Native Plant Restoration of Copper Mine Tailings: II. Field Survival, Growth, and Nutrient Uptake

Abstract

AbstractCopper mine tailings are difficult to revegetate due to nutrient deficiencies, high acidity, and metal toxicities. Despite these poor substrate properties, native species may be preferred for restoration for ecological and economic reasons, as they may require less long‐term maintenance. In this study, amended and unamended mine tailings are contrasted with a natural soil and gravel for factors potentially limiting to growth. Twelve individuals of five native species (big‐leaf maple, western yarrow, Sitka alder, pearly everlasting, and fireweed) were grown in five different field plots. Plots consisted of: (i) copper mine tailings, (ii) natural soil, (iii) 15 cm of gravel over tailings, (iv) biosolids plus wood chips with 15 cm gravel over tailings, and (v) gravel. Survival was highly variable by species and plot type, with highest survival among all species with pearly everlasting, and highest survival by treatment with the natural soil and biosolids plus wood chips with gravel over tailings. Treatments resulted in a significant difference (p = 0.05) in species biomass production, with the biosolids resulting in highest biomass in all species except big‐leaf maple. Plant nutrient content was also higher with the biosolids. The tailings were extremely acidic and had high exchangeable AI. Sitka alder was most tolerant of the tailings, despite high AI uptake, and was productive across all plot types, possibly due to its tolerance of metals and high nutrient use efficiency. Both Sitka alder and pearly everlasting show promise for revegetating copper mine tailings, although with a biosolids and gravel amendment other native species may do equally well.