Runoff and soil loss responses of restoration vegetation under natural rainfall patterns in the Loess Plateau of China: The role of rainfall intensity fluctuation

Vegetation restoration is effective at combating soil erosion. The intensity distribution within rainfall events (rainfall pattern) has undergone evident variations under global change, which was crucial for hydrological and erosive processes. However, the responses of runoff and soil loss to natural rainfall patterns under restored vegetation are not fully understood. In this study, the rainfall hyetograph, runoff and soil loss data from forestland, shrubland and grassland plots were collected during 2012-2016 in the Yangjuangou catchment, a typical hilly and gully catchment in the Loess Plateau of China. The roles of natural rainfall pattern on runoff and soil loss were explored, and the consistency of these effects among three land use types was examined. The erosive rainfall events were grouped into three rainfall patterns based on the occurrence time of the most intense rainfall, including the early-peak, center-peak and late-peak patterns. The results indicated that the early-peak pattern contributed to approximately 50 % of erosive events, which also yielded the significantly larger RC (runoff coefficient) (0.91 -3.07 %) and larger SLC (soil loss coefficient) (0.07 -0.13 gm- 2 mm -1) compared to center-peak (0.08 -0.11 % and 0.005 -0.010 gm- 2 mm -1) and late-peak pattern (0.14 -1.05 % and 0.003 -0.010 g m- 2 mm -1). Generally, the influences of rainfall pattern on runoff and soil loss were consistent between the three land use types. The RC-SLC relationships were well described by a power function, and the early-peak (0.022) and center-peak pattern (0.027) showed larger magnitude term compared to the late-peak pattern (0.010), revealing larger capacity of runoff to produce erosion. This study shed light on the crucial role of natural rainfall pattern in yielding runoff and soil loss from vegetated hillslopes, and highlighted that the early-peak pattern may be responsible for triggering serious soil erosion in the semi-arid environment.