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7.1 Introduction 151

7.2 MTEs as a Class of Systems for Testing the Hypotheses Generated by the Assertion that Biodiversity Affects System Functioning 154

7.3 Features of MTEs 154

7.3.1 Climate 154

7.3.2 Substrates 155

7.3.3 Vegetation 155

7.3.4 Fauna 156

7.3.5 Humans in MTEs 158

7.4 Influences of Diversity on System Function in MTEs 159

7.4.1 Landscape diversity and productivity 160

7.4.2 Functional mcchanisms of biodiversity 161

7.4.3 Functional groups 163

7.4.4 Keystones 166

7.4.5 Biodiversity and its support of human utility 167

7.4.6 Intraspecific variation and system function in the Mediterranean basin 168

7.4.7 Pleistocene herbivores in the Californian palaeolandscape 169

7.4.8 Formation shifts in South African MTEs 169

7.4.9 Land fragmentation in the wheatbclt of western

Australia 172

7.4.10 Modelling the influence of diversity on system function 173

7.5 MTE Research and the Global Forum 173

7.6 Summary 176 Acknowledgements 177 References 177

8 Biodiversity and Tropical Savanna Properties: A Global View 185

Olio T. Solbrig, Ernesto Medina and Juan F. Silva

8.1 Introduction 185

8.2 Savanna Structure and Function 190

8.2.1 Dynamics of savanna resources 191

8.2.2 Demographic and physiological characteristics of savanna species 195

8.2.3 Species diversity and ecosystem stability 196

8.3 A Model of Savanna Function 197

8.4 Effect of Species Diversity on Ecosystem Function 200

8.4.1 Invasion of South American and Australian savannas by African grasses 200

8.4.2 Species changes resulting from fire exclusion 201

8.4.3 Species changes resulting from herbivore introduction or exclusion 202

8.4.4 Changes resulting from increases or removal of trees and shrubs 204

8.5 Resilience and Ecosystem Function 205

References 205

9 Impact of Biodiversity on Tropical Forest Ecosystem Processes 213

Gordon //. Orians, Rodolfo Dirzo and J. Hall Cushman

9.1 Introduction 213

9.2 Environmental Gradients in Tropical Forests 214

9.2.1 Moisture 214

9.2.2 Fertility 215

9.2.3 Elevation 216

9.3 Stability and Species Richness 217

9.4 Functional Groups 218

9.5 Energy Flow and Material Processing Interfaces 219

9.6 Biodiversity and Functioning of Tropical Forests 219

9.6.1 Energy flow 221 Primary productivity and biomass accumulation 221 Within-plant carbon allocation and consumption 222 Animal-animal interactions 224 Detritus-detritivores 224

9.6.2 Materials processing 225 Atmosphere-organism 225 Biotic interface 226 Plant soil 227 Atmosphere-soil 228 Soil-water tabic 228 Empirical studies 228

9.6.3 Functional properties over longer temporal scales 229 Provision and maintenance of structure 229 Resistance to invasion 229

9.6.4 Functional properties over larger spatial scales 230 Water distribution and quality 231 Atmospheric properties and feedbacks 231 Landscape and waterscape structure 231 Animal movements 231

9.7 Biodiversity and Response to Disturbances 232

9.8 Research Agenda 232

9.9 Concluding Remarks 234

References 236

10 Island Ecosystems: Do They Represent "Natural Experiments" in

Biological Diversity and Ecosystem Function? 245

Peter M. Vitousek, Lloyd L. Loope, Henning Adsersen and

Car la M. D'Antonio

10.1 Introduction 245

10.2 Biological Diversity and Ecosystem Function 249

10.2.1 Diversity and ecosystem function near steady state 250

10.2.2 Disturbance, diversity and ecosystem function 251

10.2.3 Invasion, extinction and ecosystem function 252

10.3 Opportunities for Research 254

10.4 Summary 255

Acknowledgements 256

References 256

11 Biodiversity and Agroecosystem Function 261

M.J. Swift, J. Vandermeer, P.S. Ramakrishnan, J.M. Anderson,

11.1 Introduction 261

11.1.1 Agroecosystem function 263

11.2 Agroecosystcms, Agricultural Intensification and Biodiversity 263

11.2.1 Agricultural intensification 263

11.2.2 The variety of agricultural systems 264 Shifting agriculture 264 Rotational fallow 264 Home gardens 265 Compound farms 265 Mixed arable-livestock farming 265 Intensified agroforestry systems 266 Intercropping and crop rotation 266 Specialized cash-crop systems 267 Modern farming systems 267

11.2.3 Impact of agricultural intensification on biodiversity 268

11.2.4 Patterns of change 270 Impact on the above-ground fauna of intensification in the Central American coffee ecosystem 270

Impact of land-use change on the soil biota 271

Hysteresis 273

11.3 Relationships between Biodiversity and Function in

Agroecosystems 275

11.3.1 The issue of scale and functional domains 275

11.3.2 The plant subsystem 276 Principles of resource capture 278 Traditional management of plant diversity 280

11.3.3 Biodiversity and pest management 281

11.3.4 Biodiversity controls on nutrient cycling and soil processes 285

11.4 Biodiversity and the Design of Agricultural Systems 289

11.5 Conclusions: Biodiversity, Agroecosystems and Landscapes 291

11.5.1 Biodiversity and agroecosystem function 291

11.5.2 Agroecosystems and biodiversity conservation 292 References 294

12 Freshwater Ecosystems: Linkages of Complexity and Processes 299

S. Carpenter, T. Frost, L. Persson, M. Power and D. Soto

12.1 Introduction 299

12.1.1 Uses of freshwaters 299

12.1.2 Vulnerability of freshwater resources 299

12.1.3 Assessing vulnerability of freshwater resources 301

12.2 Complexity and Ecosystem Processes in Freshwaters 303

12.2.1 Strong interactions, cascades and complementarity 303

12.2.2 Characteristics of strong interactions 304 Productivity gradients and fishes 305 Hydrology, disturbance and river food webs 309

12.3 Predictive Capability and Prospects for Learning 313

12.3.1 Characteristics of Chilean lakes 314

12.3.2 Potential shifts in Chilean lakes 314

12.3.3 Learning and adapting to surprise 317

12.4 Maintaining Biodiversity of Freshwaters 318

12.5 Summary 320 Acknowledgements 321 References 321

13 Biodiversity and Ecosystem Processes in Tropical Estuaries: Perspectives of Mangrove Ecosystems 327

Robert R. Twilley, Samuel C. Snedaker, Alejandro Yáñez-Arancibia and Ernesto Medina

13.1 Introduction 327

13.2 Biodiversity of Mangroves 328

13.3 Forest Structure and Ecosystem Function 335

13.3.1 Mangrove-specific effects on nutrient dynamics 335

13.3.2 Ecological type and litter dynamics 337

13.4 Mangrove Faunal Guilds and Ecosystem Function 339

13.4.1 Crabs 339

13.4.2 insects 342

13.4.3 Benthos and epibionts 344

13.5 Microbial Processes and Ecosystem Function 347

13.6 Nekton Biodiversity and Mangrove Food Webs 348

13.7 Vulnerability of Biodiversity in Tropical Estuaries 354

13.7.1 Land-use change 354

13.7.2 Global climate change 356

13.8 Summary 358 Acknowledgements 359 References 360

14 Predictability and Uncertainty in Community Regulation: Consequences of Reduced Consumer Diversity in Coastal Rocky Ecosystems 371

Gary W. Allison, Bruce A. Menge, Jane Lubchenco and Sergio A. Navarre te

14.1 Introduction 371

14.2 Global Impacts on Biodiversity in Coastal Regions 372

14.3 Shallow-water Hard-bottom Communities: Model Systems for Evaluating Consequences of Diversity Loss 374

14.3.1 Approach 374

14.3.2 Diversity components considered 375

14.3.3 Consequences of consumer loss: Selected examples 376 Strong prédation: Keystone effects 376 Strong prédation: Diffuse effects 379 Weak prédation 380

14.3.4 Conclusions from the survey 381

14.4 Conceptual Synthesis 381

14.4.1 Classification 381

14.4.2 Predictions 383

14.4.3 Caveats 384

14.4.4 Uses 385

14.5 Conclusion 386 Acknowledgements 386 References 387

15 Biodiversity and Ecosystem Function of Coral Reefs 393

Terence J. Done, John C. Ogden, William J. Weibe and B.R. Rosen

15.1 Introduction 393

15.1.1 Use, abuse and management of coral reefs 397

15.1.2 Chapter goals and some definitions 397

15.2 A Conceptual Framework 398

15.2.1 Carbon pathways, reef function and reef degradation 398

15.2.2 Trophic roles 401

15.2.3 Bioconstructional roles 402 Bioconstructors 402

Modifiers 403

15.2.4 Facilitating roles 405

15.3 Ecosystem Processes at Scales of Whole Reefs and Zones 406

15.3.1 Whole reefs 406

15.3.2 Zones 407

15.3.3 Ecosystem processes and "reef health1' 408

15.4 Biodiversity Loss and Ecosystem Dysfunction 409

15.4.1 Facilitators as links between humans, biodiversity and ecosystem 409 Crown-of-thorns starfish 410 Caribbean sea urchin 410 East African sea urchin 412

15.4.2 Water quality and land runoff effects On biodiversity and ecosystem function 413

Mechanisms for nutrient impacts on coral reefs 413

Symbiont diversity as a basis for adaptation? 413 Landscape/seascape diversity as buffers protecting coral reefs 414

15.5 Biodiversity and Resilience 414

15.5.1 Replenishment of populations 414

15.5.2 Life history strategies, resilience and resistance 415

15.6 Summary, Recommendations, and Conclusions 416

15.6.1 Summary 416

15.6.2 Recommendations 417 Scientific research needs 4!7 Applications to management of coral reefs 418 The need for international collaboration 418

15.6.3 Conclusion - biodiversity and ecosystem function, from genes to regions 419

Acknowledgements 420

References 420

Contributing Authors and Affiliations 428

16 Human Impact, Biodiversity and Ecosystem Processes in the Open

Ocean 431

Mark Chandler, Les Kaufman and Sandor Mulsow

16.1 Introduction 421

16.2 Patterns of Open-Ocean Biodiversity 433

16.2.1 Structure of the waterscape 433

16.2.2 Phyletic diversity 436 Differences at higher phyletic levels 440 Are open-ocean communities cosmopolitan? 441

16.3 Human Impacts on Biodiversity of the Open Ocean 441

16.3.1 Addition and subtraction of species 444

16.3.2 Addition and redistribution of chemical substances 444

16.3.3 Indirect alteration of ecological processes 445

16.4 Biodiversity and Ecosystem Processes: General Thoughts 447

16.4.1 Structure and stability of open-occan ecosystems 448

16.4.2 Niche breadth 449

16.5 Biodiversity and Ecological Processes: Empirical Evidence 450

16.5.1 Nutrient regeneration in the pelagic zone (microbial loop) 450

16.5.2 Pelagic biomass production 452 Eutrophication and introductions 458

16.5.3 Pelagic benthic coupling (export of benthic material to the benthos) 459

16.5.4 Productivity and nutrient regeneration in the benthos 460

16.5.5 Ocean-atmosphere coupling 461

16.5.6 Open-ocean continental-shelf coupling 462

16.6 Conclusions 463 Acknowledgements 465 References 465

17 What We Have Learned about the Ecosystem Functioning of

Biodiversity 475

H.A. Mooney, J. Hall Cushman, Ernesto Medina, Osvaldo E. Sala and E.-D. Schulze

17.1 Background 475

17.2 General Program Conclusions 476

17.3 Lessons from Specific Biomes 477

17.3.1 Mediterranean ecosystems 477 On disturbance/diversity/functioning 477

17.3.2 The open ocean 478 Managing in the dark 478

17.3.3 Tropical forests 478 The time dimension 478

17.3.4 Mangroves 479 The link between the land and the sea 479

17.3.5 Agroecosystems 479 On simplification and substitution 479

17.3.6 island ecosystems 480 On simplicity due to dispersal 480

17.3.7 Cold and dry ecosystems 480 On simplicity due to limiting waters 480 On simplicity due to cold temperature 480

17.3.8 Lakes and rivers 481

Responses to massive impacts 481

17.3.9 Coastal ecosystems 481 Keystones and compensations 481

17.3.10 Coral reefs 482 Complexity 482

17.3.11 Boreal forests 482 Low diversity and low redundancy 482

17.3.12 Temperate and tropical grasslands 482 Where experiments are most tractable 482

17.3.13 Temperate forests 483 Diversity and function over evolutionary time 483

17.3.14 Concluding remarks 484 References 484

Index 485

Contributors

Henning Adsersen

Department of Plant Ecology. Botanical Institute, University of Copenhagen, 0ster Farimagsgade 2D, DK 1353 Copenhagen K, Denmark

Gary W. Allison

Department of Zoology, Oregon State University, Corvallis, OR 97331, USA

J. M. Anderson

Rothamstcd Experimental Station, Harpendcn, Herts AL5 2JQ, UK F. A. Bazzaz

Biological Laboratories, 16 Divinity Avenue, Harvard University, Cambridge, MA 02138, USA

John Bryant

Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775, USA

S. Carpenter

Center for Limnology, University of Wisconsin, Madison, WT 53706. USA Mark Chandler

New England Aquarium, Central Wharf, Boston, MA 02110, USA F. Stuart Chapin, III

Department of Integrative Biology, University of California, Berkeley, CA 94720, USA

J. Hall Cushman

Department of Biology, Sonoma State University, Rohnert Park, CA 94928, USA

Carta M. IVAntonio

Department of Integrative Biology, University of California, Berkeley, CA 94720, USA

George W. Davis

Stress Ecology Research Unit, National Botanical Institute, Private Box X7, Claremont 7735, South Africa

Rodolfo Dirzo

C'entro de Ecologia UNAM, Apartado Postal 70-275, Mexico 045JO, DF Mexico

Terence J. Done

Australian Institute of Marine Science, PMB 3, Townsville MC, Queensland 4810, Australia

T. Frost

Trout Lake Station, 10810 Country Highway N, Boulder Junctions, WI 54512, USA

Yrjö Haila

Satakunta Environmental Research Center, University of Turku, Turku, Finland

Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92717, USA

Richard J. Hobbs

CSIRO, Division of Wildlife and Ecology, LMB 4, PO Midland, WA 6056, Australia

L. F. Huenneke

Department of Biology, New Mexico State University, Las Cruces, NM 88003, USA

Les Kaufman

Boston University Marine Program, Boston University, Boston, MA 02215, USA

Jon E. Keeley

Department of Biology, Occidental College, 1600 Campus Road, Los Angeles, CA 90041, USA

T. Koike

Department of Environmental Science and Resources, Tokyo University of Agriculture and Technology, Fuchu 183, Tokyo, Japan

Christian Körner

Botanisches Institut, University of Basel, Schönbeinstrasse 6, CH-4056 Basel, Switzerland

W. K. Lauenroth

Department of Range Ecosystem Science, Colorado State University, Fort Collins, CO 80523, USA

Lloyd L. Loope

National Biological Survey, Halcakala National Park, Makawao, Maui. HI 96768, USA

Jane ( uhchenco

Department of Zoology, Oregon State University, Corvallis, OR 97331, USA S. J. McNaughton

Department of Biology, Syracuse University. 130 College Place, Syracuse, NY 13244, USA

Ernesto Medina

I VIC, Centro de Fcologia, Apartado 21827, Caracas 1020-A, Venezuela Bruce A. Menge

Department of Zoology, Oregon State University, Corvallis, OR 97331, USA

David J. Mladenoff

Wisconsin DNR Bureau of Research and Department of Forestry, University of Wisconsin, Madison, WI 53706, USA

Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA

Sandor Mulsow

Marine Chemistry Division, Bedford Institute of Oceanography, PO Box 1006, Dartmouth, Nova Scotia B3M 4A2, Canada

K. J. Nadelhoffer

Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543, USA

Sergio A, Navarrete

Department of Zoology. Oregon Stale University, Corvallis, OR 97331, USA

I. Noble

RSBS Ecosystem Dynamics Group, Australian National University, Canberra, ACT 2601, Australia

John C. Ogden

Florida Institute of Oceanography, 830 First Street South, St. Petersburg, FL 33701, USA

International Centre for Research in Agroforestry (ICRAF), PO Box 30677, Nairobi, Kenya

Gordon H. Orians

Department of Zoology, Box 351800, University of Washington, Seattle, WA 98195, USA

John Pastor

Natural Resources Research Institute, 5013 Miller Trunk Highway, University of Minnesota. Duluth, MN 55811, USA

Serge Payette

Centre d'Etudes Nordiques, Université Laval, Sainte-Foy, Québec G IK 7P4, Canada

L. Persson

Department of Animal Ecology, University of Umea, S-9Û1 87 Umea, Sweden

M. Power

Department of Integrative Biology, University of California, Berkeley, CA 94720, USA

P. S. Ramakrishnan

School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067, India

David M. Richardson

Institute for Plant Conservation, University of Cape Town, Private Bag, Rondebosch 7700, South Africa

Department of Paleontology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK

G. Rusch

Department of Ecological Botany, Uppsala University, Box 559, S-75122 Uppsala. Sweden

Osvaldo E. Sala

Departamento de Ecología, Universidad de Buenos Aires, Facultad de Agronomía, Av. San Martin 4453, Buenos Aires 1417, Argentina

Lehrstuhl für Pflanzenökologie, Universität Bayreuth, Postfach 101251, D-95440 Bayreuth, Germany

Juan F. Silva

CIELAT, Facultad de Ciencias, Universidad de los Andes, Mérida. Venezuela

Samuel C. Snedaker

Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA

Otto T. Soibrig

Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Avenue, Cambridge, MA 02138, USA

D. Soto

Facultad de Pesquerías y Oceanografía, Universidad Austral de Chile. Campus Pel luco. Casilla 132?, Puerto Montt, Chile

Tropical Soil Biology and Fertility Programme, UNESCOROSTA, PO Box 30592, Nairobi, Kenya

S. Takatsuki

Laboratory of Wildlife Ecology, School of Agriculture and Life Science. University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113, Japan

Robert R. Twiliey

Department of Biology, University of Southwestern Louisiana. Lafayette, LA 70504, USA

J. Vandermeer

Department of Biology, University of Michigan, Ann Arbor. MI 48109, USA

Peter M. Vitousek

Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA

William J. Wiebe

Department of Microbiology, University of Georgia, Athens, GA 30602, USA

Alejandro Yáñez-Arancibia

EPOMEX Program, University of Campeche, Apartado Postal 520, Campeche 24030, México

Xinshi Zhang

Institute of Botany, Chinese Academy of Science, 141 Xizhimcnwal Avenue, Beijing 100044, China

1 The SCOPE Ecosystem Functioning of Biodiversity Program

H.A. MOONEY, J. HALL CL'SHMAN, ERNESTO MEDINA, OSVALDO E. SALA AND E.-D. SCHULZE

Li BACKGROUND

As natural ecosystems are increasingly impacted by human activities, resulting in disruptions of system interactions and losses of populations, and even species, there has been increasing concern about how we are modifying the ecosystem processes that originate from and maintain these systems, and that benefit humankind. The Scientific Committee on Problems of the Environment (SCOPE) launched a program in 1991 to assess the state of our knowledge of the role of biodiversity, in all its dimensions, in ecosystem and landscape processes. This effort was part of the larger program, DIVER-SITAS, which focuses on the science of biodiversity and was initially co-sponsored by SCOPE, the International Union of Biological Sciences (IUBS) and UNESCO (United Nations environmental, Scientific, and Cultural Organization). The SCOPE program was guided by a Scientific Advisory Committee that included David Hawksworth, Brian Huntley, Pierre Lasserre, Brian Walker, Ernesto Medina, Harold Mooney, Valeri Neronov, Ernst-Detlef Schuize and Otto Solbrig. The overarching questions that were agreed upon for this program were:

1. Does biodiversity "count" in system processes (e.g. nutrient retention, decomposition, production, etc.), including atmospheric feedbacks, over short- and long-term time spans, and in face of global change (climate change, land-use, invasions)?

2. How is system stability and resistance affected by species diversity, and how will global change affect these relationships?

The SCOPE program was designed not only to synthesize our knowledge for

Functional Roles of Biodiversity: A Global Perspective

Edited by H.A. Mooney, J.H. Cushman, E. Medina. O.E. Sala and E.-D. Schulze fj^fVy © 1996 SCOPE Published in 1996 by John Wiley & Sons Ltd UNfir the functional role of biodiversity, but also to develop the basis for an experimental program for inclusion in the International Geosphere Biosphere Programme. As is discussed in Chapter 17 (Conclusions), the information base from which we build was not especially designed to answer the questions posed above. Until recently, and with exceptions in part due to stimulation from this program, there has been virtually no experimentation in this rather ccntral area. One reason for this has been the past separation of the research areas of population ecology and ecosystem ecology, a separation which this program attempted to bridge.

In the following sections we outline the structure of the SCOPE program, followed by a description of an expansion of the program under the auspices of the Global Biodiversity Assessment conducted by the United Nations Environmental Programme.

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