202 THE STUDY OF PLANT COMMUNITIES • Chapter VIII 



The feeding of cottontail rabbits ordinarily affects natural vege- 

 tation but little. However, if a peak in their fluctuating population 

 comes at the time of a bad winter with much snow, they can do 

 serious damage to seedlings and even to larger trees from which 

 they eat the bark. Because of selective feeding, snowshoe rabbits 

 may change the course of forest succession. 68 



FlG. 95. Injuries to seedlings and saplings resulting from feeding by ro- 

 dents and larger animals may strongly influence the development of stands 

 and the nature of future vegetation. (1) Young ponderosa pine girdled by 

 porcupine. (2) Scotch pine browsed by deer the year after planting. All 

 needles and buds eaten. (3) A pine seedling eaten back by rabbits in three 

 successive winters. Such seedlings can never make normal trees.— U. S. Forest 

 Service. 



Rodents that eat bark by preference may cause considerable 

 damage, especially if their feeding is selective as to species. Porcu- 

 pines are in this category, and beavers are even more destructive 

 because their activities are concentrated around their dams. Here 

 they cut down and strip the bark from the trees they most prefer 

 nearest their ponds and then gradually extend their operations to 

 surrounding slopes. Their dams, too, affect conditions locally, for 

 they maintain ponds that sometimes flood large areas, modify 

 drainage, and even affect the water table. This may sometimes be 

 desirable, sometimes not. 



Man.— The effects of man upon vegetation are fundamentally 

 similar to those of lower animals. The greater the concentration of 



