Ecology and Spatial Risk Assessment of the Douglas-Fir Beetle
Authored By: J. R. Withrow Jr., J. F. Negron
John R. Withrow, Jr. and Jose F. Negron
SI International, Inc. and USDA Forest Service Rocky Mountain Research Station
The Douglas-fir beetle (Dendroctonous pseudotsugae Hopk.) is a major mortality agent of Douglas-fir (Pseudotsugae menziesii Mirbel Franco) across the western United States. Douglas-fir beetle populations have reached epidemic levels, resulting in an estimated 60,000 trees killed in 2004 alone in Colorado. Efforts to spatially quantify risk of future infestation hold the promise of focusing and prioritizing management activities. Previous studies of the Douglas-fir beetle and related species have indicated the importance of beetle population dynamics and spatial movement in effectively quantifying risk for a given location. Aerial survey data provide a spatially explicit representation of the locations, sizes, shapes, and intensities of various forms of forest damage, including damage from the Douglas-fir beetle. These data are utilized as a proxy variable for the presence of the Douglas-fir beetle, and a novel GIS technique is introduced that has proven useful in using such data for quantifying the spatio-temporal dynamics of Douglas-fir beetle infestations. The technique results not only in quantitative indications of Douglas-fir beetle population dynamics and spatial movement, but also a spatial risk map that quantifies probabilities of infestation in an upcoming year.
corresponding author:
John R. Withrow, Jr.
SI International, Inc.
2629 Redwing Road, Suite 110
Fort Collins, CO 80526
johnwithrow@fs.fed.us
