Utilisation de bio intrants en vue d'améliorer la végétalisation des rejets miniers ferrifères en milieu nordique
|Advisor:||Boudreau, Stéphane; Khasa, Phambu|
|Abstract:||The Schefferville region is in the Labrador Trough, an important geological belt crossing Quebec and Labrador where most of the Canadian iron production is extracted. The extraction of iron ores in this region has resulted in large deposits of mine tailings (overburden and waste rock). Due to their poor physico-chemical characteristics for plant growth and the harsh climatic conditions, the natural colonization of these mining materials deposits by plant species is greatly limited. Considering the ecological functions of beneficial symbiotic associations between plants and soil fungi in natural ecosystems, as well as the usefulness of organic amendments such as biochar, peat moss and compost in improving the physico-chemical properties of depleted and destructured substrates, it was hypothesized that inoculation of seedlings of plant species native to the Schefferville area with native fungal isolates alone or in combination with organic amendments would allow the establishment of a plant community on these materials. To this end, in this thesis project, four experiments were conducted in the greenhouse with plant species native to the Schefferville region in the presence of fungal isolates isolated from their rhizosphere, and different organic amendments. The first experiment consisted in evaluating the growth capacity of Salix planifolia stem cuttings planted horizontally and vertically on waste rock, overburden, and peat moss. We obtained higher early shoot production, survival rate and biomass production of cuttings in overburden compared to waste rock. These results also indicated that horizontal cuttings had higher survival rates and quickly produced more shoots than vertical cuttings. Therefore, horizontal cuttings were dipped and inoculated with Rhizoscyphus ericae #22 and Meliniomyces sp and Phialocephala fortinii inocula in sterilized and unsterilized waste rock in the second experiment. Results suggested a limited response of cuttings to the inoculated fungal strains. The P. fortinii strain had a neutral effect on cutting survival rate, shoot production, and biomass production. In contrast, Rhizoscyphus ericae #22 and Meliniomyces sp showed some effect, although not very pronounced, on the performance of cuttings. In the 3rd experiment, we tested the impacts of 4 levels of peat moss and biochar, alone or in combination on the growth and establishment of Betula glandulosa and Alnus crispa seedlings on overburden. Results showed no positive effect of biochar or peat moss on seedling growth. The much-expected positive synergy between biochar and peat was not detected. In the 4th experiment, we explored the combined effects of compost and two fungal microbial consortia in the presence of B. glandulosa and A. crispa seedlings in waste rock. As expected, the combination of the two amendment sources did not stimulate seedling growth compared to an individual application. However, a contrasting effect of compost was detected, with a positive effect on B. glandulosa seedling growth and a neutral effect on A. crispa seedling growth. The native fungi consortium had a neutral effect on the growth of both plant species. In contrast, for A. crispa, the introduction of an exotic strain (Laccaria bicolor) reduced seedling growth. In conclusion, the various results obtained during this thesis project did not confirm the beneficial effect of inoculation treatments with different fungal strains and addition of organic amendments. However, they did demonstrate that the shrub species used can grow on the overburden, a substrate that could be used in subsequent restoration projects.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||10 January 2022|
|Collection:||Thèses et mémoires|
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