Center for Permafrost (CENPERM), Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, DK-1350, Copenhagen, Denmark.
Section for Forest, Nature and Biomass, Department of Geosciences and Natural Resource Management, University of Copenhagen, Rolighedsvej 23, Frederiksberg, 1958 C, Denmark.
Glob Chang Biol. 2017 Feb;23(2):966-976. doi: 10.1111/gcb.13400. Epub 2016 Jul 15.
Arctic ecosystems are characterized by a wide range of soil moisture conditions and thermal regimes and contribute differently to the net methane (CH ) budget. Yet, it is unclear how climate change will affect the capacity of those systems to act as a net source or sink of CH . Here, we present results of in situ CH flux measurements made during the growing season 2014 on Disko Island (west Greenland) and quantify the contribution of contrasting soil and landscape types to the net CH budget and responses to summer warming. We compared gas flux measurements from a bare soil and a dry heath, at ambient conditions and increased air temperature, using open-top chambers (OTCs). Throughout the growing season, bare soil consumed 0.22 ± 0.03 g CH -C m (8.1 ± 1.2 g CO -eq m ) at ambient conditions, while the dry heath consumed 0.10 ± 0.02 g CH -C m (3.9 ± 0.6 g CO -eq m ). These uptake rates were subsequently scaled to the entire study area of 0.15 km , a landscape also consisting of wetlands with a seasonally integrated methane release of 0.10 ± 0.01 g CH -C m (3.7 ± 1.2 g CO -eq m ). The result was a net landscape sink of 12.71 kg CH -C (0.48 tonne CO -eq) during the growing season. A nonsignificant trend was noticed in seasonal CH uptake rates with experimental warming, corresponding to a 2% reduction at the bare soil, and 33% increase at the dry heath. This was due to the indirect effect of OTCs on soil moisture, which exerted the main control on CH fluxes. Overall, the net landscape sink of CH tended to increase by 20% with OTCs. Bare and dry tundra ecosystems should be considered in the net CH budget of the Arctic due to their potential role in counterbalancing CH emissions from wetlands - not the least when taking the future climatic scenarios of the Arctic into account.
北极生态系统的土壤湿度条件和热量状况差异很大，对甲烷（CH ）净收支的贡献也不同。然而，目前尚不清楚气候变化将如何影响这些系统作为 CH 源或汇的能力。在这里，我们展示了 2014 年在格陵兰岛西部迪斯科岛生长季节进行的原位 CH 通量测量结果，并量化了不同土壤和景观类型对净 CH 预算的贡献以及对夏季变暖的响应。我们在环境条件和增加的空气温度下，使用开顶式气室（OTC）比较了裸地和干燥石楠荒地的气体通量测量值。在整个生长季节，裸地在环境条件下消耗了 0.22 ± 0.03 g CH -C m（8.1 ± 1.2 g CO -eq m），而干燥石楠荒地消耗了 0.10 ± 0.02 g CH -C m（3.9 ± 0.6 g CO -eq m）。随后，将这些吸收速率扩展到整个研究区域（0.15 平方公里），该景观还包括湿地，季节性综合甲烷释放量为 0.10 ± 0.01 g CH -C m（3.7 ± 1.2 g CO -eq m）。结果是，在生长季节，整个景观的净 CH 汇为 12.71 kg CH -C（0.48 吨 CO -eq）。随着实验变暖，季节性 CH 吸收速率出现了不显著的趋势，在裸地减少了 2%，在干燥石楠荒地增加了 33%。这是由于 OTC 对土壤湿度的间接影响，土壤湿度对 CH 通量起着主要的控制作用。总的来说，由于北极未来气候情景的考虑，OTC 会使 CH 的净景观汇增加 20%。裸地和干燥的冻原生态系统应该考虑在北极的净 CH 预算中，因为它们在平衡湿地 CH 排放方面可能发挥作用——尤其是在考虑到北极未来的气候情景时。
