Soil water variability as a function of precipitation, temperature, and vegetation: a case study in the semiarid mountain region of China

Seasonal variations of soil water content over 16 months at three typical sites of the Qilian Mountain were investigated to understand the controlling factors in regulating soil moisture content and dynamics. In this study, we quantified soil moisture response to cumulative rainfall events and freezing and thawing processes. The significant response depth of soil moisture after rainfall was 0-40 cm, and the forms of effective rainfall in this semiarid region: consecutive, with small dry intervals, and a few small rainfall events, with the cumulative amount of no less than 18.5 mm. Not only vegetation but also topography and soil texture were the primary controlling variables for soil moisture dynamics in this mountain ecosystem. The freezing temperature in 0-100-cm soil depth was in the range of -1.66 to 1.73 degrees C, and the thawing temperature was in the range of -0.54 to 0.84 degrees C; soil aspect and water content were the main controlling factors in the freezing and thawing points in this mountain region. The results of this study contributed to identifying the major controls on soil moisture content in mountain ecosystems and will provide basis for ecological restoration in arid regions.