Soil and vegetation development along a 10-year restoration chronosequence in tailing dams in the Xiaoqinling gold region of Central China

Gold mining has increased sharply in response to global demand. Gold extraction usually causes the formation of tailing dams, in which organic matter and microbial activity decrease, and this consequently constrains plant growth. However, a full understanding of plant-soil interaction and plant community development in terms of natural restoration of gold mine tailing dam has not yet been developed. Three tailing dams, which had been naturally restored for 2 (R2), 5 (R5), and 10 (R10) years in the Xiaoqinlin gold region of Central China, were chosen to explore soil and plant community development in August, 2015. This study showed that soil bulk density and pH value were the lowest, whereas soil organic carbon, total nitrogen, microbial biomass carbon and nitrogen were the highest in the R10 tailing dam across two soil depths (0-10 cm and 10-20 cm). Soil organic carbon, total nitrogen, microbial biomass carbon and nitrogen decreased with soil depth across the restoration periods. The highest ratio of soil organic carbon to total nitrogen in the R10 tailing dam suggests that the rate of soil organic carbon accumulation may be restricted by the total nitrogen content in the long-term. Restoration stimulated plant community diversity and productivity, due to increment in soil nutrient content and microbial biomass carbon and nitrogen. The various ratios of root biomass to aboveground plant biomass among three tailing dams were caused by the shifting of the plant community composition from annual to perennial varietals. The mechanism by which plant-soil interaction and plant community composition change over time can be used to guide restoration programs in tailing dams in Central China.