Typescript (photocopy). / Digitized by Kansas Correctional Industries

The nitrogen cycle is one of the key macronutrient cycles that controls the distribution of life on Earth. The nitrogen cycle is composed of a series of distinct microbially mediated processes which may be affected differently with warming. Climate change is likely to affect all components of the nitrogen cycle. However, the extent to which each component will be affected and how this will alter interactions in natural systems is unknown. Here we used laboratory and field experiments to investigate the effect of warming on nitrogen cycling. We used a combination of pure cultures, in-situ measurements and laboratory manipulations of environmental samples to explore responses in freshwater and marine systems. In pure cultures of denitrifying bacteria, denitrification rates increased by 117-164%, with a 4oC temperature increase (11.5-15.5oC). In freshwater mesocosms, long term warming rates of sediment denitrification increased by 247%, with no significant thermal response of sediment nitrification within these systems. Marine sediment rates of denitrification and anammox increased by 4.69-16.23% and 3.71-35.39% respectively, depending on N substrate. Whereas a 3oC temperature increase in the water of the ETNP OMZ increased denitrification and anammox rates by 52.5% and 52.9% respectively, with no significant thermal response of nitrogen fixation in the OMZ surface waters. From this study, nitrogen removal processes increase with increasing temperature across systems but internal transformation and fixation of N show little to no thermal response. Further investigation into the causes of the observed variation in responses, such as substrate limitation and identification of microbes involved, will allow us to better understand and therefore better predict cross-system responses of the nitrogen cycle to global warming.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1978. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 29-30. / B.S.

Typewritten Includes bibliographical references

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 126-140). Also available on the World Wide Web.

Thesis (Dr. rer. nat.)--Philipps-Universität Marburg, 2002. / Title from PDF t.p. (viewed on Apr. 24, 2007). Includes bibliographical references (p. 143-163).

Thesis (Ph. D. (soil science))--Washington State University, May 2007. / Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 45-54). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 148-163).

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2002. / Vita. Includes bibliographical references (leaves 153-161).