Active rehabilitation of Amazonian sand mines converges soils, plant communities and environmental status to their predisturbance levels

Abstract

The continuous monitoring of mineland rehabilitation is paramount for identifying deviations from desired trajectories and providing assessments for environmental agencies. In this study, we analyzed soil texture and chemical properties, vegetation development and soil respiration along rehabilitation chronosequences including nonrehabilitated areas, areas at different rehabilitation stages and reference sites covered by native forests in three sand mines in the Carajás National Forest, eastern Amazonia, Brazil, to estimate their rehabilitation status. For nine environmental variables related to ecological processes, vegetation structure, and community diversity, we computed response ratios in relation to predisturbance levels found in native reference sites and integrated them into an index of rehabilitation status using a multivariate approach. Our analyses showed that the soil chemical properties and tree community composition of the rehabilitated minelands converged over time to those of native ecosystems. All environmental indicators and the overall rehabilitation status increased with rehabilitation time, indicating that rehabilitation interventions set the rehabilitation trajectory on a desired path. Although most indicators did not achieve predisturbance levels, we conclude that rehabilitation activities can effectively reduce the environmental impacts of sand extraction in Amazonia over short time periods, thereby contributing to the recovery of ecosystem services and the protection of biodiversity.