CHAPTER XIII 

 THE DEVELOPMENT OF COMMUNITIES 



Syngenetics is concerned with the rise and decline of plant com- 

 munities and seeks to discover the laws which regulate their succession. 

 It endeavors to solve the problems of the origin, development, and 

 transformation of plant communities. What has been the origin of a 

 given community? What potentialities for development he within 

 it? What are the external factors which have influenced it? Whither 

 do natural processes lead in the development of the vegetation of a 

 climatically uniform region? 



Whereas formerly the vegetational changes of a given "topograph- 

 ical locality" was the central point of the investigation (Rlibel, 1913, 

 p. 903; Du Rietz, 1921), today the leading emphasis is being more and 

 more directed to the evolution of the community itself. The principle 

 of development is coming to replace the purely formal study of 

 succession. 



Historical. — Kerner was the real founder of the doctrine of the 

 development of communities. "What a thrill there is in the study of 

 the developmental processes of each society and in following its origin, 

 maturity, and decHne, " he writes enthusiastically in his "Pflanzenleben 

 der Donaulander" (1863, p. 12). Warming (1895) first called atten- 

 tion to the universality of vegetational change. The honor of grasping 

 the full meaning of the dynamics of vegetation belongs to the North 

 American scholars Cowles and Clements. The former in 1899 laid 

 the foundation of the dynamic concept of vegetation which still 

 prevails in the British and American schools of plant ecology. 

 Clements sought to discover the great principles common to vegeta- 

 tional development throughout the world and to arrange them sys- 

 tematically (1916). He worked out methods for investigating the 

 dynamic processes and sought to place the classification of communities 

 on a dynamogenetic foundation. He has been criticized (Gams, 

 1918; Llidi, 1921) for neglecting the static features of vegetation. 

 His dynamics are often hypothetical, and the static social units are 

 indispensable as a foundation for any study of vegetation. 



The recent textbook of Weaver and Clements (1929) has devoted 

 several pages to the elucidation of a purely deductive classification 



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