| Summary: | Understanding seasonal soil erosion and deposition rates and their spatial distribution along sloping farmlands are necessary for erosion prediction technology and implementing effective soil conservation practices. To date seasonal change of soil erosion and soil redistribution on long gentle hillslopes are not fully quantified due to the variable erosive forces in different seasons. A multi-tracer method using rare earth elements (REE) was employed to discriminate seasonal changes of soil erosion and its spatial distribution on a sloping farmland driven by snowmelt runoff, wind force and rainfall-runoff. A long-slope runoff plot with 5 m wide and 320 m long located in the typical Mollisol region of China was divided into eight segments, each of which was 40 m long and tagged with one of eight REE oxides. The spot method of a partial-area tagging scheme was employed and a grid-based layout was used for REE application. Results showed that annual soil erosion rate was 3251.0 t km−2 for the whole runoff plot, in which snowmelt runoff erosion contributed 537.3 t km−2, wind erosion 363.1 t km−2 and rainfall-runoff erosion 2350.6 t km−2. Surface runoff is the main external erosive force of hillslope soil erosion, accounting for 88.8% of the total annual soil loss. Furthermore, for the eight slope segments of the 320-m long hillslope, the sediment transport ratios of each slope segment caused by snowmelt runoff and rainfall-runoff erosion were more than 23.5% and 34.7%, respectively. The results will enrich the understanding of seasonal soil erosion on long hillslopes.
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