Dominant Effect of Ecological Restoration on Microbial Carbon Cycle in Plant Rhizosphere of Mining Areas

Rhizosphere microorganisms play critical roles in biogeochemical processes including carbon cycling; however, their linkages to carbon-cycling functions under distinct mine restoration approaches remain unclear. In this study, we compared natural and artificial vegetation restoration via metagenomic sequencing to characterize rhizosphere microbial communities and carbon-cycling functional genes. Artificial restoration (AR) decreased soil electrical conductivity (EC) and salt content (SC) while increasing total phosphorus and available phosphorus by 12.33% and 16.44%, respectively. AR also elevated the relative abundances of genes responsible for degrading aromatic compounds, lignin and starch, along with genes participating in carbon-fixation pathways. Taxa of the Actinomycetia, Chloroflexi, and Solirubrobacterales served as the primary contributors to genes encoding 2-isopropylmalate synthase, α-glucosidase, malate synthase, and α-mannosidase, as well as carbon-fixation-related genes, including aconitate hydratase (ACO), methylmalonyl-CoA mutase subunit (E5.4.99.2A), pyruvate orthophosphate dikinase (ppdK), and phosphoenolpyruvate carboxylase (ppc). Moreover, the relative abundances of carbon-fixation genes exhibited significant positive correlations with EC, SC, nitrate nitrogen (NO3−-N) and ammonium nitrogen (NH4+-N). Overall, microorganisms in AR soils hold relatively high genetic potential for carbon sequestration and decomposition. Such rhizosphere carbon-cycling functions are jointly shaped by restoration strategies and vegetation community composition, and our findings offer key theoretical support for mine ecological restoration.