Native Plant Restoration of Copper Mine Tailings: I. Substrate Effect on Growth and Nutritional Status in a Greenhouse Study

Copper mine tailings are difficult to revegetate using native plants unless amendments are added to reduce acidity, decrease metal solubility, and improve nutrient availability. In this study, the effects of two amendments were tested for their ability to improve growth and survival of two native plant species growing in copper mine tailings. Unamended tailings from an abandoned copper mine in Washington State were compared with native soil, sandy gravel from local glacial outwash, tailings with a 15‐cm sandy gravel cap, and biosolids with sandy gravel over tailings. Two native plants, Sitka alder [Alnus viridis subsp. sinuata (Regel) A. Love & D. Love] and pearly everlasting [Anaphalis margaritacea (L.) Benth. & Hook. f.], were grown in a greenhouse for 3 to 4 mo in pots of each substrate. Plant biomass was determined and elemental composition of plant tissues were compared among substrates. Survival of both species was 100% in all treatments, but biomass production varied greatly among treatments, with the highest growth in the biosolids and gravel amendment and lowest growth in unamended tailings. Nutrient content varied by species and substrate with high AI concentrations in Sitka alder. Results suggest that N availability is most limiting to pearly everlasting and P is most limiting to Sitka alder. Use of biosolids in conjunction with gravel appears to be an effective tailings amendment.