Spectral response and spatial pattern of Fraser fir mortality and regeneration, Great Smoky Mountains, USA

High elevation Fraser fir (Abies fraseri) forests of the Southern Appalachi ans have undergone widespread mortality since the introduction of the balsa m woolly adelgid in the 1950s. Resulting changes in ecosystem pattern and p rocess (e.g., stand dynamic processes) have greatly affected floral and fau nal communities. In this project, we integrated field observations, geograp hic information system topographic models, and 1988-1998 satellite imagery to analyze spatial and temporal conditions of Fraser fir and spruce-fir eco systems in Great Smoky Mountains National Park. Tasseled cap indices (brigh tness, greenness, and wetness) and associated spectral changes for Landsat TM digital data were statistically modeled by topographic variables. Spectr al changes were recorded using change vector analysis (CVA) and spherical g eometry at multiple scales: individual sites, local ridges, and across the east-west gradient of the study area. Significant relationships were found between elevation and observed spectral changes and among mountain sites re presenting the east-west chronosequence of adelgid infestation. Topographic derivatives were related to tasseled cap and CVA measures in summary stati stics, regression, and correlation analysis, revealing significantly differ ent mortality and regeneration pathways that were a function of topographic settings. Geographic variations of these vectors also detail the scope of east-west and localized upslope progression of fir mortality. The applicati on of CVA provided the ability to summarize variation in spectral changes ( magnitude and direction) and to ascribe measures to mortality and regenerat ion processes.