EFFECTS OF CLIMATE AND FOREST STRUCTURE ON DURATION OF FOREST TENT CATERPILLAR OUTBREAKS ACROSS CENTRAL ONTARIO, CANADA

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Abstract
We examined the effect of forest structure and climate on large-scale and long-term patterns of outbreaks of forest tent caterpillar,Malacosoma disstriaHbn., across central Ontario. This was done using previously published data on outbreak duration and forest heterogeneity, combined with high-resolution climatic data simulated by the recently developed Ontario Climate Model. Our analysis, which eliminates some of the spatially confounding effects of forest structure and climate, suggests that both the predicted long-term temperature minimum for the coldest month and the predicted growing degree-days in the first 6 weeks of the growing season are important determinants of outbreak duration, with colder weather being associated with shorter outbreaks. Forest heterogeneity accounts for more variation in outbreak duration than either of the climatic variables.