sedge -meadow and woodland stages, and finally the climax 

 forest, while the xerosere may consist of the crustose lichen, foliose 

 lichen, moss, herbaceous, and shrub stages, and finally the climax 

 forest. ^^^ The progression may be regarded as an over-all trend 

 or a general sequence of transformation of plant communities or 

 ecosystems which occupy an area. It is a sequence of replacement 

 of one community by another of a different kind, the result being 

 a procession of communities on a given area, culminating in the 



Figure 5-5. Forest fire is an initial cause of secondary suc- 

 cession. August, California. (U.S.D.A. Soil Conservation 

 Service.) 



152 • Dyxmanmics o£ Comsmmsmities 



