Spatiotemporal patterns and influencing factors of soil moisture at a global scale

Soil moisture (SM) is influenced by changes in meteorological elements and vegetation, as well as by environmental heterogeneity. Due to the prevalence of extreme events in the past two decades, this complexity is growing in the 21st century. In this study, the global spatiotemporal trend of SM and its possible influencing factors were investigated by using the satellite-based ESA CCI SM from 2000-2021. The results reveal global SM generally declines at a rate of -1x10(-4) m(3)m(-3)yr(-1), dominated by a drying trend in the southern hemisphere. From a global perspective, the driving force of precipitation and vegetation on SM fluctuation is stronger than that of temperature. Different environmental variables ( e.g., land cover, soil texture, and terrain) have different regulatory effects on SM changes. In contrast to other types, there are general wetting trends of SM in croplands, savannas, forests, loam soils, and high elevations (> 1000 m). The response of SM to temperature and vegetation is greatly limited under barren and forests, respectively. The impact of temperature on SM is enhanced with increasing clay content or decreasing sand content. The high positive correlation between precipitation and SM is rarely influenced by environmental factors compared to temperature and vegetation.