A Simulation Approach for Predicting the Effect of Douglas-Fir Tussock Moth Defoliation on Juvenile Tree Growth and Stand Dynamics
Abstract:A spatially dependent tree growth projection model was developed and used to simulate juvenile grand fir, Abies grandis (Dougl.) Lindl., Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, and ponderosa pine, Pinus ponderosa Laws., in northern Idaho. Simulated experiments using the model examined the effects of Douglas-fir tussock moth, Orgyia pseudo-tsugata McDunnough, defoliation on stand dynamics during the first 40 years of stand development. The sequence and intensity of the defoliation episodes were varied for different combinations of age, stand density, and tree species composition at the time of the first defoliation. The results are summarized in statistical models which predict the long-term effects of tussock moth defoliation on stand dynamics. Results indicate that the insect regulates primary forest production by reducing stand biomass and by redistributing growth energy from host to nonhost trees by altering intertree competitive relationships to the advantage of nonhosts. Forest Sci. 27:685-700.
Document Type: Journal Article
Affiliations: Professor, College of Forestry, Wildlife and Range Sciences, University of Idaho, Moscow, Idaho 83843
Publication date: December 1, 1981
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