水蚀风蚀交错区植被恢复对土壤生态功能的影响

The water-wind erosion crisscross region, characterized by fragile ecological environments, serves as a vital ecological barrier and the core area for the construction of the Three-North Shelterbelt Forest Program, China. Vegetation restoration is the main measure of ecological construction in this area, and its impact on soil ecological function is the core of ecological effect evaluation, as well as the basis for the selection and optimal allocation of vegetation restoration measures. Currently, the method of spatial substitution for time is mostly employed when investigating the environmental effects of different vegetation restoration measures. This method struggles to eliminate differences among treatments in terms of prerestoration land use patterns, site conditions, restoration duration, soil texture, and other factors, leading to considerable uncertainty in the results of studies. In contrast, the establishment of long-term observation plots under the same initial conditions can provide accurate comparisons among treatments. Therefore, investigating the environmental effects of different vegetation restoration measures under the same initial conditions not only deepens the understanding of the mechanisms underlying the interactions between vegetation and environment in fragile ecological zones but also provides scientific evidence for the selection of vegetation restoration measures in water-wind erosion intersection areas. In this study, we analyzed the effects of natural grassland (dominant species is Stipa bungeana), artificial grassland (Medicago sativa), and artificial shrubland (Caragana korshinskii) on topsoil properties, microbial communities, and soil ecological functions in a 15-year vegetation restoration plots in the water-wind erosion crisscross region. We revealed the characteristics of the changes in soil ecological functions and their driving factors under different vegetation restoration types, which is expected to provide a theoretical basis for the selection and scientific management of the vegetation restoration measures in this area. The results showed that vegetation restoration (especially Caragana korshinskii and Medicago sativa) significantly increased soil carbon and nitrogen content, soil moisture, microbial community diversity, complexity, and stability of the network compared to cropland. Additionally, vegetation restoration significantly increased soil microbial quotient and the abundance of nitrogen-fixing functional genes but reduced the biodegradability of organic carbon and metabolic quotient, thereby promoting the sequestration and stabilization of soil carbon and nitrogen. However, vegetation restoration significantly increased the abundance of functional genes related to the denitrification process. Leguminous artificial vegetation (Caragana korshinskii and Medicago sativa) had a greater positive effect on the top soil ecological functions than natural grassland, which was related to changes in soil environmental factors and microbial communities. The results indicated that leguminous plants were more effective in restoring the ecological function of surface soil in the water-wind erosion crisscross region, and had a greater potential for application in ecological restoration. However, considering that vegetation restoration usually results in excessive depletion of deep soil moisture and increases the abundance of denitrification function genes, its effects on deep soil ecological functions and greenhouse gas emissions should be taken into account.