PRIMARY AND SECONDARY SUCCESSION. 171 



represents a third or fourth attempt to develop a climax forest, as do most of 

 the New England forest areas. These successions have been called secondary 

 successions, but might better be called repetitive associations, because the 

 deforestation causes the area to revert to an aspect which is a combination of a 

 former succession with the successions which ordinarily follow it. The term 

 'secondary' does not carry with it the idea of more than one attempt at repe- 

 tition, while repetitive carries with it no limit in the number of attempts. " (435) 



These suggestions afford a striking illustration of the danger of generalizing 

 upon the basis of a first study and that made upon a very limited area. The 

 superficial fact of repetition is taken as more important than the process of 

 development itself. It is not even recognized that "initial" or primary succes- 

 sions are repeated again and again in the same climax, as well as in the same 

 spot. Moreover, the figure on page 442 indicates that there is no essential 

 difference between the stages of burn "repetitive" and "initial" successions, 

 a conclusion wholly impossible under the terms of an exact quantitative 

 study. 



Warming (1896 : 350) had already distinguished between changes in vege- 

 tation due to (1) the production of new soil and (2) changes in old soil, or in 

 the vegetation covering it, particularly those caused by man. While this is 

 not the full or exact distinction between primary and secondary succession, 

 it does include much of it. The same idea is more clearly brought out in his 

 earlier distinction (1892) between primary and secondary formations, in which 

 the latter comprise those due to the influence of man. Tansley (1911 : 8) and 

 his colleagues have used this concept of primary and secondary processes in 

 connection with the study of succession in British vegetation. It has been 

 adopted in America by Shantz (1905 : 187), Jennings (1908 : 291; 1909 : 306), 

 Schneider (1911:290), Dachnowski (1912:223, 257), Gates (1912, 1915), 

 Cooper (1913:11), Negri (1914:14), Pool (1914 : 304r-306), Bergman and 

 Stallard (1916) and others. 



Cowles's system. — Cowles (1911 : 168) has classified successions as (1) re- 

 gional, (2) topographic, and (3) biotic. He states that : 



"In succession, we may distinguish the influence of physiographic and of 

 biotic agencies. The physiographic agencies have two aspects, namely, 

 regional (chiefly climatic) and topographic. (168) In regional successions it 

 would seem that secular changes in climate, that is, changes which are too 

 slow to be attested in a himian lifetime, and which perhaps are too slow to 

 be attested in a dozen or a hundred lifetimes, are the dominating factors. 

 Regional successions are so slow in their development that they can be studied 

 almost alone by the use of fossils. It is to be pointed out that great earth- 

 movements, either of elevation or subsidence, that is, the far-reaching and 

 long-enduring epeirogenic movements, as contrasted with the oscillations of 

 coast-lines, must be considered in accounting for regional successions- the 

 elevation of the Permian and the base-leveUng of the Cretaceous must have 

 played a stupendous part in instituting vegetative change. (170) 



"In striking contrast to secular successions, which move so slowly that we 

 are in doubt even as to their present trend, are those successions which are 

 associated with the topographic changes which result from the activities of 

 such agents as running water, wind, ice, gravity, and vulcanism. In general, 

 these agencies occasion erosion and deposition, which necessarily must have a 

 profound influence upon vegetation. As might be expected, the influence of 



