Engelmann spruce data 1991, 1992 



1-20 21-40 41-60 61-80 81-100 



Percent Basal Circumference Killed 



Figure 16 — Relationship of spruce beetle 

 to basal fire injury of Engelmann spruce. 



Total 



1-20 21-40 41-60 61-80 81-100 

 Percent Basal Circumference Killed 



Total 



Figure 18 — Percent insect infestation of 

 whitebark pine by fire-injury class. 



Subalpine fir data 1991, 1992 



1-20 21-40 41-60 61-80 81-100 Total 

 Percent Basal Circumference Killed 



Figure 17 — Percent insect infestation of 

 subalpine fir by fire-injury class. 



50 



40 



5 30 



20 



10 



1989 



Uninjured Douglas-fir 



(Pseudotsuga menziesii) 



1990 



1991 



Year 



Figure 19 — Percent Douglas-fir mortality caused 

 by insect infestation during 4 postfire years. 



1992 



based on actual infestation of green trees observed 

 during the 1991, 1992, and 1993 surveys. 



In Douglas-fir, insects— particularly Douglas-fir 

 beetle— infested uninjured trees on permanent plots 

 starting in 1989, the first postfire year (Amman 1991). 

 This trend continued in 1990, Amman and Ryan (1991) 

 showed 46 percent of the uninjured Douglas-fir as 

 infested. Results of the extensive surveys in 1991 

 and 1992 show that infestation of uninjured trees was 

 high in 1989, but was somewhat lower in 1990 and 

 1991. However, a substantial increase occurred in 

 infestation rates from 1991 and 1992: 4 to 12 percent 

 (fig. 19). Most of the 1992 increase was due to Dou- 

 glas-fir beetle. 



Although we did not sample Douglas-fir beetle 

 populations by removing bark, observations by Pasek 

 and Schaupp (1992) in the Clover Mist Fire areas 



located in the Shoshone National Forest, which is 

 adjacent to Yellowstone National Park, have general 

 application. They observed brood reduction from 1990 

 levels that was attributed to prolonged extreme cold 

 temperatures. Reduced brood survival could account 

 for the low tree mortality occurring in 1991. We ob- 

 served the large increase in Douglas-fir mortality in 

 1992 is close to the upper limit of the 1.5 to 3.0 fold in- 

 crease predicted by Pasek and Schaupp (1992) based 

 on their sampling of Douglas-fir beetle populations. 



In lodgepole pine, infestation of uninjured trees 

 changed from 2 percent in 1991 to 7 percent in 1992. 

 Most of this was attributed to pine engraver. A pat- 

 tern of infestation by year is similar to that in Dou- 

 glas-fir. Although infestation of lodgepole was high 

 in 1989, a decline was observed from 1990 through 

 1991; however, a substantial increase occurred in 



8 



