334 BRAUN 



(geologically speaking) and the degree of advancement of the erosion cycle. 

 Much of the vegetation of old areas (or of mature topography), if undis- 

 turbed, has reached stability, and a mosaic or pattern of intergrading climax 

 communities is seen. In young areas, areas of immature topography, succes- 

 sion is still active and much of the vegetation is not climax. Convergence of 

 seres toward a regional climax is best illustrated in such areas. And it is in 

 such areas that the possibility of further development or change is indicated; 

 that is, the stability of the regional climax is open to question. 



It should be realized that the terminology which has developed and the 

 concepts implied are a result of the ecologist's need to classify (see Cooper, 

 1926). In the few areas where undisturbed forest of any extent still remains, 

 patterns of vegetation can be determined and the relationships of communities 

 can be investigated. Throughout almost all the Eastern Deciduous Forest, 

 only small fragments of primary forest remain; no patterns are discernible. 

 The need to classify remains, and the isolated sample must be assigned to a 

 place in the system of classification, although it has no place in a concrete 

 transect of vegetation. Such difficulties do not arise in local studies. 



An understanding of the structure of our eastern forests is not dependent 

 on agreement as to concepts. It is dependent on the recognition of develop- 

 ment, of the existence of types of communities, and of climax; of climax as 

 a long-term expression of regional factors, both climatic and local, stable as 

 far as human life span is concerned, stable in relation to developmental com- 

 munities of comparable life form, but nevertheless changing in accord with 

 changes in regional factors. 



Our forest vegetation has its roots in the early evolutionary history of 

 angiosperms, their rise and their geographic spread as continental history 

 permitted. The great deployment of deciduous forest (the eoclimax of Clem- 

 ents) came in Tertiary time. Related climaxes with the same general climatic 

 features occur in widely separated geographic areas, in eastern America and 

 eastern Asia, for example. These comprise a Clementsian panclimax, whose 

 parts originated from the ancestral Tertiary forest. In America, that climax 

 believed to be most like the ancestral Tertiary forest is the Mixed Meso- 

 phytic Forest climax. Its similarity to the mixed forest of China has been 

 pointed out by Chaney, who has seen both the forests of China and the 

 mixed mesophytic forests of the Cumberland Mountains, the area of best de- 

 velopment of INIixed Mesophytic Forest. 



Differentiation of the Deciduous Forest has resulted because of environ- 

 mental changes related to progress of erosion cycles and to climatic changes. 

 Awareness of and understanding of succession in its broadest aspects help to 

 unravel the complex pattern of eastern forest vegetation. 



Twenty years ago, in the Cumberland Mountains, great areas of the Ken- 

 tucky slopes of Big Black Mountain and of the northwest slope of Pine Moun- 

 tain were clothed with almost unbroken primary forest, affording, by the 



