Closure process of bauxite tailings facilities: The induction of ecological succession can enhance substrate quality in the initial phase of revegetation

Abstract

Within the mining sector, the revegetation process is increasingly recognized as a global imperative for the closure of tailings facilities. Nonetheless, revegetation strategies on bauxite tailings pose a substantial challenge due to very low or non-existent organic matter content in the substrate. The objective of this study was to investigate the efficacy of inducing ecological succession on bauxite tailings substrates. For this purpose, field experiments were conducted during twelve months with varying conditions of organic matter supplementation. In the control treatment (T3), only tree seedlings were planted on unamended tailings; the T2 treatment introduced both tree planting and green manure; the T1 treatment combined tree seedlings, green manure, and decaying wood. Dendrometry variables, phenological phases, litter production, mortality rate (M_r), and soil's physicochemical parameters (organic matter, soil bulk density, porosity, stability, and nutrient content) were assessed. The T1 treatment displayed the highest OM content (27.08 g kg⁻¹) and CEC values (3.40 cmol_c dm⁻³) at 0–5 cm. The highest biomass production by Crotalaria spectabilis Röth was obtained at T1 (7.81 t ha⁻¹), however, Canavalia ensiformis (L.) DC. produced similar amounts of biomass at T1 and T2. Among tree species, Hymenaea courbaril L. showed the highest mortality rate (16 %). The best results of natural colonization were observed at T2 (111 %). The induction of ecological succession enhanced chemical attributes in the surface layer and promoted the establishment of tree species during the initial stages of closing bauxite tailings facilities. The T1 treatment exhibited the most significant enhancements in substrate fertility within the 0–5 cm layer, T2 proved to be the most favorable for the spontaneous entry of shrub and tree species, and T3 represented the slowest method to achieve substrate improvements and plant colonization during the initial stages of revegetation.