The exploitation of mineral resources may present important environmental consequences, among which the accumulation of mine tailings and the emission of greenhouse gases (GHG). Non-acidic mine tailings entails land-use change, airborne dust nuisance, and degradation of the landscape, when GHG emissions and land use change contributes to global warming.
The reforestation of mine tailings is suggested as an approach to both restore site productivity and to offset GHG emissions. Since non-acidic tailings are believed to exhibit physicochemical characteristics hostile to plant growth (low fertility, cation exchange capacity and organic matter content), the use of organic amendments could counter these limitations and allow shrub and tree species to establish and grow thus fostering ecosystem reconstruction and net CO2 uptake. The present study was designed to determine which combination of amendments and planted woody species is most favorable for the reclamation of mine tailings. An experimental design at Mont-Wright (ArcelorMittal, Fermont, QC, Canada; 52°46’N, 67°20’O) was established to compare three soil substrates, three organic amendments – pulp and paper mill sludge (PPMS), forest humus (topsoil), or the “Norco” mixture, composed of chicken manure and a grass species mix – and three woody species – Pinus banksiana, Alnus crispa and a Pop sp. clone. Soil samples and plants were collected at different occasions during the first growing season to obtain data on fertility, carbon stocking, microbiology, survival and growth rates.
Results/Conclusions
Statistical analyses revealed that forest humus significantly promotes the survival and growth of woody species, compared to the other organic amendments tested. In addition to the beneficial effect on plants, this amendment increased the concentrations of P, K, Ca, Mg, and Fe in the root environment of plants. The addition of topsoil also significantly reduced the soil bulk density, base saturation (S.B.) and pH. These modifications of the physicochemical properties suggest a path towards enhanced soil support capacity, allowing an increased retention of nutrients that make them available for plant growth and microorganisms, altogether promoting the establishment of a cover of woody plants. After one year of growth, all of the planted woody species performed similarly.