Peatland degradation restructures microbial communities and reduces soil multifunctionality through amplified β-diversity turnover

Soil multifunctionality (SMF) integrates multiple ecosystem processes essential for ecosystem stability, organic matter decomposition, nutrient transformation, and energy flow. Peatlands occupy a small fraction of the terrestrial surface, yet their high water tables and anaerobic conditions sustain diverse biogeochemical processes and relatively high SMF. However, drainage, climate change, and intensified human activities disrupt these conditions and drive widespread peatland degradation. Here, we integrated two field experiments from Northeast China with a global meta-analysis of 54 studies to assess how peatland degradation affects soil microbial communities and SMF. Degradation increased soil pH, reduced lignin- and lipid-rich structural carbon, enhanced hydrolytic enzyme activity, elevated CO2 emissions, and ultimately lowered SMF. Land-use conversion exerted substantially stronger negative effects on SMF than natural peatland degradation. In both bacterial and fungal communities, changes in microbial β diversity consistently exceeded those in α diversity across degraded peatlands. Random forest and structural equation modelling identified β diversity as the strongest predictor of SMF. Meta-analysis results further confirmed that peatland degradation consistently reshapes microbial community composition, while effects on α diversity remain limited. Overall, shifts in microbial β diversity emerge as a key mechanism constraining peatland SMF, providing insights into how degradation alters soil processes and ecosystem functioning.