Response of Soil Microbial Communities Between Different Vegetation Types in the Greater and Lesser Khingan Mountains Ecotone in Northeast China

The Greater and Lesser Khingan Mountains ecotone exhibits transitional characteristics between northern coniferous forests and cold-temperate mixed coniferous-broadleaf forests. However, it remains unknown how vegetation characteristics and soil properties jointly influence the structural patterns of soil microbial communities within the forest systems of this ecological transition zone. Therefore, we used high-throughput sequencing and soil physicochemical analysis to investigate the response mechanisms of soil microbial communities during forest succession (five representative natural secondary forests) and their environmental driving factors. The results showed that the bacterial communities in the Greater and Lesser Khingan Mountains ecotone were primarily dominated by Proteobacteria, Acidobacteriota, Actinobacteriota, Chloroflexi, and Verrucomicrobiota, while the fungal communities were primarily dominated by Basidiomycota and Ascomycota. Their relative abundances exhibited significant differences dependent on vegetation types. Different vegetation types significantly influenced the α-diversity of soil microbial communities at the study site; however, there were no significant differences in microbial α-diversity except for the bacterial Chao 1 index. The pH, NO₃^--N, NH₄⁺-N, MAOC, TN, TP, and DOC significantly influenced bacterial communities, while DOC and pH were the key environmental factors shaping soil fungal communities. This study reveals the synergistic succession patterns among vegetation, soil, and microorganisms, providing a microbiological basis for high-latitude cold-region forest restoration under climate change.