GPP ESTIMATION IN THE HEIHE RIVER BASIN BASED ON A LIGHT USE EFFICIENCY MODEL

摘要

Light use efficiency model is one of the methods to retrieval regional scale Gross Primary Productivity (GPP). In this study, GPP of the Heihe River Basin in China from 2011 to 2015 were inversed by light use efficiency model. In this kind of the models, Photosynthetic Active Radiation (PAR) and the fraction of absorbed photosynthetically-active radiation (FPAR) were the key parameters. Usually, PAR and FPAR were inversed without distinguishing direct and diffuse radiation. However, several researches show that due to the stronger transmission of diffuse radiation in the canopy and avoidance of the light-saturation phenomenon of direct radiation in the canopy leaves, photosynthesis is more efficient under the action of diffuse radiation. So in this article PAR and FPAR were inversed by models which can distinguish direct and diffuse radiation. And the retrieved daily GPP results were validated by field measurements from flux sites of GPP.