Grassland (i Oiiliiiiud) 

 development of hopping; locomotion 



among animals of, 329-330 

 differences in moisture require- 

 ments of species of as reason 



for sutxiivision into plant 



associations, 324 

 distribution of during Pliocene and 



Pleistocene eras, 326 

 during post-Pleistocene period in 



North America, 290-291 

 effect of earthworms on soil of, 



164 

 elimination of predators from and 



overpopulation, 128-129 

 extension of in North America, 324 

 factors in reinvasion of by decidu- 

 ous forests, 326 

 failure of trees to spread into due 



to precipitation, 324 

 first evolution of, 326 

 fleetness of animals in, 326-327 

 herbivorous animals favored in, 



125-126 

 •■invasion" of forest in by means 



of man, 300 

 invasion of over Great Plains as 



factor in creating western and 



eastern forest biociations, 307- 



308 

 invertebrate communities in, 124- 



125 

 large herbivorous ungulates as 



reaching largest populations 



in, 328 

 life- history of meadow-vole in, 142 

 list of most important genera 



of grasses in North American, 



325 

 marked similarities of on all 



continents except for species 



composition, 324 

 microclimate of: 

 differences in between north and 



south facing slopes, 124 

 distribution of animals in relation 



to, 124 

 names for in various countries, 324 

 North American, biociation of: 

 birds in, 326 

 extension of into deciduous and 



coniferous forest biomes, 326 

 faciations of, 326-327 

 mammals in, 326 

 occurrence of ponds or potholes 



in, 330 

 origin of short grasses of, 326 

 origin of tall grasses of, 326 

 overgrazing in and change in 



members and kinds of animals 



present in, 128 

 precipitation in North American, 



324 



Grassiand (i aiitiuiicd) 

 protective coloration of animals 



of, 329 

 recording of rainfall in, 121 

 relation of North American to 



Eurasian due to similar 



derivation, 326 

 relative humidity of compared to 



forest- edge and forest, 121 

 retreat of during post-glacial 



xerothermic period, 326 

 segregation of animals by south- 

 ward extension of during 



Pleistocene era, 286-288 

 short, hazards in cultivation of, 



330 

 similarity of biociations of in rest 



of world to North American, 



327-328 

 spread of Indians in after use of 



horses, 330 

 tall, high productivity of for cereal 



crops, 330 

 temperature of: 

 as compared with that of forest, 



121 

 as factor in separating temperate 



from tropical, 324-325 

 range of, 324-325 

 trampling of soil of by large 



terrestrial animals, 164-165 

 use of by man: 

 early difficulties in, 330-331 

 in past as poor, 330 

 surmounting of difficulties in, 



330-331 

 through dry farming, 330 

 vertebrate communities in, 125 

 vertical gradients in microhabitat 



factors in, 122 

 Grassland Vegetation {see also 



Forests; Grassland; Grazing): 

 ability of to tolerate considerable 



grazing, 325 

 and propagation of perennial 



grasses, 120 

 and retention of foliage by conifer- 

 ous trees, 121 

 and shedding of foliage by decidu- 

 ous trees, 121 

 as consumed by invertebrates, 



126-127 

 as food for big-game mammals, 



127-128 

 bunch grasses, defined . 120 

 dangers of grazing on by rodents, 



127 

 dangers of heavy grazing on, 125- 



126 

 depth of rooting of, 325 

 division of into categories, 120 

 forbs in: 

 as sod formers, 120 



Grassland Vegetation (C Oiiliuiied) 

 de/uied. 120 

 occurrence of, 325 

 grazing and protein production of, 



125-126 

 growth of after dry-season fires, 



325 

 growth of and weather conditions, 



325 

 in climax stage, 325 

 in cold climates, evergreens as 



part of, 120 

 in forest- edges, 120 

 in warm climates, broad- leaved 



deciduous trees as part of, 120 

 on north- facing slopes, 124 

 on south-facing slopes, 124 

 percentages of that can be safely 



used for grazing, 125-126 

 perennial grasses as dominants 



of, 325 

 plant associations consisting of in 



North America, 325 

 renewal of each year, 120 

 stimulation of by grazing, 125-126 

 strata of, described. 121 

 terminal buds of not injured by 



grazing, 125-126 

 transition area in, 120 

 Grazing (see also Grassland 



Vegetation): 

 after dry- season fires in tropical 



climates, 325 

 among animals on arctic tundra, 



320 

 by invertebrates, 126-127 

 deforming of trees and shrubs 



through, 192 

 detrimental effects of and brows- 

 ing in forests, 177 

 effect of on grassland vegetation, 



125-126 

 moderate, as stimulating high 



productivity of grasses, 328 

 of primitive herds of bison, 328 

 overgrazing, as producer of change 



in kinds and numbers of animals 



in grassland, 128 

 overgrazing, prevention of by 



predators, 128-129 

 Gravity: 

 adjustments of organisms to 



counteract, 96 

 positive reaction of sea-shore 



animals to, 352 

 Grinnell, Joseph, and development 



of concept of ecological niche, 



245 

 Growth-forms, 7 



Index 42' 



