Several studies also explored the depth

Fig. 3. Distribution within a HPOB profile of the determination coefficients for the power function relationships between the mean soil volumetric water content and its standard deviation at various soil depths based on data from 91 locations.Figure optionsDownload full-size imageDownload as PowerPoint slide
3.2. Profile distribution of temporal stability characteristics for SWC
3.2.1. Standard deviation of relative difference (SDRD) and Spearman's rank correlation (rs)
Profile distributions of the mean SDRD over space and of the mean rs over time are presented in Fig. 4. The mean SDRD tended to decrease with increasing soil depth, ranging from 20.1% (10 cm) to 5.7% (280 cm) (Fig. 4a). These values within the 0–200 cm layer significantly decreased with soil depth (p < 0.01, Pearson test), implying that temporal stability increased with increasing soil depth. Furthermore, the temporal stability of locations was notably less for the 10 cm depth (20.1%) than for the 20 cm depth (14.6%).