ABSTRACT Arctic wetlands are significant sources of atmospheric methane and the observed accelerated climate changes in the arctic could cause a change in methane dynamics. Methane oxidation would be the key process to control methane emission from wetlands. In this study, we determined the potential methane oxidation rate of the wetland soils of a taiga–tundra transition zone in northeastern Siberia. Peat soil samples were collected in summer from depressions covered with tussocks of sedges and Sphagnum spp. and from mounds vegetated with moss and larch trees. An aerobic bottle incubation experiment demonstrated that the soil samples collected from depressions in the moss- and sedge-dominated zones exhibited active methane oxidation with no time lag, while the mound soils showed no methane oxidation under the given conditions. The potential methane oxidation rates of the soils at 15°C ranged from 94 to 496 nmol h−1 g−1 dw. The immediate and active methane oxidation was observed over the depths studied (0–40 cm) including the water-saturated anoxic layers; the maximum methane oxidation rate was recorded in the layer above the water-saturated layer. The methane oxidation rate was temperature-dependent, but substantial methane oxidation was observed even at 0°C particularly for the moss soil samples. Soil samples collected from the frozen layer of Sphagnum peat also showed immediate methane consumption when incubated at 15°C. The present results suggest that the methane oxidizing bacteria in the wetland soils could survive under anoxic and frozen conditions keeping their potential activities and immediately utilize methane when the conditions become favorable. On the other hand, the inhibitor of methane oxidation (difluoromethane) did not affect the methane flux from the sedge and moss zones in situ, which suggested the minor role of plant-associated methane oxidation.

中文翻译：

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西伯利亚东北部针叶林-苔原交错带北极湿地土壤甲烷氧化潜力

摘要 北极湿地是大气甲烷的重要来源，观测到的北极气候加速变化可能导致甲烷动态发生变化。甲烷氧化将是控制湿地甲烷排放的关键过程。在这项研究中，我们确定了西伯利亚东北部针叶林-苔原过渡带湿地土壤的潜在甲烷氧化率。泥炭土壤样品是在夏季从覆盖着莎草丛和泥炭藓的洼地中收集的。以及长满苔藓和落叶松的土丘。好氧瓶培养实验表明，从苔藓和莎草主导区的洼地采集的土壤样品表现出活跃的甲烷氧化，没有时间滞后，而土丘土壤在给定条件下没有表现出甲烷氧化。土壤在 15°C 时的潜在甲烷氧化速率范围为 94 至 496 nmol h−1 g−1 dw。在所研究的深度（0-40 厘米），包括水饱和的缺氧层，观察到直接和活跃的甲烷氧化；最大甲烷氧化速率记录在水饱和层上方的层中。甲烷氧化速率与温度有关，但即使在 0°C 下也观察到大量的甲烷氧化，特别是对于苔藓土壤样品。从泥炭冰冻层收集的土壤样品在 15°C 下培养时也显示立即消耗甲烷。目前的结果表明，湿地土壤中的甲烷氧化细菌可以在缺氧和冷冻条件下存活，保持其潜在活性，并在条件有利时立即利用甲烷。