Reduced Snow Cover Increases Wintertime Nitrous Oxide (N₂O) Emissions from an Agricultural Soil in the Upper U.S. Midwest

• Published in: Ecosystems (New York) Vol. 20; no. 5; pp. 917 - 927
• Main Authors: Ruan, Leilei, Robertson, G. Philip
• Format: Journal Article
• Language: English
• Published: New York Springer Science + Business Media 01.08.2017; Springer US; Springer; Springer Nature B.V
• Subjects: Agricultural land; agricultural soils; Agriculture; Biomedical and Life Sciences; Cropping systems; Ecology; Emissions; Environmental Management; Fluxes; Freeze thaw cycles; Freeze-thawing; Freezing; Geoecology/Natural Processes; greenhouse gas emissions; Hydrology/Water Resources; Life Sciences; Midwestern United States; Nitrogen; Nitrous oxide; Northern Hemisphere; Original Articles; Plant Sciences; Pools; snow; Snow cover; Snow removal; snowpack; Soil dynamics; Soil erosion; Soils; winter; Zoology; Midwest states; Midwestern United States; greenhouse gases; automated chambers; snow cover; freeze–thaw cycles; nitrous oxide (N; soil aggregates; soil nitrogen; O; climate change
• ISSN: 1432-9840; 1435-0629
• DOI: 10.1007/s10021-016-0077-9

Throughout most of the northern hemisphere, snow cover decreased in almost every winter month from 1967 to 2012. Because snow is an effective insulator, snow cover loss has likely enhanced soil freezing and the frequency of soil freeze–thaw cycles, which can disrupt soil nitrogen dynamics including the production of nitrous oxide (N₂O). We used replicated automated gas flux chambers deployed in an annual cropping system in the upper Midwest US for three winters (December–March, 2011–2013) to examine the effects of snow removal and additions on N₂O fluxes. Diminished snow cover resulted in increased N₂O emissions each year; over the entire experiment, cumulative emissions in plots with snow removed were 69% higher than in ambient snow control plots and 95% higher than in plots that received additional snow (P < 0.001). Higher emissions coincided with a greater number of freeze–thaw cycles that broke up soil macroaggregates (250–8000 µm) and significantly increased soil inorganic nitrogen pools. We conclude that winters with less snow cover can be expected to accelerate N₂O fluxes from agricultural soils subject to wintertime freezing.