The Biome 449 



climate with latitude and with altitude result in differences in the 

 sefection of dominant species. Each of these various geographical 

 combinations of dominants constitutes a faciation of the community. 

 Variations of the dominant species on a more local scale when deline- 

 able are termed lociations. 



The subdominant members of a community may also form recog- 

 nizable groups. These subdivisions have been called "societies" but 

 this term is unsatisfactory in this connection because of its specific 

 use for highlv integrated animal groups within the same species as 

 seen in insect colonies. If we again take a climax deciduous forest 

 as an illustration, the shrubs, seasonal herbs, and cryptogamic plants 

 as well as the various categories of animal life may be regarded as 

 constituting definite groups of subdominants. Many aquatic com- 

 munities including benthic plant and animal groups may be similarly 

 subdivided, but with the smaller life forms local subdivisions are not 

 as conspicuous as in communities dominated by the larger vegetation. 

 Subdivision of communities involving plankton and nekton are even 

 less clearly defined because of the mobility of the medium and the 

 organisms. 



Many ecologists feel that communities and their subdivisions cannot 

 be as clearly distinguished as suggested by the foregoing terms, and 

 that no system of community classification is really satisfactory. 

 Some investigators feel that each community is a law unto itself, as 

 argued by Gleason (1926), since each is composed of whatever plants 

 and animals have reached the area and have found conditions toler- 

 able. As the inhabitants in each situation have grown and multi- 

 plied, the community and its environment have changed until a stable 

 condition has been reached. If similar climax communities develop, 

 it is because similar conditions happened to exist, but an indefinite 

 amount of individual variation is possible. 



Regardless of the method of classifying communities, each biome 

 is found to consist of several major communities (or associations) in 

 the climax condition and of many minor communities. Between or 

 within the major climax communities the developmental stages of 

 these communities can be recognized and also other community types 

 produced by local variations in the environment. In the deciduous 

 forest biome, for example, grass and brush communities are found that 

 may eventually mature into forest communities. Also present are the 

 communities of ponds, marshes, rock ledges, and sand hills that will 

 not be converted into deciduous forest for a long time but are definite 

 members of the biome. A certain amount of cohesion within the 

 biome is provided by plant species common to two or more communi- 



