Greater soil contribution to vegetation growth in dry regions than in humid regions

Abstract

The response of vegetation growth to soil moisture is mediated by soil properties, but how and to what extent soil properties affect the response have remained unclear. In this study, we first quantify the global patterns of soil contribution to vegetation growth by establishing a nonlinear vegetation-soil moisture response model. We find that soil properties primarily regulate the nonlinear vegetation-soil moisture response by adjusting the soil moisture optima (SMpoint), which was defined as the peak in a fitted unimodal model. The impacts of soil properties on SMpoint range from − 0.18 cm3/cm3 to 0.16 cm3/cm3. Significant soil impacts on vegetation growth can be positive or negative, depending on soil impacts on SMpoint. In dry regions (Aridity index < 0.65), by adjusting soil water use, soil properties explained 62% of the vegetation growth change on average, and the average change in vegetation growth driven by soil property impacts was only 21% of that in humid ecosystems. Linking soil properties to vegetation responses to soil moisture is important to improve our understanding of droughts and their soil determinants. The results of our study provide insights into the role of soil properties in influencing global vegetation soil water uses and a new framework to consider the impacts of soil properties in global vegetation models.