ABSTRACT 



Stands of aspen on the Gros Ventre elk winter range of northwestern 

 Wyoming are suffering high mortality and are not regenerating satisfacto- 

 rily. If the 1970 mortality rate (3.6 percent) continues, about a two-thirds 

 reduction in the numbers of tree-sized aspen can be expected by year 

 2000. Collected evidence suggests that the mortality rate is unusually 

 high because of a combination of pathogenic fungi, injurious insects, and 

 physiological stress that follow bark wounding of tree trunks. Elk and 

 possibly moose are suspected of causing most of these severe trunk in- 

 juries. Sooty bark canker, Cytospora canker, and stem-boring insects 

 were the most common pests associated with tree mortality. The pros- 

 pect for aspen on the elk winter range is especially critical because of the 

 heavy impact of browsing and pests on aspen sprouts which prohibits 

 natural replacement of the dying aspen overstory. 



