Impacts of Amendments to Promote Mine Revegetation: Response of Perennial Native Plants
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Past mining activities in the United States have left a legacy of heavy metal contaminated soils that require remediation to allow for increased phytostabilization and reduced soil and water pollution. Of special concern to EPA’s Region 10 is the Formosa mine superfund site located in south-central Oregon. This site has a large area of acidic mine tailings where it is difficult to establish vegetation. In an in situ field study, we evaluated the effects of tilling the tailings (1) without adding any amendments, (2) with amendments (lime, biosolids) + potassium, (3) with amendments + biochar; and (1), (2) or (3) plus inoculation with locally-sourced microbes (LSM) on survival and growth responses of plants. Six perennial native plant species were used: Anaphalis maragitacea, Carex inops, Chamerion Angustifolium, Elymus glaucus, Lupinus sericeous, and Potentilla gracilis with responses determined over two years. Enhanced survival and growth was positively related for all species in amended plots with an increase in tailing pH and decreased tailing concentrations of extractable metals (e.g., Al, Cu, Fe, Mn, Zn) compared with unamended plots. There were no LSM effects to date. Elymus glaucus grew especially well and became dominant in the amendments + biochar plots over time. This study highlights the potential for soil amendments developed under the U.S. Environmental Protection Agency, Office of Research and Development and U.S. Department of Agriculture, Agricultural Research Service biochar research programs to improve soil chemistry and enhance plant growth; thus increasing the potential for success of vegetation reestablishment on degraded soils and mining impacted soils in Superfund sites across the United States.