Some areas near Flin Flon, MB and Creighton, SK are devoid of vegetation due to a variety of mining, smelting, forestry activities and forest fires that have occurred since the 1930’s. This study investigated the use of soil amendments to enhance revegetation in these areas. The study was comprised of two main components, an in situ study and a growth chamber trial. The in situ component was conducted to determine the efficacy of soil amendments that could be utilized in a revegetation program. The growth chamber trial examined if the amount of moisture present in the soil would have an influence on the success of vegetation survival and growth. The in situ study was conducted near Flin Flon, MB and Creighton, SK over two growing seasons and consisted of replicated treatments imposed at 12 sites. Tree seedlings [trembling aspen (Populus tremuloides Michx.) and jack pine (Pinus banksiana Lamb.)] and understory species [tufted hairgrass (Deschampsia cespitosa L.) and American vetch (Vicia americana Muhl.)] were planted at each site. Each site also received soil amendments; bone meal and meat biochar (BMB), compost, commercial mycorrhizal inoculant (EMF) and, willow biochar (WB) in combination with dolomitic limestone and fertilizer. Each site also had a control that received an application of only dolomitic limestone and fertilizer. The growth chamber trial utilized the same plant species and soil amendments as the field trial with the exclusion of willow biochar. In general, soil amendments did not influence the survival or growth of the tree seedlings in situ or in the growth chamber trial. However, the compost amendment increased survival and growth of the tufted hairgrass significantly in the growth chamber trial and to a lesser extent in the field trial. Compost also positively influenced the pH and base saturation of the soil compared to the other amendments. The mycorrhizal inoculant increased the rate of mortality of tree species in the growth chamber trial. Moisture did not influence the survival and growth of the seedlings or understory species or the efficacy of the amendment treatments in this study.

HudBay Minerals (formerly the Hudson Bay Mining and Smelting Co., Limited) has operated a Zn and Cu processing facility in Flin Flon, MB since the 1930’s. Located in the Boreal Shield, the area surrounding the mine complex has been severely impacted by both natural (forest fires) and the anthropogenic disturbance, which has adversely affected recovery of the local forest ecosystem. Zinc is one of the most prevalent smelter-derived metals in the soils and has been identified as a key factor limiting natural revegetation of the landscape. Because metal toxicity is related more to speciation than to total concentration, Zn speciation in soils from the impacted landscape was characterized using X-ray absorption fine structure, X-ray fluorescence mapping and µ-X-ray absorption near edge structure. Beginning with speciation at a micro-scale and transitioning to bulk speciation was able to determine Zn speciation and link it to two distinct landform characteristics: (1) soils stabilized by metal tolerant grass species—in which secondary adsorption species of Zn (i.e., sorbed to Mn and Si oxides, and as outer-sphere adsorbed Zn) were found to be more abundant; and (2) eroded, sparsely vegetated soils in mid to upper slope positions that were dominated almost entirely by smelter derived Zn minerals, specifically Franklinite (ZnFe2O4). The long-term effect of liming on pH and Zn speciation was examined using field sites limed by a community led organization over a ten year period. Upon liming to a pH of 4 to 4.5, the eroded, sparsely vegetated soils where found to form a Zn-Al-Hydroxy Interlayer Material (HIM) co-precipitate, reducing the phytotoxicity of both Zn and Al and allowed for boreal forest vegetation to recovery quickly in these areas. The grass stabilized soils experienced a steady pH increase, as compared to a sporadic pH increase in the heavily eroded soils, as the buffering capacity was overcome allowing for a transition between multiple adsorption species based upon the point of zero charge of reactive soil elements. Ultimately reaching a near neutral pH after ten years, this allowed for the formation of stable Zn-Al-layered double hydroxide (LDH) soil precipitates and significantly reduced concentrations of plant available Zn.