Data from: Reduced snow cover increases wintertime nitrous oxide (N2O) emissions from an agricultural soil in the upper U.S. midwest

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.1967年至2012年间，北半球绝大多数区域的冬季各月份积雪覆盖范围均呈缩减态势。由于积雪是高效绝热介质，积雪覆盖减少可能加剧土壤冻融程度并提升土壤冻融循环频次，而冻融循环会干扰土壤氮素动态过程，其中包括一氧化二氮（nitrous oxide, N2O）的产生。本研究于美国中西部北部的一年生耕作系统中布设重复式自动化气体通量箱，于2011-2013年的3个冬季（12月至次年3月）开展原位试验，以探究积雪移除与积雪添加对N2O通量的影响。各年度中，积雪覆盖缩减均导致N2O排放量升高；整个试验周期内，积雪移除样地的累积排放量较自然积雪对照样地高出69%，较积雪添加样地高出95%（P < 0.001）。更高的N2O排放量与更多的冻融循环相伴出现——冻融循环可破碎土壤大团聚体（250–8000 μm），并显著提升土壤无机氮库储量。综上，冬季积雪覆盖减少将可能加速经历冬季冻融的农田土壤的N2O通量排放。