Global pattern and determinants of grassland net ecosystem productivity: a synthesis based on chamber method

Abstract Grasslands are key components of terrestrial ecosystems, and their net ecosystem productivity (NEP) plays a vital role in the global carbon cycle and climate change mitigation. However, the geographical patterns and determinants of global grassland NEP remain poorly understood. Compared to the eddy covariance method, chamber techniques offer cost-effective, flexible, and widely applicable alternatives for NEP monitoring. In this study, we compiled a global grassland NEP dataset by integrating 1,521 chamber-based measurements from 275 sites, providing a comprehensive basis for assessing its spatial patterns and driving factors. Our results reveal the site-level mean value of 16.36 mg C m-2 h-1 for NEP, suggesting that global grasslands may function on average as carbon sinks. Furthermore, NEP exhibits pronounced a geographical pattern, decreasing with latitude. Grassland NEP variation is primarily influenced by vegetation and climate. Although individual factors exert substantial effects on NEP variation, their interactions are also critical, highlighting the context-dependency of grassland carbon dynamics. Our study elucidates variations and determinants of global grassland NEP, providing a crucial baseline for improving the accuracy of regional and global carbon sequestration estimations.