Revealing soil erosion and sediment sources using 137Cs and fingerprinting in an agroforestry catchment

Abstract

Soil erosion and accompanying sediment issues have a significant impact on environmental sustainability. However, there is not currently a clear understanding of the relationship between soil erosion and sediment sources at the catchment scale, which has led some researchers to regard areas with severe soil erosion as the main sediment source. This view does not apply in all circumstances.•This paper uses 137Cs to study the average annual erosion rate of different land use types. The results show that the erosion rates of woodland, sparse woodland and farmland areas were 400, 1756, and 2771 t·km−2·a−1, respectively, multiplied by the corresponding area. Surface soil erosion levels in the catchments of the three types accounted for 11%, 26% and 25%, respectively, and the total accounted for 62% when the gully bank accounted for 38%.•Fingerprinting technique results show that the relative source contributions of woodland, farmland, sparse woodland and gully bank areas to sediment at the small catchment outlet were 4%, 10%, 48% and 38%, respectively. The results reveal that the detachment process of soil and the transport process of sediment with runoff were internally related and independent of each other.•By comparing on-site erosion rates with downstream source contributions, we have a clearer understanding of soil erosion and subsequent sediment transport process in the agroforestry catchment in mountainous areas.We emphasize the importance of governance and management in areas with severe soil erosion, mainly targeting types such as hillslope framland. In addition, sparse woodland and gully banks should be given more attention, as they account for a large proportion of sediment in the downstream catchment.