Nitrous Oxide Emissions in a Semi-Arid Prairie Pothole Landscape: Event-Based Triggers.

Accurate predictive models of nitrous oxide and other greenhouse gas emissions require comprehensive and continuous field flux measurements to provide high quality model input data. In Western Canada, background nitrous oxide emissions tend to be relatively low and hence easy to incorporate into a model. Event-based emissions, however, present a significant challenge; emission events represent a large proportion of the annual cumulative emissions but are highly variable in space and time. Although precipitation and the corresponding increase in water-filled pore space are typically regarded as important triggers for event-based emissions they cannot be reliably used to predict all major emission events. Clearly there is some other unidentified trigger that is vital to our understanding. Given the tremendous investment of time and money required to collect comprehensive field measurements, there are few datasets with sufficient resolution to explore what this unidentified trigger might be. Here we present results of a comprehensive three-year nitrous oxide emission study in a semi-arid Prairie Pothole landscape in Saskatchewan, Canada. Using this large dataset, we: a) quantify mean cumulative nitrous oxide emissions by field element, including emissions from mineral wetlands embedded in the landscape, b) classify the detectable temporal patterns, and c) identify the dominant trigger(s) for the major event-based emissions.