Manganese tolerance and phytoremediation potential of Schima superba: Implications for sustainable biomass utilization and mine land restoration

Heavy metal stress poses a serious threat to plant health, soil fertility and ecosystem stability. This study investigated the extent of heavy metal contamination in mining affected soils of Hezhou, China and evaluated the phytoextraction potential of ten native woody plant species. Soil and plant tissues were analyzed for cadmium, chromium, copper, manganese, nickel, lead, and zinc concentrations. Soil contamination was evaluated using the pollution index, index of geo-accumulation, and potential ecological risk index, while phytoremediation potential was evaluated through bio-concentration factor, bio-accumulation factor, translocation factor, and metal accumulation patterns. Manganese (Mn) was the dominant contaminant in both soils and plant tissues, followed by nickel and zinc. Plant species exhibited significant variations in their metal accumulation capacities, with Schima superba exhibiting the highest Mn accumulation, reaching 13,487.81 mg kg⁻¹ in leaves and displaying TF values greater than 6.0, indicating strong Mn uptake, translocation ability and its hyperaccumulator characteristics. To further investigate Mn tolerance mechanisms, Schima superba seedlings were exposed to different Mn concentrations under controlled conditions. Mn (100 mmol · L −1 ) significantly enhanced plant biomass and antioxidant activities of SOD, POD, CAT, accompanied by elevated MDA and proline accumulation after 10 d post treatment. Furthermore, Mantel analysis revealed strong positive associations between antioxidant defense responses and growth traits, with the strongest correlation observed between SOD and CAT (r = 0.97, P < 0.001), suggesting coordinated antioxidant regulation under Mn stress. These findings demonstrated that Schima superba is a promising native woody species for Mn phytoremediation and ecological restoration. Its high biomass production also provides opportunities for future biomass valorization, linking mine-land restoration with sustainable bioresource utilization and circular bioeconomy strategies.