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Biogeochemical Cycling and Microbial Communities in Native Grasslands:Responses to Climate Change and Defoliation Open Access


Other title
Greenhouse Gas Emissions
Soil Microbial Community
Climate Change
Nitrogen Cycling
Global Warming
Carbon Cycling
Type of item
Degree grantor
University of Alberta
Author or creator
Attaeian, Behnaz
Supervisor and department
Scott X. Chang (Renewable Resources)
James F. Cahill (Biological Sciences)
Examining committee member and department
Edward W. Bork (Agricultural, Food and Nutritional Science)
James F. Cahill (Biological Sciences)
Scott X. Chang (Renewable Resources)
Luo, Yiqi (Botany and Microbiology)
Yongsheng Feng (Renewable Resources)
Department of Renewable Resources

Date accepted
Graduation date
Doctor of Philosophy
Degree level
Ongoing climate change has emerged as a major scientific challenge in the current century. Grassland ecosystems are considered net carbon (C) sinks to mitigate climate change. However, they are in turn, influenced by climate change and management practices, providing feedback to climate change via soil microbial community and biogeochemical fluxes. In this thesis, I examined the impact of warming, altered precipitation, and defoliation on soil microbial composition and function, C and N dynamics, and fluxes in soil respiration (CO2), nitrous oxide (N2O) and methane (CH4), together with other belowground ecosystem functions, within two ecosites in a northern native temperate grassland in central Alberta, Canada, over a two-year period. Fungi-to-bacteria ratio was not affected by climatic parameters or defoliation, indicating a high degree of resistance in the below ground community to the treatments imposed. However, C substrate utilization was influenced by warming and defoliation, as was soil microbial biomass. In contrast, soil respiration (or C loss) was not. Soil respiration acclimatized rather quickly to warming, and N2O and CH4 effluxes showed minor responses to warming at both ecosites, regardless of defoliation. These results suggest warming is unlikely to lead to positive climate change feedback due to soil-based responses, regardless of ongoing land use. However, altered precipitation (± 50%) demonstrated greater impacts on C and N fluxes relative to warming and defoliation. Increased precipitation stimulated soil C loss to the atmosphere, potentially generating positive feedback for climatic warming in this northern temperate grassland.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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