Validación de productos MODIS relacionados con la estimación de flujos de carbono en una dehesa

Several studies have demonstrated the potential of the images obtained by MODIS TERRA and AQUA platforms for global analysis of parameters related to the structure and functioning of vegetation critical for estimating and modeling the water and carbon exchanges between the biosphere and atmosphere at a global scale. However, recent works have revealed the existence of large errors (Pisek et al., 2007, Sea et al., 2011) showing that some products lack the robustness and consistency required, particularly for drought prone ecosystems with a complex structure of vegetation, such as Mediterranean ecosystems The main objective of this study is the validation of MODIS TERRA and AQUA products using field measurements in order to quantify the possible differences and analyze their potential causes. We have analysed a series of MOD/MYD13, MOD/MYD15, MOD/MYD17products acquired between 2009 and 2011 in a “dehesa” located in Caceres province which has an "eddy covariance" tower included in the FLUXNET international network. These results show low correlation for LAI (Leaf Area Index) (r2 = 0.67), but high correlation for NDVI (Normalized Difference Vegetation Index) (r2 = 0.92) and gross primary productivity or GPP (r2 = 0.80). However, although MODIS collects fine temporal dynamics of flows and structural changes in the ecosystem, there are some important differences between MODIS products, including NDVI and GPP, and terrain data