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अमूर्त

Changes in Alaskan Tundra Ecosystems Estimated from MODIS Greenness Trends, 2000 to 2010

Christopher Potter, Shuang Li,Robert Crabtree

Trends in the monthly moderate resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) time-series were analyzed for tundra ecosystems of Alaska over the past decade. Results showed that 10% of all tundra-dominated areas in Alaska were detected with significant (p<0.05) positive or negative MODIS growing season EVI trends from 2000 to 2010. Nearly three-quarters of these pixel areas were detected with significant positive growing season EVI trends. This 3:1 ratio of positive to negative EVI trends was consistent across both wetland and nonwetland tundra cover categories. Ecoregions of Alaska that revealed the highest density of positive areas for tundra growing season EVI slope were along the Pacific coast, namely the western Arctic Foothills, the Seward Peninsula, and the southern coastal plain. Associations between annual temperature and moisture patterns and tundra EVI trends across these regions revealed that change patterns in both the climate moisture index (CMI) and growing degree days (GDD) were related to increasing tundra EVI growing season trends. Results showed a notable association between the largest positive trends in MODIS greenness and annual warming trends of greater than 2 GDD per year.