Soil Moisture Estimation and Its Influencing Factors Based on Temporal Stability on a Semiarid Sloped Forestland

Abstract

Soil water content (SWC) plays a crucial role in the hydrological cycle and ecological restoration in arid and semi-arid areas. Studying the temporal stability of SWC spatial distribution is a requirement for the dynamic monitoring of SWC and the optimization of water resource management. The SWC in a Pinus tabulaeformis Carr. forest on the slope of the Loess Plateau of China were analyzed in five soil layers (0–100 cm with an interval of 20 cm) in the rainy and dry seasons from July 2014 to November 2017. The mean SWC was estimated and the main factors affecting the temporal stability of the SWC were further analyzed. Results showed that the SWC had strong temporal stability during the two seasons for several consecutive years. The temporal stability of SWC and the number of representative locations varied with season and depth. The elevation, soil total phosphorus (STP), clay, silt, or sand content of the representative locations approached the corresponding mean value of the study area. A single representative location accurately represented the mean SWC for the five depths in the rainy and dry seasons (RMSE <2%; rainy season: 0.81 < R2 < 0.94; dry season: 0.63 < R2 < 0.83; p < 0.01). The mean relative difference (MRD) and the relative difference standard deviation (SDRD) changed with the seasons and were significantly correlated with elevation, root density, and sand and silt content in two seasons (p < 0.05). Elevation, root density, and sand content were the main factors influencing the change of SWC temporal stability in different seasons. The results provide scientific guidance to monitor SWC by using a small number of locations and enrich our understanding of the factors affecting the temporal stability of SWC in the rainy and dry seasons of the Loess Plateau of China.

Impact of Historical Agrarian Landforms on Soil Water Content Variability at Local Scale in West Carpathian Region, Slovakia

“…The higher SD, CV, and SDMR values indicate the lower SWC stability at the upper soil layer (Table 2). Due to the low SWC spatial variability in deeper soil layers, the MRD variation range tends to decrease with depth, regardless of the seasonal fluctuation [49]. Similar to previous research findings, the average SDRD values tend to decline as well with increasing soil depth [20,50].…”

Role of time variant and invariant terms on soil moisture spatio‐temporal variability in a subhumid coastal wetland

“…Average variability in S tn was similar at 0.35 m and 0.50 m depths. Previous studies have reported increasing variability with depth (Gao et al, 2015; Hu et al, 2010) and decreasing variability with depth (Cheng et al, 2017; Duan et al, 2017; Martinez et al, 2013; Xu et al, 2021). The difference between studies and soil properties, topography, and subsoil characteristics within each region are the reasons for the increase or decrease in soil moisture variability with depth that can explain the different conclusions obtained in other studies (Vanderlinden et al, 2012).…”

“…Moreover, there are studies in which higher variation in soil moisture was found in topsoil measurements (e.g. 0–0.20 cm) compared to the subsoil (0.20–0.50 m), for example, (Cheng et al, 2017; Duan et al, 2017; Martinez et al, 2013; Xu et al, 2021), and vice versa (Gao et al, 2015; Hu et al, 2010). These factors, meteorology/climatology, soil properties, and vegetation, affect the mean soil moisture mean and variance relation differently and might be intertwined depending on the region, scale of the study and measurement depth below the surface (Suo et al, 2018).…”

“…The (temporal) variability of RD referred by Gao et al (2015) as a precision term reflects the degree of (in)stability of the MRD. Its application has been conducted across a range of scales and yielded promising results in terms of understanding such variabilities and their controls (soil properties, vegetation, topography, and rainfall) and finding the most representative location of the spatial mean soil moisture in an area of interest (Dari et al, 2019;Hao et al, 2020;Vanderlinden et al, 2012;Zhao et al, 2020).…”