Modification of Succession 445 



on a small scale in many local habitats. One example is furnished 

 by the activity of certain animals in maintaining open "glades" on the 

 surface of rocks in the tidal zone (Fig. 12.10). The browsing of 

 limpets at the margins of their territories shears away the enlarging 

 basal holdfasts of the red algae that would normally grow over the 

 rock surface in the course of succession. Another animal, Idotea 

 viridis, bores holes in the fronds of the algae so that they break away 

 easily and thus assists in affecting succession in this microhabitat. 



In contrast to the situations mentioned above the activities of man 

 may sometimes add a stage beyond the usual climax. In certain 

 parts of southern California the climax vegetation formerly consisted 

 of grass or chaparral. When man introduced the eucalyptus from 

 Australia, this tree established extensive stands replacing the former 

 vegetation and adding a forest stage to the previously recognized limit 

 to succession in the region. 



Ecologists have taken such an interest in pointing out the occur- 

 rence of succession and its importance under various circumstances 

 that emphasis has failed to be laid upon the fact that in some regions 



Photo by H. IS. .\f,.oif 



Fig. 12.9. Pineland community in southern Florida, consisting principally of 



pines, palmettos, and sawgrass. After such an area is burned over, the same type 



of community is reestablished directly. 



