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

We examined the effect of forest structure and climate enlarge-scale a nd long-term patterns of outbreaks of forest tent caterpillar, Malacos oma disstria Hbn., across central Ontario. This was done using previou sly published data on outbreak duration and forest heterogeneity, comb ined with high-resolution climatic data simulated by the recently deve loped Ontario Climate Model. Our analysis, which eliminates some of th e spatially confounding effects of forest structure and climate, sugge sts that both the predicted long-term temperature minimum for the cold est month and the predicted growing degree-days in the first 6 weeks o f the growing season are important determinants of outbreak duration, with colder weather being associated with shorter outbreaks. Forest he terogeneity accounts for more variation in outbreak duration than eith er of the climatic variables.