Plant Establishment on Angle of Repose Mine Waste Dumps

Angle of repose slopes associated with mine waste dumps are difficult to revegetate due to steep slope angle, poor soil properties, and potential for extensive soil erosion. We examined the extent that seed movement, seedling establishment, soil characteristics, nutrient availability, and water availability were responsible for limiting plant establishment or survival on steep (average slope ~80%), south-facing angle of repose slopes at a gold mine north of Elko, Nev. Four treatments were established: 1) unaltered mine waste soil; 2) mine waste soil with fertilizer; 3) mine waste soil draped with at least 0.3 m of a fine-textured coversoil; and 4) treatments 2 and 3 combined. All treatments had study plots that received either broadcast seeds or containerized transplants. Seedlings from broadcast seeds only emerged on plots that were coversoiled, but transplants survived in all treatments. Thus, coversoiling was necessary at this site for seedling germination and establishment, but survival of transplants in unaltered mine waste soil indicated that nutrient availability, soil-root contact, and water availability were sufficient for plant survival. In addition, long distance transport of seeds down stable, angle of repose slopes was not detected during the first growing season after seeding, indicating that the lack of seedlings on angle of repose slopes was not due to movement of seeds down-slope. However, coversoiling resulted in unstable slope surfaces; both erosion and soil mass wastage were observed on coversoiled treatments. Thus, although coversoiling increased establishment and survival of plants on angle of repose slopes, slope stabilization is necessary to ensure the success of revegetation efforts and to prevent the coversoil from eroding and moving downslope.