Examining the potential effects of phytophagous insect frass on forest nitrogen cycling at the Coweeta Hydrologic Laboratory from 1999 to 2001

Human alteration of the global nitrogen cycle has increased the importance of understanding the major sources, sinks, and fluxes of the cycle within natural ecosystems. One poorly understood component of the nitrogen cycle in forest ecosystems is the contribution of phytophagous insect frass on soil N-cycling dynamics. This study proposes to investigate the influence of frass on (1) the dynamics of soil N-cycling; (2) the loss of N from the ecosystem via leaching; (3) the slow cycle decomposition of post-herbivore leaf litter; and (4) the overall potential of soil near the Coweeta Hydrologic Laboratory to retain nitrogen. Red Oak (Quercus rubra [Fagaceae]) saplings will be subjected to defoliation by the seasonal phytophagous insect larvae of the White-Marked Tussock Moth (Orgyia leucostigma [Lepidoptera: Lymantriidae]) and the frass added to the soil in a factorial, controlled experimental design. Soil nutrient concentrations, leachate nutrient concentrations, "soil" respiration, and leaf quality will be measured. The project is expected to increase our understanding of the complex relationship between above-ground and below-ground nitrogen cycling dynamics as well as inform the current debate concerning the relative impacts and importance of human versus natural alterations to the nitrogen cycle.