Temporal stability analysis of surface and subsurface soil moisture for a transect in artificial revegetation desert area, China

Temporal stability analysis is a statistical approach for describing the persistence of spatial patterns and characteristic behavior of soil moisture. Using temporal stability method, we aimed to identify statistically stable locations to estimate mean soil moisture content and examine the feasibility of confirming temporally stable locations by using other properties that were themselves relatively temporally stable. The temporal stability of near-surface soil moisture contents were investigated at three depths at the hillslope scale in an artificial revegetation desert area, China. Soil moisture were measured at soil depth of 0–6, 0–15 and 0–30 cm, using temporary frequency-domain reflectometry (FDR) and time domain reflectometry (TDR), at ten locations along a hillslope with relatively homogeneous soil properties and vegetation cover but contrasting topography during May to September in 2006. Summary variables were determined at corresponding locations. Results indicated that strong temporal persistence existed at three depths, and the temporal stability was more pronounced at deep soil layer than at soil surface. The temporal stability characteristics were relatively lack in a state of transition from wet to dry. Identified statistically stable locations at three depths represented well for the mean soil moisture content; the offset values were 0.011, 0.002 and 0.001 m3 m−3 at 0–6, 0–15 and 0–30 cm depth, respectively. The representative site for 0–6 cm soil layer can serve as a good indicator of soil moisture at other depths. Elevation and soil properties were the leading factors affecting the spatial and temporal distribution of soil moisture at the hillslope scale. The mean soil moisture contents at different depths can be predicted by other topographic and edaphic factors. This study is expected to be useful in characterizing mean soil moisture content in soil profiles on a hillslope scale, which helps to a good management of soil water on sloping land in desert areas.