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dc.contributor.authorBuckeridge, Kathleenen
dc.date2009-09-25 23:29:53.103
dc.date.accessioned2009-09-27T18:47:12Z
dc.date.available2009-09-27T18:47:12Z
dc.date.issued2009-09-27T18:47:12Z
dc.identifier.urihttp://hdl.handle.net/1974/5230
dc.descriptionThesis (Ph.D, Biology) -- Queen's University, 2009-09-25 23:29:53.103en
dc.description.abstractSoil nitrogen availability to plants is a fundamental control on the structure and functioning of arctic tundra ecosystems. Despite recent evidence that biogeochemical and microbial dynamics during the non-growing season impact nitrogen availability to plants in tundra ecosystems, very little is known about soil microbial patterns and mechanisms for nutrient mobilization in the winter, spring and fall. In this dissertation I have examined the environmental and microbial controls on seasonal nitrogen mobilization in a widespread Canadian low arctic birch hummock tundra ecosystem. In particular, I have investigated the potential for increased winter snow depth and different above-ground vegetation-types to alter soil microbial community patterns and nutrient mobilization from organic matter into plant-available pools. First, I demonstrated that experimentally deepened winter snow altered soil microbial physiology during winter, defined as increased microbial carbon limitation to growth and activity. Second, I established that deepened snow enhanced spring nutrient mobilization during distinct environmental phases, producing large peaks in the soil microbial biomass and soil solution carbon, nitrogen and phosphorus during snow thaw. Third, I showed that laboratory predictions of early-spring air temperature freeze-thaw cycles promoting tundra soil nitrogen loss are not relevant, as the soil environment and soil biogeochemistry were relatively stable after snow melt and before plant growth began. Fourth, I demonstrated that microbial functional groups did not differ strongly under different tundra vegetation types, but higher quality shrub litter induced positive feedbacks on soil carbon availability and soil nitrogen mineralization in the late summer. Finally, I illustrated that annual patterns of tundra soil microbial community structure and composition were strongly linked to soil biogeochemistry and that significant shifts in fungal/bacterial ratios occur during snowmelt. This research suggests two broad conclusions: a) that soil microbial activity is responsive to changes in above-ground vegetation; and b) that seasonal changes in microbial community structure and microbial biochemistry are strongly correlated. Therefore, the synchronicity of microbial seasonal succession and plant species-specific timing of nitrogen uptake is a critical factor restricting the potential for ecosystem N losses at spring thaw and ultimately in supplying growth-limiting nutrients to plants in the following summer.en
dc.format.extent4760257 bytes
dc.format.mimetypeapplication/pdf
dc.language.isoengen
dc.relation.ispartofseriesCanadian thesesen
dc.rightsThis publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.en
dc.subjectEcosystem Ecologyen
dc.subjectArctic Tundraen
dc.subjectSoil Microorganismsen
dc.subjectNitrogenen
dc.subjectPhosphorusen
dc.subjectCarbonen
dc.titleControls on Seasonal Nitrogen Cycling in Canadian Low Arctic Tundra Ecosystemsen
dc.typethesisen
dc.description.degreePhDen
dc.contributor.supervisorGrogan, Paulen
dc.contributor.departmentBiologyen
dc.degree.grantorQueen's University at Kingstonen


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