Research papersRunoff and soil erosion of field plots in a subtropical mountainous region of China

- We analyze 1576 rainfall-runoff-soil loss events at 36 experimental plots.
- Soil loss of five common land use and four different slopes were quantified.
- Soil loss of plots of local crops and orchards were quantified.
- Almost half of the rainfall events caused soil erosion at the study area.
- A single soil loss event can contribute more than the average annual soil loss.

Anthropogenic pressure coupled with strong precipitation events and a mountainous landscape have led to serious soil erosion and associated problems in the subtropical climate zone of China. This study analyzes 1576 rainfall-runoff-soil loss events at 36 experimental plots (a total of 148 plot-years of data) under a wide range of conditions in subtropical mountainous areas of China where slope farming is commonly practiced. The plots, which have standardized dimensions, represent five common types of land use and have four different slopes. Event-based analyses show that almost half of the total rainfall caused soil erosion in the study area. The dominant factor controlling the runoff coefficient is the slope gradient rather than the land use type. The maximum soil lossfor crop plots under steep tillage (35°) is 5004 t km−2 for a single event. Among the common local crops, the average soil loss values increase in the following order: buckwheat < mung bean < sesame. Among the most widespread grasses, orchards and crops, the soil loss increase in the following order: red clover < nectarine < orange < maize. A large proportion of the soil loss is caused by a small number of extreme events. The annual average soil loss of the 44 plots ranges from 19 to 4090 t km−2 year−1. The annual soil loss of plots of different land use types decrease in the following order: bare land (1533 t km−2 year−1) > cropland (1179 t km−2 year−1) > terraced cropland (1083 t km−2 year−1) > orchard land (1020 t km−2 year−1) > grassland (762 t km−2 year−1) > terraced orchard land (297 t km−2 year−1) > forest and grassland (281 t km−2 year−1).