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
Abstract
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.
