COMMUNITY SUCCESSION AND DEVELOPMENT 



575 



From this general theoretical background 

 there emerges an important principle at the 

 level of the biome, the principle of con- 

 vergence. In general, under natural condi- 

 tions, the several seres (edaphic and 

 climatic) tend to converge, in time, in a 

 climax community. This is a climatic climax 

 as opposed to an edaphic climax, and, 

 presumably, endures as long as the pre- 



max may be composed of a variety of dom- 

 inant tree species (Fig. 213), in differing 

 combinations and frequencies, including 

 hemlock, beech, sugar maple, red oak, 

 American elm, wild black cherry, chestnut, 

 tulip, live oak, and magnolia, among others. 

 For detailed analysis of this forest climax 

 type, consult the following studies and 

 their extensive bibliographies, that partially 



Fig. 213. Climatic climax (hemlock-beech-maple), subclimax (white pine), and second growth 

 on the Northern Allegheny Plateau of Pennsylvania. ( After Hough & Forbes. ) 



vailing cHmate endures. The structure of 

 the climax community of a sere may vary 

 with latitude and with altitude. For ex- 

 ample, within the deciduous forest biome 

 of eastern North America, the climatic ch- 



Postclimax may be regarded as a relict of a 

 former climax, held under edaphic control in 

 an area the climate of which is no longer 

 favorable for development of the climax. 



Preclimax and subclimax are terms often 

 used to designate a serai stage that just pre- 

 cedes the climax. 



Proclimax is a term used for those com- 

 munities that suggest the extent or the per- 

 manence of a climax, but are not controlled by 

 climate. 



Disclimax is a community that originates and 

 is maintained by some form of disturbance. 



Open the subject: Braun (1935, 1947), Cain 

 (1943, 1944, 1945), Frothingham (1915), 

 Gordon (1940), Harshberger (1911), 

 Hough and Forbes (1943), Kendeigh 

 (1946), Lutz (1930), Nichols (1935), 

 Odum (1943), and Potzger (1946). 



As an example of the principle of con- 

 vergence, the region of northwestern 

 Indiana, in the deciduous forest biome, is 

 selected on historical grounds. The follow- 

 ing organization shows convergence in this 

 area from four separate seres: namely, sand 

 ridge, clay bluff, pond, and flood-plain. 



This classical convergence diagram may 

 vary in its details from locality to locality, 

 and is still receiving modification at the 

 hands of specialists without altering its 

 central theme. The original was prepared 



