ECOLOGICAL PRINCIPLES OF NATURE CONSERVATION

CONSERVATION ECOLOGY SERIES: Principles, Practices and Management

Series Editor:

Dr E. Duffey Cergne House, Church Street, Wadenhoe, Peterborough

PE85ST, UK

Editorial Board

Professor L. Hansson (Sweden) Professor W. Erz (Germany) Professor P. Blondin (France) Dr S. Hopper (Australia)

Titles published in the Series:

Ecological Principles of Nature Conservation L. Hansson

Further titles are in preparation.

ECOLOGICAL PRINCIPLES OF

NATURE CONSERVATION Applications in Temperate and

Boreal Environments

Edited by

LENNART HANSSON

Department of Wildlife Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden

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British Library Cataloguing in Publication Data

The ecological principles of nature conservation. I. Hansson, Lennart 639.9

ISBN 1851667180

Library of Congress Cataloging-in-Publication Data

The Ecological principles of nature conservation/edited by Lennart Hansson. p. cm.-(Conservation ecology series)

Includes bibliographical references and index. ISBN 1-85166-718-0 1. Nature conservation. 2. Ecology. I. Hansson, Lennart, 1938-

II. Series. QH75.E27 1992 333.95'16-dc20

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Preface

This volume is the first in a series entitled Conservation Ecology: Principles, Practices and Management, a theme which Elsevier's pioneer­ing journal Biological Conservation has promoted since its foundation thirty-three years ago. The science of conservation ecology is now widely acknowledged as an essential component in the planning and develop­ment of activities which change or modify our natural environment. Nevertheless in spite of much research and publicity, there is still a wide gap between theory and practice. Today it is especially important to try to bridge this gap by interpreting the results of ecological research so that they are understandable and relevant to a wide range of land managers, agriculturalists, foresters, and those working in the many categories of protected areas. The volumes in this series are designed to fulfil this purpose, and also to play an important educational role for students of the environmental sciences in schools, universities and other institutions.

In most industrial countries the public is becoming acutely aware of the demands made on our rural landscape by intensive agriculture and forestry, new roads, urban expansion and industrial development with the consequent loss of habitat diversity, wildlife, hedgerows, wetlands, ancient woodland and meadows. Ecologists are now considering how these trends can be reversed and the research required to recreate a varied and attractive landscape including the restoration of native woodlands, meadows, heaths and other wildlife communities. The Conservation Ecology series will review the available information and show how it can be applied to current problems in nature conservation.

When the proposed series was first discussed with the Editorial Board we were delighted when Professor L. Hansson (through a research team of the Swedish Environmental Protection Agency of the Agricultural University of Uppsala) offered us an introductory volume on the general

v

VI PREFACE

principles of conservation ecology. The twelve chapters cover a wide range of environmental disciplines and present much new scientific data in the examination of ecological concepts relevanfto wildlife and land­scape management. Together they form an excellent basis for the succeed­ing volumes in the series, which will discuss conservation priorities and management of major ecosystems and landforms.

The principles discussed in this first volume are widely applicable in many parts of the world, especially temperate and boreal regions. On the other hand, the Scandinavian viewpoint is of particular interest as it provides new ideas on well-known concepts based on a long-established tradition of ecological research applicable to nature conservation. Many of the case studies described will be new to readers in other countries­for example the preservation needs of the faunas and floras of the extensive Scandinavian archipelagoes and boreal forests. Professor Hansson and his colleagues are to be congratulated on the high standard of science achieved.

The Conservation Ecology: Principles, Practices and Management series has five other titles in preparation dealing with marine conservation, recreational ecology, management of freshwater ecosystems, and the problems of wetland conservation and coastal formations. The ultimate aim of the series is to cover a comprehensive range of ecosystems throughout the world where sufficient ecological knowledge is available to discuss the scientific basis for conservation management.

Eric Duffey

Acknowledgements

This book is largely a result of a fairly comprehensive research pro­gramme at the Swedish Environmental Protection Agency on 'Remnant Habitats in Production Landscapes'. Most of the present authors have been conducting research projects with grants from this Agency. We are very grateful for the continuing support from the Agency and its research officers, and especially thank Tor-Bjorn Larsson for initiatives and seminars leading towards this synthesis.

We thank Elsevier Science Publishers, and especially Eric Duffey for their great interest in our project and their rapid and exhaustive replies to our queries. We are impressed by the swift and careful subediting of our chapters by Eric and Rita Duffey. As English is a necessary yet foreign language for all of us, they have performed a considerable task in amending incorrect wording or plain abuse of their language. We admire the patient discussions of terms and concepts that took place during this subediting. In addition, we also received many hints about unknown papers and alternative interpretations.

vii

Lennart Hansson and all authors

List of Contributors

P. ANGELSTAM

Swedish Environmental Protection Agency, Grimso Wildlife Research Station, S-77031 Riddarhyttan, Sweden S. As Department of Zoology, Uppsala University, P.O. Box 561, S-75122 U ppsala, Sweden J. BENGTSSON

Department of Ecology and Environmental Research, Swedish University of Agricultural Sciences, P.O. Box 7072, S-750 07 Uppsala, Sweden T. EBENHARD

Department of Zoology, Uppsala University, P.O. Box 561, S-75122 U ppsala, Sweden B. EHNSTRCM

Department of Plant and Forest Protection, Swedish University of Agricul­tural Sciences, S-750 07 Uppsala, Sweden. L. ERICSON

Department of Ecological Botany, University of Umed, S-90187 Umed, Sweden P.-A. Esseen Department of Ecological Botany, University of Umed, S-90187 Umed, Sweden L. HANSSON

Department of Wildlife Ecology, Swedish University of Agricultural Sciences, P.O. Box 7002, S-750 07 Uppsala, Sweden

O. JENNERSTEN

Department of Zoology, Uppsala University, P.O. Box 561, S-75122 U ppsala, Sweden

ix

x LIST OF CONTRIBUTORS

J. LOMAN

Department of Ecology, Lund University, Ecology Building, S-223 62 Lund, Sweden A.P. M0LLER

Department of Zoology, Uppsala University, P.O. Box 561, S-75122 U ppsaia, Sweden C. NILSSON

Department of Ecological Botany, University of Umea, S-90187 Umea, Sweden S.G. NILSSON

Department of Ecology, Ecology Building, S-223 62 Lund, Sweden J. ROBERTSON

Department of Wildlife Ecology, Swedish University of Agricultural Sciences, P.O. Box 7002, S-750 07 Uppsala, Sweden K. SJOBERG

Department of Wildlife Ecology, Swedish University of Agricultural Sciences, S-901 87 Umea, Sweden L. SODERSTROM

Department of Ecological Botany, University of Umea, S-90183 Umea, Sweden C. SOLBRECK

Department of Plant and Forest Protection, Swedish University of Agricul­tural Sciences, S-750 07 Uppsala, Sweden L. SVENSSON

Department of Systematic Botany, University of Lund, O. Vallgatan 18-20, S-22361 Lund, Sweden B. WIDEN

Department of Systematic Botany, University of Lund, O. Vallgatan 18-20, S-223 61 Lund, Sweden

Contents

Preface

Acknowledgements

List of Contributors

v

vii

IX

Chapter 1

Chapter 2

Introduction: Applied Ecological Principles and their Implementation in Nature Conservation

Conservation of Communities-The Importance of Edges, Surroundings and

1

Landscape Mosaic Structure 9

2.1. Introduction 9

2.2. Definitions 2.2.1. Community ecology 2.2.2. Metapopulation dynamics . 2.2.3. Landscape ecology 2.2.4. Scale problems

2.3. Swedish landscape types

12 12 12 13 14

16

2.4. Local and regional manifestations of edge-effects 19 2.4.1. Types and definitions of edges. 23 2.4.2. Direct and indirect abiotic effects 24 2.4.3. Predation. 28 2.4.4. Other interactions 35 2.4.5. Conclusions about edge-effects 36

2.5. Landscapemanagement 37 2.5.1. Ripple effects due to loss of keystone species 38 2.5.2. Landscape grain and interdispersion of

habitat types 42

xi

xii CONTENTS

2.5.3. Key or indicator species, properties and processes 46

2.5.4. Effects on communities in terms of pollution on a regional scale 48

2.6.' Management implications 51 2.6.1. Be careful when analysing data on

communities and assemblages 51 2.6.2. Conservation by creating reserves or by

management 52 2.6.3. Conservation of resources versus nature

conservation 54 2.6.4. To manage or to be passive-that is the

question 55

2.7. A plea for the future . 56 2.7.1. Preserve the remaining natural forests . 56 2.7.2. Create buffer zones around reserves . 57 2.7.3. Develop strategic land-use planning 57 2.7.4. Enhance the natural variation in forests 57 2.7.5. Increase numbers of (old) broad-leaved trees 57 2.7.6. Plant native trees 58

Acknowledgements 58

References 58

Chapter 3 Conservation of Plant and Animal Populations in Theory and Practice 71

3.1. Introduction 71

3.2. Species extinctions 74 3.2.1. Definitions of scale 74 3.2.2. Body size and extinction 75

3.3. The importance of population size 76 3.3.1. Minimum viable population sizes 76 3.3.2. Stochastic population variability 78

3.4. The importance of habitat area 78 3.4.1. Species with fragmented habitats 78 3.4.2. Fragmentation models . 80 3.4.3. Single large or several small reserves 82 3.4.4. Area requirements. 84 3.4.5. Habitat diversity and reserve

delimitation I. . . . 86

CONTENTS xiii

3.5. The importance of species interactions 87 3.5.1. Trophic level, keystone species, and

species vulnerability 87 3.5.2. Species introductions 91

3.6. Disturbance regimes and habitat quality 95 3.6.1. Pristine disturbances 95 3.6.2. Man-made disturbances 100

3.7. Conclusions 101

References 102

Chapter 4 Conservation of Genetic Variation in Plants-The Importance of Population Size and Gene Flow . 113

4.1. Introduction 113

4.2. Some basic population genetics 114 4.2.1. Population size and genetic variation 114 4.2.2. Genetic drift-the random variation in

allele frequencies 116 4.2.3. Inbreeding 116 4.2.4. Gene flow 117 4.2.5. Selection 120 4.2.6. Local differentiation 121 4.2.7. Measures of genetic diversity 121

4.3. Effects of genetic sub structuring of plant populations 122 4.3.1. Inbreeding depression . 122 4.3.2. Outbreeding depression 125 4.3.3. Genetic substructuring of plant

populations-conclusions 127

4.4. 'The real world'-measures of population structure and gene flow . 128 4.4.1. Neighbourhood size 129 4.4.2. Estimates of gene flow . 131 4.4.3. Genetic structure 133

4.5. Discussion 145

4.6. Conclusions and further research needs 150

Acknowledgements 151

References 151

xiv CONTENTS

Chapter 5 The Ecology of Dispersal in Relation to Conservation 162

5.1. Introduction 162

5.2. Bryophytes and lichens 165 5.2.1. General background 165 5.2.2. Diaspore production 166 5.2.3. Diaspore transport 167 5.2.4. Establishment . 168 5.2.5. Dispersal in time . 169 5.2.6. Regional dynamics and dispersal 169 5.2.7. Conservation aspects of dispersal 171

5.3. Insects. 172 5.3.1. Flight and migration in insects 172 5.3.2. Two examples of migrating insects 173 5.3.3. Migration in the life of the individual 175 5.3.4. Variation in the tendency to migrate 176 5.3.5. Genetic and environmental determinants of

migration 177 5.3.6. Migration as part of a life history

syndrome 178 5.3.7. The role of migration in population

dynamics 179 5.3.8. Migration and insect fauna conservation 182

5.4. Small mammals 185 5.4.1. Factors releasing dispersal. 185 5.4.2. Dispersal in time and space 185 5.4.3. Dispersal and population persistence 187

5.5 General conclusions 189

References 192

Chapter 6 Archipelagoes and Theories of Insularity 201

6.1. Introduction 201 6.1.1. Natural history of the Swedish

archipelagoes 203 6.1.2. Cultural history 205 6.1.3. Why are archipelagoes important for

nature conservation? 207

6.2. Theories of insularity 208 6.2.1. A static versus a dynamic viewpoint 208 6.2.2. Species richness theories 210

Chapter 7

6.2.3. 6.2.4.

CONTENTS

Theories of metapopulation dynamics What are the features of successful island species?

xv

214

216

6.3. Scandinavian case studies 220 6.3.1. Island size and species richness. Area per se,

habitat diversity or sampling? . 220 6.3.2. Colonizations, extinctions, and

metapopulation dynamics 228

6.4. Implications for conservation . 243 6.4.1. General recommendations 243 6.4.2. Metapopulations . 243 6.4.3. Changes in species composition with

fragmentation . 244 6.4.4. Conservation in an archipelago 245

Acknowledgements 246

References . 246

Boreal Forests-The Focal Habitats of Fennoscandia 252

7.1. Introduction 252

7.2. Biotic zonation 254 7.2.1. Vegetation zones 254 7.2.2 Vegetation classification 255 7.2.3. Biotic zonation of animals 256

7.3. The natural forest . 257 7.3.1. Community structure 257 7.3.2. Community dynamics 261 7.3.3. Features of special importance. 265

7.4. Man's impact 284 7.4.1. The past-multiple utilization of the forest 284 7A.2. The present-the industrial forest 287

7.5. Effects of forestry on the fauna and flora 292 7.5.1. Consequences of clear-cutting management 292 7.5.2. Reduced tree ages . 294 7.5.3. Fire elimination 294 7.5.4. Changed tree species composition 296 7.5.5. Reduced input of coarse woody debris . 297 7.5.6. Effects of forest management on avifauna 299

xvi

Chapter 8

CONTENTS

7.6. Conservation strategies for the future 300 7.6.1. How to maintain diversity? 300 7.6.2. Preserving and maintaining natural forests. 302 7.6.3. A forestry that maintains biodiversity 306

Acknowledgements 311

References 311

Forested and Open Wetland Complexes 326

8.1. Introduction 326

8.2. Definitions 327 8.2.1. Wet forests 327 8.2.2. Wetlands without a tree canopy 329

8.3. Environmental factors . 330

8.4. Disturbance history 331

8.5. Species changes 332 8.5.1. Flora 332 8.5.2. Mammals 333 8.5.3. Birds 334 8.5.4. Amphibians 336 8.5.5. Invertebrates 336

8.6. The future. 336

8.7. Case studies 337 8.7.1. Cypripedium calceolus 337 8.7.2. Evernia divaricata 337 8.7.3. Pytho kolwensis 338

8.8. Significance of wet forests and wetlands in a landscape context . 340 8.8.1. Historical perspective 340 8.8.2. The present situation 344

8.9. Recommendations . 346

Acknowledgements 347

References 347

Chapter 9

CONTENTS

Conservation Management of Riparian Communities

9.1. Introduction

9.2. The system

9.3. Pattern and process in riparian habitats 9.3.1. Species composition 9.3.2. Species richness 9.3.3. Interactions with adjacent habitats.

9.4. Conservation . 9.4.1. Introduction 9.4.2. General recommendations.

Acknowledgements

References

xvii

352

352

353

356 356 359 362

364 364 365

368

368

Chapter 10 Forests in the Temperate-Boreal Transition-Natural and Man-Made Features . 373

10.1. Introduction 373

10.2. Landscape changes and vegetation history. 374

10.3. Vegetation dynamics . 376

10.4. Forestry and forest processes 378

10.5. Acidification and pollution-new threats to hemiboreal forests 380

10.6. Animal communities 380 10.6.1. Mammals 380 10.6.2. Birds . 382 10.6.3. Insects. 386

10.7. Conclusions with conservation recommendations 388

References 389

xviii CONTENTS

Chapter 11 Conservation Biology in Agricultural

Habitat Islands . 394

11.1. Introduction 394

11.2. Case studies 397 11.2.1. The critical habitats for carabid beetles on

farmland 397 11.2.2. Bird diversity in the agricultural landscape 403 11.2.3. Bird nest predation and habitat island size 405 11.2.4. Pollination ecology on habitat islands . 409 11.2.5 .. Reproductive success of the field fleawort

Senecio integrifolius in relation to habitat fragmentation and habitat quality 415

11.3. General conclusions 419

Acknowledgements 421

References 421

Epilogue 425