Keynote Speech (Soil microbial community shows clear changes in soil recovery process in a tin-mining area on Belitung Island, Indonesia.)

Abstract

Mineral mining often alters the soil environment and reduces the sustainability of the surrounding environment. Recovery of soil physical and chemical properties after tin mining on tropical Belitung Island, Indonesia, has been a painstaking process, even after more than 100 years of reclamation. This study aimed to determine which parameters of soil properties are responsible for the slow recovery and whether there are other properties that show more rapid changes. Physical, chemical, and biological properties of the soil were measured at different time periods after tin mining: soil samples were collected from three areas at 0-, 1-, and 6-years postmining and from an adjacent natural forest as a reference site. Soil moisture, 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 decrease in particulate matter and, despite the absence of clay, a significant increase in water holding capacity and a 0.2% increase in organic carbon after 6 years. Copper, iron, manganese, and zinc in the soil changed little. Lead and cadmium were present in very small amounts. The soil bacterial community clearly varied with the age of the land, with actinobacteria predominating in the first few years after mining, but after 6 years, proteobacteria had established themselves in the mined area. The degree of land recovery was more clearly described by including the results of the microbial community analysis in the principal component analysis. This study examined more clear changes in soil properties on land after tropical tin mining. Soil and bacterial properties can be used as markers to monitor land restoration progress.