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dc.contributor.authorChristiansen, Casper Tai
dc.contributor.otherQueen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.))en
dc.date2016-01-29 07:11:46.924en
dc.date.accessioned2016-01-29T20:23:27Z
dc.date.issued2016-01-29
dc.identifier.urihttp://hdl.handle.net/1974/13988
dc.descriptionThesis (Ph.D, Biology) -- Queen's University, 2016-01-29 07:11:46.924en
dc.description.abstractClimate change is leading to warmer temperatures and greater snowfall in Arctic regions. Microbial decomposition activities are strongly regulated by temperature, and therefore climate warming is projected to enhance decay of the vast tundra soil organic matter pool, releasing CO2 into the atmosphere and nutrients into the soil solution. By contrast, increased soil nutrient availability promotes plant growth and changes in vegetation, both of which may enhance plant uptake of CO2 from the atmosphere. Consequently, depending on the net balance between these increases in CO2 release and uptake, tundra ecosystems may end up contributing globally significant feedbacks to a changing climate, further exacerbating environmental change. In this thesis, I modelled the effects of changes in seasonal climate on litter decay rates and ecosystem carbon (C) and nutrient pools in a variety of tundra vegetation-types. Specifically, I investigated how short- (one year) and longer-term (up to 9 years) experimentally-deepened winter snow and summer warming impact microbial communities and biogeochemical dynamics using experimental plots located in distinct ecosystems across the Canadian, Greenlandic, and Norwegian Arctic. Summer warming reduced surface litter decomposition in both relatively dry and wet ecosystems, likely because of evaporation-induced desiccation. In contrast, deepened snow had negligible effects on litter decay rates. However, tall birch shrub vegetation significantly stimulated litter decomposition, presumably due to a positive feedback from their greater litter inputs, enhancing soil nutrient pools and thereby microbial decomposition activities. Regarding plant and soil dynamics, the longer-term impacts of deepened snow included enhanced evergreen shrub growth and dominance over deciduous shrubs, but this increase in ecosystem C storage was dwarfed by 60 times greater soil C loss from the subsoil mineral layer. Soil bacterial community structure was much more strongly influenced by depth variation in edaphic properties down the thawing soil profile than by seasonal change from winter to autumn. However, despite greater diversity with depth, the seasonal thaw significantly affected community structure and biomass similarly throughout the soil profile. Altogether, this research suggests that summer warming may slow surface litter decomposition, but that deepened snow may result in substantial soil C losses that greatly exceed plant C uptake.en_US
dc.languageenen
dc.language.isoenen_US
dc.relation.ispartofseriesCanadian thesesen
dc.rightsQueen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canadaen
dc.rightsProQuest PhD and Master's Theses International Dissemination Agreementen
dc.rightsIntellectual Property Guidelines at Queen's Universityen
dc.rightsCopying and Preserving Your Thesisen
dc.rightsCreative Commons - Attribution-Non-commercial-No Derivate Works - CC BY-NC-NDen
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.subjectClimate Changeen_US
dc.subjectWinteren_US
dc.subjectEcosystem Ecologyen_US
dc.subjectArcticen_US
dc.titleSeasonal Controls on Litter and Soil Carbon and Nutrient Cycling in Arctic Tundra Ecosystems and Potential Impacts of Climate Changeen_US
dc.typeThesisen_US
dc.description.restricted-thesisPlease restrict this thesis for 1 (one) year. This request is due to all data chapters (Chapters 2-6) currently being in review or pending submission for review (for publication) in high ranking international scientific journals. These journal often require that the work/data not being published/available elsewhere at time of submission.en
dc.description.degreePh.Den
dc.contributor.supervisorGrogan, Paulen
dc.contributor.departmentBiologyen
dc.embargo.terms1825en
dc.embargo.liftdate2021-01-27


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