Temporal stability of soil moisture under different land uses/cover in the Loess Plateau based on a finer spatiotemporal scale

Abstract

Abstract. The Temporal stability of soil moisture (TSSM) is an important factor to evaluate the value of available water resources in a water-controlled ecosystem. In this study we used the evapotranspiration-TSSM (ET-TSSM) model and a new sampling design to examine the soil water dynamics and water balance of different land uses/cover types in a hilly landscape of the Loess Plateau under a finer spatiotemporal scale. Our primary focus is to examine the difference among soil water processes, including the wet-to-dry (WTD) process triggered by precipitation and the dry-to-wet (DTW) process caused by radiation among varied land uses/cover types. Three vegetation types and bare land were selected in the sampling scheme. For each land uses/cover type, four microplots (60 cm × 60cm) were established, and the soil moisture was measured at the central point (CP) and four ambient points (AP). The results indicated that (1) the bare land (plot1) was sensitive to the influence of rainfall and radiation compared with other land uses types; (2) Andropogon (plot2) and Spiraea pubescens (plot4) more efficiently represented the average soil moisture of the different land uses/cover in the WTD and DTW processes, respectively, in the CP position. In contrast, the bare land and Artemisia coparia (plot3) seemed to be more representative of the average soil water content in the AP position; (3) the ET-TSSM model demonstrated that, in the WTD processes, although Spiraea pubescens land use reached the net deficit of the soil water storage condition was longest, the vegetated land uses have a higher capacity of water consumption than bare land and more easily affected the serious condition of the soil water deficiency at the end of WTD processes. We concluded that a finer spatiotemporal scale in the TSSM study could be a new method to describe the effect of plant on soil moisture dynamics triggered by precipitation or radiation and that the improvement of the application of the TSSM-based model to hydrological processes could be a promising research subject in the future.