230 THE STUDY OF PLANT COMMUNITIES • Chapter IX 



Recognition of Local Climax.— The variations of a formation 

 (associations) are not always immediately obvious, particularly in 

 areas of transition from one association to another. Because of dis- 

 turbance by man, the climax vegetation once present in virgin 

 stands over wide areas has practically disappeared. We now, there- 

 fore, must rely upon small samples of climax vegetation, often 

 disturbed; or, when even these are lacking, we must determine the 

 climax on the basis of studies of succession. There may, therefore, 

 be different interpretations, and errors are possible. To illustrate : 

 It was generally believed for years that short grasses constituted 

 the climax of the plains. Added evidence and reinterpretation in- 

 dicated to many ecologists that mid-grasses are climax and short 

 grasses are disclimax maintained by modern grazing under the 

 conditions of periodic drought. 



A climax association must, of course, conform to the criteria 

 that delimit the formation of which it is a member. To check these 

 criteria, it becomes necessary to know the successional trends of 

 the vicinity in detail, to know the composition and structure of 

 the postulated climax and subfinal stages of succession, and to dis- 

 tinguish preclimax and postclimax communities and habitats. Thus 

 it becomes necessary to know something of related associations as 

 well as the one involved. Finally, the history of the region, both 

 recent and geological, is desirable for proper interpretation of ob- 

 servations. 



The climax must be a community capable of maintaining itself 

 indefinitely under existing climatic conditions. It must be the final 

 community in all successional trends in the region except those 

 isolated instances of edaphic or physiographic variation producing 

 preclimax or postclimax by compensating for climate. It must 

 recur throughout the area under average conditions, or the evi- 

 dence from succession must indicate its potential presence. 



General Procedure in Local Study.— The desirability of fa- 

 miliarity with the area as a whole has been emphasized. Observa- 

 tion and note-taking should proceed at the same time that literature 

 is searched to learn the historical aspects of the area and the rela- 

 tionships of its flora to that of surrounding climaxes. With con- 

 tinued observation, certain ideas will develop as to probable and 

 possible successional relationships and the relative position of dif- 



