Negative associations between aboveground and belowground biodiversity were primarily driven by specific microbial groups mediated by abiotic factors

Background and aims: Despite increasing evidence of strong relationships between plants and soil microbial communities, most studies on this topic have been controlled experimental studies at small spatial and temporal scales. Methods: In this study, we examined the relationships between tree communities and soil microbial communities by examining 1,287 soil samples collected from a 20-ha subtropical forest plot using high-throughput sequencing. Results: We found a negative association between above- and belowground biodiversity, primarily driven by the interactions between tree communities and six specific soil microbial genera (Bryobacter, ADurb.Bin063-1, Russula, Archaeorhizomyces, Tolypocladium, and Trichoderma). These interactions were mediated by abiotic factors, particularly metal elements, which were positively correlated with the relative abundance of these specific microbial groups but negatively correlated with tree richness. Random forest analysis revealed that Archaeorhizomyces was most strongly correlated to the total basal area of evergreen and deciduous trees. Additionally, structural equation modeling indicated that the indirect impact of abiotic factors on Archaeorhizomyces was mediated by the total basal area of trees. Conclusion: Overall, our results provide robust observational evidence for the intricate relationship between tree diversity and soil microbial communities at a large scale, revealing that specific microbial genera and abiotic factors, particularly metal elements, play crucial roles in regulating this relationship. Effective management of these interactions is essential for maintaining ecosystem function and resilience in subtropical forests.