Formation of new erosion-deposition patterns after farmland conversion: The major role of topography

Abstract

The “Grain for Green” project has a profound impact on the allochthonous process of erosion sediment stripping and transportation, which in turn interferes with the distribution of erosion patterns. Therefore, understanding the changes in erosion patterns after farmland conversion and the factors controlling the new patterns of erosion distribution are essential for understanding the mechanism of slope erosion. Accordingly, this study investigated the formation of new erosion patterns and their control factors after farmland conversion by field sampling combined with nuclear tracing (137Cs) techniques, considering the “Grain for Green” project on the Loess Plateau as the study focus. We found that the implementation of the “Grain for Green” project can significantly reduce soil erosion intensity and create a new erosion-sediment source-sink pattern on the slope. The conversion of farmland to grassland can effectively store soil organic carbon as well as more environmentally sensitive active organic carbon, and the sorting effect on sediment particles is more obvious. Meanwhile, using stepwise regression, we found that the key limiting factor affecting the erosion intensity of farmland is the topography; the response of topographic factors to erosion is much higher than the physicochemical properties of the soil itself. By quantified the direct and interactive contributions to erosion intensity, we find that the direct contributions of silt and relief amplitude were 0.48 and 0.46 in farmland, while slope (0.16), Roughness (0.20) and Relief amplitude (0.33) in grassland, respectively. The interactive contributions were 0.06 and 0.30 in farmland and grassland. The conversion of farmland to grassland results in an increase in the factors that resist erosion and the factors interact more closely with each other to limit the occurrence of soil erosion. Our study provides scientific support for a deeper understanding of the slope erosion mechanism.