Abstract:Vegetation restoration and reconstruction in arid and semi-arid areas are highly dependent on precipitation, and any slight change in precipitation pattern will have an impact on its ecosystem. Taking three main cover types of desert steppe in Yanchi County of Ningxia, floating sand land, native grassland and Caragana woodland as research objects, the precipitation and soil moisture from 2015 to 2017 were continuously observed by automatic weather station and soil moisture meter, the soil moisture dynamics of 0—250 cm soil layer and the responses to different levels of precipitation were analyzed. The results showed that the soil moisture of floating sand land increased from the surface to the deep layers, and the native grassland and Caragana woodland had the increasing-decreasing-increasing trends; seasonal changes in water content were divided into stable soil moisture period (December to February of the following year), soil moisture accumulation period (March to May), soil moisture decay period (June to mid-August) and soil moisture recovery period (late August to November). Small precipitation events less than 5 mm had almost no effect on soil moisture; moderate precipitation events (5~25 mm) and heavy precipitation events (25~40 mm) could supplement soil moisture in 0—20 cm soil layer or 0—40 cm soil layer in floating sand land. Extra-large precipitation event was needed for the water supplement of 40—100 cm soil layer. Floating sand land was the most sensitive to precipitation, followed by Caragana woodland, and native grassland was the most lagging. Precipitation amount, precipitation intensity, soil water content before precipitation and soil physical properties all affected soil water infiltration. When precipitation was consistent, soil type was the important factor determining soil moisture dynamics. Vegetation could redistribute soil profile moisture, which is particularly important in arid region ecosystem, and determines the corresponding relationship between vegetation types and soil types.