Abundance, Activity and Community Structure of Nitrifier and Denitrifier Communities in Agro-Ecosystems

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dc.contributor.advisorDunfield, Kari
dc.contributor.authorThompson, Karen
dc.date.accessioned2016-01-06T21:16:40Z
dc.date.available2016-01-06T21:16:40Z
dc.date.copyright2016-01
dc.date.created2015-12-15
dc.date.issued2016-01-06
dc.degree.departmentSchool of Environmental Sciencesen_US
dc.degree.grantorUniversity of Guelphen_US
dc.degree.nameDoctor of Philosophyen_US
dc.degree.programmeEnvironmental Sciencesen_US
dc.description.abstractSoil microbial communities are functionally diverse, responding to distal and proximal regulators of activity and functioning on multiple temporal and spatial scales due to the complex heterogeneity of the soil system. Soil microbial denitrifying and nitrifying communities drive terrestrial N2O emissions. Research was conducted on the effects of agricultural management on these communities in order to develop guidelines on agricultural practices which may mitigate these emissions. Climate and associated changes in the soil environment were large drivers of these communities, with results of multi-year studies indicating that differences in temperature and soil moisture distinctly affected the size of denitrifier communities. Choice of annual vs. perennial biomass crops, and the harvesting practices used in perennial systems also affected the size of these communities, and residue return increased the activity of the N2O-reducing community over a growing season. Next-generation sequencing was used to link changes in the structure of nitrifier and denitrifier communities with agricultural practices that were associated with differences in field-scale N2O fluxes; specific indicator operational taxonomic units (OTUs) and nosZ gene abundances were largely responsible for driving differences in these communities. Analysis of nitrifier and denitrifier communities paired with changes in N isotopes gave complementary inferences about the production mechanisms of N2O in the field. Together, this body of research gives a comprehensive picture of the many factors that affect the functioning of these communities, and indicates that management practices influence the abilities of these communities to produce and consume N2O. Future research focusing on linking changes in nitrifier and denitrifier soil microbial communities with agricultural management and associated N2O fluxes within specific climatic regions, geographies, and soil types is required in order to better understand the mechanisms controlling these communities and how these communities may be manipulated through management choices to mitigate soil N2O emissions.en_US
dc.description.sponsorshipOntario Ministry of Agriculture, Food and Rural Affairs
dc.description.sponsorshipOntario Graduate Scholarship
dc.description.sponsorshipOntario Graduate Fellowship (OGF)
dc.description.sponsorshipNatural Science and Engineering Research Council
dc.description.sponsorshipCanadian Research Chair (CRC) Program
dc.description.sponsorshipAgricultural Greenhouse Gas Program (AGGP)
dc.identifier.urihttp://hdl.handle.net/10214/9457
dc.language.isoenen_US
dc.publisherUniversity of Guelphen_US
dc.rights.licenseAll items in the Atrium are protected by copyright with all rights reserved unless otherwise indicated.
dc.subjectbiomassen_US
dc.subjectbiofuelen_US
dc.subjectqPCRen_US
dc.subjectsequencingen_US
dc.subjectmiscanthusen_US
dc.subjectswitchgrassen_US
dc.subjectcornen_US
dc.subjectsoybeanen_US
dc.subjectnitrogen cyclingen_US
dc.subjectnirSen_US
dc.subjectnirKen_US
dc.subjectnosZen_US
dc.subjectamoAen_US
dc.subjectcrenamoAen_US
dc.subjectnitrificationen_US
dc.subjectdenitrificationen_US
dc.titleAbundance, Activity and Community Structure of Nitrifier and Denitrifier Communities in Agro-Ecosystemsen_US
dc.typeThesisen_US
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