Growth and physiology of mycorrhizal plants in soil containing enhanced non-segregating oil sands tailings
Creators: Wang, Gaosen
Publisher: name: University of Alberta Library
Year: 2024

<p>Open-pit mining of oil sands in Alberta, Canada, has resulted in a large-scale land disturbance of the boreal forest ecosystem and produced large amounts of tailings. To improve the effectiveness of the tailings solidification process and to make the tailings less harmful to vegetation, the novel oil sands tailings management technologies of the enhanced non-segregating tailings (eNST) and enhanced-spiked non-segregating tailings (esNST) have been developed. However, the full impact of these tailings on vegetation remains to be determined. Most plant species form symbiotic associations with fungi, which benefit plants, especially in poor-quality soils and under stressful conditions. The effects of eNST and esNST on the growth of mycorrhizal plants used for oil sands reclamation are little known. Therefore, in my thesis research, I carried out two studies to examine the growth and physiology of mycorrhizal plants growing in soil containing eNST and esNST.  In the first study, velvetleaf blueberry (Vaccinium myrtilloides) and Labrador tea (Ledum groenlandicum) were inoculated with Oidiodendron maius and Pezoloma ericae and grown in the peat mineral mix (PMM) that is commonly used as the reclamation soil, PMM/eNST (1:1, by volume), and PMM/esNST (1:1, by volume) for eight weeks. Then, the growth parameters, gas exchange, and tissue concentrations of chlorophyll and elements were measured in plants. The addition of eNST and esNST to PMM significantly increased the pH of the growth substrate and reduced its nutrient concentrations and water holding capacity. After eight weeks of treatments, both eNST and esNST significantly reduced velvetleaf blueberry and Labrador tea growth, reduced chlorophyll concentrations, net photosynthesis and transpiration rates, and increased leaf Na concentrations. Inoculation with the P. ericae and O. maius notably improved plant responses to tailings, with P. ericae showing more pronounced benefits. Compared with non-inoculated plants, mycorrhizal plants had lower leaf Na and B concentrations, higher P concentrations, as well as net photosynthesis rates, and dry weights, especially when exposed to esNST.  In the second study, jack pine (Pinus banksiana) and white spruce (Picea glauca) were inoculated with Laccaria bicolor and subjected to PMM (control), PMM/eNST (1:1, by volume), PMM/esNST (1:1, by volume), eNST, and esNST treatments for eight weeks. The growth of jack pine and white spruce was severely impaired by eNST and esNST, with significant reductions in chlorophyll concentration, net photosynthesis, and total dry weights. This may be partly attributed to imbalanced nutrient absorption due to high Na concentrations in the leaves. Jack pine was more sensitive to tailings compared with white spruce and exhibited greater growth reductions compared with white spruce. However, the addition of PMM significantly increased the concentrations of K and Ca in jack pine and white spruce needles, and the improved nutrient balance likely contributed to the alleviation of tailings effects on the physiology and growth of plants. Inoculation with L. bicolor further enhanced plant tolerance to tailings, reduced needle B concentrations in jack pine seedlings treated with eNST, and needle B and Na concentrations in white spruce seedlings treated with eNST and esNST. The improvement of physiology and growth of plants exposed to eNST and esNST by L. bicolor demonstrates the importance of mycorrhizal associations for plants in reclamation areas affected by oil sands tailings and their potential for improving revegetation efforts.</p>