Microbial community shifts indicate recovery of soil physical properties in a post-tin-mining area on Belitung Island, Indonesia

Mineral mining often results in changes to the soil environment, reducing the sustainability of the surrounding environment. Restoring the physical and chemical properties of soil in post-tin-mining areas on the tropical island of Belitung, Indonesia, has been a laborious process after more than 10 decades of land reclamation. We aimed to determine which parameter of the soil properties was responsible for the slow recovery process and if there were other properties that indicated more rapid changes. We measured the physical, chemical, and biological properties of soils of different periods in the post-tin-mining areas. We sampled soil from three areas: 0, 1, and 6 years after mining and an adjacent natural forest as a reference site. The soil water content, hydraulic conductivity, bulk density, particle distribution, mineral content, and soil microbial composition were measured in the field and analyzed in the laboratory. The soil showed a fine particle loss and despite the absence of clay, water-holding capacity was significantly increased in the 6-year-old soil. Organic carbon increased by 0.2% after 6 years of reclamation. Copper, iron, manganese, and zinc in the soils fluctuated less. Minimal amounts of Pb and Cd were found. Soil bacterial communities shift with land age. Actinobacteria were dominant a few years after mining, while Proteobacteria colonized the mined area after 6 years. This study examined the more profound changes in the soil properties of tropical post-tin-mined land. Soil and bacterial characteristics can be used as markers to monitor the progress of land rehabilitation.