LTREB: Exotic Pests, Nitrogen Saturation, and Nutrient Cycling in a Northeastern Forest

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Lovett0129138This LTREB project will support sustained research on the direct and indirect effects of two exotic pests that threaten the forests of the eastern US, the gypsy moth and the hemlock wooly adelgid. The gypsy moth is the most important defoliator of eastern forests. It preferentially attacks oak-dominated forests and causes widespread defoliation during periodic outbreaks. The hemlock woolly adelgid is a more recently introduced pest that is devastating hemlock trees in the mid-Atlantic states and New England. It is an aphid-like insect that feeds exclusively on hemlocks, and generally results in 100% mortality of trees within several years after infestation. The research questions here involve the effect of these pests on the nitrogen cycle of forests. Both of these pests are occurring against the backdrop of elevated levels of nitrogen deposition due to nitrogen oxide emissions from fossil fuel combustion and ammonia emission from agricultural activities. These is a strong probability of a complex interaction between nitrogen deposition and the effects of these pests on the nitrogen cycles of the forest ecosystems under study. This LTREB project will continue measurements of forest productivity and nutrient cycling in long-term study plots in Millbrook, NY. The plots include both oak plots in the zone likely to be affected by the gypsy moth, and hemlock plots in an area soon to be infested with hemlock woolly adelgid. In addition, a long-term N-addition experiment in an oak forest will be maintained, as well. This work has direct relevance to management of eastern forests, in that gypsy moth and hemlock woolly adelgid are two of the most devastating pests in the region. The phenomenon of nitrogen saturation and its effects on forest health and the quality of surface waters, is an emerging management and policy issue in the eastern US. Thus, the study of the interaction of these two stresses is of both scientific and practical importance.