Characterization of soil moisture legacy controls of nitrous oxide production and reduction in terrestrial soils
Ooi, Sean Khan
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Permalink
https://hdl.handle.net/2142/129585
Description
Title
Characterization of soil moisture legacy controls of nitrous oxide production and reduction in terrestrial soils
Author(s)
Ooi, Sean Khan
Issue Date
2025-04-25
Director of Research (if dissertation) or Advisor (if thesis)
Yang, Wendy H
Doctoral Committee Chair(s)
Kent, Angela D
Committee Member(s)
Sanford, Robert A
Heath, Katy D
Department of Study
School of Integrative Biology
Discipline
Ecol, Evol, Conservation Biol
Degree Granting Institution
University of Illinois Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
nitrous oxide, soil moisture, stable isotopes, drainage class
Abstract
Nitrous oxide (N2O) production and reduction by soil microbes is strongly influenced by soil moisture content, but the legacy effect of long-term soil moisture regimes on these two processes is not well-understood. In my dissertation, I explored how divergent soil moisture legacies can lead to differing N2O emission dynamics under similar contemporary soil moisture conditions, thereby contributing to notoriously high spatial variation in N2O emissions. I also investigated the role of the relative timing of N2O reduction vs. production as a potential microbial response to frequent anoxia exposure through flooding. In my second chapter, I show that microtopography-driven differences in long-term soil moisture regimes can lead to the formation of distinct N2O production and reduction patterns across soil drainage classes, and that these patterns can shift in response to flooding stress. In my third chapter, I examined how drought and subsequent drought recovery change the N2O emission dynamics of soil through the loss of N2O reduction capacity. In my fourth chapter, I present the method development and use-case test of an automated 15N2O pool dilution technique that leverages an automated multiplexer design and laser spectroscopy to achieve high-throughput measurements of simultaneous N2O production and reduction. My dissertation highlights the importance of soil moisture legacies in controlling N2O reduction capacity, which in turn determines N2O emission potential of soils. My research showed that changes to the timing of N2O reduction following anoxia could be a soil microbial community response to frequent anoxia and was highly vulnerable to drought conditions. Finally, my dissertation demonstrates the conceptual need and methodological means for high temporal resolution measurements of N2O production vs. reduction to advance understanding ofN2O emissions.
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