Recovery of soil phosphorus on former bauxite mines through tropical forest restoration

Abstract

Soil phosphorus (P) is a major driver of forest development and a critically limited nutrient in tropical soils, especially when topsoil is removed by mining. This nutrient can be present in soils in the form of different fractions, which have direct consequences for P availability to plants and, consequently, for restoration success. Therefore, understanding how the stocks of different soil P fractions change over the restoration process can be essential for guiding restoration interventions, monitoring, and adaptive management. Here, we investigated the recovery of soil P fractions by forest restoration interventions on bauxite mine sites in the Brazilian Atlantic Forest. We assessed the concentration of different fractions of soil organic and inorganic P at (1) a bauxite mine prepared for restoration; (2) two former bauxite mines undergoing forest restoration for 6 and 24 years; and (3) an old-growth forest remnant. Overall, restored areas recovered levels of labile organic P (P o-NaHCO 3) at 5-40 cm and of moderately labile organic P (P o-NaOH) at different depths, exhibiting concentrations similar to those found in a conserved forest. The use of P-rich fertilizers and forest topsoil may have greatly contributed to this outcome. Some other fractions, however, recovered only after 24 years of restoration. Other inorganic P fractions did not differ among mined, restored, and conserved sites: nonlabile P i (residual P and P-HCl), labile P i (P i-NaHCO 3), and moderately labile P i (P i-NaOH). Forest restoration was able to promote efficient recovery of important soil P fractions, highlighting the value of restoration efforts to mitigate soil degradation by mining.

Multifunctional soil recovery during the restoration of Brazil's Atlantic Forest after bauxite mining

“…So its fast accumulation in ecosystems undergoing restoration is critical for their ecological sustainability. An earlier study conducted in the same region showed that restoration interventions successfully recovered different P fractions (Bizuti et al., 2020), which may have been key to enhance primary productivity and litter production, given the naturally low levels of P in tropical soils, especially in mined substrates (Shrestha & Lal, 2011; Vitousek et al., 2010).…”

“…Mining is one of the most profitable activities in the world, but it is also one of the most damaging on the environment. Often located in high‐diversity and endangered ecosystems, like the Jarrah Forests in Australia (Koch & Hobbs, 2007), the Atlantic Forest of Brazil (Bizuti et al., 2020) or the Congo Basin Forest in Africa (Edwards et al., 2014), mining activities jeopardize biodiversity and ecosystem functioning through the removal of vegetation and topsoil. As a consequence, mining is often associated with a strong reduction of organic matter and nutrient stocks in the soil (Tripathi et al., 2016).…”

“…the organic surface layer of soils) after stripping. The rehabilitation of mined sites with topsoil respreading was shown to allow for the recovery of nutrient cycling (Quintela‐Sabarís et al., 2018), soil organic carbon (Rivera et al., 2014), soil microbial communities (Banning et al., 2011), P fractions (Bizuti et al., 2020) and vegetation composition and growth (Koch, 2007). These studies have focused on one or few facets of soil recovery in mined sites, thus lacking a comprehensive, holistic overview of soil health (Rinot et al., 2019).…”

Phosphorus adsorption in a degraded soil under forestry recovery after bauxite mining in Paragominas, eastern Amazon, Brazil

“…To mitigate phosphorus deficiency in tropical soils, especially in areas under recovery, it is common to apply high doses of phosphate fertilizers aiming for a more efficient growth of vegetation, which often does not occur due to the dynamics of adsorption. Therefore, studies involving soil P adsorption and availability are important for the success of soil fertilization programs, especially in forest recovery projects (Bizuti et al, 2020).…”

Phosphorus supply affects seedling growth of mycorrhizal but not cluster-root forming jarrah-forest species

“…Fertiliser is prescribed for ecological restoration where there is insufficient quantity or availability of soil nutrients (Whisenant 1999). Consequently, the application of fertiliser is considered necessary, to replace nutrients lost in vegetation and soils, and best practice, to kickstart restoration of native plants and ecosystems after surface mining in Brazil, Canada, and Australia (Bizuti et al 2020;Pinno et al 2012;Tibbett 2010). Yet, in other restoration contexts the removal of soil nutrients is often required to kickstart restoration (e.g.…”