EVOLUTION OF ECOLOGICAL CONCEPTS 353 



sighted as possible, of its presence and its underlying sources and necessity. 



4. All these concepts and approaches have a partial character; they bring 

 into order and comprehension only a small fraction of the information avail- 

 able to us. No one of them, however exhaustively applied, nor all of them 

 together, can ever bring into a pattern of understanding all the available 

 information about natural communities. 



5. Finally, these concepts are to some extent interdependent, since the 

 definition of one may influence another; but they are not interdependent 

 in any simple, direct, and necessary way. There is no necessary correspondence 

 between climax stability and regional prevalence of vegetation, between 

 climax regions and floristic natural areas, between limits of dominance and 

 of community types, between associations in the international and associa- 

 tions in the American sense. Rather than assuming that such necessary cor- 

 respondence exists, it may be best to pursue each approach on its own terms 

 for its own merits, with a minimum of assumption derived from other ap- 

 proaches, and to see then what degree of correspondence may or may not 

 appear, in what way the results of one approach may or may not illuminate 

 the results of another. 



Experiences with the eastern forests and other natural communities since 

 the time of Clements suggest a change of attitude from unquestioning faith 

 in ecological concepts as part of nature and unquestioning assurance in the 

 sufficiency of one's own system of interpretation toward greater modesty 

 before the complexities of natural communities and the limitations of ecolo- 

 gists' understanding. They suggest an attitude of tolerance and open-minded- 

 ness, and eclecticism in practice, with regard to the varied possible concepts 

 and approaches to natural communities, no one of which is uniquely deter- 

 mined by nature, each of which may contribute to understanding in a comple- 

 mentary relation to others. They suggest a greater self-consciousness in 

 the use of ecological concepts, a continuing awareness of the role of the man 

 in the interaction of ecologists and natural communities by which ecological 

 understanding grows, of the extent to which the function of the scientist 

 is not simple discovery, but the creation of means of understanding. 



SUMMARY 



1. Study of the eastern forests of North America has been the source of 

 many ecological concepts, some of which became part of the widely influential 

 system of Clements. Such concepts as formation and association, succession 

 and climax, dominance, vegetational phylogeny, and the complex organism 

 were synthesized by Clements into an orderly, coherent, deductive system of 

 vegetation interpretation. 



2. Further experiences in the eastern forests and elsewhere have led to 

 changing views of these concepts: 



