Response of soil nutrients and erodibility to slope aspect in the northern agro-pastoral ecotone, China

Abstract. Soil erosion, considered a major environmental and social problem, leads to the loss of soil nutrients and the degradation of soil structure, impacting plant growth. However, data on the effects of land use changes caused by vegetation restoration on soil nutrients and erodibility at different slope aspects is limited. This study was conducted to detect the response of soil nutrients and erodibility of different slope aspects in a typical watershed of the northern agro-pastoral ecotone in China. The following indexes were used to determine the improvement of soil nutrients and erodibility through a weighted summation method: comprehensive soil nutrient index and comprehensive soil erodibility index. The results showed that the vegetation types with the highest comprehensive soil quality index (CSQI) on the western, northern, southern, and eastern slopes were Pinus sylvestris and Astragalus melilotoides (1.45), Caragana korshinskii and Capillipedium parviflorum (2.35), Astragalus melilotoides (4.78), and Caragana korshinskii and Lespedeza bicolor (5.00), respectively. Slope aspect had a significant effect on understory vegetation characteristics, soil nutrients, and soil erodibility. Understory vegetation and soil characteristics could explain 50.86–74.56 % of the total variance in soil nutrients and erodibility of slope aspect. Mean weight diameter, total phosphorus, saturated hydraulic conductivity, and soil disintegration rate were the main factors affecting CSQI on different slope aspects. Our study suggested the combinations of species, such as C. korshinskii and L. bicolor, were the best species to include on any slope aspect in regards to improving soil nutrients and soil erodibility.