Abstract

Re-vegetation of mine waste environments faces numerous challenges: from geochemical and physical barriers to plant establishment, need for organic substrates, growth of beneficial microbes and nutrient availability, and promoting long-term sustainability of vegetative covers. In this presentation we will look at 2 studies focussed on the on Ni-Cu rich sulfide tailings and waste rock in the Sudbury, Ontario mining camp. In the first study we will discuss the application of blended municipal compost and biosolids at a tailings management area and compare the performance of blends of lime stabilized municipal biosolids and compost at nine different rates over thick (1 m) municipal compost covers planted with agricultural crops. Based on biogeochemical variability of the substrates four and ten years after application of the initial compost cover, the experimental plots could be classified into three categories: “Low” rate (0–100 t ha−1 biosolids), “Medium” rate (200–800 t ha−1), and “High” rate (1600–3200 t ha−1) treatments. We found that biosolids addition reduced C:N ratio and available phosphorus in the cover. Inorganic carbon and solubility of Ni and Cu increased by biosolids addition. Biosolids addition also reduced abundance of microorganisms involved in humification. In the second study we investigated vegetation community dynamics after 48 years of succession along two legacy Ni–Cu mine tailings and waste rock deposits with and without various site amendments (i.e. liming and fertilization) and planting. Metal/acid tolerant pioneer plants (Betula papyrifera, Populus tremuloides, Pohlia nutans) appeared to facilitate the establishment of less tolerant species. Conifers and nitrogen-fixers less tolerant to site conditions were planted at the fully amended (limed, fertilized, planted) mine tailings site in the 1970s, but conifers were not propagating at the site or facilitating understory succession. The planted nitrogen-fixing leguminous species Lotus corniculatus was, however, associated with increased diversity. Together these studies have implications for long-term reclamation strategies in acidic mine waste deposits contrasting organic vs. chemical amendments and their ability to support sustainable vegetation communities.