LTREB: Effects of Insect Defoliation on Nitrogen Loss from Forest Ecosystems

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9527781 Lovett This project addresses the role of insect outbreaks and nitrogen deposition in controlling the cycling and loss of nitrogen from forest ecosystems. Crucial long-term data sets on gypsy moth abundance, forest defoliation, and nutrient cycling in upland oak forests of southeastern New York State will be maintained. These forests are subject to periodic gypsy moth outbreaks as well as elevated atmospheric deposition of nitrogen from nitrogen oxide pollution. In addition, an experiment is proposed which will clarify the role of nitrogen availability and defoliation in regulating nitrogen loss, and will hasten the effects of nitrogen accumulation that would occur over a much longer time period from atmospheric deposition. The hypothesis being tested states that because of their nitrogen limited vegetation and high immobilization potential in the soil, oak forests will initially show only small nitrogen losses after defoliation. However, as nitrogen accumulates in the forests from atmospheric deposition or fertilization, the amount of nitrogen lost after defoliation events will increase. The results of this study will elucidate the role of ecosystem nitrogen accumulation in controlling nitrogen losses after defoliation, and will help evaluate the interactive effects of insect defoliation and elevated nitrogen deposition, two simultaneous stresses affecting northeastern forests.