Dataset associated with “Characterizing the importance of denitrification for N2O production in soils using natural abundance and isotopic labelling techniques”

This dataset was collected for the author's second dissertation chapter. Data was collected both in the Loch Vale Watershed in Rocky Mountain National Park in Colorado and the Limited Irrigation Research Farm near Greeley, Colorado. All data was analyzed at Colorado State University from June-August 0f 2018. This dataset includes both soil physical and chemical properties from both of the soil sampling sites, and it includes greenhouse gas data from laboratory soil incubations. Specifically, from the incubations we measured N2O concentration and N2O isotopic composition.Nitrous oxide (N2O), a potent greenhouse gas that contributes significantly to climate change, is emitted mostly from soils by a suite of microbial metabolic pathways that are nontrivial to identify, and subsequently, to manage. Using either natural abundance or enriched stable isotope methods has aided in identifying microbial sources of N2O, but each approach has limitations. Here, we conducted a novel pairing of natural abundance and enriched assays on two dissimilar soils, hypothesizing this pairing would better constrain microbial sources of N2O. We incubated paired natural abundance and enriched soils from a corn agroecosystem and a subalpine forest in the laboratory at 10-95% soil saturation for 28 hr. The natural abundance method measured intramolecular site preference (SP) from emitted N2O, whereas the enriched method measured emitted 15N2O from soils amended with 15N-labelled substrate. The isotopic composition of emitted N2O was measured using a laser-based N2O isotopic analyzer, yielding two key findings. First, both methods revealed that denitrification was the primary source of N2O in all soils: isotopic enrichment revealed clear NO3- reduction to N2O, while SP indicated a likely combination of fungal and bacterial denitrification. Second, we quantified, to our knowledge for the first time, persistent (>55%) β-position-specific enrichment in N2O emitted from 15NO3- -amended soils. This counter-intuitive enrichment pattern could be indicative of co-denitrification, an understudied but potentially important contributor to N2O emissions. Our work revealed the ubiquity of denitrification among the soils tested. Future pairings of natural abundance and enriched methods could better characterize diverse denitrification pathways.Environmental Defense FundThe Graduate Degree Program in Ecology Small Research Gran