In most Gros Ventre plots there were numerous aspen sprouts (X = 653 per acre) , 

 but far too few escaped browsing and pests for successful replacement of overstory 

 mortality. In fact, replacement was occurring on only three of the 100 sample plots. 

 Insects and diseases were injurious to sprouts in addition to the detrimental effect of 

 browsing by elk, moose, deer, cattle, and rodents. The aspen leaf miner was prevalent 

 and Mavssonina leaf blight and leaf hoppers were observed. On some of the wetter sites, 

 Pollaccia shoot blight was devastating. Sprouts that were stripped of leaves by moose 

 late in the growing season were particularly sensitive to frost injury, which may par- 

 tially account for the severe impact of browsing. 



A study of the associated vegetation in the aspen sample plots reinforces the 

 conclusion that much of the Gros Ventre aspen is changing. Of the 100 sample plots, 

 only 13 plots showed a species composition that was essentially identical to the stable 

 Populus tremuloides-Symphorioavpos oreophitus habitat type described by Reed (1971). 

 Nevertheless, there is some encouragement from these 13 plots because their 1970 mor- 

 tality rate was only about two-thirds of that in the remaining 87 plots. Also, these 

 plots contained a greater proportion of trees in the smallest size class, in which mor- 

 tality was only about one-third that of the remaining 87 plots. This supports general 

 observations suggesting that some stands of aspen will persist much longer than others. 

 Forty-seven of the 100 plots had spruce or fir saplings in their understory; this, and 

 the abundance of plants such as buffaloberry {Shepherdia canadensis) , indicate that 

 perhaps half of the aspen in the Gros Ventre occupy sites that are somewhat like the 

 Abies lasiocarpa-Pyrola secunda habitat type of Reed (1969). It could also be argued, 

 however, that the occurrence of plants such as pinegrass, balsamroot (Balsamorhiza 

 sagittata) , and sagebrush {Artemisia tvidentata) , along with the presence of conifer 

 saplings in 73 plots, is indicative of a state of browsing disclimax (in the sense of 

 Beetle 1968) in otherwise stable aspen. In either case, it is evident that if the 

 current trends continue, perhaps one-half to three-fourths of the area now in aspen 

 will succeed to conifers. Some of the remaining will go to shrub, grass, and forb 

 communities, and at best, only a token amount will remain as a dominant aspen type. 



The high rate of mortality in the aspen overstory on the Gros Ventre elk winter 

 range appears to be caused mostly by a mixture of pathogenic fungi and insects which 

 invade trees wounded by big game. The situation is critical because the combination of 

 heavy browsing and pests prevents aspen sprouts from replacing dead trees. If current 

 trends continue, most of the aspen type will ultimately be eliminated from the Gros 

 Ventre winter range. Additional data about the potential for regenerating these aspen 

 stands are needed before an aggressive and intensive management program can be initiated 

 to preserve both the aspen type and the big game herds. 



15 



