Plants at the margin: ecological limits and climate change

Cover......Page 1
Half-title......Page 3
Title......Page 5
Copyright......Page 6
Contents......Page 9
Preface......Page 15
Acknowledgements......Page 17
Part I: The nature of marginal areas......Page 19
1. Recognizing margins......Page 21
1.2 Margins and climate change......Page 23
1.3 Limits to distribution......Page 26
1.3.2 Resource availability......Page 27
1.3.3 Resource access and conservation in marginal areas......Page 33
1.5 Demographic factors......Page 35
1.6 Relict species and climate change......Page 37
1.6.2 Climatic relicts......Page 38
1.7 Endangered species......Page 41
1.8 Agricultural margins......Page 42
1.9 Conclusions......Page 44
2 . Biodiversity in marginal areas......Page 47
2.2.1 Definitions of biodiversity......Page 49
2.2.2 Problems of scale and classification......Page 52
2.2.3 Variations in assessing genetic variation......Page 53
2.4 Disturbance and biodiversity......Page 54
2.4.1 Grazing......Page 55
2.4.2 Fire......Page 60
2.5 The geography of marginal plant diversity......Page 61
2.5.1 The South African Cape flora......Page 63
2.5.2 Mediterranean heathlands......Page 66
2.5.3 Mediterranean-type vegetation worldwide......Page 68
2.5.4 The Brazilian Cerrado......Page 69
2.6 Plant diversity in drylands......Page 70
2.7 Plant diversity in the Arctic......Page 75
2.8 Conclusions......Page 77
Part II: Plant function in marginal areas......Page 79
3. Resource acquisition in marginal habitats......Page 81
3.1 Resource necessities in non-productive habitats......Page 83
3.2 Adaptation to habitats with limited resources......Page 86
3.2.1 Capacity adaptation......Page 87
3.2.2 Functional adjustment......Page 88
3.2.3 Adverse aspects of capacity adaptation......Page 90
3.2.4 Climatic warming and the vulnerability of specific tissues......Page 92
3.3 Habitat productivity and competition......Page 95
3.3.1 Plant functional types......Page 96
3.4.1 Two-class life strategies......Page 99
3.4.3 Four-class life strategies......Page 101
3.5 Resource allocation......Page 102
3.6.1 Competition for resources in marginal areas......Page 103
3.6.2 Deprivation indifference......Page 104
3.6.3 Deprivation indifference through anoxia tolerance......Page 105
3.6.4 Avoiders and tolerators......Page 107
3.7.1 Light......Page 108
3.7.2 Precipitation......Page 109
3.7.3 Ground water......Page 110
Dew......Page 111
Fog......Page 112
3.7.4 Carbon......Page 114
3.7.5 Nitrogen......Page 116
3.7.6 Phosphate......Page 118
3.7.7 Phosphate availability at high latitudes......Page 119
3.8.1 Mycorrhizal associations in the Arctic......Page 120
3.9 Nutrient retention in marginal areas......Page 121
3.10 Changes in resource availability in the Arctic as a result of climatic warming......Page 124
4. Reproduction at the periphery......Page 127
4.2.1 Pre-zygotic and post-zygotic limitations to seed production......Page 129
4.3 Germination and establishment in marginal areas......Page 132
4.4.1 Reproduction in flood-prone tropical lake and river margins......Page 134
4.5.1 Transient and stable hybrids......Page 136
4.5.2 Hybrid swarms......Page 138
4.5.3 Spartina anglica - common cord grass......Page 140
4.5.4 Senecio squalidus - the Oxford ragwort......Page 141
4.6 Genetic invasion in marginal areas......Page 144
4.6.1 Invasion and climatic warming......Page 145
4.6.2 Climatic warming, disturbance and invasion......Page 148
4.7.1 Diversity of plant form in drought-prone habitats......Page 149
4.7.2 Desert seed survival strategies......Page 152
4.8 Flowering in arctic and alpine habitats......Page 153
4.8.1 Annual arctic plants......Page 158
4.9 Mast seeding......Page 160
4.10 The seed bank......Page 164
4.10.1 Polar seed banks......Page 165
4.11 Biased sex ratios......Page 166
4.12.1 Asexual reproduction......Page 171
4.13 Longevity and persistence in marginal habitats......Page 173
4.14 Conclusions......Page 176
Part III: Marginal habitats – selected case histories......Page 177
5. Arctic and subarctic treelines and the tundra–taiga interface......Page 179
5.1.1 Migrational history of the tundra-taiga interface......Page 181
5.2.1 Relating distribution to temperature......Page 184
5.2.2 Krummholz and treeline advance......Page 187
5.3.1 Boreal migrational history......Page 192
5.4.1 Post-fire habitat degradation......Page 196
5.4.2 Treelines and paludification......Page 197
5.4.3 History of paludification......Page 199
5.4.4 Bog versus forest at the tundra-taiga interface......Page 201
5.5 Homeostasis and treeline stability......Page 203
5.6 Boreal forest productivity at high latitudes......Page 205
5.6.1 Physiological limits for tree survival at the tundra-taiga interface......Page 206
5.6.2 Carbon balance......Page 208
5.6.5 Overwintering photosynthetic activity......Page 209
5.7 Future trends at the tundra-taiga interface......Page 211
6. Plant survival in a warmer Arctic......Page 215
6.2 Signs of change......Page 217
6.3.1 Mapping arctic margins......Page 222
6.4.1 Reassessment of ice cover in polar regions......Page 223
6.4.2 Molecular evidence for the existence of glacial refugia at high latitudes......Page 229
6.5 Habitat preferences in high arctic plant communities......Page 231
6.5.2 Ice encasement and the prolonged imposition of anoxia......Page 232
6.6 Mutualism in arctic subspecies......Page 233
6.7 Polyploidy at high latitudes......Page 234
6.8 Arctic oases......Page 237
6.9 Phenological responses to increased temperatures......Page 239
6.10 Conclusions......Page 242
7. Land plants at coastal margins......Page 243
7.1 Challenges of the maritime environment......Page 245
7.1.1 The concept of oceanicity......Page 246
7.1.2 Physical versus biological fragility......Page 249
7.2.1 Foreshore plant communities......Page 253
7.2.2 Dune systems of the North Atlantic......Page 256
7.2.3 Arctic shores......Page 258
7.3.1 Antarctic shores......Page 264
7.3.2 New Zealand......Page 266
7.4.1 Salt marshes and mudflats......Page 268
7.4.2 Rising sea levels and mudflats......Page 269
7.5.1 Cliffs and caves......Page 270
7.5.2 North Atlantic cliffs......Page 272
7.6.1 Mangrove swamps......Page 274
7.7.1 Drought tolerance......Page 281
7.7.3 Surviving burial......Page 282
7.7.4 Flooding......Page 285
7.8 Conservation versus cyclical destruction and regeneration in coastal habitats......Page 287
7.9 Conclusions......Page 289
8. Survival at the water’s edge......Page 291
8.1 Flooding endurance......Page 293
8.1.1 Life-form and flooding tolerance......Page 295
8.2.1 Radial oxygen loss......Page 299
8.2.2 Thermo-osmosis......Page 300
8.3 Responses to long-term winter flooding......Page 302
8.3.1 Surviving long-term oxygen deprivation......Page 303
8.4.1 Unflooding - the post-anoxic experience......Page 304
8.5 Responses to short-term flooding during the growing season......Page 305
8.5.1 Disadvantages of flooding tolerance......Page 307
8.6.1 Phenotypic plasticity in amphibious species......Page 308
8.6.2 Speciation and population zonation in relation to flooding......Page 309
8.7 Aquatic graminoids......Page 310
8.7.2 Sweet flag (Acorus calamus)......Page 313
8.7.3 Reed sweet grass (Glyceria maxima)......Page 316
8.7.4 The common reed (Phragmites australis)......Page 318
8.8 Tropical versus temperate trees in wetland sites......Page 319
8.9 Conclusions - plants with wet feet......Page 323
9. Woody plants at the margin......Page 325
9.1 Woody plants beyond the treeline......Page 327
9.2 Woody plants of the tundra......Page 329
9.3 Montane and arctic willows......Page 332
9.4 Mountain birches......Page 336
9.4.1 Biogeographical history of mountain birch......Page 340
9.5.1 Biogeographical history of dwarf birch......Page 341
9.6 Ecological sensitivity of woody plants to oceanic conditions......Page 342
9.7 Juniper......Page 344
9.8.1 Relating heathlands to climate......Page 347
9.8.2 Possible migration behaviour......Page 350
9.9 New Zealand: a hyperoceanic case study......Page 352
9.10 Conclusions......Page 355
10. Plants at high altitudes......Page 357
10.1 Altitudinal limits to plant survival......Page 359
10.2 Mountaintop isolation......Page 361
10.2.1 Inselbergs - isolated mountains......Page 363
10.2.2 African inselbergs......Page 365
10.3 Aspects of high-altitude habitats......Page 366
10.3.1 Geology and mountain floras......Page 368
10.3.3 Mountain topography and biodiversity......Page 370
10.4.2 Adapting to fluctuating temperatures......Page 373
10.4.3 Protection against high levels of radiation at high altitudes and latitude......Page 374
10.4.4 Effect of UV radiation on alpine vegetation......Page 377
10.4.5 Oceanic mountain environments......Page 378
10.4.6 Phenological responses of mountain plants......Page 379
10.5 Alpine vegetation zonation - case studies......Page 381
10.5.2 Tropical and subtropical mountains - East Africa......Page 382
10.5.3 South America......Page 383
10.6 The world's highest forests......Page 384
10.7 High mountain plants and climate change......Page 387
10.7.2 Effects of increased atmospheric CO2 on high mountain vegetation......Page 390
10.8 Alpine floral biology......Page 394
10.9 Conclusions......Page 397
11. Man at the margins......Page 399
11.1 Human settlement in peripheral areas......Page 401
11.2 Past and present concepts of marginality......Page 402
11.2.1 Agricultural sustainability in marginal areas......Page 404
11.3 Man in the terrestrial Arctic......Page 407
11.3.1 Acquisition of natural resources at high latitudes......Page 409
11.3.2 Future prospects for the tundra and its native peoples......Page 413
11.4 Man on coastal margins......Page 414
11.4.1 Human acceleration of soil impoverishment in oceanic regions......Page 416
11.4.2 Sustainable agriculture in oceanic climates: Orkney - an oceanic exception......Page 421
11.5.1 Coastal wetlands......Page 422
11.5.2 Human settlement in reed beds......Page 423
11.5.3 Agricultural uses of wetlands......Page 424
11.5.4 Recent developments in bog cultivation......Page 427
11.6.1 Transhumance......Page 429
11.6.2 Terrace farming......Page 431
11.7 Conclusions......Page 435
12. Summary and conclusions......Page 437
12.1 Signs of change......Page 439
12.2 Vegetation responses to climate change......Page 440
12.3 Pre-adaptation of plants in marginal areas to climatic change......Page 441
12.4 Physical fragility versus biological stability and diversity......Page 442
12.5.1 Regeneration and the role of margins......Page 444
12.6 Future prospects for marginal areas......Page 448
References......Page 451
Author index......Page 479
Species index......Page 483
Subject index......Page 489