Topsoil volume optimization in the restoration of post‐mined areas

Transferring topsoil to severely degraded areas, such as mined areas, is an effective restoration technique. However, topsoil from pristine areas is a limited resource, making it important to seek techniques that optimize its use. Thus, this study assessed the effects of adding a small topsoil volume (10 L/m2 or 1 cm layer), a seed mix of 14 species, and litter (30 L/m2) alone and in different combinations in the restoration of a rupestrian grassland area degraded by bauxite mining. The substrate in the degraded area was turned prior to applying treatments. Vegetation cover, density of individuals, and species richness were measured 30 months after the experiment was set up. The isolated use of each material and the simultaneous addition of topsoil to the seed mix were not effective. The simultaneous use of topsoil, litter, and seed mix provided the best result, presenting the highest vegetation coverage (60%), density (67 ind/m2), and species richness (26 in 12 m2). Although, to a lesser extent, the combination of seed mix and litter also presented satisfactory results. The combination of the three materials promoted the revegetation of an area that had been without vegetation for around 50 years, presenting a density of individuals and species richness comparable to those obtained with the use of thick topsoil layers (15–30 cm). Furthermore, the topsoil volume used was optimized.