Estimating Global Gross Primary Production Using an Improved MODIS Leaf Area Index Dataset.

Remote sensing and process-coupled ecological models are widely used for the simulation of GPP, which plays a key role in estimating and monitoring terrestrial ecosystem productivity. However, most such models do not differentiate the C3 and C4 photosynthetic pathways and neglect the effect of nitrogen content on V max and J max , leading to considerable bias in the estimation of gross primary productivity (GPP). Here, we developed a model driven by the leaf area index, climate, and atmospheric CO 2 concentration to estimate global GPP with a spatial resolution of 0.1° and a temporal interval of 1 day from 2000 to 2022. We validated our model with ground-based GPP measurements at 128 flux tower sites, which yielded an accuracy of 72.3%. We found that the global GPP ranged from 116.4 PgC year − 1 to 133.94 PgC year − 1 from 2000 to 2022, with an average of 125.93 PgC year − 1 . We also found that the global GPP showed an increasing trend of 0.548 PgC year − 1 during the study period. Further analyses using the structure equation model showed that atmospheric CO 2 concentration and air temperature were the main drivers of the global GPP changes, total associations of 0.853 and 0.75, respectively, while precipitation represented a minor but negative contribution to global GPP. [ABSTRACT FROM AUTHOR]