Abstract
Insight into the rainfall-soil moisture (SM) response to land cover is
critical for soil hydrological process modeling and management. In this
study, five typical land-cover types (forest, shrub, grass, crop, and
bare land) and four rainfall patterns (heavy, intermediate, light, and
continuous rains) were selected to assess the effects of SM response
characteristics on the Loess Plateau of China. We monitored SM at five
depths on each land-cover type at 1-h intervals over the growing season
of 2019. The results showed that rainfall patterns and land-cover
typestogether determined the SM response process and infiltration
efficiency. A minimum accumulated rainfall amount of 5 mm was the
threshold to trigger a 10-cm SM response. Rain events with higher
intensity and smaller sum triggered a quick surface SM response, while
larger amounts could percolate deeper and faster. Land-cover change
significantly altered the rainfall-SM response dynamics and rainwater
utilization efficiency after 20 years of ecological construction.
Revegetation sites (mean values of forest, shrub, and grass) increased
the soil wetting depth by 14.7%, shortened the SM response time by
27.3%, and accelerated the SM wetting front velocity by 67.2%, which
promoted a 35.2% rainfall transformation rate (RTR) across the 1-m
profile over all rainfall events (R 1-13). Moreover,
planted forest showed the highest RTR of R 1-13 and the
maximal increase in soil water storage, which did not aggravate the soil
water deficit across the 1-m profile over the growing season. Therefore,
we present evidence that planted forests, instead of shrubs, may be
beneficial for water conservation if precipitation is greater than 550
mm. The findings of this study prove the role of revegetation on
rainwater infiltration capacity and efficiency and can help improve the
management of afforestation in arid and semiarid regions.