Bacterial richness is negatively related to potential soil multifunctionality in a degraded alpine meadow

Fungal richness and community composition are known to be positively associated with soil multifunctionality. However, the contributions of bacterial and fungal communities to the multiple soil functions of alpine meadow ecosystems have not been widely examined. Here, we surveyed the soil in Qinghai-Tibetan alpine meadows and classified the extent of degradation as undegraded, lightly degraded, moderately degraded, and severely degraded to clarify the associations between microbial diversity (including bacteria and fungi) and potential soil multifunctionality. Bacterial and fungal compositions were detected by sequencing of the 16S rDNA and internal transcribed spacer amplicons, respectively. Functions associated with nutrient cycling (dissolved organic nitrogen and carbon, available phosphorus, NO3–, NH4+, C, N, P-cycle enzymes) and climate regulation (CO2 and N2O emissions) were also examined. Bacterial, rather than fungal, richness was negatively associated with potential soil multifunctionality, which decreased along the degradation gradient. Structural equation modeling explained 79.6% of the variation in potential soil multifunctionality and confirmed that, in addition to bacterial community richness and composition, organic carbon and moisture were important drivers of potential soil multifunctionality. These results suggest that higher bacterial richness is associated with lower potential soil multifunctionality in alpine meadow ecosystems. Among the bacterial taxa, only ~ 12% of bacterial genera were identified as predictors of multifunctionality, suggesting functional redundancy of the bacterial community in the meadow ecosystem. Rhodanobacter, Mucilaginibacter, Rhodococcus, and Bosea, belonging to the Proteobacteria and the Actinobacteria phyla were identified as critical for maintaining potential soil multifunctionality. Our results suggest that bacterial richness is negatively related to potential soil multifunctionality in alpine meadow ecosystems and there is no correlation between potential multifunctionality and fungal richness.