Trajectories of Terrestrial Vegetation Productivity and Its Driving Factors in China's Drylands

Climate change and large-scale ecological restoration programs have profoundly influenced vegetation greening and gross primary productivity (GPP) in China's drylands. However, the specific pathways through which climatic factors and vegetation greening influence GPP remain poorly understood. This study examines the spatiotemporal changes in GPP across China's drylands from 2001 to 2020 and investigates the direct and indirect effects of climatic factors and leaf area index (LAI) on GPP. The results reveal that the overall improvement in vegetation cover has positively increased GPP in these regions. Although the direct effects of climatic factors on GPP are minimal, they exert a substantial indirect effect by regulating vegetation growth, highlighting that LAI is a key intermediary in mediating the effects of climatic factors on GPP. Furthermore, these complex interactions vary significantly along the aridity gradient. This study emphasizes the necessity of comprehensively considering the intricate interactions among multiple climate and vegetation factors. China's drylands have undergone significant vegetation greening and ecological restoration, characterized by transitions toward forests, grasslands, and croplands. These changes have greatly enhanced gross primary productivity (GPP), a key indicator of ecosystem health and functionality. This study reveals that the increase in GPP results from the combined effects of climate change and improved vegetation cover. Although climatic factors like temperature, precipitation, and solar radiation directly affect GPP to a lesser extent, they indirectly boost it by altering vegetation growth conditions. Among the various factors, the increase in vegetation cover has the most direct and substantial positive effect on GPP, especially in semi-arid and dry sub-humid regions, where ecological restoration efforts are concentrated. Furthermore, the study indicates that the center of gravity for vegetation productivity in China's drylands is gradually shifting westward, and predicts that most areas will maintain the current trend of increasing vegetation productivity. Overall, under the dual impetus of climate change and greening initiatives, the vegetation in China's drylands has exhibited strong vitality. This not only benefits ecological environment improvement but also supports climate change mitigation and contributes to carbon peaking and carbon neutrality goals. The trend of gross primary productivity in China's drylands has shown a marked increase, especially after 2011 The leaf area index serves as a crucial intermediary in modulating the indirect effects of climatic factors on gross primary productivity The complex interactions between climatic factors and the leaf area index on gross primary productivity vary along the aridity gradient