Soil Emissions of Nitrogen Trace Gases: Leveraging the Decommissioning of the Desert FACE Site

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Terrestrial ecosystems are an important component of the global carbon cycle and as a consequence have the potential to influence the rate of climate change. For approximately 10 years, The U.S. Department of Energy (DOE) has been supporting a series of Free Air CO2 Enrichment (FACE) experiments to evaluate the effects of elevated atmospheric carbon dioxide (CO2) concentration on terrestrial ecosystems. One such experiment is the Nevada Desert FACE Facility (NDFF) in the Mojave Desert. No other experiment has continuously applied elevated CO2 to a desert ecosystem. The DOE is in the process of terminating its FACE experiments. This decommissioning process represents a unique opportunity to complete a comprehensive analysis of how a desert ecosystem functions under elevated CO2. During the shut down, DOE will only support research on ecosystem carbon storage. This NSF research will leverage the DOE support to enable investigations of the effects of elevated CO2 on desert nitrogen cycling. The research will: 1) examine the amount and the isotopic signature of nitrogen throughout the ecosystem, 2) measure how nitrogen cycles and transforms within the soil and how this changes after the additional carbon dioxide is removed, and 3) measure the magnitude and isotopic composition of nitrogen gases emitted from the ecosystem following the removal of the elevated CO2 treatment.In addition to influencing the overall response of the ecosystem to elevated CO2, changes in ecosystem nitrogen cycling have the potential to influence regional air quality, acidification of precipitation, food production, and human health. This is especially true in the arid southwest because it is among the fastest growing regions in the US. A firm understanding of the controls on emissions of nitrogen gases will help inform future policy and remediation decisions. Other broader impacts of the research include: (1) teaching and training of undergraduate and graduate students, (2) participation of underrepresented groups, and (3) dissemination of results to non-academic audiences.