574 



THE COMMUNITY 



to its potential toleration within a given 

 sere or microsere. 



In general, when the edaphic pond sere 

 passes into a cat-tail marsh (Fig. 210), 

 other organisms appear— for example, musk- 

 rats and red- winged blackbirds (Beecher, 

 1942). Eventually the marsh tends to 

 pass into either grassland or forest, depend- 



Bolleri deposited receaCly D 







Fig. 212. Diagram of succession and devel- 

 opment from the edaphic bog to edapliic bog- 

 forest climax, or to the regional climatic cli- 

 max forest. (After Transeau, Sampson and 



Tiffany. ) 



ing upon the biome involved. Hence there 

 is, through time, a merging of the edaphic 

 sere into the cUmatic sere of the area. 

 Figure 211 shows the general development 

 taking place in a pond sere, in diagram- 

 matic form, and the eventual diflFerentiation 

 into grassland or forest. 



Bogs often have the same end point as 

 ponds, but reach their terminal stage by a 

 different form of development. Here the 

 edaphic bog sere is characterized by filling 

 partially from the top downward, concen- 

 tric zones of vegetation gradually moving 

 centripetally, building up a supporting 

 mass of debris and rootlets that eventually 

 can support fairly large trees, and conse- 

 quently encroaching on the open water in 



the bog center. In contrast to ponds, the 

 bog is usually acid, and the sere sup- 

 ports many species of plants and animals 

 rare or absent from ponds and lakes. This 

 edaphic bog development is illustrated in 

 Figure 212. 



From the preceding discussion several 

 general tendencies may be stated. (1) 

 Communities are not static, but are in a 

 more or less continuous state of directional 

 change. (2) These changes may arise (a) 

 from intracommunity biotic interactions, or 

 development, or (h) from extracommunity 

 physical forces, as exemplified by physio- 

 graphic influences involved in erosion and 

 deposition, or (c) from a combination of 

 developmental and physical forces. (3) The 

 result is the gradual alteration of the com- 

 munity through time, and the appearance of 

 species populations better adjusted to the 

 changed conditions, e.g., a succession of 

 communities over a given area, known col- 

 lectively as a sere. (4) Within each com- 

 munity, several smaller developmental or 

 successional sequences take place, each 

 sequence forming a microsere. (5) The sere 

 then, may be viewed as a series of stages, 

 starting with a pioneer stage, or stages {as- 

 socies) , and ending with a climax stage, 

 which is relatively stable under existing 

 climatic conditions. (6) We may differen- 

 tiate between microsere and sere, in that 

 the former has no stable end product or 

 cUmax, in the strict sense of the word. (7) 

 We may differentiate between edaphic 

 seres, controlled by such local conditions 

 as soil or water, and climatic seres that are 

 under the general control of the prevaihng 

 climate, and end in a climax community." 



* The terminology concerning the climax is 

 complex, and has shifted in meaning, and 

 in shades of meaning, at the hands of many 

 students. This is not a subject for the unwary 

 or for the impatient. 



In this book we have used the term "cHmax" 

 in the traditional sense, as a relatively stable, 

 terminal community of a sere— for example, the 

 cUmax beech-sugar maple forest, or one of its 

 equivalents. It should be pointed out, never- 

 theless, that there are other usages of the 

 term— for example, that a climax is a synonym 

 of the plant formation, or, more broadly, of 

 the biome. 



Five terms, at least, are involved in this gen- 

 eral area of theory. They are postclimax, pre- 

 climax, suhclimax, proclimax, and discUmax. 

 They are discussed in Carpenter (1938), Clem- 

 ents and Shelford (1939), and Costing (1948). 



