Photosynthetically Active Radiation and Foliage Clumping Improve Satellite-Based NIRv Estimates of Gross Primary Production

Monitoring gross primary production (GPP) is necessary for quantifying the terrestrial carbon balance. The near-infrared reflectance of vegetation (NIRv) has been proven to be a good predictor GPP. Given that radiation powers photosynthesis, we hypothesized (i) addition photosynthetic photon flux density (PPFD) information NIRv would improve estimates GPP and (ii) further improvement obtained by incorporating distribution in canopy provided foliar clumping index (CI). Thus, used data from FLUXNET sites test these possible improvements comparing performance model based solely on with two other models, one combining PPFD NIRv, CI each cover type. We tested models different types cover, at various latitudes over seasons. Our results demonstrate daily type improves its ability estimate was related foliage organization, given (CI) affects use drives productivity. Evergreen needleleaf forests are greatest estimation after information, likely as result their greater constraints. Vegetation more determinant sensitivity changes than latitude or seasonality. advocate incorporation into algorithms estimates.