HR: 0800h
AN: B41A-0165    [Abstracts]
TI: New Developments in the Remote Estimation of the Fraction of Absorbed Photosynthetically Active Radiation in Crops
AU: Vina, A
EM: vina@msu.edu
AF: Department of Fisheries and Wildlife, Michigan State University, 13 Natural Resources Building, East Lansing, MI 48824 United States
AU: * Gitelson, A A
EM: gitelson@calmit.unl.edu
AF: University of Nebbraska, 102 Nebraska Hall, Lincoln, NE 68588-0517 United States
AB: The fraction of absorbed photosynthetically active radiation, fAPAR, is an important biophysical characteristic in models of gas exchange between the terrestrial boundary layer and the atmosphere, as well as in the analysis of vegetation productivity. Synoptic estimation of fAPAR has been performed by using NDVI as a linear proxy of fAPAR, despite the saturation of NDVI at fAPAR beyond 0.7. This paper analyzes the NDVI/fAPAR relationship in row crops (i.e. maize and soybean), and evaluates alternative vegetation indices to overcome the loss of sensitivity of NDVI at moderate-to-high vegetation biomass. Red-edge NDVI, which uses NIR and a band around 700 nm, Green NDVI and the recently proposed Wide Dynamic Range Vegetation Index (WDRVI), which uses red and NIR bands only, were found to be sensitive to fAPAR variation along its entire range and exhibited significant increase in sensitivity to fAPAR. The choice of the alternative index depends on the spectral characteristics of the sensor system at hand. Red-edge NDVI appears to be the best index for such estimation. It can be used in satellite systems with spectral bands in the red edge region (e.g., ESA's MERIS, NASA's Hyperion). The WDRVI exhibited high sensitivity to fAPAR at its entire range of variation. It can be employed to estimate fAPAR using such sensors as MODIS, Landsat and AVHRR, among others. The implications of these findings are far-reaching. Diverse regional to global studies requiring synoptic data on terrestrial vegetation will benefit from the increased accuracy of fAPAR estimation through the WDRVI, the Red edge NDVI, and the Green NDVI.
DE: 0402 Agricultural systems
DE: 0422 Bio-optics
DE: 0480 Remote sensing
DE: 4806 Carbon cycling (0428)
SC: Biogeosciences [B]
MN: Fall Meeting 2005