FERTILIZATION TO OPTIMIZE GROWTH OF TREE SEEDLINGS ON RECLAIMED OIL SANDS SITES
Successful establishment of boreal tree seedlings like trembling aspen (Populus tremuloides Michx) and white spruce (Picea glauca (Moench) Voss.) in reclaimed oil sands mining sites is often limited by low nutrient availability and competition from the ground cover vegetation like planted cover crops and weeds. Competing vegetation can adversely affect seedling establishment by augmenting the impacts of moisture and nutrient stress. Despite high potential of barley (Hordeum vulgare L.) and oats (Avena sativa) as cover crops in oil sands reclamation, it was not well known how these crops interact with fertilization to influence early survival and growth of tree seedlings. This study evaluated the potential of fertilization and other silvicultural practices to improve revegetation success in oil sands sites reclaimed with peat-mineral mixture. Fertilizer application significantly increased height and root collar diameter (RCD) of tree seedlings in controlled environment greenhouse conditions, but not at a field research site near Fort McMurray, Alberta. In a greenhouse study, alleviating soil moisture stress significantly increased height, RCD, and biomass of tree seedlings. Vigorous growth of ground cover vegetation stimulated by fertilizer addition in both the greenhouse and field, largely controlled survival and growth responses of tree seedlings. Survival rates of tree seedlings were significantly decreased with increased fertilizer application rates, and no positive growth responses were observed in the field. Maximum seedlings survival (92%) was recorded without fertilization. Trembling aspen was sensitive to ground cover competition, whereas white spruce was unaffected. The inherent fertility of the peat-mineral mixture appeared sufficient for establishment and early growth of planted tree seedlings in recently reclaimed oil sands sites. Fertilization appeared to increase competition between tree seedlings and cover vegetation by promoting increased growth and competition for other resources like water. Effects on growth over the longer term (several years) should be evaluated in future studies.
Reclamation, Fertilization, Aspen and Spruce
Master of Science (M.Sc.)