Global patterns of dried soil layers and environmental forcing

Abstract

AbstractDeep soil drought represents a low level of deep soil water status that is unsuitable for vegetation growth and transpiration. It can be exacerbated through the excessive water uptake by vegetation during climate droughts, while signs of deep soil drought remain unclear worldwide due to a lack of unified methods and comparative data. In this study, we performed a literature search, focusing on deep soil water profiles (>2 m) and quantification of the degree of deep soil drought as indicated by dried soil layers (DSLs). The results revealed the following: (1) DSLs were distributed worldwide, with mean values of 2.2 ± 0.5 m, 3.3 ± 3.9 m, 14.6% ± 8.3%, and 0.66 ± 0.14 for the formation depth, thickness, soil water content, and quantitative index, respectively; (2) at the global scale, DSLs were more common and more severe under forestland, including shrubland, than under grassland and farmland; (3) DSLs were shaped directly by rooting depth and soil particle composition and indirectly by land use, soil thickness, terrain, and climate. The preliminary investigation of DSL distribution confirms the existence of DSLs globally, something that has not been addressed in previous studies. Our study provides an early warning of DSL formation in association with rooting depth and soil particle composition under an increased drought condition, which in turn harms vegetation production and sustainability.