Understanding the processes that influence and control carbon cycling in Arctic tundra ecosystems is essential for making accurate predictions about what role these ecosystems will play in potential future climate change scenarios. Particularly, air–surface fluxes of methane and carbon dioxide are of interest as recent observations suggest that the vast stores of soil carbon found in the Arctic tundra are becoming more available to release to the atmosphere in the form of these greenhouse gases. Further, harsh wintertime conditions and complex logistics have limited the number of year-round and cold-season studies and hence too our understanding of carbon cycle processes during these periods. We present here a two-year micrometeorological data set of methane and carbon dioxide fluxes, along with supporting soil pore gas profiles, that provide near-continuous data throughout the active summer and cold winter seasons. Net emission of methane and carbon dioxide in one of the study years totalled 3.7 and 89 g C m^−2 a^−1 respectively, with cold-season methane emission representing 54 % of the annual total. In the other year, net emission totals of methane and carbon dioxide were 4.9 and 485 g C m^−2 a^−1 respectively, with cold-season methane emission here representing 82 % of the annual total – a larger proportion than has been previously reported in the Arctic tundra. Regression tree analysis suggests that, due to relatively warmer air temperatures and deeper snow depths, deeper soil horizons – where most microbial methanogenic activity takes place – remained warm enough to maintain efficient methane production whilst surface soil temperatures were simultaneously cold enough to limit microbial methanotrophic activity. These results provide valuable insight into how a changing Arctic climate may impact methane emission, and highlight a need to focus on soil temperatures throughout the entire active soil profile, rather than rely on air temperature as a proxy for modelling temperature–methane flux dynamics.

中文翻译：

---

北极苔原生态系统中生态系统规模的冷季甲烷和二氧化碳通量的环境控制

了解有关影响和控制北极苔原生态系统中碳循环的过程，对于准确预测这些生态系统在未来潜在的气候变化情景中将发挥何种作用至关重要。尤其是，甲烷和二氧化碳在空气中的表面通量引起了人们的关注，因为最近的观察表明，北极苔原中发现的大量土壤碳正以这些温室气体的形式释放到大气中。此外，严酷的冬季条件和复杂的物流限制了全年和寒冷季节研究的数量，因此也限制了我们对这些时期碳循环过程的理解。我们在这里展示了两年的甲烷和二氧化碳通量的微气象数据集，以及支持的土壤孔隙气体分布，可以在整个夏季和冬季寒冷的季节提供近乎连续的数据。在一个研究年度中，甲烷和二氧化碳的净排放量总计为3.7和89？g？C？m^{â???? 2} â????一个^{â???? 1}分别与表示全年共54A ????％冷季甲烷排放。在其它年，甲烷和二氧化碳的净排放总量分别为4.9和485A ????Gâ???? CA ????米^{â???? 2} â????一个^{â???? 1}分别，这里的冷季甲烷排放量占全年总排放量的82％。比以前在北极冻原中报告的比例更大。回归树分析表明，由于相对较高的气温和较深的积雪深度，因此土壤层较深– 发生大多数微生物产甲烷活动的地方 保持足够的温暖以维持有效的甲烷生产，同时表层土壤温度同时保持足够冷以限制微生物的甲烷营养活性。这些结果提供了有关北极气候变化如何影响甲烷排放的有价值的见解，并强调了需要关注整个活动土壤剖面中的土壤温度，而不是依靠空气温度来模拟温度-甲烷通量动力学。