The respective effects of atmospheric vapor pressure and soil moisture on ecosystem productivity in Southwest China

Drought is considered as a key factor restricting the growth of plants. It is critical to investigate the impact of drought stress on vegetation and understand the respective effects of Soil Moisture (SM) and Vapor Pressure Difference (VPD) on ecosystem production for ecological sustainability. For the Southwest China, the respective impacts of VPD and SM on the productive capacity of regional ecosystems are still unknown. To capture the drought stress over Southwest China, Solar-induced fluorescence (SIF) was selected as a reliable indicator of regional ecosystem production and applied to analyze the impact of SM and VPD using data binning. In this study, PAR and FPAR data were incorporated to calculate SIFyield, eliminating the influence of PAR and FPAR on SM and VPD, which was used to analyze the spatiotemporal correlation between SM, VPD, and SIFyield. And then a data-binned method was applied to compare the implications of low SM and high VPD for each SIFyield quantitatively. Finally, vegetation coverage data was used to conduct a statistical analysis of the correlation of VPD, SM, and SIFyield under different vegetation types and further learn the correlation between these parameters. The results revealed that the impact of high VPD on SIFyield was notably more prominent in regions with 75% vegetation coverage. High correlation between SM and SIFyield was found over forest and shrub, and SM large influence on VPD and SIFyield over grassland types. These new findings will be valuable for future agriculture, forestry breeding, and cultivation over this eco-fragile region.