«S^~^' 



western areas, particularly in the Sierra Nevada, 

 chaparral may occur in dense stands after fires and 

 persist for a long time. 



Since the burn subsere in coniferous forest com- 

 monly includes the aspen-birch associes, many of the 

 typical animals in this stage are deciduous forest and 

 forest-edge species, although there is a penetration of 

 coniferous forest species as well. The birds and mam- 

 mals are not generally very numerous in the aspen- 

 birch community, but ground invertebrates may be 

 more abundant here than in the poorly decomposed 

 acidic ground duff found in the coniferous climax. 



ANIMAL COMMUNITIES 



Although the plant communities that make 

 up the stages of the different land seres and subseres 

 we have described are numerous and varied, the num- 

 ber of distinct animal communities that can be clearly 

 recognized are few. Actually, we can distinguish in 

 eastern North America only the animal communities 

 of grassland, forest-edge, deciduous forest, south- 

 eastern evergreen forest and coniferous forest. Each 

 of these communities varies in the different habitats 

 of rock, sand, and clay, and in the various subseres, 

 but the variations are of minor significance and are 

 best treated as facies of the larger communities. 



by one of spruce as 

 frees now forming ir 

 reach nnaturlty (cou 

 Forest Service). 



ndergro 

 >sy U.S. 



SUMMARY 



For terrestrial living, animals must actively 

 support themselves against gravity, obtain water, and 

 prevent excessive water losses from the body. They 

 must be equipped to endure a wide range of fluctuat- 

 ing temperatures, to secure oxygen, to endure in- 

 tense solar radiation, adjust to diurnation (day and 

 night) and aspection (seasonal changes), and yet 

 maintain close contact with the substratum. 



Succession occurs on all primary bare areas, such 

 as rock, sand, clay, and floodplains, and in such 

 secondary bare areas as abandoned fields, pastures, 

 and burns. In humid regions, all seres converge to 

 the same climax community. There are normally 

 more plant than animal stages in any sere. The suc- 

 cession program of animal communities correlates 

 with the succession program of vegetation-types or 

 life-form of the plant dominants, not with plant com- 

 munities identified by the taxonomic composition of 

 the plant dominants. In eastern North America, we 

 can distinguish only the grassland, forest-edge, de- 

 ciduous forest, southeastern evergreen forest, and 

 coniferous forest terrestrial animal communities. 



Rock, sand, and clay 1 19 



