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Effects of Canada Bluejoint Grass Competition, N Fertilization, and Litter Layer Removal on Soil N Processes and Tree Growth

Matsushima, M. 2005. M.Sc. Thesis. Dept. Renewable Resources, University of Alberta, Edmonton, AB


The mechanisms of Canada bluejoint grass (Calamagrostis canadensis (Michx.) Beauv.) competition is not well understood. I examined the effects of competition, N fertilization, and litter layer removal on soil N processes and the growth of planted white spruce (Picea glauca (Moench.) Voss). Weed and litter removal increased soil temperature and net N mineralization (in mineral soil) and nitrification rates (in LFH and mineral soil). Litter removal increased litter decomposition rates, probably due to increased soil temperature. Nitrogen fertilization increased N mineralization rates but also the growth of bluejoint in the field experiment. Weed control significantly increased tree diameter growth, and foliar N concentration and content. Mineral N supply rates (measured by the ion-exchange membrane technique) and tree diameter growth were positively related in the field experiment. I conclude that weed control and litter removal had positive effects on increasing N availability and applying N fertilizer without weed control was inefficient in improving tree growth. A complimentary growth chamber experiment showed that sufficient moisture availability might enhance the competitiveness of bluejoint for limited N.