Phytostabilization of acidic mine tailings with biochar, biosolids, lime, and locally-sourced microbial inoculum: Do amendment mixtures influence plant growth, tailing chemistry, and microbial composition?

Abandoned mine lands present persistent environmental challenges to ecosystems and economies; reclamation is an important step for overcoming these challenges. Phytostabilization is an elegant and cost-effective reclamation strategy, however, establishing plants on severely degraded soils is problematic, often requiring soil amendments. We evaluated whether amendment mixtures composed of lime, biochar, biosolids, and locallysourced microbial inoculum (LSM) could alleviate the constraints that hinder phytostabilization success. We hypothesized that 1) plants grown in tailings amended with lime, biochar, and biosolids (LBB) would establish faster and grow larger than plants grown in tailings amended with lime only, and 2) the LSM source would influence microbial community function and structure in amended mine tailings. We conducted a greenhouse study that simulated in situ conditions to measure the influence of LBB-LSM amendment blends on plant growth, plant nutrients, metal concentrations, microbial function, and microbial community structure. Blue wildrye [Elymus glaucus Buckley ssp. Jepsonii (Burtt Davy) Gould] was grown in tailings collected from the Formosa mine site amended with various combinations of LBB-LSM. The above and belowground biomass of plants grown in mine tailings amended with LBB was 3 to 4 times larger than the biomass of plants grown in tailings amended only with lime. Although the LSM addition did not influence immediate plant growth, it did affect nutrient content and altered the rhizosphere community composition. As such, it is not yet clear if LSM-driven alterations in microbial membership will advance mine reclamation strategies by improving long-term growth.