Seasonal changes of soil erosion and its spatial distribution on a long gentle hillslope in the Chinese Mollisol region

Authors: WANG, LEI - Northwest A&f University; ZHENG, FENLI - Northwest A&f University; LIU, GANG - Northwest A&f University; Zhang, Xunchang; Wilson, Glenn; SHI, HONGQIANG - Northwest A&f University; LIU, XUJUN - Heilongjiang Province Hydraulic Research Institute

Submitted to: International Soil and Water Conservation Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2021
Publication Date: 2/10/2021
Citation: Wang, L., Zheng, F., Liu, G., Zhang, X.J., Wilson, G.V., Shi, H., Liu, X. 2021. Seasonal changes of soil erosion and its spatial distribution on a long gentle hillslope in the Chinese Mollisol region. International Soil and Water Conservation Research. https://doi.org/10.1016/j.iswcr.2021.02.001.
DOI: https://doi.org/10.1016/j.iswcr.2021.02.001

Interpretive Summary: Understanding seasonal soil erosion and deposition rates and their spatial distribution along sloping farmlands is necessary for improving erosion prediction technology and implementing effective soil conservation practices. To date seasonal changes of soil erosion and soil redistribution on long gentle hillslopes are not fully understood due to changes of erosive forces or agents with seasons. A multi-tracer method using rare earth elements (REE) was employed to differentiate seasonal changes of hillslope soil erosion and its spatial distribution on a sloping farmland driven by snow melt, wind and rainfall. A large runoff plot, 5 m wide and 320 m long located in the typical Mollisol region of China, was divided into eight segments, each tagged with one REE tracer with a partial area tagging scheme in a grid-based layout. Soil erosion and redistribution were evaluated by grid sampling the REE-tagged zones on the soil surface. Annual soil erosion rate was 3251 t km-2 for the whole runoff plot, in which snowmelt erosion contributed 537.3 t km-2, wind erosion 363.1 t km-2 and rainfall erosion 2350.6 t km-2. Distribution of soil erosion after snow melting and rainy seasons showed that severe soil erosion occurred in the middle and lower slopes and a large proportion of sediment was deposited at the toeslope. However, the distribution of soil erosion after the windy season showed an alternating patchy distribution. Sediment delivery ratios of each slope segment caused by snowmelt and rainfall erosion were more than 23.5%. Moreover, with the combined erosion, the slope length of 120-240 m tended to be the most severely eroded section. Understanding the impacts of different erosive forces on seasonal soil erosion will enable erosion scientists and soil conservationists to improve erosion prediction technologies and developing best soil conservation practices.

Technical Abstract: Understanding seasonal soil erosion and deposition rates and their spatial distribution along sloping farmlands is 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 understood due to the variable erosive forces in different seasons. A multi-tracer method using rare earth elements (REE) was employed to discriminate seasonal change of hillslope soil erosion and its spatial distribution on a sloping farmland driven by snow melting, wind force and rainfall. A large runoff plot with 5 m wide, 320 m long located in the typical Mollisol region of China was divided into eight segments, each 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. Soil erosion and redistribution were evaluated by grid sampling the REE-tagged zones on the soil surface. Annual soil erosion rate was 3251 t km-2 for the whole runoff plot, in which snowmelt erosion contributed 537.3 t km-2, wind erosion 363.1 t km-2 and rainfall erosion 2350.6 t km-2. Distribution of soil erosion after snow melting and rainy seasons showed that severe soil erosion occurred in the middle and lower slopes and a large proportion of sediment was deposited at the toeslope. However, the distribution of soil erosion after the windy season showed an alternating patchy distribution. Sediment delivery ratios of each slope segment caused by snowmelt and rainfall erosion were more than 23.5%. Moreover, after the interaction of the three erosive forces of snow melting, wind force and rainfall, the slope length of 120-240 m tended to be the most severe soil erosion location. The main fluctuation periods of soil erosion rate along the slope length were between positions of 167 and 203 m. Understanding the impacts of different erosive forces on seasonal soil erosion will provide references for the development of erosion prediction technologies and best soil conservation practices.