COMMUNITY SUCCESSION AND DEVELOPMENT 



571 



whole process. In the broadest of terms, the munities. Each of these communities is in 



earth's surface is divisible ecologically into its own state of flux, as discussed previously 



a relatively few formations of usually great (Chap. 28), but, in the larger view, each 



extent. These climatically controlled areas represents a relatively fixed point in the sere 



are known as hiomes, and are to be dis- of which it is a part. 



Fig. 208. Development of the profundal stratum in water-supply reservoirs. Note that the 

 time on the horizontal axis of the figure is not plotted on a uniform scale. The vertical axis of 

 the figure is plotted on a uniform scale of number of organisms per square meter. (After 

 Gersbacher, from Clements and Shelford. ) 



cussed in the following chapter, but their 

 serai aspects must be touched upon at 

 this time. 



Within the confines of each of the 

 climatically controlled biomes there are 

 almost innumerable major and minor com- 



This is an essential comprehension for 

 an over-all appreciation of the principle of 

 succession, as well as for that of the biome. 

 Within each community, development is 

 taking place, including the several micro- 

 seres operating upon the whole; each com 



