Temporal stability of soil water storage in diverse soil layers

Knowledge of soil water storage (SWS) within soil profiles is crucial when selecting appropriate practices for the restoration of vegetation. To study the temporal stability of SWS and identify representative locations in diverse soil layers, an analysis of temporal stability was performed using Spearman rank correlation coefficients and relative differences. From July 2008 to October 2010, the SWS of three soil layers (0–1, 1–2, and 2–3 m) were measured using a neutron probe at 91 locations on a hillslope on the Loess Plateau, China. A total of 20 SWS datasets were collected over the period of measurement. The results showed that the variability of SWS decreased over time and increased over space with the increase in soil depth. High Spearman rank correlation coefficients (p < 0.01) indicated a strong temporal stability of spatial patterns for all soil layers. Temporal stability increased with increasing soil depth. Furthermore, the closer two soil layers were within a given profile and the deeper any two adjacent soil layers were, the more similar were the temporal patterns. A significant negative correlation (p < 0.01) existed between the status of soil moisture and temporal stability, and the dependency increased with soil depth. With increasing soil depth, more locations were able to estimate the mean SWS of the area. None, however, represented the mean values for all three soil layers separately.

► Temporal stability of various soil depths were determined on a hillslope. ► Spatial heterogeneity increased under increasing moisture conditions. ► Temporal stability became stronger with increasing soil depth. ► Correlation between soil water and temporal stability increased with soil depth. ► Different locations were representative of different soil depths.