50 



40 



1 



a 30 

 I 



8 20 



10 



Uninjured Lodgepole pine 



{Pinus con ton a) 



1989 



1990 



1991 



1992 



Year 



Figure 20 — Percent lodgepole pine 

 mortality caused by insect infestation 

 during 4 postfire years. 



1992 (fig. 20). Perhaps the prolonged extreme cold 

 temperatures that Pasek and Schaupp (1992) attrib- 

 uted to Douglas-fir beetle mortality also affected pine 

 engraver survival. The 1992 upward swing in infesta- 

 tion ended, and no additional mortality of uninjured 

 trees was tallied in 1993. 



In Engelmann spruce, infestation of uninjured trees 

 showed a steady increase during each of the 4 post- 

 fire years (fig. 21). Spruce beetle accounted for most 

 of this infestation. The increase of 2 percent in 1991 

 to 8 percent in 1992 suggests that beetles probably 

 built up in fire-injured trees and began infesting more 

 of the uninjured trees. Because spruce beetle have a 

 2-year cycle, the large increase in 1992 would be the 

 result of populations surviving in trees infested in 

 1990. 



50 



40 



l 3 

 I 



C 



5 2 



£ 



10 



Uninjured Engelmann spruce 



(P/coa engelmannlf) 



1989 



1990 



1991 



1992 



Year 



Figure 21 — Percent Engelmann spruce 

 mortality caused by insect infestation 

 during 4 postfire years. 



Although infestation figures for 1992 were higher 

 than those for 1991, there was a decline in 1993. How- 

 ever, with drought conditions continuing to prevail 

 in the Greater Yellowstone Area, Douglas-fir beetle 

 may continue to kill large numbers of trees. Off-plot 

 observations showed considerable infestation of trees 

 in unburned stands, but pine engraver populations 

 probably will decline after the year that they infest 

 standing, uninjured trees (Sartwell and others 1971). 



Conclusions 



From the extensive surveys conducted in 1991, 

 1992, and 1993, we conclude that bark beetle and 

 delayed tree mortality due to fire injury significantly 

 alter mosaics of green and fire-injured trees, that 

 insect infestation increases with the percent of basal 

 circumference killed by fire, and that bark beetle 

 populations appear to increase in fire-injured trees 

 and then infest uninjured trees. 



References 



Amman, G. D. 1991. Bark beetle-fire associations in the Greater 

 Yellowstone Area. In: Nordvin, S. C; Waldrop, T. A., eds. Pro- 

 ceedings of the Fire and the Environment Symposium; 1990 

 March 20-24; Knoxville, TN: 313-320. 



Amman, G. D.; Ryan, K. C. 1991. Insect infestation of fire-injured 

 trees in the Greater Yellowstone Area. Res. Note INT-398. 

 Ogden, UT: U.S. Department of Agriculture, Forest Service, 

 Intermountain Research Station. 9 p. 



Bedard, W. D. 1950. The Douglas-fir beetle. Circular 817. Wash- 

 ington, DC: U.S. Department of Agriculture. 10 p. 



Blackman, M. W. 1931. The Black Hills beetle. Tech. Publ. 36. 

 Syracuse, NY: Syracuse University, New York State College 

 of Forestry. 77 p. 



Cole, W. E.; Amman, G. D. 1969. Mountain pine beetle infesta- 

 tions in relation to lodgepole pine diameters. Res. Note INT-95. 

 Ogden, UT: U.S. Department of Agriculture, Forest Service, 

 Intermountain Forest and Range Experiment Station. 7 p. 



Furniss, M. M. 1959. Reducing Douglas-fir beetle damage: how 

 it can be done. Res. Note INT-70. Ogden, UT: U.S. Department 

 of Agriculture, Forest Service, Intermountain Forest and Range 

 Experiment Station. 6 p. 



Furniss, M. M. 1965. Susceptibility of fire-injured Douglas-fir to 

 bark beetle attack in southern Idaho. Journal of Forestry. 63: 

 8-11. 



Hopkins, A D. 1905. The Black Hills beetle. Bull. 56. Washington, 

 DC: U.S. Department of Agriculture, Bureau of Entomology. 

 24 p. 



Massey, C. L.; Wygant, N. D. 1954. Biology and control of the En- 

 gelmann spruce beetle in Colorado. Circular 944. Washington, 

 DC: U.S. Department of Agriculture, Forest Service. 35 p. 



Miller, J. M.; Keen, F. P. 1960. Biology and control of the western 

 pine beetle. Misc. Publ. 800. Washington, DC: U.S. Department 

 of Agriculture. 381 p. 



Mitchell, R. G.; Martin, R. E. 1980. Fire and insects in pine culture 

 of the Pacific Northwest. In: Martin, R. E.; [and others], eds. 

 Proceedings, 1980 sixth conference on fire and forest meteorol- 

 ogy. Washington, DC: Society of American Foresters: 182-190. 



Pasek, J. E.; Schaupp, W. C, Jr. 1992. Populations of Douglas-fir 

 beetle in green trees three years after the Clover Mist Fire on 

 the Clarks Fork Ranger District, Shoshone National Forest, WY. 

 R2-92-01. Fort Collins, CO: U.S. Department of Agriculture, 

 Forest Service, Renewable Resources Staff, Rocky Mountain 

 Region Biological Evaluation. 13 p. 



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