Vegetative response to climate change in the Big Pine Creek watershed along a 2,500 meter elevation gradient using Landsat data

摘要

This paper presents a time series study of an alpine ecosystem in the Big Pine Creek watershed in California's Eastern Sierra Nevada Mountain's. Seventy five sample sites along a 2,500 meter elevation gradient are analyzed for trends in surface reflectance based on vegetative density using USGS data derived from Landsat imagery for the 1984 through 2013 time frame. Three vegetative indices, NDVI, SAVI, and MSAVI_2 as well as the Tasseled Cap transformations for Brightness (TC_B), greenness (TC_G), and wetness (TC_W) are explored. We found that over the time period of the study, significant increases in vegetation are occurring at densely vegetated sites at almost all elevations within the watershed while less change and even some significant declines in vegetation are seen in moderately and sparsely vegetated sites. Sparsely vegetated sites show distinct bifurcation in their response with the lower elevations seeing declines and the upper elevations seeing increases in vegetation. Several sites show significant declines in both the visible and near infrared regions suggesting there are compositional changes taking place consistent with climate induced range shifts. This study provides a useful insight into the ecological response of the Big Pine Creek watershed to recent climate change.