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In this thesis, I describe three experimental studies that investigate the hotly debated role of competition in structuring communities in unproductive habitats. The studies were done in a boreal forest understory plant community in the southwestern Yukon. The first study was a traditional neighbour removal experiment. Ten of the most common species were transplanted as seedlings into transects with and without neighbours in a factorial design with two levels of water addition and two levels of fertilizer addition. The presence of neighbours increased survival and biomass of 6 species indicating a facilitative effect of neighbouring plants. The second study used the Community Density Series (CDS) methodology. The...
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In this thesis, I examine the timing of breeding in 3 raptorial birds, red-tailed hawks (Buteo jamaicensis), the goshawks (Accipiter gentilis) and great-horned owls (Bubo virginianus). Specifically, I test Lack's 1954 theory that birds typically begin to breed such that the young bird's greatest demand for food will coincide later with the greatest abundance of available prey. Lack's theory predicts that birds which successfully match the timing of breeding to the peak in prey fledge more young that pairs which do not. This study was part of the larger Kluane Boreal Forest Ecosystem Project .... Detailed information on weather, prey density and timing of the peaks in prey availability was gathered annually. I examined...
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