Mining activities come with environmental issues, like residue production and greenhouse gas (GHG) emissions. The reclamation of non-acidic mine tailings by planting trees is promising in order to both restore the degraded ecosystems and offset GHG emissions. Given their low inherent soil content of organic carbon (SOC), and the revegetation with perennial grasses as the business as usual prescription, the reforestation of non-acidic mine tailings shows significant potential as a mitigation measure by creating a carbon sink through organic matter accumulation in the biota. In this field experiment on reclaimed non-acidic mine tailings at the Niobec site (St-Honoré, QC, Canada), the amendment of tailing surfaces with an industrial organic waste (paper mill sludge (PMS)) was compared to a conventional organic amendment (liquid cattle manure or LCM) as alternative methods promoting reclamation success. Three planted woody species – Alnus viridis ssp. crispa, Picea glauca and Picea abies – were combined to two herbaceous plant mixes (low-growing mix (LGM), high-growing mix (HGM)) representing the baseline scenario. The soil variables measured to evaluate site support capacity were the concentration of P, K, Ca, Mg, mineral N and potentially mineralizable N, cation exchange capacity (CEC), base saturation (BS), bulk density and water stable aggregates. The survival and growth rates, dry mass and nutrient status (N, P, K, Ca and Mg) of the planted seedlings were also monitored during the first year after reforestation.
Overall, the alders showed the highest growth and biomass accretion rates among planted woody species after one year of growth. The amendments did not significantly influence the morphological variables of both white and Norwegian spruces, while the alder dry mass was significantly decreased by the amendment with PMS. The use of LGM increased growth rates of all planted species. The LCM decreased the concentration of certain soil nutrients, mostly when used with LGM. The use of LCM with LGM also decreased the P/Al ratio, potentially allowing further leaching of P in the environment. The PMS increased foliage concentrations of certain nutrients for white spruce, while Norwegian spruce and alder responded differently in presence of this amendment. This study gives important information on the early response of woody plant growth and nutrition and soil physicochemical properties related to different reclamation methods, and new GHG mitigation approaches.