ABSTRACT Spatiotemporal variability of available soil moisture (ASM) complicates soil water resource management and vegetation restoration in the Chinese Loess Plateau (CLP). Our objectives were to investigate the spatial variability and temporal stability of ASM at different slope positions and estimate deep and mean profile ASM using ASM from representative soil layers. The mean relative difference (MRD), associated standard deviation of relative difference (SDRD), index of temporal stability (ITS), mean absolute value of bias error (MABE) and root mean squared error (RMSE) were used to identify representative soil layers. The estimation accuracy was verified by absolute error (AE), relative error (RE), RMSE and Nash‐Sutcliffe efficiency coefficient (NSE). The results suggested that (1) the dynamics of ASM exhibited complexity. The ASM for the top, middle and bottom slopes varied within the range of 5.76%–14.24%, 5.85%–10.74% and 3.38%–6.69%, respectively. (2) The correlations of ASM amongst different soil layers varied across slope positions. The highly significant positive correlation was observed below 200 cm soil layer at the bottom slope ( r = 0.96, p < 0.001). (3) The ASM estimation at the middle slope was more reliable than other slope positions. The representative soil layer (600–700 cm) explained 78.50% and 94.00% variability of deep and mean profile ASM, respectively. (4) The estimation for mean profile ASM was more accurate than deep ASM. The RMSEs were 1.95% and 1.84%, 1.92% and 0.94%, 2.70% and 1.84% for deep and mean profile ASM at the top, middle and bottom slopes, respectively. This work proposes an indirect method for determining mean profile ASM in the fragmented terrain area on the CLP; it also can reliably estimate deep soil moisture that cannot be measured due to the presence of Calcaric Regosol.
Dong et al. (2026) studied this question.