COMMUNITY ORGANIZATION: METABOLISM 



511 



view of community structure, the terrestrial 

 edaphon and the aquatic benthos occupy 

 the first two (lowermost) strata in the 

 vertical gradient of stratification. From the 

 viewpoint of trophic levels, the edaphon is 

 a composite of a?, A^, A*, As, with, in un- 

 common situations, some participation in Ai. 

 From the view of structural size of organ- 

 isms forming the community, the edaphon 

 and plankton are similar. 



Feeding relations in nearly all com- 

 munities are expressible qualitatively as a 

 food web (food-cycle of Elton, 1927, p. 



log habitat are all directly or indirectly 

 parts of the food web of the forest com- 

 munity. Such a web involves all the lesser 

 food webs, of small habitat niches, of 

 habitats and of strata. For example the 

 oyster bed and the coral reef are relatively 

 independent of each other in many ways, 

 but both depend upon the marine plankton 

 for food supply. 



Even distinct, relatively independent 

 major communities exchange energy across 

 their ecotones. Many large animals range 

 over a territory that embraces a great va- 



g. 168. Food web of the major marine community. ( After Sverdmp, Johnson, and Fleming. ) 



56). That is, the several species populations 

 of a community form many food chains that 

 intertwine, anastomose, or cross one another 

 to produce a single complex web that in- 

 cludes all the constituent organisms, in all 

 the strata (Fig. 168). 



A simple food chain is seldom found 

 under natural conditions as a complete 

 entity. Even within the confines of a rela- 

 tively limited habitat, such as a decaying 

 log, the feeding relations are not in the 

 form of a simple food chain (Fig. 169). 



Furthermore, the animal and plant con- 

 stituents of the food web of the prostrate 



riety of communities. Such wide-ranging 

 forms are usually important ecologically, 

 and influence biotically the several serai 

 stages (Chap. 29) through which they 

 move. Famihar examples are the moose and 

 the lynx in the coniferous forest biome of 

 North America (Chap. 30). Such forms 

 have been called permeants by Shelford 

 and Olson (1935). 



Contiguous but ecologically diflFerent 

 communities, each with its own food web, 

 are frequently visited by diflFerent animals 

 of the several communities involved. Such 

 movements take place periodically in hiber- 



