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dc.contributor.authorWeiss, Marissaen_US
dc.identifier.otherbibid: 8213882
dc.description.abstractHumans now dominate the nitrogen cycle by producing more biologically available nitrogen (N) than all natural processes combined. Over the past 150 years, northeastern forests have seen a four to ten-fold increase in N deposition as a result of anthropogenic activities such as agriculture and industry. Most of this added N is retained in surface soils. N deposition has the potential to alter atmospheric carbon dioxide (CO2) by influencing rates of decomposition of the vast reservoir of soil organic matter. N deposition may also change the soil nitrogen cycle, influencing the ability of soils to retain N. The objective of this work was to measure the response of decomposition and N retention to added N in northeastern forest soils. I used a cross-site lab experiment with soils from five long-term N addition experiments to measure the effects of long-term N fertilization on CO2 release, microbial biomass, heavy soil C (ie: mineral-associated), light soil C (ie: not mineralassociated), dissolved organic carbon (DOC), and the activities of four C-degrading enzymes. In response to a short-term pulse of N applied to soils in the lab, I focused on changes in CO2 and C degrading enzymes. To study the effects of N addition on N retention, I added a 15N tracer to incubating soils, and measured the partitioning of the tracer into several soil N pools. I found evidence to support the hypothesis that N fertilization can stimulate decomposition of easily degraded labile C such as sugars and starches; I measured transient increases in CO2 respiration and a cellulose-degrading enzyme with a shortterm pulse of N at one site. N inhibited decomposition of harder to degrade, ligninbased C compounds, decreasing CO2 respired during the first week of a year long incubation at four sites, along with microbial biomass and the lignin-degrading enzyme phenol oxidase. Soils with more organic matter appear to retain more N; light fraction 15N retention was positively correlated with soil %C. N addition reduced 15N retention in mineral soils.en_US
dc.subjectnitrogen additionen_US
dc.subjectsoil microbial processesen_US
dc.titleShort And Long-Term Effects Of Nitrogen Fertilization On Carbon And Nitrogen Cycles In Northeastern Forest Soilsen_US
dc.typedissertation or thesisen_US Universityen_US of Philosophy D., Ecology
dc.contributor.chairGoodale, Christine Len_US
dc.contributor.committeeMemberFahey, Timothy Jamesen_US
dc.contributor.committeeMemberDrinkwater, Laurie Een_US

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