Bacterial Communities Are Strongly Associated with Soil Multifunctionality During Revegetation of Copper Mine Wastelands

Vegetation restoration is critical for ecosystem recovery in abandoned mining areas, yet how restoration age affects soil multifunctionality (SMF) and the underlying microbial regulatory mechanisms remains poorly understood. The space-for-time substitution method was employed in this study. Along a revegetation chronosequence (Restoration 1 year (R1), Restoration 10 year (R10), Restoration 30 year (R30), Restoration 45 year (R45)) in copper mine wasteland in Tongling, China, the dynamics of soil functions, SMF, and microbial communities were quantified, with the key factors influencing soil functions and the most important predictors of SMF subsequently identified. The results showed that the soil moisture regulation function recovered relatively slowly, whereas nutrient cycling functions and SMF were generally enhanced with advancing revegetation. Specifically, these functions all reached their maximum values at R30 (0.39, 0.45, and 0.28, respectively), followed by declines at R45 (−0.74, −0.09, and −0.20, respectively). Furthermore, the soil microbial communities exhibited successional characteristics of increased diversity but reduced dominance. Redundancy analysis indicated that aboveground biomass (AGB), belowground biomass (UGB), and soil total copper were key environmental variables associated with variations in multiple soil functions. Linear regression analysis showed that fungal diversity indices, plant biomass (AGB and UGB), soil total cadmium, and soil total zinc exhibited significant linear relationships with SMF. Random forest analysis further identified UGB, bacterial Simpson index, and fungal Shannon–Wiener index as key predictors of SMF. Importantly, bacterial communities played a more important role in influencing SMF than fungal communities. These results advance the understanding of key drivers of ecosystem functional recovery in mine lands and provide a theoretical basis for optimizing soil function restoration strategies. Ultimately, these findings provide new insights for advancing efforts aimed at halting land degradation and safeguarding biodiversity in degraded mining ecosystems.