Succession and Climax 431 



indefinitely in each biotope is known as the climax. In other situa- 

 tions doubt exists as to whether the communities would ever be un- 

 disturbed for long enough to enable an equilibrium condition or 

 climax to be reached. For example, waterways in the black spruce 

 muskeg of Alaska cause melting of the frozen ground with a conse- 

 quent destruction of the spruce vegetation through the caving in of 

 the surrounding terrain and a conversion of the area to treeless bogs. 

 In time the spruce forest with frozen ground becomes reestablished 

 and the cycle appears to continue indefinitely (Drury, 1952). In 

 such situations the whole area might be considered as being in the 

 climax condition and the alternation of vegetation types merely fluc- 

 tuations within the climax. Possibly analogous fluctuations or cyclic 

 changes in the fauna and flora occur in the oceanic community. This 

 type of fluctuation within communities that are apparently in the 

 climax condition will be further discussed in the latter part of this 

 chapter. 



When a climax community has become established, it tends to 

 remain in possession of the area because it does not change the en- 

 vironment so as to injure itself or to favor the growth of different 

 dominant species, and because its members can resist all competition 

 from the outside. The succession of communities leading to a recog- 

 nized type of climax is termed a sere. Seres composed of different 

 sequences of communities typify different situations. 



On land the type of climax community in which the sere culminates 

 is often determined primarily by the climate, and similar climax com- 

 munities dominated by plants often extend over large regions. In 

 local areas with special edaphic or physiographic conditions, or sub- 

 ject to recurring fire or disease, a type of community different from 

 the surrounding region may be displayed. Clements ( 1936 ) and his 

 followers originally believed that given sufficient time every local area 

 would eventually develop the same type of climax communitv— the 

 type characteristic of the region as a whole under the prevailing 

 climate, and that the continuing existence of a different type of com- 

 munity in a local area was due to "arrested succession." Subse- 

 quently ecologists have abandoned the strict application of the mono- 

 climax theory based on climate alone, and many have adopted a 

 polyclimax theorv in which the tvpe of communitv that maintains 

 itself in each area is regarded as the climax for that area. Since 

 communities do not form a sharply delineated mosaic but grade into 

 one another with many variations of species composition according to 

 local conditions, Whittaker (1953) has proposed a climax pattern 



