^....;^ 



Figure 5-6. Change produced by caribou compacting and 

 exposing mineral soil by heavy utilization during the early 

 spring calving season, leads to increased aggregation of 

 Festuca altaica in the Betula glandulosa community. Sep- 

 tember, 1957, Black Lake, central Alaska. 



Figure 5-7. Change in dense vegetation caused by the 

 pocket gopher (Thomomys fossor). August, Grand Mesa 

 National Forest, Colorado. (U. S. Forest Service.) 



