Modelling the effects of 300-year cropland expansion on soil erosion in Northeast China

Abstract. Historic soil erosion induced by long-term croplands’ expansion is less reported, which greatly inhibits understanding long-term soil erosion process and soil erosion conservation. In the present study, the reconstructed historical cropland and the RUSLE model was integrated to assess potential erosion changes during 1700 to 2020 in the black soil region, Northeast China (NEC). During the past over 300 years, cropland expanded from near zero to 0.07 million km² by 1900 and further to 0.35 million km² in 2020 from flat or gentle areas to steeper slopes. Affected by expanded croplands, soil erosion was intensified markedly over 300 years, with mean erosion rates increasing from 1.24 to 2.81 t·ha^-1·yr^-1 and total soil loss rising from 0.15 to 0.35 Gt·yr^-1. Cropland accounted for 78 % of the areas and soil erosion exceeded the tolerable value (i.e., 2 t·ha^-1·yr^-1) in 2020. Cumulative erosion depth averaged 3.7 cm across the whole croplands and reached 9.13 cm in areas with > 120-year cultivated period. The land cultivation history as well as its induced soil erosion exhibited distinct latitudinal pattern characteristics. These results highlight the importance of the effect of long-term land cultivation history on the cumulative impacts of soil erosion, and provide a scientific basis for sustainable management for the black soil region, NEC and similar regions in the world.