THE RELATIONSHIP BETWEEN NOAA-AVHRR NDVI AND ECOREGIONS IN UTAH

A comparison was made between 3 years of NOAA Advanced Very High Resol ution Radiometer (AVHRR) normalized difference vegetation index (NDVI) and an Environmental Protection Agency derived ecoregion map of Utah. NOAA-AVHRR NDVI data representing 61 B-week periods were extracted fr om the USGS ''Conterminous U.S. AVHRR Biweekly Composites'' CDs for 19 90-1992. An ecoregion map of Utah was extracted from the 1:7,500,00 '' Ecoregions of the United States'' database compiled by Omernik (1987). Mean and variance statistics for each 2-week period were compared bet ween ecoregions. With the exception. of two Omernik ecoregions, the Co lorado Plateau and Northern Basin and Range, yearly mean NDVI values w ere significantly different. The Colorado Plateau and Northern Basin. and Range were significantly different during the latter part of summe r and early fall. NDVI variation was found to be a function of interac ting climatic, topographic, and latitudinal zonation that influence ve getation growth. These factors also influence ecoregion boundary delin eation.; Results suggest that ecoregions may be characterized based on phenological variation of vegetation components using NDVI distributi on maps as surrogates for vegetation production.