Simulated climate warming alters host tree quality for forest tent caterpillar

Climate warming, drought, and insect outbreaks are key factors contributing to global patterns of increased tree mortality and forest dieback. Thus, there is a critical need to understand and predict how climate change will influence and interact with insect pests to reduce forest productivity. Our study investigates potential consequences of climate warming on interactions between an outbreak herbivore, forest tent caterpillar (Malacosoma disstria Hübner), and two of its preferred host tree species, trembling aspen (Populus tremuloides) and paper birch (Betula papyrifera). We examined plant-herbivore interactions in a field-based forest warming experiment located in northern Minnesota (B4WarmED) and in laboratory bioassay studies. We evaluated various insect performance traits and foliar quality traits, including nutritional and defensive chemistry. To date, this research has demonstrated both direct and indirect effects of warming on plant-herbivore interactions. Specifically, results revealed warming-induced changes in foliar nitrogen and condensed tannins and larval growth and consumption rates. Moreover, results suggest that climate warming may result in greater damage to host trees, although our study indicates such effects are likely to be context-dependent, with changes in foliar quality varying among species, years, and sites.