Bio-intrusion barrier made of plants with allelopathic effects to improve long term perfomance of cover with capillary barrier effects

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Acid mine drainage (AMD) resulting from oxidation of sulphide minerals contained in mine wastes is undoubtedly the more serious environmental problem of the mining industry. To avoid AMD generation, covers with capillary barrier effects (CCBE) can be built to limit oxygen availability for the underlying acid generating mine waste. Even if the performance of CCBEs has been demonstrated in the field over the short-term, the long-term efficiency still has to be proven. One of the factors that could affect the long-term performance of CCBE is bio-intrusion, more specifically tree roots. This project aims at evaluating the capacity of bio-intrusion barrier made of plants with allelopathic effects to limit long term deterioration of CCBE caused by tree-root invasion. Allelopathic effects (AE) can be defined as the inhibition of germination and growth of a certain species of plant, by the use of another. To reach the project objectives, three plant species with allelopathic effects: Bluejoint reedgrass, sheep laurel and bog Labrador tea will be propagated within 120 experimental plots (3m x 3m). Two-year seedlings of trembling aspen, balsam poplar, black spruce, speckled alder and willow (identified as the most problematic species for the long term stability of the LTA CCBE) will be planted in the experimental plots. Different approaches will be used to evaluate the impact of plants with allelopathic effects on the targeted trees: the evolution of morphological characteristics of the trees, roots architecture, chemical analysis of plant tissue, soil and water. In parallel, the influence of the plants with AE on the CCBE water budget will be evaluated to see if the plants affect the performance to limit oxygen migration. At the end, the proposed project will give answers to some fundamental biological questions about allelopathic compounds and root properties interactions, as well as developing a practical approach for the design of bio-intrusion barriers on CCBE.