Temporal stability of soil moisture under slope protection by vegetation

The temporal stability of soil moisture is a key index to explore the water distribution pattern and reveal the hydrological characteristics and long-term stability for ecological slopes. In this study, a large-scale outdoor slope model covered by Magnolia multiflora is used. By measuring the real-time soil moisture at the depth of 0~100 cm, the spatiotemporal dynamics are firstly discussed. Then characteristics of the temporal stability at different depths are analyzed by using the Spearman correlation coefficient, relative difference method and index of time stability. Finally, a method for estimating the soil moisture of the ecological slopes is proposed. The results show that the soil moisture distribution has obvious spatiotemporal heterogeneity and depth dependence. The vegetation intervention can significantly reduce the soil moisture at the depth of 0~100 cm. Compared with that of the bare slopes, the variability level increases by 60.6%, indicating that the spatiotemporal heterogeneity is obviously aggravated. Meanwhile, under long-term protection of vegetation, the spatial pattern of soil moisture has weak temporal similarity to each other. At a certain depth, the alternation of dry and wet soils increases obviously. The temporal stability is significantly reduced by vegetation. Moreover, the representative measuring points of soil moisture can be well determined by MRD and ITS. The proposed prediction method can accurately estimate the average water content in the study area. It may provide a theoretical basis for rational arrangement of monitoring points and researches on hydrological characteristics and long-term stability for ecological slope.