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Savanna Woody Plants and Large Herbivores. Edition No. 1

  • ID: 5227072
  • Book
  • October 2019
  • 784 Pages
  • John Wiley and Sons Ltd

Insights on current research and recent developments in understanding global savanna systems

Increasingly recognized as synonymous with tropical grassy biomes, savannas are found in tropical and sub-tropical climates as well as warm, temperate regions of North America. Savanna Woody Plants and Large Herbivores examines the interactions between woody plants and browsing mammals in global savannas - focusing primarily on the C4 grassy ecosystems with woody components that constitute the majority of global savannas - and discusses contemporary savanna management models and applications. 

This much-needed addition to current research examines topics including the varying behavior of browsing mammals, the response to browsing by woody species, and the factors that inhibit forage intake. Contributions from an international team of active researchers and experts compare and contrast different savanna ecosystems, offering a global perspective on savanna functioning, the roles of soil and climate in resource availability and organism interaction, and the possible impacts of climate change across global savannas.

  • Fills a gap in literature on savanna management issues, including biodiversity conservation and animal production
  • Applies concepts developed in other biomes to future savanna research
  • Complements contemporary books on savanna or large herbivore ecology
  • Focuses on the woody component of savanna ecosystems and large herbivore interactions in savannas
  • Compares tree-mammal systems of savannas and other eco-systems of temperate and boreal regions
  • Provides numerous case studies of plant-mammal interactions from various savanna ecosystems

Savanna Woody Plants and Large Herbivores is a valuable addition to those in fields such as ecology, wildlife and conservation biology, natural resource management, and environmental science.

Note: Product cover images may vary from those shown

List of Contributors xv

Preface xix

Part I Introduction 1

1 Distribution and Determinants of Savannas 3
Sally Archibald, William J. Bond, William Hoffmann, Caroline Lehmann, Carla Staver, and Nicola Stevens

1.1 Introduction 3

1.2 Evolutionary History of Savanna Vegetation and Fauna 4

1.3 Defining Savannas 7

1.3.1 Are Savannas Tropical Systems? 7

1.3.2 Distinguishing Savannas from Grasslands 7

1.3.3 Distinguishing Savannas from Forests 8

1.4 Global Determinants of Savannas 9

1.4.1 Mesic Transition: Points of Contention 10

1.4.1.1 The Role of Nutrients 10

1.4.1.2 Rainfall Seasonality 10

1.4.2 Mesic Transition: Toward Resolution 11

1.4.3 Mesic Transition: Unresolved Ideas 12

1.4.4 Arid Transition 12

1.4.5 Arid Transition: Toward Resolution 13

1.4.6 Determinants of Temperate Savannas 14

1.5 Functional Differences Between Savannas 14

1.5.1 Temperate vs Tropical Savannas 14

1.5.2 Functional Differences Within Tropical Savannas 15

1.6 Conclusions and the Future of Savanna Ecosystems 17

References 17

2 African and Asian Savannas: Comparisons of Vegetation Composition and Drivers of Vegetation Structure and Function 25
Jayashree Ratnam, Chintan Sheth, and Mahesh Sankaran

2.1 Introduction 25

2.2 Climate and Vegetation Formations 27

2.3 Fine‐Leaved and Broad‐Leaved Savannas: Vegetation Structure, Composition, and Geographic Distribution 30

2.4 Role of Bottom‐Up Drivers in Regulating Vegetation Structure: Climate and Soil Nutrients 33

2.5 Role of Top‐Down Forces: Fire and Herbivory 36

2.6 African and Asian Savannas in the Anthropocene 40

References 42

3 Savannas of Australia and New Guinea: Vegetation and the Functional Role of Extant and Extinct Fauna 51
Garry D. Cook, William J. Bond, Edmund C. February, and Richard J. Williams

3.1 Introduction 51

3.2 The Biota of Australia’s and New Guinea’s Savannas 51

3.3 Climate, Landforms, and Fire 53

3.4 Human History and Impacts 54

3.5 Are Native Mammals Irrelevant? 55

3.6 Was Ecosystem Functioning Different Prior to Human Dispersal to Australia? 57

3.7 Critique of the “Nutrient Poverty/Intense Fire” Theory 58

3.8 Australia’s Lost Megafauna 61

3.9 Habitat Variation and the Pleistocene Megafauna 64

3.10 Impacts of Herbivores in Australian Savannas 64

3.11 Toward a New Hypothesis of Plant–Animal Interactions in Australian Savannas 66

References 67

4 South American Savannas 77
Fabian Borghetti, Eduardo Barbosa, Leandro Ribeiro, José Felipe Ribeiro, and Bruno Machado Teles Walter

4.1 Introduction 77

4.2 Origin of South American Savannas 77

4.3 Distribution and Diversity of South American Savannas 78

4.4 Northern Savannas 80

4.4.1 Colombo–Venezuelan Llanos 80

4.4.1.1 Orinoco Llanos 80

4.4.1.2 Llanos Orientales 84

4.4.2 Gran Sabana 85

4.4.3 Rio Branco–Rupununi Savannas 85

4.4.3.1 Rio Branco Savannas 86

4.4.3.2 Rupununi Savannas 86

4.4.4 Savannas of Amapá 87

4.5 Southern Savannas 87

4.5.1 Savannas of Humaitá 87

4.5.2 Savannas of Pará 87

4.5.3 Beni Savannas 88

4.5.4 Cerrado 89

4.5.4.1 Cerrado (Sensu Stricto) 91

4.5.4.2 Cerrado Park 92

4.5.4.3 Palm Groves 92

4.5.4.4 Vereda 92

4.5.4.5 Campo Limpo (“Open Grassland”) 92

4.5.4.6 Campo Sujo (“Dense Grassland”) 92

4.5.4.7 Campo Rupestre (“Rocky Field”) 96

4.5.5 Pantanal 96

4.5.6 Chaco 97

4.6 Effects of Water Deficit, Herbivory, and Fire on Vegetation Dynamics 102

4.6.1 Water Deficit 102

4.6.2 Herbivory 103

4.6.3 Fire 104

4.7 Climate Change, Anthropogenic Pressure, and the Future 106

4.8 Concluding Remarks 109

4.9 Acknowledgments 109

References 110

5 Savannas of North America 123
Norma L. Fowler and Brian Beckage

5.1 Introduction 123

5.1.1 Definitions 123

5.1.2 Climatic Patterns 126

5.2 Fire 127

5.3 Grazing 128

5.4 Biodiversity 129

5.5 Conservation 129

5.6 Oak Savannas 130

5.6.1 Central US, South‐Central Canada, Northern Sierra Madre (Mexico) Oak Savannas 130

5.6.2 California Oak Savannas 132

5.6.3 South‐West (Arizona, New Mexico, Northern Mexico) Oak Savannas 132

5.6.4 Pacific Northwest Oak Savannas 132

5.6.5 East‐Central US: Glades, Barrens, and Other Forest Openings 132

5.6.6 Oak‐Dominated Shrub Savannas 133

5.7 Pine Savannas 133

5.7.1 South‐Eastern US Pine Savannas 133

5.7.2 Rocky Mountains Pine Savannas 134

5.8 Juniper Savannas 135

5.8.1 Juniper Savannas in the Western Mountains 135

5.8.2 Eastern Red Cedar Savannas 138

5.8.3 South‐Central US and Northern Sierra Madre Oriental Juniper Savannas 138

5.9 Mesquite Savannas 138

5.10 Northern and High‐Elevation Savannas 140

5.11 Shrub Savannas 140

5.12 Conclusions 141

5.13 Acknowledgments 141

References 141

6 Socioeconomic Value of Savannas 151
Wayne Twine

6.1 Introduction 151

6.2 Land Tenure and Land Use 153

6.3 Livestock Farming 155

6.3.1 Overview 155

6.3.2 Commercial Livestock Farming 157

6.3.3 Subsistence Livestock Farming 157

6.4 Wildlife Industry 159

6.4.1 Overview 159

6.4.2 Ecotourism 161

6.4.3 Hunting 162

6.4.4 Animal Products 163

6.4.5 Game Breeding and Live Sales 164

6.5 Commercial Timber 164

6.6 Non‐timber Products 164

6.6.1 Uses 164

6.6.2 Economic Value 166

6.6.2.1 Non‐monetary Income 166

6.6.2.2 Cash Income 167

6.6.2.3 Environmental Income 168

6.7 Conclusion 169

References 170

Part II Herbivores 181

7 Ecology of Smaller Animals Associated with Savanna Woody Plants: The Value of the Finer Details 183
Colleen Seymour and Grant Joseph

7.1 Introduction 183

7.2 Woody Plant Seed Herbivory 184

7.2.1 Seed Herbivores 184

7.3 Woody Plant Seed and Fruit Dispersal 187

7.3.1 Diplochory 187

7.3.1.1 Seed Dispersal by Birds 188

7.3.1.2 Invertebrate Seed Dispersal 189

7.3.2 Fruit Dispersal 189

7.4 Woody Plant Seedling Establishment 190

7.5 Leaves and Herbivory 191

7.6 Pollination and Nectarivory 193

7.7 Nutrient Cycling 195

7.8 Conclusions 199

References 201

8 Evolution of Large Mammal Herbivores in Savannas 213
Daryl Codron

8.1 Introduction 213

8.2 Herbivore Dietary Niches 215

8.3 Diversification of Browsers and Grazers 220

8.4 Effects of Vegetation Change 223

8.5 Herbivore Body Size 226

8.6 Pleistocene Extinctions and Contemporary Herbivore Diversity 228

8.7 Summary 233

References 234

9 Browser Population–Woody Vegetation Relationships in Savannas: From Bites to Landscapes 245
Melissa H. Schmitt and Adrian M. Shrader

9.1 Introduction 245

9.2 Factors Influencing Diet Selection 246

9.2.1 Browser Traits that Influence Foraging 247

9.2.1.1 Body Size 247

9.2.1.2 Gut Morphology 248

9.2.2 Woody Plant Traits that Influence Browsers 248

9.2.2.1 Seasonality 248

9.2.2.2 High Nutrient Levels (Positive) 249

9.2.2.3 Chemical Defenses (Negative) 250

9.2.2.4 Physical Defenses 252

9.2.2.5 Mutualisms 253

9.2.3 Herbivore Coping Mechanisms 253

9.3 Browser Impacts on Vegetation 255

9.3.1 Biomass Removal (Small and Large) 255

9.3.2 Impacts on Seeds 256

9.4 Feedback from Browsed Plants to Browsers 257

9.4.1 Lowered Food Availability 257

9.4.2 Habitat Changes 259

9.4.3 Change in Landscapes of Fear 260

9.4.4 New Growth 261

9.4.5 Nutrient Hot Spots 261

9.4.6 Browsing Lawns 261

9.5 Scaling from Bites to Browser Population Dynamics 262

9.5.1 Population Dynamics 263

9.5.2 Intake and Population Size 263

9.5.3 Food Availability, Food Quality, and Population Dynamics 264

9.5.4 Future Research 265

9.6 Conclusions 265

References 265

10 Predator Effects on Herbivore Dynamics and Behavior: What Mechanisms Lead to Trophic Cascades in Savannas? 279
Simon Chamaillé‐Jammes, Marion Valeix, and Joris Cromsigt

10.1 Introduction 279

10.2 Consumptive Effects of Predation 280

10.2.1 Concepts, Theory, and Evidence from Biomes Other than Savanna 280

10.2.1.1 Additive Versus Compensatory Mortality 281

10.2.1.2 Predator Functional Response 282

10.2.1.3 Ecosystem Characteristics 284

10.2.2 Evidence from Savannas 285

10.2.2.1 Additive Versus Compensatory Mortality 286

10.2.2.2 Predator Functional Response 288

10.2.2.3 Ecosystem Characteristics 288

10.3 Non‐consumptive Effects of Predation 290

10.3.1 Concepts, Theory, and Evidence from Biomes Other than Savanna 290

10.3.1.1 Landscape Use 290

10.3.1.2 Vigilance and Grouping Strategies 291

10.3.1.3 The Importance of Food–Safety Trade‐Offs 292

10.3.1.4 Demographic Costs of Behavioral Adjustments 293

10.3.2 Evidence from Savannas 293

10.3.2.1 Landscape Use 293

10.3.2.2 Vigilance and Grouping Strategies 295

10.4 Cascading Effects of Consumptive and Non‐consumptive Effects of Predation on Lower Trophic Levels 296

10.5 The Times they are A‐changin’: Changes in Megaherbivory, Migration Patterns, and Climate 297

References 299

Part III Woody Plants 309

11 Physiological Traits of Savanna Woody Species: Adaptations to Resource Availability 311
Edmund C. February, Corli Coetsee, Garry D. Cook, Jayashree Ratnam, and Benjamin Wigley

11.1 Introduction 311

11.2 Soil Nutrients and Root Responses 314

11.3 Leaf Phenology and Available Water 317

11.4 Competition for Resources 321

References 323

12 Patterns and Determinants of Woody Plant Growth in Savannas 331
Anthony Swemmer and David Ward

12.1 Introduction: The Relevance of Growth Rates 331

12.2 Determinants of Growth Rates 333

12.2.1 Seedlings 334

12.2.2 Saplings 342

12.2.3 Adults 344

12.2.4 Demographic Significance 344

12.2.4.1 Growth Trajectory 345

12.2.4.2 Size or Age of Individuals 345

12.2.4.3 Above vs Below Ground 345

12.2.4.4 Plant Part 347

12.2.4.5 Interacting Factors 347

12.2.4.6 Experimental Conditions 348

12.2.4.7 Individual vs Population Growth 348

12.2.4.8 Time and Size 348

12.2.4.9 Species 348

12.2.5 The Value of Long‐Term Research 349

12.3 Modeling Growth 350

12.3.1 Insights from Published Data 351

12.3.2 Predicting Rates from Environment or Phylogeny 353

12.3.3 Deficiencies in Growth Rate Data 356

12.4 Conclusions 357

12.A Appendix: Growth Rate Data 358

References 428

13 Fire and Browsers in Savannas: Traits, Interactions, and Continent‐Level Patterns 439
Gareth P. Hempson, Sally Archibald, and Carla Staver

13.1 Introduction 439

13.2 Browser and Fire Attributes 440

13.2.1 How do Fire and Browsers Compare as Consumers of Woody Plants? 440

13.2.1.1 Frequency and Seasonality 440

13.2.1.2 Selectivity, Intensity, and Scale 440

13.2.1.3 Elimination Thresholds 442

13.2.2 Plant Responses to Fire and Browsing 442

13.2.2.1 Defense Traits 442

13.2.2.2 Architecture 443

13.2.2.3 Resprouting and Bud Protection 444

13.2.2.4 Fire‐ and Browser‐Traps 445

13.2.2.5 Reproduction and Seedling Recruitment 446

13.3 Fire–Browser Interactions 447

13.3.1 Consequences of Fire for Browsers 447

13.3.1.1 Post‐Fire Environment 448

13.3.1.2 Woody Plant Regeneration 449

13.3.1.3 Decadal Fire Regimes 450

13.3.2 Browser Feedbacks to Fire 451

13.3.2.1 Browser Facilitation of Fire 451

13.3.2.2 Negative Feedbacks of Mixed‐Feeders 451

13.3.3 Fire–Browser Vegetation Impacts 452

13.3.3.1 Sapling Escape 452

13.3.3.2 Elephant Bark Stripping and Canopy Breakage 452

13.4 Biogeography of Fire and Browsing in Africa 453

13.4.1 Continental‐Scale Patterns of Fire and Browsing 455

13.4.2 Fire–Browser Regimes 457

13.4.3 Fine‐ vs Broad‐Leaved Savannas 457

13.5 Synthesis 460

References 460

14 Woody Plant Architecture and Effects on Browsing Herbivores in Savannas 469
Tristan Charles‐Dominique, Jean‐Francois Barczi , and Simon Chamaillé‐Jammes

14.1 Introduction 469

14.2 Factors Limiting Bite Size 471

14.3 Factors Limiting Biting Rate 474

14.4 Simulating Plant–Herbivore Interactions at the Individual Plant Scale 476

14.4.1 Plant Growth Model 477

14.4.2 Virtual Browsing and Consequences for Plant Fitness 478

14.4.3 Virtual Experiment Set‐up 478

14.4.4 Simulation Results 480

14.4.4.1 Effect of Leaf Size 481

14.4.4.2 Effect of Short Shoots 481

14.4.4.3 Effect of Spines 482

14.4.4.4 Effect of Cage Architecture 482

14.4.4.5 Effect of Short Shoot Induction 482

14.4.4.6 Effect of Sprouting 482

14.4.5 Significance of Simulation Results 482

14.5 Future Directions for Modeling Plant–Herbivore Interactions 483

Acknowledgments 483

14.A Appendix 484

References 484

15 Browsing Herbivore–Woody Plant Interactions in Savannas 489
Peter Frank Scogings and Juan H. Gowda

15.1 Introduction 489

15.1.1 The raison d’être 489

15.1.2 Approach 490

15.2 Feedback Between Woody Individuals and Browsing Herbivores 492

15.2.1 Shoot Growth 492

15.2.2 Spinescence 493

15.2.3 Nutrients and Phenolics 494

15.2.4 Is Positive Feedback Widespread? 495

15.3 Selective Browsing and Shifts in Woody Vegetation Composition and Structure 497

15.3.1 Recruitment and Mortality 497

15.3.2 Community Composition and Structure 500

15.4 Linking Responses of Woody Individuals and Communities to Functional Traits 501

15.5 Future Directions 504

15.5.1 Key Gaps 504

15.5.2 Standardizing Methods 505

References 539

16 Mesobrowser Abundance and Effects on Woody Plants in Savannas 551
David J. Augustine, Peter Frank Scogings, and Mahesh Sankaran

16.1 Introduction551

16.2 Mesobrowser Abundance in Savannas 552

16.3 Mesobrowser Diets in Savannas 559

16.4 Mesobrowser Effects on Woody Plant Communities 561

16.4.1 Hluhluwe‐iMfolozi Park, South Africa 564

16.4.2 Central Laikipia, Kenya 565

16.4.3 Chobe National Park, Botswana 567

16.4.4 Kruger National Park, South Africa 568

16.5 Evidence from Long‐Term Perspectives 569

16.6 The Influence of High Densities of Individual Mesobrowser Species 570

16.7 Water, Nutrients, and Mesobrowsers 571

16.8 Synthesis 573

Acknowledgments 576

References 576

17 Megabrowser Impacts on Woody Vegetation in Savannas 585
Norman Owen‐Smith, Bruce Page, Gabriella Teren, and Dave J. Druce

17.1 Introduction 585

17.2 Use of Woody Plants Versus Grasses and Other Plant Forms 586

17.3 Selection for Size Classes and Woody Plant Parts 589

17.4 Plant Damage Imposed and Mortality 590

17.5 Plant Species Selected 592

17.6 Landscape Transformations Caused by Elephants, Along with Fire 599

17.7 A Cautionary Note 602

17.8 Overview 602

References 604

18 Indirect Effects of Browsing Herbivores in Savannas 613
Corli Coetsee, Dario Fornara, Antoinette Veldtman, and Benjamin Wigley

18.1 Introduction 613

18.2 Indirect Effects of Browsers on Other Fauna 614

18.2.1 Mammals 614

18.2.1.1 Large Herbivore Effects on Rodents 614

18.2.1.2 Mesobrowser Effects on Other Herbivores 615

18.2.1.3 Megaherbivore Effects on Mesoherbivores 616

18.2.1.4 Interactions Among Browsers Where the Type of Browser is Not Apparent 616

18.2.1.5 Interactions Among Megaherbivores 617

18.2.1.6 Summary 617

18.2.2 Birds 617

18.2.2.1 Summary 619

18.2.3 Reptiles and Amphibians 619

18.2.3.1 Summary 619

18.2.4 Invertebrates 619

18.2.4.1 Summary 621

18.3 Effects on Ecosystem Processes 622

18.3.1 Carbon Cycling 622

18.3.1.1 Consumption of Vegetation by Browsers Affects Ecosystem Carbon Pools 622

18.3.1.2 Changes in Litterfall Affect Soil Carbon 625

18.3.1.3 Global Change Can Override the Effects of Herbivory on Soil Carbon 625

18.3.1.4 Summary 626

18.3.2 Soil Nutrient Cycling and Soil Nutrient Pools 626

18.3.2.1 Changes in Litter Quality 626

18.3.2.2 Herbivore Effects on both Litter Quality and Quantity 629

18.3.2.3 Summary 629

18.4 Conclusions 629

References 630

Part IV Synthesis 643

19 Water Limitation, Fire, and Savanna Persistence: A Conceptual Model 645
Brian Beckage, Gabriela Bucini, Louis J. Gross, William J. Platt, Steven I. Higgins, Norma L. Fowler, Matthew G. Slocum, and Caroline Farrior

19.1 Introduction 645

19.2 Conceptual Model 646

19.2.1 Water Limitation 648

19.2.2 Fire 650

19.2.3 Fire Feedbacks 651

19.2.4 Other Processes 652

19.3 Summary 653

Acknowledgments 654

References 654

20 Savanna Ecosystem Models: What Should a Clever Modeler Code? 661
Gregory Kiker and Peter Frank Scogings

20.1 Introduction 661

20.2 Local‐Scale Aspects of Woody Plant–Browser Interactions 662

20.3 Model Designs for Plant–Herbivore Interactions 663

20.3.1 Plant‐Focused Models 666

20.3.2 Herbivore‐Based Models 668

20.3.3 Integrated Models: Adding Complexity into Plant–Herbivore Models 670

20.4 Discussion 672

References 674

21 Woody Plants and Large Herbivores in Savannas: Ancient Past – Uncertain Future 683
Peter Frank Scogings and Mahesh Sankaran

21.1 Introduction 683

21.2 Woody Plants 685

21.3 Large Herbivores 688

21.4 Interactions Between Woody Plants and Browsers 690

21.4.1 Adaptations of Woody Plants to Browsing by Mesobrowsers 690

21.4.2 Woody Community Responses to Mesobrowsers and Megaherbivores 692

21.4.3 Indirect Effects of Browsing 696

21.5 Models 698

21.5.1 General Conceptual (Qualitative) Models 698

21.5.2 Mathematical (Quantitative) Models 700

21.6 The Future 701

References 703

Index 713

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Mahesh Sankaran
Peter Frank Scogings
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