Testing a Satellite Data-based Light-use Efficiency Model for Mapping Primary Production

摘要

We test a Light Use Efficiency model of primary production parameterized with satellite data for the West African Sahel. We forgo a formal validation of the model due to problems of spatial scale and data limitations. Instead, we generate maps showing model robustness via Monte Carlo simulation. The precision of our GPP (Gross Primary Production) estimates is acceptable, but worsens for the northern fringes of the Sahel. We also map the locations where errors in the driving variables are responsible for the bulk of uncertainty in predicted GPP, in this case the water stress factor and the NDVI. Comparisons with an independent model of primary production, CENTURY, are relatively poor. A spatially exhaustive evaluation of our GPP map is carried out by regressing randomly sampled observations against integrated NDVI, a method traditionally used to quantify absolute amounts of primary production.