A TREE AND A PLANT COMMUNITY COMPARED 189 



We shall see that the development of such a community is just 

 as definite as is that of any other type of individual. In other words, 

 it was just as certain that this would in time develop into a beech- 

 maple forest and not into some other kind of community as it is that 

 an acorn will develop into an oak tree and not into a hickory or some 

 other kind of tree. 



120. A Tree and a Plant Community Compared.— We have stated 

 that a plant community is born, it grows and develops, matures. 



Fig. 82.— a mature forest community of birch, beech, maple and hemlock. 

 (Photograph by A. G. Varela. Courtesy of H. L. Shantz and the U. S. Depart- 

 ment of Agriculture.) 



reproduces, and may die, like any other individual. It will be 

 profitable now, before taking up the details of the structure of plant 

 communities, to compare the life cycle of a plant community with 

 that of a tree (a cell community). In order to make the comparison 

 less abstract we will compare a beech-maple community with an oak 

 tree. 



A plant community always starts on some kind of a bare area 

 and a bare rock surface will serve as well as any. This bare area then 

 represents a sort of potential plant succession— a possible place for 

 the birth of a plant community. But a plant community will never 

 develop here until something comes in from the outside. Turning 



