Mining Tailings Effects on Soil Quality and Performance of Two Native Species of Atlantic Forest: Implications for Restoration

Mining activities significantly contribute to environmental pollution by releasing chemical contaminants into ecosystems, making natural recovery challenging. In this study, we amended the mining tailings from the Fundão dam with reference soil to simulate the heterogeneity of tailings concentrations to which native species are exposed. We aimed to identify the tailings concentration that best supports the development of two native species, Deguelia costata and Peltophorum dubium. Our results showed that substrates with lower concentration of tailings had an increase in organic matter content and higher acidity. In contrast, substrates with higher tailings concentration showed increased levels of toxic metals; yet these metals seemed not to be readily available to plants, as evidenced by the enhanced biomass accumulation and improved seedling quality in these subtracts. Conversely, the reference soil, being nutritionally deficient and acidic, may have led to increased absorption of toxic metals by the plants. This resulted in reduced growth and increased activity of antioxidant enzymes and synthesis of flavonoids. Both species selectively accumulated iron in the roots and manganese in the leaves, without reaching phytotoxic levels. The findings unequivocally demonstrate that D. costata and P. dubium exhibited remarkable resilience by successfully thriving and growing in highly contaminated substrates (up to 100% mining tailings). Hence, both D. costata and P. dubium prove to be highly suitable candidates for the restoration of areas devastated by iron mining activities.