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Townsend, P.A., K .N. Eshleman, and C. Welcker. 2004. Remote sensing of gypsy moth defoliation to assess variations in stream nitrogen concentrations. Ecological Applications 14:504-516. In a Nutshell: Problem - There may be complex interactions between N deposition and outbreaks of insect pests that regulate the transport of pollutants from terrestrial environments to surface waters. Defoliation by the gypsy moth caterpillar represents a recurring disturbance that can impact water quality across large spatial scales in the eastern U.S. What - Quantitative changes in satellite imagery were used to derive indices of forest change due to gypsy moth outbreaks, and these indices were then related to changes in the N status of surface waters. Findings - Percent non-forested land cover accounted for only 8-33% of the spatial variation in nitrate-N concentrations, while multivariate models that also included change vector statistics from satellite imagery accounted for 72-80% of the spatial variation. Jack-knifed residuals were close to actual measurements, indicating that remote sensing models could be used to predict variations in N concentrations for watersheds in the region. Potential Applications - Remote sensing may be provide a useful means of predicting spatially varying relationships between ecosystem status and water quality conditions across regional scales and allow assessments of watershed disturbances as part of land management. |
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