Lazar Julia G, Addy Kelly, Welsh Molly K, Gold Arthur J, Groffman Peter M
J Environ Qual. 2014 Nov;43(6):1844-52. doi: 10.2134/jeq2014.02.0065.
Beaver ponds, a wetland type of increasing density in the northeastern United States, vary spatially and temporally, creating high uncertainty in their impact to greenhouse gas (GHG) emissions. We used floating static gas chambers to assess diffusive fluxes of methane (CH), carbon dioxide (CO), and nitrous oxide (NO) from the air-water interface of three beaver ponds (0.05-8 ha) in Rhode Island from fall 2012 to summer 2013. Gas flux was based on linear changes of gas concentrations in chambers over 1 h. Our results show that these beaver ponds generated considerable CH and CO emissions. Methane flux (18-556 mg m d) showed no significant seasonal differences, but the shallowest pond generated significantly higher CH flux than the other ponds. Carbon dioxide flux (0.5-22.0 g m d) was not significantly different between sites, but it was significantly higher in the fall, possibly due to the degradation of fresh leaves. Nitrous oxide flux was low (0-2.4 mg m d). Overall, CH and CO comprised most of the global warming potential, 61 and 38%, respectively. The shallowness of the beaver ponds may have limited the time needed for CH oxidation to CO before CH escaped to the atmosphere. Beaver dams also increase the aerial extent of hydric soils, which may transform riparian areas from upland GHG sinks to wetland GHG sources thereby changing the net global warming potential. Further studies tracking the pattern and conditions of beaver pond creation and abandonment will be essential to understanding their role as GHG sources.
海狸池塘是美国东北部密度不断增加的一种湿地类型，其在空间和时间上存在差异，这使得它们对温室气体（GHG）排放的影响具有高度不确定性。我们使用浮动静态气室，评估了2012年秋季至2013年夏季罗德岛州三个海狸池塘（面积为0.05 - 8公顷）气 - 水界面的甲烷（CH₄）、二氧化碳（CO₂）和一氧化二氮（N₂O）扩散通量。气体通量基于气室内气体浓度在1小时内的线性变化。我们的结果表明，这些海狸池塘产生了大量的CH₄和CO₂排放。甲烷通量（18 - 556毫克·米⁻²·天⁻¹）没有显著的季节差异，但最浅的池塘产生的CH₄通量明显高于其他池塘。二氧化碳通量（0.5 - 22.0克·米⁻²·天⁻¹）在不同地点之间没有显著差异，但在秋季显著更高，这可能是由于新鲜树叶的降解。一氧化二氮通量较低（0 - 2.4毫克·米⁻²·天⁻¹）。总体而言，CH₄和CO₂分别占全球变暖潜能值的61%和38%。海狸池塘的浅度可能限制了CH₄在逸出到大气之前氧化为CO₂所需的时间。海狸坝还增加了水成土的面积，这可能会使河岸地区从陆地温室气体汇转变为湿地温室气体源，从而改变全球变暖潜能净值。进一步跟踪海狸池塘形成和废弃的模式及条件的研究对于理解它们作为温室气体源的作用至关重要。
