Application of spherical statistics to change vector analysis of Landsat data: Southern Appalachian spruce-fir forests

This study sought to develop a modified change vector analysis (CVA) using normalized multidate data from Landsat TM to examine spruce-fir ecosystems. The introduction of the balsan woolly adelgid (Adelges piceae) to the Grea t Smoky Mountains in the late 1950s resulted in widespread mortality of Fra ser fir (Abies fraseri), prompting the need for research on disturbance and regeneration. Drawing from methods in spherical statistics, the extended C VA technique measured absolute angular changes and total magnitude of Tasse led Cap indices (brightness, greenness, and wetness). Polar plots and spher ical statistics summarized change vectors to quantify and visualize both ma gnitude and direction of change. Results separated vectors for forest stand s by extent a,ld time interval since infestation, as found along the crest of Smokies Range. Changes in the greenness-wetness plane improved predictio n of fir class more than brightness-greenness change. Linear discriminant f unctions found that magnitude and vector angles combined to predict change class 72% correct with three classes and 57% correct in six spruce-fir clas ses. The technique demonstrates the ability of change vectors in multiple b iophysical dimensions to differentiate forest disturbance and regeneration trends as an alternative to nominal forest or land cover classifications. ( C) Elsevier Science Inc., 2000.