Nitrous oxide is a potent greenhouse gas, with about ~300 times the climate warming potential of carbon dioxide. Nitrous oxide is produced and released to the atmosphere by microbes that cycle nitrogen in soils and sediment, often in response to excess nitrogen. High-latitude ecosystems typically contribute little nitrous oxide to the atmosphere because of limited availability of the forms of nitrogen conducive to nitrous oxide production. However, exceptionally large fluxes of nitrous oxide are increasingly documented from arctic and sub-arctic soils that are subject to cryoturbation or thawing permafrost. It remains unclear how this nitrous oxide is produced and how long disturbed soils might generate emissions. This project will support training in several analytical approaches for determining the quantity and pathways of nitrous oxide production in soils. Research will focus on Alaskan ecosystems that are subject to wildfire and permafrost thaw. Researchers will also adapt and apply novel methods with stable isotopes to determine the microbial pathways producing nitrous oxide. Determining how nitrous oxide is produced will decrease uncertainty in predicting how ecosystems respond to changing regimes of fire and permafrost and clarify how ecosystems might in turn influence the climate system.
Several studies over the past decade have documented significant emissions of nitrous oxide (N2O) from arctic soils where permafrost is thawing. However, these studies have not revealed the biological processes generating N2O, which might include denitrification, nitrification, and nitrifier-denitrification. Because the pathways of N2O production in high-latitude soils remain unknown, it is presently difficult to forecast potential emissions under warmer, more nutrient-rich, and fire-prone conditions predicted for high-latitude ecosystems. An Alaska-based research team will work with the nitrogen analytical facility at the Cary Institute of Ecosystem Studies to apply and optimize novel analytical approaches. These studies will include real-time production of N2O in response to manipulated soil conditions, and analysis of isotopomers (describing site preference of 15N), which can identify the microbial pathway producing N2O. These approaches will be applied across precipitation events, seasonal, and successional time scales and spatial gradients encompassing variation in nitrogen inputs, permafrost, and burn history within the region of spatially discontinuous permafrost in Interior Alaska. Goals of the research include identifying the microbial pathways that produce N2O in high-latitude soils and testing hypothesized relationships between nitrogen cycling and the fire, permafrost, and moisture regimes of the boreal forest. Establishing these relationships is an essential step toward identifying potential positive feedback loops between nitrogen cycling and climate warming in high-latitude ecosystems.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
