Canadian Forest Service Publications

Disturbance, forest age, and mountain pine beetle outbreak dynamics in BC: A historical perspective. 2004. Taylor, S.W.; Carroll, A.L. Pages 41-51 in T.L. Shore, J.E. Brooks, and J.E. Stone, editors. Mountain Pine Beetle Symposium: Challenges and Solutions, October 30-31, 2003, Kelowna, British Columbia, Canada. Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Victoria, British Columbia, Information Report BC-X-399. 298 p.

Year: 2004

Issued by: Pacific Forestry Centre

Catalog ID: 25032

Language: English

Availability: PDF (download)

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During the past 85 years, there have been four large-scale outbreaks by the mountain pine beetle (Dendroctonus ponderosae) in the pine forests of British Columbia. Using contemporary forest inventory data in combination with wildfire and logging statistics, we developed a simple age-class projection model to estimate changes in pine age-class distribution between 1910 and 2110. We compared past and present mountain pine beetle activity to forest age structure, and projected future forest conditions relevant to mountain pine beetle susceptibility. "Backcast" forest conditions suggest that during the early 1900s, approximately 17% of pine stands were in age classes susceptible to mountain pine beetle attack. Since then, the amount of area burned by wildfire in British Columbia has significantly decreased. This reduction in wildfire has resulted in an increase in the average age of pine stands to the present day such that approximately 55% of pine forests are in age classes considered susceptible to mountain pine beetle. At the present rate of disturbance, average stand age is forecast to continue to increase, but the amount of susceptible pine will decline following 2010 and stabilize at about 18% by 2110. The extent of mountain pine beetle outbreaks was correlated with the increase in amount of susceptible pine during 1920-2000. However, outbreak extent increased at a greater rate than the increase in susceptible forest indicating that other factors such as climate may be affecting mountain pine beetle epidemics. Theoretical fire-return cycles of 40 - 200 years would generate a long-term average susceptibility range of 17% - 25% over large areas. This suggests that the extent of age-related, mountain pine beetle-susceptible pine forests in British Columbia is beyond the natural range of variability at a provincial scale.