PREFACE ....................................................... vii
ACKNOWLEDGEMENTS ............................................... ix
1 INTRODUCTION ................................................. 1
2 HISTORY AND PRESENT STATE OF TIMBERLINE RESEARCH ............. 5
2.1 Early timberline research ............................... 5
2.2 Modern timberline research .............................. 7
3 DEFINITIONS, TERMINOLOGY .................................... 11
4 PHYSIOGNOMIC AND ECOLOGICAL DIFFERENTIATION OF MOUNTAIN
TIMBERLINE .................................................. 29
4.1 Tree species at timberline ............................. 29
4.1.1 Influence of geological and floral history ...... 29
4.1.2 Tree species at temperate and northern
timberlines ..................................... 32
4.1.3 Tree species at timberlines in the southern
hemisphere and in the tropics ................... 42
4.2 Relationship of timberline elevation to macroclimate
climate character, and the mass-elevation effect ....... 49
4.3 Ecological conditions and processes at the
timberlines ............................................ 58
4.3.1 Heat deficiency ................................. 58
4.3.2 Carbon balance, carbon limitation ............... 61
4.3.3 Frost tolerance and damage ...................... 65
4.3.3.1 Temperate and northern timberlines ..... 65
4.3.3.2 Tropical timberlines ................... 73
4.3.4 Winter desiccation and abrasion ................. 75
4.3.5 Soil temperature ................................ 86
4.3.6 Wind ........................................... 104
4.3.7 Snow cover ..................................... 107
4.3.7.1 Distribution and characteristics of
snow cover ............................ 108
4.3.7.2 Effects of the snow cover on sites .... 111
4.3.8 Soils .......................................... 122
4.3.9 Topography/geomorphology ....................... 135
4.3.9.1 Slope gradient and geomorphic
structure ............................. 136
4.3.9.2 Exposure .............................. 162
4.3.10 Regeneration ................................... 167
4.3.10.1 Seed-produced regeneration ............ 167
4.3.10.2 Vegetative reproduction ............... 182
4.3.11 Influence of site conditions on growth form .... 188
4.3.12 Influence of trees and tree stands on site
conditions ..................................... 220
4.3.13 Influence of animals on timberline ............. 244
4.3.13.1 Large herbivorous mammals ............ 245
4.3.13.2 Burrowing herbivorous mammals ........ 253
4.3.13.3 Birds ................................ 254
4.3.13.4 Defoliating insects (Epirrita
autumnata, Operophtera brumata) ...... 264
4.3.14 Anthropogenic impact on timberline ............. 268
4.3.14.1 Lowering the timberline .............. 268
4.3.14.2 After-effects of timberline decline
and present impact ................... 278
5 TIMBERLINE FLUCTUATIONS .................................... 293
5.1 General aspects ....................................... 293
5.2 Timberline fluctuations in the past ................... 297
5.3 Driving processes and adverse factors controlling
present timberline dynamics ........................... 299
5.4 Regional variation in timberline response after the
'Little Ice Age' ...................................... 301
5.5 Conclusions and perspectives .......................... 326
6 TIMBERLINE PROSPECTS AND RESEARCH NEEDS .................... 335
REFERENCES .................................................... 343
INDEX ......................................................... 421
|
