Unravelling the dynamics of soil microbial communities under the environmental selection and range shift process in afforestation ecosystems

The process of forest range shift not only affects the vegetation aboveground but also influences the dynamics of belowground microbial communities. To investigate the changes in soil under forest range shift, we examined the natural forest soil microbiome along with its corresponding physicochemical properties, as well as the afforestation of natural forest by seedlings and sowing. By utilizing natural forests and employing different afforestation methods, we simulated the three stages of forest range shift: the staging stage, regeneration, and colonization. We employed network analysis and phylogenetic assemblages to examine the structure of soil microbial communities during these three stages in a macro-environmental change context. Ordination and regression analyses were also used to explore the correlation between microorganisms, environmental factors, and changes in their niches. The findings revealed that different afforestation (range shift) types led to distinct microbial compositions. Seedling afforestation exhibited similarities to mature forests, suggesting a significant influence on below-ground microorganisms. In contrast, sowing-based afforestation resulted in small changes in soil microbes, indicating a legacy effect on grassland soils. The impact of the rhizosphere on microbial composition remained consistent across the three forest types. Overall, this study underscores the significance of forest range shift in shaping soil microbial communities and emphasizes the need to consider these dynamics in forest management and restoration endeavours.