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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2019-98
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-98
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 01 Apr 2019

Submitted as: research article | 01 Apr 2019

Review status
This discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). The manuscript was not accepted for further review after discussion.

Methane oxidation potential of the arctic wetland soils of a taiga-tundra ecotone in northeastern Siberia

Jun Murase1, Atsuko Sugimoto2,3, Ryo Shingubara3,a, Tomoki Morozumi3, Shinya Takano3, and Trofim C. Maximov4,5 Jun Murase et al.
  • 1Graduate School of Bioagricultural Science, Nagoya University, Nagoya, 464-8601, Japan
  • 2Arctic Research Center, Hokkaido University, Sapporo, 001-0021, Japan
  • 3Graduate School of Environmental Science, Hokkaido University, Sapporo, 060-0810, Japan
  • 4Institute for Biological Problems of Cryolithozone Siberian Branch, Russian Academy of Science, 41 Lenina ave., Yakutsk 677980, Russia
  • 5Biogeochemistry Educational and Scientific Training Center, North-Eastern Federal University, 58 Belinsky str, Yakutsk 677000, Russia
  • apresent address: Graduate School of Environmental Studies, Nagoya University, Nagoya 464-8601, Japan

Abstract. Arctic wetlands are significant sources of atmospheric methane and the observed accelerated climate changes in the arctic could cause the change in methane dynamics, where 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. A 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. The potential methane oxidation rates at 15 °C ranged from 94 to 496 nmol h−1 g−1 dw. 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 surface (0–2 cm) layer in the sedge-dominated zone and in the middle (4–6 cm) layer in the moss-dominated zone. The methane oxidation rate was temperature-dependent, and the threshold temperature of methane oxidation was estimated to be −4 to −11 °C, which suggested methane oxidation at subzero temperatures. 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 keep their potential activities even under anoxic and frozen conditions and immediately utilize methane when the conditions become favorable. On the other hand, the inhibitor of methane oxidation did not affect the methane flux from the sedge and moss zones in situ, which indicated the minor role of plant-associated methane oxidation.

Jun Murase et al.
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Jun Murase et al.
Jun Murase et al.
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We determined the potential methane oxidation rate of the wetland soils in northeastern Siberia in situ or immediately after sampling to avoid the possible influence of sample storage. The soils had a high methane oxidation potential even under anoxic and frozen conditions, while the plant-associated methane oxidation is negligible. The results show the high tolerance and resilience of methane oxidation to the unfavorable conditions, contributing to understanding the methane cycle in the Arctic.
We determined the potential methane oxidation rate of the wetland soils in northeastern Siberia...
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