Spatial variability of surface soil moisture content in a re-vegetated desert area in Shapotou, Northern China

Surface soil moisture content exhibits a high degree of spatial and temporal variability. The purpose of this study was (a) to characterize the spatial and temporal variations in soil moisture contents in the depths of 0-15 and 0-30 cm soil layer in an artificially re-vegetated desert area in Shapotou, China; and (b) to make inferences regarding the environmental factors that influence such variability. Over a period of 7-month experiment, soil moisture contents were measured with Time Domain Reflectometry (TDR) at an interval of every half a month at a grid space with 10 m intervals horizontally covering 4500 m2 area, which include a topography from dune crest to dune hollow, and again to dune crest. Results indicated that the distribution of soil moisture at the grid scale was in a pattern of normal distribution with a significant temporal-spatial variability; the variability of soil moisture decreased with decreased mean soil moisture content, and it was higher in the depth of 0-15 cm than that in the depth of 0-30 cm. Relative elevation was a main influence factor of soil moisture variability especially after rainfall events and its influence was more tremendous in the depth of 0-30 cm than that in the depth of 0-15 cm. There was a consistent time-series pattern between the vegetation cover and the soil moisture content and the relative elevation, which increased under the rainstorm events. Soil texture (particle size distribution) had an opposite time-series pattern with relative elevation and vegetation cover, and the correlation was higher in the depth of 0-15 cm than that in the depth of 0-30 cm. We may conclude that local topography and vegetation cover were the main influencing factors of soil moisture variations immediately after the rainstorm events, whereas the soil texture was an important influencing factor as the soil dried up in the study area.