Assessment of soil erosion in rolling hilly region of Northeast China using Chinese Soil Loss Equation (CSLE) model

Abstract: Black soil region in Northeast China is an important commodity grain base in China. Soil erosion can deteriorate in the valuable black soil resources; even threaten the safety of grain production. Assessment of soil erosion becomes an inevitable way to control soil erosion, and further to evaluate the benefits of soil and water conservation. However, the multi-scale complex factors can make it difficult to the accurately assess soil erosion. It is also necessary to detect the effects of land use and topography on soil erosion. Normally, the evaluation data of soil erosion include modulus, amount, and intensity of soil erosion. These indexes have different meanings and uses in regional soil erosion assessment. In order to better present the evaluation data of soil erosion, a research region was taken as Baiquan County in rolling hilly regions in Northeast China. Chinese Soil Loss Equation (CSLE) was used to quantitatively evaluate the soil erosion, and systematically analyze the influences that caused by land use and topographic factors. A "landing" scheme was proposed to achieve regional evaluation of soil erosion. The results showed that the average modulus of soil erosion in Baiquan County was 6.77 t/(hm2·a), and the area proportion of soil erosion was 39.35%, indicating a great spatial heterogeneity in soil erosion. The extremely severe erosion was mainly distributed in the hilly areas in the southeast, and the rolling hilly regions in the northwest of Baiquan. This distribution can be attributed to the slope arable land occurred in this area, together with the influence of the terrain. Specifically, the intensity of soil erosion can be high as the increase of the slope. In addition, the intensity of soil erosion showed a trend of increasing first and then decreasing, as the length of the slope becomes longer. The amount of soil erosion is also an important indicator for the evaluation of soil erosion. In the contribution to the amount of erosion, the slope from 1° to 2° showed the largest amount of erosion, followed by 3° to 5° and 2° to 3°. The slope length from 100 to 200 m can contribute the most amount of soil erosion, followed by the slope length of 200 to 400 m and 50 to 100 m. Sloping farmland was characterized by high intensity of soil erosion. Compared with the forest land, the large slope was not the main source of soil erosion amount due to high vegetation coverage and relatively low soil erosion modulus. Therefore, the sloping farmland can be the key area for soil erosion control. This infers that the selection of appropriate indicator can be significant to present the evaluation data of soil erosion. This study demonstrated that the area proportion of soil erosion can be selected for the better evaluation of regional soil erosion at the scale of small watersheds and water conservation planning. This finding can provide an effective way to achieve assessment for regional soil erosion in the "landing" scheme.