PS 58-136
Effects of climate change on forest tent caterpillar outbreak dynamics based on a century of tree-ring data
As outbreaks of forest-defoliating insects can have severe ecological and socioeconomic impacts, it is critical that we understand the influences of climate change on the population dynamics of these insects. Using a pre-existing tree-ring reconstruction of defoliation of trembling aspen (Populus tremuloides), in Manitoba, Canada by the forest tent caterpillar (Malacosoma disstria) from 1897 to 2003, we examined relationships between annual defoliation and local weather conditions (winter and spring temperature). We also investigated temporal changes in the frequency and cyclicity of outbreaks using wavelet analysis.
Results/Conclusions
We found a significant positive relationship between minimum winter temperature and defoliation, possibly due to egg mortality during extreme cold weather. Defoliation was unrelated to temperatures in spring, suggesting that thermal conditions coinciding with the larval feeding period may be less important than minimum winter temperatures. Wavelet analysis revealed the presence of cyclical oscillations in defoliation intensity but temporal shifts in cycle length; a cycle length of approximately 20 years occurred from ca. 1925-1970 after which the cycle length ranged from approximately 7-10 years. Our findings suggest that climate change leading to increasing winter temperatures might be expected to increase the severity and frequency of forest tent caterpillar outbreaks in Southern Manitoba and other areas that have historically experienced cold winters.