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，北半球大部分区域的几乎每个冬季月份的积雪覆盖均呈减少趋势。由于积雪是高效的绝热体，积雪覆盖减少可能加剧了土壤冻结程度与土壤冻融循环的发生频率，而这一过程会干扰土壤氮素动态，包括一氧化二氮（nitrous oxide, N₂O）的产生。本研究于美国中北部地区的一年生作物种植系统中布设了多组重复的自动化气体通量箱（automated gas flux chambers），在2011–2013年的三个冬季（12月至次年3月）开展实验，以探究积雪移除与积雪添加对N₂O通量的影响。实验结果显示，积雪覆盖减少会导致各年度的N₂O排放量均有所上升；整个实验周期内，积雪移除样地的累积排放量较自然积雪对照样地高出69%，较额外添加积雪的样地高出95%（P < 0.001）。更高的N₂O排放与更多的冻融循环相伴随，这类循环会破坏土壤大团聚体（soil macroaggregates，250–8000 µm），并显著提升土壤无机氮库的含量。综上，在冬季积雪覆盖减少的气候背景下，易发生冬季冻结的农业土壤的N₂O通量预计会有所提升。