3.4 Soil moisture response velocity to rainfall
Two rainfall process was selected (P1 and P9) to clarify the percolation process of rainfall (Table 4 and Fig. 5). Through the analysis of different rainfall patterns, we found that Group IV has the longest RT and the slowest wetting front velocity (WFV, cm/h) within the 1-m profile. Group II had the shortest RT, approximately 6.4 h, which was significantly lower than that of the other patterns (p<0.05). Group I had the slowest WFV of 10 cm but the fastest WFV in the 1-m profile, which surpassed 6 cm/h (Table 4).
The effect of land-cover change showed that the crop site had the longest RT and slowest WFV in the 1-m profile at a nonsignificant level across the five monitoring sites (Table 4). Nevertheless, revegetation patterns altered this condition, with a smaller RT and a larger WFV. Specifically, planted shrubs accelerated the WFV by approximately 46.7% of the surface SM and reduced the RT by approximately 33.7% across the entire profile compared to the crops. Abandoned grass and planted forest improved the soil permeability to decrease the ART by approximately 17.4% and 30.8%, respectively, and increased the WFV by approximately 87.0% and 77.9%, respectively, in the 1-m profile compared to the crops (Supplemental Fig. S3). Hence, revegetation sites decreased the RT and accelerated the WFV to a great degree.