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Global scale NDVI of arctic tundra landscapes: What does it really tell us?
Boelman, Natalie*,1, Stieglitz, Marc1, Griffin, Kevin1, 1 Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY
ABSTRACT- In order to accurately interpret global scale NDVI datasets, it is crucial that we better understand how the high spatial heterogeneity of arctic tundra vegetation translates into a single, large-scale NDVI pixel value acquired from a satellite. We have established relationships between photosynthetically active aboveground biomass to NDVI in two of the three dominant tundra vegetation communities (wet sedge, r2=0.84 and moist tussock, r2=0.6) at Imnavait Creek, Alaska (68° 37′ N, 149° 32′ W). These data demonstrate that the relationship between NDVI and aboveground biomass is not constant between vegetation communities and therefore the interpretation of global scale NDVI values may not be straightforward. We also compared data sampled from various altitudes (1 m, 4 m, 15 m, 50 m,100 m, 1.7 km and 705 km), and therefore different field of view (FOV) sizes. A handheld spectroradiometer fitted with a 20° field of view (FOV) restrictor was used to acquire NDVI values from the 1 m to 1.7 km sampling distances using extension poles on the ground or mounted on a helicopter. We have also included NDVI values for Imnavait Creek derived from the MODIS and Landsat sensors orbiting the Earth at 705 km. These data show that NDVI values vary among the FOVs sampled resulting from the dominant scales of "patchiness" inherent to arctic tundra landscapes.
Key words: tundra, ndvi, scaling, remote sensing