Simulation of forest carbon fluxes over greater khingan

Simulation of forest carbon fluxes over Greater Khingan based on strategy of model integration and data assimilation from 2000 to 2012 was conducted in this study. Original MODIS MOD_17 GPP (MOD_17) model was optimized over Greater Khingan using downscaled meteorological data, optimized light use efficiency, and refined GLASS fPAR products. Afterwards, representative forest plots for different forest types were selected for the integration of the optimized MOD_17 model and Biome-BioGeochemical Cycles (Biome-BGC) model. Through the model integration, the process-based model (Biome-BGC) was calibrated and then was applied to simulate the forest carbon fluxes over Greater Khingan. Meanwhile, time-series refined 8-day Global LAnd Surface Satellite (GLASS) LAI were assimilated into the calibrated Biome-BGC to improve the model performances and alleviated the uncertainties. Forest carbon fluxes (GPP, NPP, NEE) were estimated over Greater Khingan from 2000 to 2012 and NPP estimates were validated using tree ring data. Lastly, spatial statistics and trend analysis of NPP were carried out, and results showed that NPP tended to slightly increase during the study years.