2.2.1 Soil moisture monitoring
SM monitor has been established in typical land-cover sites since June 2018. At each site, an array of SM probes (EC-5 probes with a precision of ±0.1 vol. %; The METER Group, Inc., Pullman, Washington) was installed horizontally at five depths below the soil surface. According to previous studies, the SM response depth is limited to the 1-m profile of each land-cover type after the rainy season (Tang et al., 2018; Wang et al., 2013; Yu et al., 2015). Thus, we installed an SM monitoring probe in the 0-1-m profile (10, 30, 50, 70, and 100 cm) to investigate SM infiltration and the response process affected by rainfall. Meanwhile, this paper set the 10-cm soil layer as the shallowest monitoring depth to reveal the difference in surface SM response time and soil permeability after precipitation as a result of revegetation (Jin et al., 2018; Lee et al., 2017; Liu et al., 2020).
After installation, the pit was carefully refilled with original soil material and compacted to the original bulk density layer by layer to avoid perturbation as much as possible. SM was measured every h and stored in EM50 dataloggers (The METER Group, Inc., USA). The 1-h SM data from May 1 to October 31 in the growing season were used to explore the SM dynamics after rainfall.