HR: 1340h
AN: C43C-0240    [Abstracts]
TI: Large and Small Scale Mapping of High Arctic Vegetation by NDVI: Thule, Greenland
AU: * Horwath, J L
EM: horwath@u.washington.edu
AF: University of Washington, Department of Earth and Space Sciences Box 351360, Seattle, WA 98195 United States
AU: Sletten, R S
EM: sletten@u.washington.edu
AF: University of Washington, Department of Earth and Space Sciences Box 351360, Seattle, WA 98195 United States
AB: An important component of arctic climate change is the assessment and quantification of vegetation cover. One method to assess this remotely is using the normalized difference vegetation index (NDVI), a relative measure of plant cover (greenness) of an area. NDVI values are often correlated with biomass figures and used to provide a spatial context for measurements of carbon flux, and potentially for estimating the spatially distributed response of carbon flux to climate change. Significant scaling issues arise when comparing NDVI values obtained on markedly different scales. When calculated at low resolution, such as 1 km AVHRR (Advanced Very High Resolution Radiometer) satellite images, NDVI results can vary significantly from higher resolution satellite images such as ASTER (Advanced Spaceborne Thermal Emission and Reflection) or ground measurements. Differences and similarities of NDVI values calculated from ASTER satellite images (15 meter pixels) are compared to those measured at a scale of 1 meter. Using a June 2003 ASTER satellite image, five sites were selected in the vicinity of the Thule Air Base as ground control plots representing five diverse classes of NDVI. These were photographed in the field during mid and late summer using a portable NDVI camera; NDVI values were calculated at one meter resolution. These data, along with coincident 2004 ASTER satellite images and vegetation transects will be used to better depict vegetation cover and to validate the satellite scale classes of vegetation for a typical High Arctic site in the Thule area. Preliminary results indicate that higher NDVI values from the satellite imagery do not always correspond to higher densities of vegetation, as presumed. Standing water and well-developed cryptogamic crusts may alter predicted results. Used on an annual basis, this method may be used to track changes in High Arctic vegetation cover and help to better understand the environmental changes occurring in the region.
DE: 1823 Frozen ground
DE: 1851 Plant ecology
DE: 1615 Biogeochemical processes (4805)
DE: 1640 Remote sensing
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting