ANPP estimates from NDVI for the central grassland region of the United States

Several studies have suggested the existence of a positive relationship between the Normalized Difference Vegetation Index (NDVI) derived from AVHRR/NOAA satellite data and either biomass or annual aboveground net primary production (ANPP) for different geographic areas and ecosystems. We calibrated a 4-yr average of the ingegral of the NDVI (NDVI-I) using spatially aggregated values of ANPP. We also provided an estimate of the energy conversion efficiency coefficient ([Epsilon]) of Monteith's equation. This is the first attempt to calibrate a standard NDVI product for temperate perennial grasslands. We found a positive and statistically significant relationship between NDVI-I and ANPP for grassland areas with mean annual precipitation between 280 and 1150 mm, and mean annual temperature between 4 ° and 20 ° C. Depending on the method used to estimate the fraction of photosynthetic active radiation, the energy conversion officency coefficient was constant (0.24 g C/MJ), or varied across the precipitation gradient, from 0.10 g C/MJ for the least productive to 0.20 g C/MJ for the most productive sites. Key words: absorbed photosynthetic active radiation; energy conversion efficiency coefficient; grasslands; Normalized Difference Vegetation Index; net primary production; remote sensing.
The ability to translate spectral data to biologically meaningful variables is a key step in increasing the use and value of satellite information. Theoretical work provides strong support for the [...]