Direct Uses of MODIS Data to Estimate Carbon Fluxes of North American Ecosystems

摘要

In this study we examined whether the enhanced vegetation index (EVI) and the land surface temperature (LST) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) can be used directly to estimate gross primary productivity (GPP) and respiration (Re) of ecosystems at eddy covariance flux tower sites across North America. In our previous studies we have reported a good general relationship between EVI and GPP across multiple sites. Here we examine the reasons for variation in the strength of this relationship between sites, as well as the mechanistic basis for this relationship. We also tested whether Re can be estimated using a model that couples EVI and LST. Our results show that the correlation between EVI and GPP remains high through most of the range of vegetation greenness, whereas the seasonal variation in EVI was best explained by the severity of summer drought. The respiration model showed the potential of estimating Re exclusively from EVI and LST, especially for the deciduous sites. These results demonstrate that remote sensing based Carbon balance models can be considerably simplified for most vegetation types across North America.