are usually found with 30 years old trees. Due to this very slow growth the wood is prized for its strength and durability, resisting rotting for decades. The tree may be more than 60 years old before it flowers and fruits. Ecological Status The harvesting of ironwood trees before they have made a reproductive contribution will lead eventually to extinction of the species. In many parts of Indonesia this species is already regarded as endangered. The establishment of an effective conservation of the remaining stands and the establishment of breeding grounds in form of plantations is very needed (Peluso, 1992).

399

areas are often places of mining activities the study of this ecosystem could give valuable information concerning the regaining of industrial sites. Heath forest develops over poorly buffered soils. The forest community is strikingly different from all other forest types. Defense mechanisms using phenolic compounds and tannings are common resulting in a relatively poor faunal community. Ironwood forests are varying in composition, site to site and from island to island. The most characteristic tree species is Eusideroxylon zwageri, a very slow growing tree producing very durable timber.

SUMMARY Despite the fact that swamp forests, forests over limestone, forest over ultrabasic rocks, heath forests and iron wood forests have never been a major topic for ecological research, these special forest types do show very interesting adaptation patterns to their specific location. Extension swamp forest areas can be found in both, clear freshwater environments and highly acidic peat swamp areas. These areas are poor from a nutritional point of view and interesting defense mechanisms of the plants have developed there based mainly on phenolic compounds. Plant communities over limestone can be found throughout Indonesia as a mosaic of rich and poor growth dependent on the drainage pattern. Sometimes unique flora and fauna lives in these environments adapted to the relatively often occurring water stress situation. Organisms living in area of ultrabasic rocks need to be adapted to the existing mineral-rich environment. Because these

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400


MOUNTAIN FORESTS


THESIS With the tropical lowland evergreen rainforest disappearing due to a wide variety of pressures upon it, mountain forests are becoming important refuges for and sources of many plants and animals. They become the last resort for the genetic diversity in tropical South East Asia.

401

18

MOUNTAIN FORESTS Friedhelm Göltenboth, Gerhard Langenberger and Peter Widmann

OVERVIEW While large areas of Kalimantan consist of a wide expanse of flats and some mountain ranges, none of them of volcanic origin and exceeding 2,000 m altitude, all mountains on Java and Bali are volcanoes. In Sumatra, Sulawesi, Nusatenggara and the Moluccas the mountains are either formed by an uplift of sedimentary deposits or volcanic action, while in Irian Jaya (West Papua) the highest uplifted sedimentary mountain ranges can be found with peaks more than 5,000 m a.s.l. Only there the nival zone with the permanent snow line being at about 4,700 m can be found and the only still existing glacier in all of tropical South East Asia (Table 18.1). ECOSYSTEM FUNCTIONS The ecosystem functions of mountain forest are very similar to those described for the tropical lowland evergreen rainforests. The significance of forests on slopes, is even higher for the protection of watersheds through control of erosion, leakage of nutrients and control of water release. The latter function is of particular importance, since these forest formations form the upper portions of watersheds. The water holding capacity of the forest soil and the increased precipitation within intact forests leads to a more predictable water supply for irrigation and for hydroelectric power plants (Pennafiel, 1994). Water availability is increased by the presence of trees in mossy forests through wind-driven interception of moisture (Doumenge et al., 1994).

Forest Ecosystems

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TABLE 18.1.

Altitudinal zones in humid Malesia (after van Steenis, 1972 in Richards, 1996).

Zone

Altitude (m)

Vegetation

Formation

Tropical Lowland subzone Collline subzone

0-1000 0-500 500-1000

Closed high forest

Lowland tropical forest and monsoon forest

Submontane

1000-1500

Closed high forest poor in mosses

Lower montane forest

Montane

1500-2400

Closed high forest: above 2000m with decreasing stem diameter and increasing density of moss

Subalpine

2400-3600

Dense low forests with emergents, often mossy with conifers

3600

FOREST LIMIT

Low shrubs isolated or in clumps, conifers

4000

TREE LIMIT

Stony desert with grasses

4600+

PERMANENT SNOW

Alpine

Nival

4000-4500

Montane forests play a significant role for maintaining species diversity in Indonesia, since significant tracts of forests, particularly on Sumatra, Java, Bali, Nusatenggara, Sulawesi and the Moluccas are left only in higher altitudes. The degree of endemism is usually high on tropical mountains for certain taxa, particularly birds, smaller mammals and certain plant families confined to the zone above 1,000 m, for example, Ranunculaceae and Primulaceae. Abiosis Temperature decreases by about 0.6°C with every 100 m increase of altitude (Jacobs, 1988). Above 2,000 m the temperatures are regularly found with less than 10°C at night. The range of daily temperature is 15-20°C. As in lowland forest

MOUNTAIN FORESTS

the temperature range in a single day is larger than in a complete season. However, in upland areas the range can be considerably wider. Early morning hours can be very chilly, while during noon time more than 40°C can be reached on clear days. Low temperatures slow down a number of processes, like: • Metabolic processes based on chemical re actions. Generally, speed of chemical proc esses of organisms double with an increase of temperature of 10°C. • Organic and the chemical break-down proc esses in the soil. • Processes of soil formation. • Movement of water through the soil. As with other ecological factors, the averages are of no cardinal importance but the extremes in connection with the duration.


The types of soil found on mountains are generally similar than anywhere elese, but on mountains of volcanic origin the dominant type is dystrandept, a slightly weathered volcanic ash soil with a very low base saturation and a thick black topsoil. Differences in bedrock composition and climate are obviously the major factors influencing soil formation at different heights up a mountain, with the steepness of the slope and the openness of vegetation cover playing in addition important factors. Soils are generally charactericed by: • Higher soil acidity with increasing altitude. • Decrease in mineral nutrients with increas ing altitude. • Reduced abundance of soil organisms. • Less well formed structure and texture. • Peat accumulation more frequent in wetter parts. • Decomposition and weathering processes are slow. • Erosion and leaching of nutrients are com mon, in particular on steep slopes or in situa tions where cover of vegetation is sparse. • Soil is dry and nutrient poor on ridges and summits due to continous leaching. • Calcium deficit can be recorded for many montane soils. Landslides are a very common feature even under undisturbed conditions. They are much more rampant if the forest cover had been destroyed. Relative humidity in montane forests is also considerable higher than in the lowlands. At about 1,700 m it reaches 86-100% at dawn and 68-98% in the early afternoon hours, while after dark again 86 100% is reached regularly (Musser, 1982). Warm humid air from the coastal plains that is forced to ascend along mountains eventually forms clouds and rain drops start to build. Another source of moisture is the stripping of clouds by the vegetation which is called horizontal precipitation (Bruijnzeel and Proctor, 1994). Clouds can also be very persistent on mountain tops and along ranges and effectively

403

shield the vegetation from solar radiation. Often during the drier months, when the air is not saturated with water vapour, at about 2,000 m a.s.l. a belt of clouds is formed due to the effect that acending air reaches its dew point at this altitude. This dew point is reached when the temperature is low enough so that condensation of water vapour can occur and clouds of drops or dew is formed. This is only possible if dust or other particles are available for water vapour to condense upon. On clear days, on the other hand, solar radiation is more intense on high mountains than in the lowlands, since the atmosphere that also absorbs or reflects radiation, gets thinner. Ultra-violet radiation can become intense above 2,000 m. The naturally occuring ozone layer in the upper parts of the troposhere is generally thinner near the equator and therefore we do have a much reduced filter effect for UV-radiation by this ozone layer. This can lead to cell mutations in plant and animals cells, including the cells responsible for reproduction. Any UV-induced mutation can lead to new forms of organisms. Hypothetically it is therefore possible that the recorded higher endemism rate of montane environments is the result of higher cell mutation possibilities due to a higher UV-radiation intensity. Rainfall is usually irregular. The mountain areas receive more frequent rainfall but less total amount of rainfall compared to lowland areas. Great variation exists between consecutive years and the various mountain sides. Furthermore, because of the lower atmospheric pressure, fewer oxygen and carbon dioxide is available for metabolic processes. However, most Indonesian mountains are too low to easily recognize this effect. The forests on these mountain ranges gives the impression of being stunted in growth with large trees only to be found in sheltered situations.Whether the soil conditions or the direct climatic effects or the change of the communities in disperser organisms is the major factor for the formation of the

Forest Ecosystems

404


characteristic vegetation type on mountains is not yet clear. The frequency of the cloud cover or fog is certainly a very important factor determining the stature of montane forest trees. Stunting can be caused by low rate of photosynthesis and transpiration and is related to a reduced supply of nitrogen in the soil (Bruijnzeel and Procter, 1994). Forest fires probably caused by lightning seem to occur frequently in montane forests. Natural grasslands only can persist when fires are recurrent and above the tree line. Dormant volcanoes can be densely covered by montane forests. However, after eruptions, whole ecosystems can be destroyed within hours by lava or ash. Biodiversity The mountain flora in Indonesia is derived from both Asia and Australo-Melanesia. For example, in Kalimantan the genera Gentiana, Ranunculus and Viola originate from Asia while Gaultheria, Gunnera and Nertera reached Kalimantan from Australo-Melanesia. Only very few plants span the complete altitudinal range from the lowlands up to the upper montane forest. One example is the tree Dacrydium beccari subelatum (Whitmore, 1984). The majority of species is restricted to a single forest formation, with only 3% occuring in both, lowland and lower montane forest and fewer than 1% from lowland to upper montane forest (MacKinnon, 1977). Major factors influencing the vegetation on mountains are: • Altitude • Volcanic activity • Soil nutrient status • Degree of seasonality • Height of prevailing cloud cover. Producers Borneo's highest mountain forests are found in Mt. Kinabalu (4,101 m). This peak in Southeast

MOUNTAIN FORESTS

Asia is still growing by about 0.5 cm per year (Jacobson, 1986). Botanical surveys revealed that there are about 610 species of ferns or 1/5 of the world’s pteridophytes, 16 species of the 30 species found in Borneo of pitcher plants, 700-1,000 species of orchids, 25 species of rhododendrons and 78 species of fig trees. The most primitive living conifer, the Celery pine Phyllocladus hypophyllus and the link between beech and oak trees, the Trig oak Trigonobalanus verticillata is also found here (Corner, 1978). On Java the lower montain forests are rich with tree ferns. Tree ferns, mainly Cyathea are also a common component of the mountain vegetation in Sumatra, Java and Sulawesi. They can grow up to15 m high with about 1 m increment in growth per 15 years. Between the first growth of the young tree fern and the start of vertical growth several years can elapse (Tanner, 1983). The very trunk of the tree fern is a special niche for epiphytic ferns like Lindsaea pulchella. From Java alone 15 tree fern species are recorded and from Sulawesi 20 species of tree ferns from four genera are known. The center of evolution for the ant fern Lecantopteris sp. (Fig. 18.1) living in symbiosis with the ant Crematogaster sp. is found in the montane forests of Sulawesi. The shrub Strobilanthes sp. (Fam. Acanthaceae) shows a synchronized flowering and fruiting oocuring once before the entire population dies. Each species of this shrub genera has a different rhythm ranging from 5-12 years. The seedlings grow up again simultaneously. The ecological significance of this phenomenon of simultaneous fruiting is probably to lessen predation on the plant’s seeds. The upper montane forest’s most obvious characteristic on Java is the moss Aerobryum and the most common epiphyte is the lichene Usnea. The uppermost level of the upper montane forest and the subapline forest is dominated by shrubs of the family Ericaceae: Rhododenron with


FIGURE 18.1.

405

Ant-welcoming fern Lecantopteris sp.

winged seeds for wind dispersal, Vaccinium and Gaultheria with seeds dispersed mainly by birds and mammals. Different agents of pollination are crucial. Only the purple gentian Gentiana laterifolia shows to be self pollinating. While dispersal by water or mammals in the upper parts of mountains and particularly in the subalpine part are of less significance in explaining the regional distribution , wind dispersal for seeds of orchids, ferns and daisies and bird dispersal of berries might be of great importance. The means of dispersal of mountain bound plants reflected in the sometimes very specific distribution pattern of the respective montane vegetation is not yet fully understood. However, the local source of plants in montane areas is divisible into two groups (Steenis, 1972): • Those plants characrteristic of lowlands like Dipterocarpaceae, Bombaceae and Ficus. • Those plants with wide latitudinal distribution like Pinaceae, Cruciferae, Theaceae, the latter having low-(microtherm) and high (megatherm) temperature adapted species. The microthermic allochthonous flora reached Indonesia via three distinctive tracks (Fig. 18.2).

The groundflora of the upper part of mountains shows many elements usually found in temperate climates like: Gentianaceae, Primulaceae and Ranunculaceae. The most conspicuous plant is the Compositae Anaphalis javanica or Javan Edelweiss with a growth rate of only 20 cm in 13 years (Dokters van Leeuwen, 1933). Single species have been described on Mt. Sumbing in Java as 6 m tall and with a trunk diameter of 50 cm. The rarest plant on Java is the wild strawberry Potentilla polyphylla (Fam. Rosaceae) only recorded for the montane swamp areas of Mt. Papandayan (Steenis, 1972). Endemism particularly for the fauna of the subalpine region is relatively high. About 40% of the plants of the subalpine region on Mt. Kinabalu in Borneo are endemic and 37% of the plant species in the subalpine zone in Irian Jaya (West Papua). Generally, forests are getting more stunted with increasing altitude, vegetation on the ground is getting denser and epiphytes are becoming more abundant. The vegetation zonation is certainly characterized by a number of factors like soil and climate and leads to some specific features (Table 18.2):

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FIGURE 18.2.

Main tracks for the invasion of the Indonesian archipelago by microthermic allochthonous mountain plants (after Steenis, 1972).

The distribution of tree species varies not only vertically but there is also a very distinct distribution pattern on most islands from West to East. For example, the mountain forests of West Java are charcterized by four tree species: Podocarpus imbricatus (Fam. Podocarpaceae), Dacrycarpus neriifolius (Fam. Podocarpaceae), Altingsia excelsa (Fam. Hamamelidaceae) and Schima walichii (Fam. Theaceae). The volcanoe of Mt. Slamet in East Java is the eastward boundary for the latter two species. The westward boundary for Casuarina junghuniana (Fam.Casuarinaceae) is on the neighbouring Mt. Lawu. While Lithocarpus, Castanopsis and Quercus species are a prominent

MOUNTAIN FORESTS

part of the mountain forests of Sumatra, Java, Kalimantan, Sulawesi and the Molluccas the latter two are not found on Bali (Table 18.3; Fig. 18.3). The tree members of the Family Fagaceae are often found in association with the genera Agathis, Eugenia and Phyllocladus. Of special interest is Agathis dammara (Fam. Araucariaceae) found in Kalimantan, Sulawesi and throughout the Molluccans and in the Philippines because of the resin extracted from this tree used to produce varnishes, lacquers, for torches and as raw material of linoleum (Burkill, 1966). In the subalpine and upper mountain forest region, valleys and depressions are generally devoid


TABLE 18.2.

407

General characteristics of the vegetation zonation on mountains in Indonesia (after Meijier, 1959, Yamada, 1976, 1990 in Whitten et al., 1996).

• Below 1200 m • Lower montane forest (Lower Level) 1200-1800 m

Vegetation similar to Lowland Evergreen Rainforest • trees are shorter • trees less massive • more epiphythes • about 280-586 tree species of 10 cm dbh per ha

Boundary: Due to floristic factors between lowland and lower montane forest

• Lower montane forest • abundant moss (Upper level) • tree canopies more uniform Boundary: Usually abrupt but gradual on Java • Upper montane forest • trees shorter 1800-3000 m • trees become squat and gnarled • leaves are small and thick • about 1500 small trees per ha • On leaves many lichenes, mosses, bacteria and fungi

Boundary: Marked floristical, physiognomical and by species abundance

• Subalpine forest • smaller trees “ elfin forest” from about 2000 m to above • smaller leaves 3000 m • shrubs and colourful herbs and grasses dominate; rosett building common

TABLE 18.3.

Distribution of Lithocarpus and Castanopsis species in Western Indonesia (after Whitten et al., 1996).

Island Borneo Sulawesi Bali Nusantara Timur

Number of recorded species Lithocarpus Castanopsis 50 4 0 0

21 2 0 0

of trees and there is no tree species recorded which has adapted to high altitude and water logged conditions. A striking example of the effect of the so-called “Massenerhebung” phenomenon or compression of forest zones is recorded for Mt. Payung at the West of Ujung Kulon in West Java. There a very characteristic upper montane forest with stunted trees is found just 400 m a.s.l.(Bruijnzel and Procter, 1994). Another example of this effect

is found on Mt. Tangkoko in North Sulawesi with a moss and elfin forest patch on an altitude less than 1,000 m a.s.l. In general, the differences between mountains are the result of a combination of the following features: • Existence of a zone of permanent occurrence or not; this zone of permanent occurrence of a given plant species supplies seeds and spores to zones of temporary occurrence of the plant. • Age of soil. • Volcanic events. • Occurrence of zone of compression or “Massenerhebungs effect”. • Occurrence of frost pockets or not. Not only species composition changes with increasing altitude, but also morphologic features. Buttresses, cauliflory and drip tips are getting scarcer, just to mention a few (Table 18.4). The small leathery leaves of many trees of mountain forests are more resistant to seasonal droughts and possibly

Forest Ecosystems

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FIGURE 18.3.

Leaves and fruits of Lithocarpus sp.

to the higher amounts of UV radiation. Individual trees are generally shorter than in the lowlands and their often gnarld structure is the result of wind stress, periodic drought and nutrient stress (Leighton, 1982). The abundance of epiphylls on the leaves are imposing a much higher threat to the upper montane forest plants than insect damage like in the lowlands. Particularly in the subalpine area plants protect themselves with hairy, thick cuticles, wax deposites, high concentrations of protective red leaf pigments or anthocyanins, usually efficient to protect young tissues against UV radiation. Further the root shoot ratio or ratio of dry weight of the below-ground parts to the above-ground parts tends to increase with altitude. This ratio has been measured with 0.1 for the lower montane forest meaning that trunks,

MOUNTAIN FORESTS

branches and leaves together are 10 times heavier than the roots (Edwards, 1982).However, relatively extensive root systems in the higher altitudes support a relatively small above ground component, particularly in wind exposed areas. Because of the lower temperatures plants occurring predominantly in temperate zones also can thrive in Indonesian uplands. According to Jacobs (1988) the following plant families, many of them typical for temperate zones, are dominating Malesian montane forests above 1000 m: Aquifoliaceae, Balsaminaceae, Begoniaceae, Cyatheaceae, Ericaceae, Fagaceae, Symplocaceae. The trends in biomass and productivity changes observable from the lowlands to the upper montane forest can be summarized as follows (Grubb, 1974, Bruijnzeel and Procter, 1994):


TABLE 18.4.

409

Structural and physiognomic characteristics of rainforest formations on tropical mountains (Richards, 1996).

Trees Height 1 (m)

Lowland tropical 25-47 (67)

Lower montane 15-33 (37)

Upper montane 15-18 (26)

Subalpine 1.5-9(15)

Buttresses

Frequent, often large

Infrequent, when present usually small

usually none

none

Size2

Mesophyll

Mesophyll and notophyll

Microphyll -notophyll

Nanophyll microphyll pachyphyll

Drip-tips

Common in lower storeys

Frequent in lower storey

Usually none

None

Compound

Common

Occasional

Rare/none

Usually none

Climbers

Large woody

Numerous

Few/none

Usually none

Orchids

Small or herbaceous

Frequent

Sometimes abundant

Frequent; often epiphytic

Few, except on large emergent trees

Often abundant

abundant

abundant

Rather scarce except near streams

Abundant but seldom forming thick masses

Very abundant often forming thick blankets

Very abundant

Leaves

Epiphytes Vascular Bryophytes 1The

heights are those of ‘canopy’ (highest more or less continuous layer of tree crowns). Heights of emergents are given in parentheses ‘predominant’ size on Raunkiaer’s classification ( in mm2): mesophyll 4500 -18 225 microphyll 225 -2025 pachyphyll thicker leaves notophyll 2025 - 4500 nanophyll less than 225

2The

• The biomass decreases proportionatly less than height of plants, resulting in shorter, stockier trees in the upper montane forest. • Production of woody parts declines from about 3-5 t ha-1 yr-1 to about 1 t ha-1 yr-1. • The production of litter, particularly leaf litter decreases proportionately much less than biomass or production of woody parts. • Biomoss of leaves decreases proportionately much less than the total biomass. • The mean life span of leaves increases only slightly and leaves fall throughout the year with a peak during dry season.

• The leaves become thicker and harder and the leaf area per gram decreases from up to 130 to about 80 cm2 g-1. • With altitude the total production decreases and a greater proportion of production is used in making leaves. • The total litter production ranges between 6,000-7,500 kg ha-1 yr-1. • The plant invest a greater proportion of their energy in making leaves. • The carying capacity is decreasing with the altitude.

Forest Ecosystems

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Comparative estimates of the biomass and productivity for the montane forest areas of all over Indonesia are not yet available. Most single data have been collected on Java and Sulawesi (Whitten et al., 1996). Consumers It has been recorded that 81% of the entire mammal population of Borneo is restricted to altitudes below 660 m (Stevens, 1968). However, 21% of the 44 endemic mammals and 73% of the endemic birds are montane (MacKinnon et al., 1996). It seems that the mountains are a kind of Pleistocene refuges and therefore centers for speciation and endemism. With increasing altitude the following trends can be observed concerning the proportion of birds occupying different niches (Kikkawa and Williams, 1971): • The proportion of tree-nesting insectivore bird species increases. • The tree-nesting frugivores decrease. • Omnivores stay the same. • The proportion of predatory species decreases. • The proportion of ground-living birds increases. The very obvious reason for this trends is the change in food resources. This might also be a major factor for the following observations: • Primates are restricted to lowlands and lower montane forests. • The number of invertebrates particularly of butterflies declines; this is also true for the species composition. • Soil macrofauna steadily decreases and above 2,100 m usually no earthworms are found. • Beetles become more and more dominant above 1,300 m, but generally the invertebrate number declines with altitude. Particularly detrivores like carabid and staphylinid beetles take over the respective niches from ants and termites. The main soil predators are centipedes and spiders and the most dangerous invertebrate is the social wasp Vespa velutina.

MOUNTAIN FORESTS

Bumble bees (Bombus rufipes) are important pollinators in the montane areas. The phenomenon called “summit-seeking” recorded as a congregation process of winged ants, beetles and flies flying up the mountains in large numbers is not yet fully understood (Whitten et al., 1996). • Semiterrestrial crabs like Terrathelphusa kuhli can be found in the middle and lower montane forest parts. • The differences from mountain to mountain in groundfloor organisms can be striking; for example out of 40 species recorded only 4 are found on all the three neighbouring Java nese montains Mt. Merapi, Mt. Merbabu and Mt. Sindoro (Gunadi and Notosoedarmo, 1988). • The herpetofaunal zone is far less distinct than the zonation of other mammals. • No reptiles are found usually above 2,400 m while amphibia are recorded up to 3,200 m. • The steepland boundary seems to be a very important limitation to lowland species. In the montane zone of Java and Bali no native fish species is found, while two endemic amphibia Leptophryne cruenata and Philantus pallidipes are living up to an altitude of 2,500 m on Java. Generally, bird life is scarce showing a major boundary at about 1,300-1,600 m. On Sulawesi the “bird zones” from the lowlands to the mountain tops are characterized by certain bird species: • Lowland zone: Hornbills, coucals, maleo, beeeaters, pittas. • Middle zone: Doves, pigeons, drongos, songbirds. • Higher zone: Songbirds, wood cocks • Subalpine zone: Island thrush From sea level to the montane forest two species are recorded, showing a very wide altitudinal range: • Hawk-eagle, Spizaetus lanceolatus • Racket-tailed parrot, Prioniturus platurus.


Others have a quite narrow range like: Halcyon monarchus between 0-1,000m a.s.l. or Mysa sarasinorum only recorded between 2,000-3,000m a.s.l.. On Java, rhododendron flowers are visited by the Sunbird Aethopyga eximia in areas above 3,000 m. Bird species that are typical for pine forests are widespread in Southeast Asia but are not restricted to this ecosystem like the Velvet-fronted nuthatch Sitta frontalis or the Island trush Turdus poliocephalus. The smallest native mammals are shrews like Crocidura maxi and Crocidura monticola (6 cm head tail length). They are carnivorous, living on millipedes, centipedes, spiders, snails and earthworms. They need to eat daily their own bodyweight in food and are therefore active day and night hunting for prey. Both are montane mammals like the endemic rat on Java mountains, Niviventer lepturus. The very scarce food resources are often divided between different species by virtue of different activitiy periods and different means of finding food. One example is the food division between a rat and a shrew rat on Sulawesi mountains: Tateomys rhinogradoides digs into the soil and rotten wood in search for worms, while Tateomys macrocercus seeks the same worms in the moss only. Arboral mammal species are mostly not found above 1,500 2,000 m. On Sulawesi’s mountains some special mammals are found: • The frugivorous swift bat Theopterus nigrescens. • The world’s last known civet Macrogalidia musschenbroekii able to rotate its hindfeet allowing the animal to decent on vertical sur faces head-first (Wemmer et al., 1983). • The mountain anoa, Bubalus quarlesi,eating significant amounts of moss most probably because of the high water contents stored in this plant.

411

• The montane rats, often fruit-eating climbing rat species, appear to be k-selected species with relative small litters. • Rat species like Rattus marmoreus and Rattus hoffmanni are wide range species occuring from sea level up to mountain tops. On Borenean mountains more than 100 mammals have been recorded and more than 300 bird species of almost entirely Himalayan affinity. Mt. Kinabalu is one of the species richest mountains of South East Asia with a very high endemism rate: 48% of the birds and 65% of the mammals. Gibbons are rarely found above 1,250 m, but macaques have been observed up to 2,000 m. Also Yellow-throated martens (Mustela flavigula) and stink baggers (Mydans javensis) are recorded for montane forests. Generally, patterns of diversity along altitudinal transects vary between different orders of mammals. Diversity of fruit bats decreases, whereas species richness increases in rodents with increasing altitude (Heaney, 1984). Decomposers Decomposition processes in upland forests are hampered by the low temperatures, low light intensities, high rainfall and direct cloud-water interception (Pennafiel, 1994). This is the reason why organic matter can accumulate and form thick layers on the forest ground. NUTRIENT FLOW The basic principles of nutrient flow in upland forests are similar to those already described for Tropical Lowland Evergreen Rainforests. However, there are differences in quantity of flows due to different climatic conditions. In principle two cyclings of minerals are recorded: • A rapid cycling including leaves and twigs. • A slower cycling for tissues of larger woody parts.

Forest Ecosystems

412


The concentration of nutrients in leaves is about half that of their lowland forest counterparts. Most plants absorb minerals from their leaves like nitrogen and phosphorus while magnesium and calcium are not absorbed before the leaf is shed. The major external input of minerals appears to be from the rain (Edwards and Grubb, 1982) contaminated by volcanic ashes. No quantitative study on nutrient flows from montane forests in Indonesia is known. Epiphytes seem to play a significant role in nutrient flow. They deprive their host trees from nutrients from aerosols, litterfall, rainfall, throughfall and remnants from animals (Bruijnzeel and Proctor, 1994). However, at least some trees themselves seem to be able to tap the humus accumulations of their epiphytes. Litterfall in mossy forests is usually lower compared to lowland forests (Bruijnzeel and Proctor, 1994). However large quantities of litter can accumulate because of lower decomposition rates due to lower temperatures. DISTURBANCES Natural Major Disturbances The majority of mountains throughout Indonesia are volcanoes. If active, physical changes can be dramatic. Even a layer of only 1 mm ash on a leaf can reduce light penetration by 90%. The eruption of Mt. Agung on Bali in 1963 survived only 3 plants in the surrounding of the nearby temple complex Besaki: • The grass Eleusine indica (Fam.Gramineae). • The herb Ageratum conyzoides (Fam. Compositae). • The shrub Sambucus javanica (Fam. Caprifoliaceae). Early colonizers of ash slopes are genera of sedges, Vaccinium, Gaultheria, Rhododendron and Gleichenia. The ashes are very often sterile and do not easily retain moisture. Hard lava streams are the slowest to develop new vegetation. Only after about 2 years that ferns

MOUNTAIN FORESTS

and lichenes just start to occupy lava. Early colonizers are the same as on ashes. It is interesting to recall that the edelweiss Anaphalis javanica (Fam. Asteraceae) is confined to volcanoes. Around sulphur vents the closest found plants are Vaccinium varingaefolium and Selaginella feei.Blue green algae can even live in the hot muddy sulphurous pools (Kullenberg, 1982). Human Influence and Ecological Status The most important reason for the rapid dwindling of montane forests is the conversion to agricultural lands for temperate zone crops, in particular vegetables or flowers (Pennafiel, 1994) or due to fires. Most if not all mountain grasslands are manmade using fire for hunting purposes. The oil-rich leaves of rhododendron, Vaccinium and Gaultheria species catch fire easy even during light rain. Some members of the Ericaceae family are fire resistant to some extent and only one plant on Java mountains seems to be encouraged by fire: the Paraserianthus lophantha species needs fire to crack open the fruit. Pioneer plants, covering the soil relatively quick include Lantana camara (Fam.Verbenaceae) and Chromolaena inulifolium (Fam. Compositae), but repeated fires ultimatley produce Saccharum spontaneum and Imperata cylindrica “deserts”. Disturbances are long lasting in this less productive environment and regeneration is very slow and it has been shown that the montane forests are truley the most fragile ecosystem in the tropics (Ewel, 1980). Some timber trees of upland forests are of commercial importance and illegal logging is widespread. Other plants like orchids or stems of treeferns Cyathea sp. are collected for their ornamental value (Pennafiel, 1994). Prospecting and extraction of minerals and ores is a serious threat for upland forests particularly in Irian Jaya (West Papua) and Sulawesi. Large scale


413

projects like mines or power plants require infrastructure. Streets and power lines do not only destroy and disrupt forests, but also enable squatters to settle in formerly undisturbed forest tracts. IMPLICATIONS FOR EIA STUDIES Upland forests are vital components that regulate the water regime of entire landscapes. All impacts that disturb the forest cover are likely to cause major disturbances in the amount and distribution of waterflow. Upland forests usually are poorer in species than lowland forests, but degree of endemism can be very high. In order to protect maximum biodiversity it is therefore vital to protect whole watersheds from sealevel to the highest altitude since many species only have a narrow altitudinal range of occurrence (Heaney et al., 1989). The legal framework for protection of upland forest in Indonesia is already existing. In some parts of the country, like in Kalimantan, all parts above 600 m are protected, but the enforcement of even the simpliest requirements to protect the upper watershed areas are very weak. SUMMARY Upland forests have outstanding significance in water management and they hold an important fraction of Indonesian terrestrial biodiversity. Many of these species are endemic. The continued conservation of these ecosystems plays a vital role in maintaining ecosystem functions for lowland terrestrial ecosystems as well as for freshwater and coastal ecosystems.

Forest Ecosystems

414


ECOLOGY OF RICE FIELDS AND OTHER LAND USE SYSTEMS

CHAPTER V


415

Agroecosystems and Social Ecology

M

ankind has over the last two centuries influenced the given environment in an unprecedented way. In a steadily accelerating way the transformation of natural environment into anthropogenetically influenced environment is taking place, both on a local and global level. The increase in the one species called Homo sapiens is reaching in more and more places dimension that the carrying capacity of the respective environment is stretched to its limits. Also in Indonesia, people have to leave their places due to the destruction of their environment by unsound agricultural practices or effects of pollution. These people belong to the group called transmigrants. They are often called either "economical refugees" or "environmental refugees".


416




THESIS The use of the Indonesian landscape is a kaleidoscope of how man is behaving in and uses the given environment. A wide variety of landuse forms is still in existence throughout the Indonesian archipelago. This include forest dwellers still releying only on hunting and gathering of forest products, shifting cultivators and swidden farmers, using a millenium old sustainable system of slash-and burn for their pioneer-shifting methods in form of rotational fallows and dry-field usages, and permanently settled farmers with rice, coconut and sago-based agricultural practices. A major component of the landscapes on many islands of Indonesia are rice fields forming an integral part of the ecosystem but are, unlike lakes , human artifacts created and maintained by agronomic practices since many millenia. The misuse of the landscape in many areas can only be minimized if more diversified landuse systems, a majority of them tree based, will be owned by local farmers. Special scientific attention has to be given to indigenous natural resource system management which have provided the petiole in this archipelago for millennia with economic sustenance and environmental stability (Basiago, 1995). A very special aspect which needs to be researched is how to grow shade tolerant crops under trees. Marketing systems for wood and wood products that give most income value for the producers need to be developed simultaneously. The question of sustainable development being defined as "development that meets the needs of the present, without compromising the ability of future generations to meet their own needs" (Brundlandt, 1987) is instrinctly interwoven with the problems in connection with landuse system. Considerations should also be given to the CO2 storage capability of trees which could be traded against CO2-emmission of industrial plants world wide. The same is true for the protection and

417

19

ECOLOGY OF RICE FIELDS AND OTHER LANDUSE SYSTEMS Friedhelm Göltenboth, Werner Koch and Joachim Sauerborn


418


sustainable management of coral reefs, which are viewed as landuse systems here as well as special attention needs to be given to the production in the future. OVERVIEW Historically, the ecosystems most people on the smaller Indonesian islands have been depending on were coastal and near shore resources. On larger islands, like Kalimantan and New Guinea, the inner upland areas were the main place of activities of the local people. As long as people were few and resources abundant, no particular management skills to prevent depletion of resources and encourage sustainable land use practices need to be developed. When rice growing became more dominant, lowland forests were converted to paddy fields. The aquatic nature of the rice fields helped to keep this production system very stable and erosion or nutrient losses were no major concern. Rice (Oryza sativa), known as originating from Upper Myanmar, Thailand and SW-China since 7,000 years ago is today the world’s second important cereal crop after wheat and is the staple food of half the world’s population. It spread from its center of origin in South Western China via migrant Chinese to the Philippines (about second century BC) and Japan (about 300 400 BC) and reached via India Java, the Middle East, Africa, Spain, Italy and finally the USA and Australia. Wet rice cultivation spread from the plains to the hills and from irrigated fields to rain-fed fields. It is grown on a wide range of soils from pH 3 - 10 and altitudes (from 0 m - 2,500 m). It is estimated that there are more than 8000 varieties for Indonesia only (Bernsten et al., 1982) and has some unique features such as: • It can be grown in rain-fed areas and in irri gated fields. • Irrigated rice can produce yields at the same place season after season for centuries.


• It is in some culture seen as a status food. • It gives security to the farmer. But when human population increased and Portuguese conquerors and the Dutch colonisers brought new species particularly from South America which could be grown in the uplands, situation started to turn for the worst. Forests were burned to grow sweet potato, cassava, corn, and rubber trees all introduced from South America; coffee and oil palms from Africa without the proper guidance on how to manage upland farming systems sustainably. An example of all the ecosystems utilised by a farmer’s family living in a coastal village is given in Figure 19.1. The pioneer shifting cultivation with a short rotation and poor land management is neither economically nor ecologically sustainable due to the following shortcomings: • Original habitat is completely removed and changed. • The soil is exposed to sun and rain resulting in a continuing export of nutrients by erosion. • Number and type of plant species within the system and harvest yield are decreased. • Further migration and decrease of primary forest decrease the carrying capacity of the area causing low yield and consequently star vation. Permanent cultivation includes rice cultivation, home garden cultivation, mixed planting and tree corps sometimes on a very large scale like with rubber and oil palm plantations. There is a certain trend to intensify the staple food production whether rice, maize or sago and to shift from more taditional cultivation methods into more market - oriented plantations including agroforestry which combines production of food and forage crops with treeproduction. While traditional agroforestry systems can either be found as home gardens echoing in their structure a closed-canopy forest with sun-loving, half-shade loving and shade -loving plant species, or


FIGURE 19.1.

419

Range of livelihood of a farmer family in a coastal area of the smaller islands particularly in the Western part of Indonesia.

as mixed tree gardens in which few or no annual crops are grown and in which a permanent closed canopy exists, modern argoforesty can be found in three types: • As family forest with fruit and fuel wood trees planted even in fallowed swiddens like in Eastern Indonesia or East Java and Bali. • As livestock-oriented system by using par ticularly the leguminose tree Leucena leucocephala a fast-growing native of South America providing forage for the livestock, reduces soil erosion, gives shade and reduces

the impact of raindrops on the soil surface by the structure of the leaves and maintains soil fertility by being associated with symbiotic, atmospheric nitrogen-fixing bacteria living in nodules provided by the roots of the tree. • As green manure model with hedgerow sys tems on steep slopes as a measure for soil conservation and stabilisation of slopes. In Eastern Indonesia this system eventually leads to shorter fallow possibilities and per manent crop diversification.


420


The entire system of landuses is not stable but in a state of transformation and evolutionary changes. A progresssion from shifting cultivation to forms of sedentary cultivation can be observed (Fig. 19.2) The determining factors as to the type of system of landuse is adopted by the local people depends mainly on geomorphological aspects of the land and the household access to the land. The successive transformation of an entire mountain area in-between about 70 years was first described for the Mt. Sewu area in East Java (Fig. 19.3).

FIGURE 19.2.

Even entire landscapes around major settlements like Yogyakarta in Central Java are subdivided into three distinct agroecological landuse zones( Tolboom, 1991): • The Batur Agung area is mainly used to pro duce fuelwood for consumption in Yogyakarta. • The Gunung Sewu area is mainly the crop supplying area in form of a subsistence - based system. • The Ledok Wanasari area uses a fodder-based system to produce livestock.

Progression of agrosystems from shifting cultivation to agroforestry via sedentary agricultural systems based on findings in Java (after Soemarwoto, 1985).



421

A BEFORE 1840 DIPTEROCARP - FOREST

B IN 1840 ALBIZIA SP. AND FICUS SP. SAVANNA- FOREST (AFTER JUNGHUHN, 1845)

C IN 1890 IMPERATA CYLINDRICA SAVANNA WITH FIRST CROP ENCROACHMENT (AFTER VETH, 1903)

D IN 1909 IMPERATA CYLINDRICA GRASSLAND WITH MAIZE CULTIVATION AS PART OF A SHIFTING CULTIVATION SCHEME (AFTER DANES, 1910 IN WHITTEN ET AL., 1996)

FIGURE 19.3.

Progression of landuse changes at the Mt. Sewu areas in East Java (after Junghuhn, 1845, Veth, 1903, Danes, 1910).


422


Agroforestry is not an easy term to define but the most useful definition can be given as follows (Whitten et al., 1996): A system of permanent land use compatible with local cultural practices and ecological conditions, by which both annual and perennial crops are cultivated simultaneously or in rotation, often in several layers, in such a way that sustained multiple-purpose production is possible under the beneficial effect of the improved edaphic and microclimatic conditions provided by simulated forests. The actually practiced agroforestry systems cover at least 5 different cultivations system (Wirsum, 1980) (Table 19.1). The very beneficial characteristics of these kinds of agroforestry practices can be summarized as follows (Wirsum, 1980): • Proportion of nutrients in the vegetation is high. • Soil is actively and efficiently protected.

TABLE 19.1.

• Layers of vegetation allows for improved ex ploitation of water, nutrients and light. • Relatively high number of species, structural diversity, and spatial diversity. • High resilience and resistance. The comparison of different land use systems concerning their output shows the different benefits gained with the specific usage (Abdullah and Marten, 1983) (Table 19.2). When logging caused the elimination of vast areas of Indonesian forests, particularly the opening up of the formerly forested areas by relatively easy road access, the ever intrusion of this areas by the ever increasing Indonesian population speeded up dramatically. With industrial scale monocultures such as sugar cane, tobacco, rubber, oil palm, coffee and tea and through millions of small farms depending on upland

Comparison of cultivation systems in form of agroforestry patterns practiced on Java and Bali (after Wirsum, 1980).

Cultivation system

Used subsystem

Indigenous system

Rotational cropping of annual and perennial crops and

Fallow - with natural tree Fallow - with planted tree

Shifting cultivation Wonosobo system: Acacia-tobacco vegetables

Intercropping with annuals and short-lived perennials in spaces between trees

Scattered trees on or besides agricultural fields

Mixed cropping with low perennials in spaces between high perennials

Trees and agricultural crops Mixed garded Trees and forage crops for stall feeding Several local systems trees, fodder crops, and green manure crops

Multistoreyed crop as combination of long and short duration crops simultaneously

In housing compound Outside housing compound

Home garden Mixed garden

Mixed farming with crop growing and animal husbandry

In housing compound Outside housing compound

Home garden Several local systems like grazing in coconut plantations



TABLE 19.2.

Comparison of the output gained from three major landuse systems (after Abdullah and Marten, 1983).

Parameter

Rice fields Upland fields

Home gardens

Calories Protein Calcium/Iron/ Riboflavin Vitamin A Vitamin C Return on labour Return on cash

high high

low low

low low

moderate low low low low

moderate moderate moderate moderate moderate

moderate high high high high

FIGURE 19.4.

423

crops, the Indonesian landscape rapidly developed in many areas into depleted grasslands as can be seen in many parts of the country. There is a clear trend towards the plantation type of landuse not only in the lowlands but also in the uplands and a variety of improved systems of agro forestry practices are in use like (Fig. 19.4): • Alley cropping. • Natural terracing using hedge rows, thickets and live fences often in form of leguminous trees like Leucena sp., Calliandra sp., Cassia sp., Sesbena sp. and Gliricidia sp, the latter particularly in dry areas because it is very drought resistant (Rangkuti et al.,1990). Also some specific grasses are used

The impact of commonly practiced shifting cultivation (left) and improved small-scale agro-forestry systems (right).


424


like Setarium sp., Pennisetum sp. and Vetivera zizanioides. The latter grass is used as fooder, mulch, animal bedding, for handicrafts and as raw material for the extraction of fragrant oil from its roots. • Contour farming. • Replacement of chemical fertilizer, herbicides and pesticides by organic fertilizer, mulch and biological control agents. There are, however, a few examples of successful landuse schemes which have developed and are still practised in a very sustainable way in the Indonesian archipelago. This so-called indigenous resource systems are characterised as: • Permacultures. • Conserving biodiversity. • Securing property rights for the local farmers. • Producing sustainable yields. The impact on the ecosystems by modern kinds of landuses like monoculture crops and tree plantations is of great concern for many peoples, the owners of those estates, the local population and many people concerned about the degradation of the environment. ECOSYSTEM FUNCTIONS Landuse systems are originally designed for the only purpose to provide food for human consumption. In a wider sense landuse systems include all types of utilisation in all ecosystems under human influence. This may reach from hunting, gathering of medicinal products in the forests to the protection of nature reserves, national parks or seascapes. A striking example of such a succession of crop development has been studied on Halmahera (Wada , 1980).The succesional stages of development were found to be as follows: • 1st - Hunter and Gatherer; Wild sago and wild banana collectors. • 2nd - Cultivation of banana, taro and yams. • 3rd - Cultivation of two grains: • Foxtail, Setaria italica (Fam. Poaceae), cultivated some 8,000 years ago;


• Job’s tears, Coix lacryma-jobi (Fam. Poaceae). • 4th - Cultivation of dryland rice since 3500 years ago. • 5th - Introduction of American crops like: • Cassava (Manihot esculenta; Fam. Euphorbiaceae); • Sweet potatoes (Ipomoea batatas; Fam. Convolvulaceae) about 400 years ago by the early European colonialists. • 6th - Use of a complex swidden system until today with: • Up to 40 plants used; • Still exsisting elements of each phase of the agricultural development; • Intensive and extensive systems besides each other; • Use of 61 types of fruit bananas (Musa sp.; Fam. Musaceae); • Use of 6 forms of yams (Dioscorea esculenta; Fam. Dioscoreaceae) and 4 forms of taro (Colocasia esculenta; Fam. Araceae); • Increasing use of Sorghum bicolor (Fam. Poaceae) known with at least 6 varieties and maize (Zea mays; Fam. Poaceae) often grown in intercropping systems with mung beans (Vigna radiata; Fam. Fabaceae) or soybeans (Glycine max; Fam. Fabaceae). With the increase of human population and the simultaneous destruction of natural ecosystems’ vital functions, landuse systems more and more have to take over functions of natural ecosystems (Fig. 19.5). Hence, modern landuse systems have also to: • Contribute to the protection of biodiversity ge netically and physically; • Contribute to the stabilisation of the local climate; • Prevent the loss of nutrients from the area; • Prevent the eutrophication and chemical poisoning of soils and aquatic systems;


FIGURE 19.5.

425

Landuse systems as found in many places throughout the Indonesian archipelago and the interrelationships between the different systems in relation to water dependencies.


426


TABLE 19.3.

Comparison of different landuse systems and the rates of surface erosion ( after Whitten et al., 1996).

Land use system

Rate of surface erosion (t .ha-1)

Pristine forest 75 Degraded forest

1969-1973 1974-1978 1979-1983 1984-1986

0

FIGURE 20.12. "Forced" migration as expressed by the distribution of settlements of transmigrates during 1969-1986 (Source: Dir. Gen. of Transmigration, Jakarta ).

fi) (Q

3

n

-w-


479

FIGURE 20.13. Poverty

mentioned that 25.9 million people still live under the official poverty line. However, it was predicted that by the year 2005, the absolute poverty syndrome will be eradicated (Indonesian Observer, 18.10.1996,p.3). Absolute poverty is defined as being not able to buy 16 kg of rice per month (World Bank, 1994). By the end of the 1990s the number of people living in absoute poverty rose over 60% due to a severe economical crisis.

Poverty is often defined as lack of modernization or exclusion from development. Both does not hold true, because most tribal people have few posessions , but are not poor. Poverty is not a certain amount of goods, but it is a social status. As such, it is an invention of civilisation. Child Abuse In 1995 in Indonesia, about 2.2 million- 3.3 million children were part of the workforce (Feer, 1996). Children in export-oriented factories are working 7-

Socio Ecology

n

480

Goltenboth, Timotius, Milan and Margraf

13 hours daily in dangerous conditions for about US$ 4 per week (US Dept. of Labor, 1995). Children working as domestic workers are reported to earn as little as US$ 10-25 per month (Bessell, 1996). Enforcement of existing laws regarding child labour is very weak or totally neglected. There is even some divergence of opinion concerning whether child labour per se should be censured, or just child labour without adequate regulation and supervision. Nuclear Threats In Semenanjung Muria on the foot of the volcano Mt. Muria in Central Java the first nuclear power plant will be established if the plans go ahead as

proposed by the Indonesian government early in 1990 (Fig. 20.14). In principle, two forms of nuclear reaction can be utilized as source of energy: l.The fission where a neutron hits a U 235 nucleus, splitting the nucleus in two. Part of the tremendous amount of energy that bound the nucleus is released as heat, and other neutrons are ejected. This process was shown mathematically by Albert Einstein in the 1910s in his famous equation: E = me 2 • E = energy, m = mass or amount of matter, c 2 = the square of the speed of the light (214,300 km per second).

FIGURE 20.14. Drawing of the proposed first nuclear power plant in Indonesia with a potential capacity of about 7,200 MW capacity (after Kompas, 1993).

HUMAN ECOLOGY

n

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It was misused in form of the first atomic bombs which killed about 150,000 people in August 1945 in the towns of Hiroshima and Nagasaki in Japan. This process is usually used in atomic plants and is a steady threat to the environment, because radioactive radiation and material are produced during the process in the reactor. Any radioactive radiation and material or elements are highly dangerous for living organisms, causing cancer and destroying cells. 2.The second process takes place only at temperatures high enough- like those in the sun with about 5,512 °C - and is called fusion. Nuclei of tritium and deuterium fuse into an unstable nucleus that splits out a high energy neutron, leaving a nucleus of helium. In a reactor, the neutron would give up its energy as heat. No reactor of this type is at present available, but solar radiation is created by that kind of processes in the sun, delivering about 1.7 x 10 14 kW of solar radiation / earth diameter. Patterns of Conventional Development At least five major forces are at work underlying the patterns of conventional development: • First, the drive for materialism which includes only quantifiable goods and services. • Second, the notion to prefer more rather than less. • Third, policies are aimed at short term goals to be reached in a short term period. • Fourth, the process of development is centered on goods for individual consumption, but social demands such as nature and the environment are not sufficiently considered in the market. • Fifth, rationalism is the major driving force for the conventional development and values based on culture and religion are neglected.

481

Under these circumstances, natural resources are being separated from their role as part of the ecosystem. Natural resources are treated as an independent factor of production. But the functioning of ecosystems is based on certain principles: 1. The principle of interdependency where every element in a given ecosystem depends on everything else. 2.The principle of diversity showing that the more varied the ecosystem is, the more stable it becomes. 3. The principle of equilibrium of all items in the ecosystem. Meaning, organisms can survive under the given conditions. 4. The principle of efficiency, showing that virtually nothing in an ecosystem is inefficient. 5.The principle of sustainability revealing that items sustain each other within the ecosystem. With conventional development, these principles cease to function and development degrades and destructs the environment at local and global scales. The search for desirable pathways of development is one of the great challenges of the present and the future. Any development must recognize resources as being part of the ecosystem and as such uphold the respective ecological principles or face the consequences of destruction and degradation of the environment (Salim, 1992). Population Growth and Disproportionate Development Indonesia, being the 13 th largest country in the world with 1,919,270 km2 (Fig. 20.15) and the fourth largest country after China, India and the United States with regard to total population, with more than 200 million inhabitants (1997), is caught between the need for development of the population, growing about 1.9% annually, and the conservation of a unique set of ecosystems from North Sumatra in the west to Irian Jaya (West Papua) in the east. The population

Socio Ecology

n

482


FIGURE 20.15. Dimension of the Indonesian Archipelago placed on a map of Europe (after Roll, 1979). A Atlantic Ocean

MS Mediterranean Sea

of Indonesia has increased nineteen-fold over the past two centuries (Table 20.1) (Fig. 20.16). TABLE 20.1.

Increase of total population in the area of Indonesia during the last 700 years (after Hugo et al., 1987).

Year 1700

1800

1900

1995

lOMio

13Mio

40Mio

190Mio

In the last quarter of the 20 th century, the Indonesian population has grown by more than 60 %. Sumatra's population more than doubled over the

HUMAN ECOLOGY

past 25 years and its rate of growth was almost double to that of Java. Even those in the islands of Kalimantan, Sulawesi and Nusa Tenggara exceeded those of Java. Java and Bali had slower growth rates than elsewhere, due both to lower fertility and net out-migration.

Within Java, there has been a steady shift westwards in the population's center of development. This is due to rapid growth of Jakarta and West Java, whose combined population has grown twice as fast as that of the rest of Java (Fig. 20.17). The standard path of urbanization for Indonesia, particularly the island of Java, is located already near the inflexion point on the curve where

n

-w-


accelerating urbanization can be expected, especially if rates of economic growth are rapid. Jakarta has reached about 12 million inhabitants by the year 2000, being number nine in the row of the 10 biggest cities of the world (Table 20.2) (Fig. 20.18).

People (Mio) 200t-#

INDONESIA

-

-X - X -

-

JAVA

•

O O

•

OTHER ISLANDS

TABLE 20.2. 100 —

1800

1600

2000 Year

FIGURE 20.16. Comparison of population growth in Indonesia, Java and the other islands since 1600.

0

5

10

483

15 km

Growth of the population of Jakarta - area since 1940 (after Nat. Urban Deve. Strategy Project, Jakarta, UNESCO, 1989).

1940

1960

1980

2000

0.8 Mio

1.3 Mio

6.5 Mio

12.0Mio

West Java's high rate of growth compared to the rest of Java has been due to three main factors (Hugoetal, 1987): 1 .Higher fertility rates 2.Less transmigration 3. More In-migration Though not as rapid as the population growth in the other islands of Indonesia, Java's population growth in the 20th century has been very substantial and has not been in a steady trend, due to interruptions on a number of occasions before 1970 (Fig. 20.19). Concerning the population density and distribution, many regional differences and inequalities can be identified within Indonesia, such as: between urban and rural areas, among islands, among provinces, and among smaller areas. To some extent, they are a function of intergroup differences between classes, ethnic groups and sectors of the economy including the underlying differences in soils, topography and history. For example, rich volcanic soils like in Central Java have all the time attracted many settlers and the sugarplantation areas introduced during the colonial past are until today densely populated due to labor demands. Most recent projections of Indonesia's population estimates 278 million by the year 2020.

FIGURE 20.17. Growth of Jakarta between 1800 and 1985 (after Sethuraman, 1976).

Socio Ecology

n

484


24.4 23.6 MEXICO

21.3 SAO PAOLO

TOKYO

16.1 NEW YORK

15.9 CALCUTA

10.7

10.7

10.7

LONDON

TOKYO

SHANGHAI

15.4 14.7 13.7

BOMBAY SHANGHAI

8.7

RHEINRUHR

7.3

7.2

BEIJING

PARIS

TEHERAN

6.9 BUENOS AIRES

13.2

13.1

JAKARTA

BUENOS AIRES

6.6

LOS ANGELES

6.3

YEAR 2000

YEAR 1960

MOSCOW

FIGURE 20.18. The 10 largest cities and urban regions in 1960 and in the year 2000 (in millions) (UNDP, 1990).

While the birth rate dropped from 2.1% in 1980 to 1.9% in 1990 and the life expectancy rose from 42 years to 63 years since 1970, the net growth per year in the inner islands (Java, Madura and Bali) still amounts to 3.3 million people. The overall population growth rate between 1990 and 2020 is calculated as 1.5% (Fig. 20.20). In 1990, the age group of the 0-14 year old constitutes 36.8% of the population. In 1970, the population pedigree showed the form of a pyramid (Fig. 20.21). The pyramid will become more urn-shaped until the year 2020. While pyramid forms are typical for the fast growing populations, the urn-shaped forms are a characteristic of industrialized nations with a steadily shrinking number of younger people and a growing number of elderly people. There is clear evidence for a direct correlation between increasing population densities and environmental degradation. As population pressure pushes cultivation from plains and mid-watershed areas of valleys into the hills, soil erosion increases at unproportionate rates (Fig. 20.22). More than 60% of Indonesia's total population live in Java, which is just 7.2% of the land area. In this island, soil erosion exceeds other parts of the

HUMAN ECOLOGY

country by 3-20% (Birowo and Prabowo, 1987). The Javanese farmers have pushed their farming terraces up to steep slopes of more than 40 degrees. There are no longer any forest stands worth mentioning outside protected areas. At the rate of 3,000 t-km^year1, the country's soil erosion is one of the highest in the world (Bruenig, 1992). For this reason, 1 -2% of Java's topsoil is lost each year, with the burden of sediments borne by rivers and canal systems bringing far-reaching consequences such as floods and the silting up of vast coral areas, particularly in the Java Sea. EVOLUTION AND INVASION OF MAN AND DEVELOPMENT OF LAND USE PATTERN It needed about 1.3 million years to reach the present population of about 200 million people in the archipelago of Indonesia. The earliest evidence of hominids from Indonesia is fossils oiMeganthropus palaeojavanicus excavated in the Djetis bed near Sangiran in Central Java. The first true humans were recorded from the valley of the Solo River in Central Java and are dated to be between 400,000 - 500,000 years old.

n

-w-


485

N

Va

PACIFIC OCEAN

500 km

B

1 2 3 4 5 6 7 8 9

10

\

1900

1910

\^

1920

I

1930

i^

CROP FAILURE, CHOLERA EPIDEMIC INFLUENZA EPIDEMIC DEPRESSION JAPANESE OCCUPATION INDEPENDENCE STRUGGLE ECONOMIC DISRUPTION POST G 30 KILLINGS START OF FAMILY PLANNING PROGRAM INCREASED TRANSMIGRATION

\

1940

1950

1960

1970

1980 1985

YEAR

FIGURE 20.19. Twentieth - Century Population growth in Indonesia (after Hugo et al., 1987) (B) and population distribution in comparison between 1971 and 1990 (A).

Socio Ecology

n

486


Pithecantropus erectus (pithekos = monkey, anthropous = man, erectus = upright) or Java man, was found by Eugene Dubois who was in 1893 at Trinil. This Java man was about 1.65 cm tall, with about 871 cm3 of brain volume. Java man already used fire and stone tools (Megalithic culture) to hunt animals. Today this Java man is assigned to the Homo erectus group and not a "missing link" between monkeys and man, as his name, proposed by the German Ernst Heinrich Haeckel (1834-1919), indicates. His scientific name today is therefore Homo erectus erectus. His younger geographic neighbor, the Solo Man {Homo erectus soloensis) lived about 100,000 years ago. He was related to Homo erectus erectus, had already 1,200 cm3 brain, and shared the Java of his time with animals quite different from today' s wildlife. These included hippopotamus, pygmy stegodont elephants (Stegodon sompeonis), pygmy elephants

2020

1990

FIGURE 20.20. Comparison of total population of Indonesia by region for the year 1990 and 2020 (after Djajadiningrat et al., 1992). 4 Kalimantan 5 Sulawesi 6 Malukku and West Papua

1 Sumatra 2 Java and Bali 3 Nusa Tenggara

B INDONESIA 1985

80+

MALE

I

1

1

120

FEMALE

70-74

T

1 0 0 ••

60-64 50-54

8 0 ••

0.

D

§ 40-44 CD O 30-34

15.0 -LU

Ecology of Insular Southeast Asia: The Indonesian Archipelago

Southeast Asia

A Muslim Archipelago: Islam and Politics in Southeast Asia

Petroleum geology of Southeast Asia

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Frommer's Southeast Asia

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Social Dynamics in the Highlands of Southeast Asia (Handbook of Oriental Studies. Section 3 Southeast Asia)

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Ecology of Insular Southeast Asia: The Indonesian Archipelago

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A Muslim Archipelago: Islam and Politics in Southeast Asia

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Terrorism in Southeast Asia

Frommer's Southeast Asia

Theatre in Southeast Asia

The Politics of Environment in Southeast Asia

The Security Dilemmas of Southeast Asia

Social Dynamics in the Highlands of Southeast Asia (Handbook of Oriental Studies. Section 3 Southeast Asia)

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Southeast Asia: The Long Road Ahead

Southeast Asia: The Long Road Ahead,

Dictionary of the Modern Politics of Southeast Asia

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