Elymus glaucus rhizosphere microbial community response to phytoremediation amendments at the Formosa mine superfund site

Mining activities in the United States have left a legacy of heavy metal contaminated soils. The Formosa mine superfund site located in south-central Oregon is comprised of heavy metal-containing tailings from previous operations mining for copper, silver, zinc and gold. During rain and snowmelt events, leaching from tailings results in acidic water flows with high levels of contaminants entering local watersheds. Phytostabilization strategies to reduce these impacts require methods to mitigate low pH and high levels of heavy metals and provide nutrients for plants and plant-beneficial microbial populations. Addition of microbes from the uncontaminated surrounding area may also aid in plant establishment and growth. In this study, tailings at Formosa were tilled, amended, and planted with a mixture of native plants. Treatments included (1) no amendments, (2) amendments = [lime (pH mitigation) + biosolids (nutrient source)] + 2.5% biochar (heavy metal adsorption), (3) amendments + potassium equivalent to 2.5% biochar; and (1), (2) or (3) plus inoculation with locally-sourced microbes (LSM). Six perennial native plant species were planted: Anaphalis maragitacea, Carex inops, Chamerion Angustifolium, Elymus glaucus, Lupinus sericeous, and Potentilla gracilis. Rhizosphere and surrounding soils were collected from surviving E. glaucus plants and microbial community analysis performed.