budworm should not be taken lightly. Moderate to heavy 

 defoliation in epidemics reduced expected yields more 

 than 18 percent in Douglas-fir stands in British Colum- 

 bia, Canada (Alfaro and others 1985). Repeated defolia- 

 tion along with the mediocre height growth response in 

 stands like we studied could result in yield reductions of 

 more than 40 percent at rotation compared to yields from 

 stands composed of serai species. These losses simply 

 would not be acceptable on productive sites where grow- 

 ing timber is deemed important. In contrast, even-aged, 

 serai conifer regeneration established subsequent to har- 

 vest will likely incur only light defoliation and little or no 

 impact on height and diameter growth despite high 

 budworm populations in susceptible adjacent stands 

 (Carlson and others 1988). 



But if the land manager decides that management of 

 advance regeneration is his best option, after considering 

 all important resource values, here are a few suggestions 

 for enhancing timber values: 



1. Select the most vigorous individuals as leave trees. 

 These will be full crowned, deep green in color, with 

 straight boles and rapid terminal leader growth. These 

 trees will release quickest and grow fastest. 



2. Remove all of the overstory stand as soon as pos- 

 sible, preferably in one cutting. Try to minimize logging 

 damage to the residual understory because the shade- 

 tolerant species are highly vulnerable to stem and root 

 diseases if they are injured. 



3. Provide the residual stand with room to grow. A 

 thinning 3 to 4 years following overstory removal may be 

 appropriate. Thinning will reduce susceptibility to west- 

 ern spruce budworm and will encourage rapid growth of 

 residual trees. 



4. Give preference to serai tree species. There will al- 

 ways be a few of these in the understory. 



REFERENCES 



Alfaro, A. J.; Thomson, A. J.; Van Sickle, G. A. 1985. 

 Quantification of Douglas-fir growth losses caused by 

 western spruce budworm defoliation using stem analy- 

 sis. Canadian Journal of Forest Research. 15: 5-9. 



Arno, Stephen F. 1980. Forest fire history in the Northern 

 Rockies. Journal of Forestry. 78(8): 460-465. 



Barger, Roland L. 1980. The forest residues utilization 

 program in brief. In: Environmental consequences of 

 timber harvesting. Gen. Tech. Rep. INT-90. Ogden, UT: 

 U.S. Department of Agriculture, Forest Service, Inter- 

 mountain Forest and Range Experiment Station: 7-24. 



Benson, Robert E.; Gonsior, Michael J. 1981. Tree damage 

 from skyline logging in a western larch/Douglas-fir 

 stand. Res. Pap. INT-268. Ogden, UT: U.S. Department 

 of Agriculture, Forest Service, Intermountain Forest 

 and Range Experiment Station. 15 p. 



Carlson, Clinton E.; Campbell, Robert W.; Theroux, 

 Leon J.; Egan, Thomas, H. 1984. Ants and birds reduce 

 western spruce budworm feeding injury to small 

 Douglas-fir and western larch in Montana. Forest 

 Ecology and Management. 9: 185-192. 



Carlson, Clinton E.; McCaughey, Ward W.; Theroux, 

 Leon J. 1988. Relations among stand structure, disper- 

 sal of second-instar western spruce budworm, defolia- 

 tion, and height growth of young conifers. Canadian 

 Journal of Forest Research. 18(6): 794-800. 



Carlson, Clinton E.; Schmidt, Wyman C; Fellin, David G.; 

 Wulf, N. William. 1985. Silvicultural approaches to 

 western spruce budworm management in the Northern 

 U.S. Rocky Mountains. In: Sanders, C. J.; Stark, R. W.; 

 Mullins, E. J.; Murphy, J., eds. Recent advances in 

 spruce budworms research. Proceedings — CANUSA 

 Spruce Budworms Symposium; 1984 September 16-20; 

 Bangor, ME. Ottawa, ON: Canadian Forestry Service: 

 281-297. 



Ferguson, Dennis E. 1988. Growth of regeneration defoli- 

 ated by spruce budworm in Idaho. Res. Pap. INT-393. 

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

 Service, Intermountain Research Station. 13 p. 



Ferguson, Dennis E.; Adams, David L. 1980. Response of 

 advance grand fir regeneration to overstory removal in 

 northern Idaho. Forest Science. 26(4): 537-545. 



Grizzle, James E.; Starmer, C. Frank; Koch, Gary G. 

 1969. Analysis of categorical data by linear models. 

 Biometrics. 25: 489-504. 



Hamilton, David A. 1986. A logistic model of mortality in 

 thinned and unthinned mixed conifer stands of north- 

 ern Idaho. Forest Science. 32: 989-1000. 



Helms, John A.; Standiford, Richard B. 1985. Predicting 

 release of advance reproduction of mixed conifer species 

 in California following overstory removal. Forest Sci- 

 ence. 31(1): 3-15. 



Johnson, Phillip C; Denton, Robert E. 1975. Outbreaks of 

 the western spruce budworm in the American Northern 

 Rocky Mountain area from 1922 through 1971. Gen. 

 Tech. Rep. INT-20. Ogden, UT: U.S. Department of 

 Agriculture, Forest Service, Intermountain Forest and 

 Range Experiment Station. 144 p. 



Johnstone, W. D. 1978. Growth of fir and spruce advance 

 growth and logging residuals following logging in west- 

 central Alberta. Inf. Rep. NOR-X-203. Edmonton, AL: 

 Canadian Forestry Service, Northern Forestry Research 

 Centre. 16 p. 



Marsden, Michael A. 1983. Modeling the effect of wildfire 

 frequency on forest structure and succession in the 

 Northern Rocky Mountains. Journal of Environmental 

 Management. 16: 45-62. 



McCaughey, Ward W.; Schmidt, Wyman C. 1982. Under- 

 story tree release following harvest cutting in spruce-fir 

 forests of the Intermountain West. Res. Pap. INT-285. 

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

 Service, Intermountain Forest and Range Experiment 

 Station. 19 p. 



Nichols, Thomas J. 1988. The relationship between west- 

 ern spruce budworm defoliation levels and growth of 

 individual Douglas-fir and grand fir trees. Forest 

 Science. 34(2): 496-504. 



Oliver, William W. 1986. Growth of California red fir 

 advance regeneration after overstory removal and thin- 

 ning. Res. Pap. PSW-180. Berkeley, CA: U.S. Depart- 

 ment of Agriculture, Forest Service, Pacific Southwest 

 Forest and Range Experiment Station. 6 p. 



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