Afforestation promotes aggregational differentiation of soil nutrient and microbial community in the erosive degraded ecosystem

Afforestation has been viewed as the most effective natural measure to restore the erosive degraded ecosystems. However, the role of soil inherent heterogeneity on soil quality and microbial communities in afforestation remains elusive. Here, three land types of soil were collected and separated into four aggregate sizes to explore the effects of afforestation in erosive degraded ecosystem on soil quality and microbial community at the aggregate level. Afforestation increased soil aggregate stability and aggregate-associated variance of soil nutrients, e.g. OM, TN and TP. Compared to the bareland or farmland, four nutrition-related enzyme activities, including invertase, urease, alkaline phosphatase and catalase, were significantly enhanced in the woodland. Interestingly, afforestation promoted the varies of bacterial alpha-diversity with aggregate size, but had trivial impacts on fungal alpha-diversity, indicating that the aggregational differentiation of bacterial alpha-diversity was more sensitive in response to afforestation than fungal alpha-diversity. For each land-use type, more fungal taxa variation with aggregate size than bacteria. Afforestation also enhanced more microbial taxa, especially fungal taxa, were susceptible to soil aggregate size. Furthermore, afforestation strengthened bacterial and fungal community dissimilarities between adjacent aggregates and non-adjacent aggregates. Our findings contribute to understand the fate of soil quality and microbial communities after vegetation restoration in degraded ecosystems at the soil aggregate scale.