The incidence of diseases and insects in aspen foliage in 1970 expressed in terms 

 of presence in all plots (n=100) is shown in the following tabulation: 



Plot 



Problem Causal organism incidence 



Aspen leaf miner Phyllocnistis populiella 53 



Aspen leaf blight Marssonina populi 13 



Aspen shoot blight Pollaccia vadiosa 8 



Inasmuch as only the more obvious injuries and pests were recorded, the frequency 

 and various types of tree damage problems probably are underestimated in these tabula- 

 tions. For example, conks (used to indicate incidence of heart and buttrot) were evident 

 on less than 2 percent of the trees sampled, but heartrot was present in 33 percent of 

 the increment cores examined for age data. Furthermore, some types of aspen damage in 

 the Gros Ventre were not included because they occurred outside the 100 sample plots. 

 For example, beaver {Castor canadensis) had damaged trees immediately adjacent to one 

 plot but there was no beaver damage in any of the plots. 



Many of the problems listed in the tabulations on pages 9 and 10 are combined in 

 the mortality figures shown in the tabulation on page 7. For instance, Pomes applanatus 

 had rotted the roots of at least three trees that succumbed to windfall. Likewise, 

 heartrot was present in many other trees that were included in "wind breakage," and at 

 least one tree broke off at a Ceratocystis canker. 



In addition to the direct effects of bark injury caused by game and rodents, it 

 was also noted that 90 percent of the sooty bark cankers occurred in the lower part of 

 trees where the trunks had been scarred by animals. Elk were responsible for most of 

 these bark scars, but moose, mice, and hares also contributed. 



Of the foliage pests, shoot blight was limited to sprouts, but leaf blight and 

 the aspen leaf miner occurred both on sprouts and on overstory leaves. Aspen leaf 

 hoppers were rare, but occurred on sprouts in at least one plot. 



Associated Understory Vegetation 



The mean understory vegetation was composed of about 49 percent forbs , 36 percent 

 grasses and occasional sedges, 12 percent shrubs, and 3 percent conifer saplings. Each 

 of these groups contained a diversity of species. The frequency of occurrence of the 

 more conspicuous trees, shrubs, and forbs are presented in table 1. Grasses and sedges 

 were not identified except for pinegrass {Calamagrostis rubescens) , which on an average 

 occupied 66 percent of the ground cover in the eight plots in which it occurred. 

 Although forbs were present in all plots and grasses or sedges were found in all but 

 one plot, shrubs were absent from 10 plots and conifer saplings were missing in 27 plots. 



10 



