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https://doi.org/10.5194/bg-2019-116
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-116
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 23 Apr 2019

Research article | 23 Apr 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

The ratio of methanogens to methanotrophs and water-level dynamics drive methane exchange velocity in a temperate kettle-hole peat bog

Camilo Rey-Sanchez1,a, Gil Bohrer1, Julie Slater2, Yueh-Fen Li3, Roger Grau-Andrés2, Yushan Hao2, Virginia I. Rich3, and G. Matt Davies2 Camilo Rey-Sanchez et al.
  • 1Department of Civil and Environmental Engineering and Geodetic Science, The Ohio State University, Columbus, Ohio, 43210, USA
  • 2School of Environment and Natural Resources, The Ohio State University, Columbus, Ohio, 43210, USA
  • 3Department of Microbiology, The Ohio State University, Columbus, Ohio, 43210, USA
  • acurrent address: Department of Environmental Science, Management and Policy, University of California-Berkeley, California, 94720, USA

Abstract. Peatlands are a large source of methane (CH4) to the atmosphere, yet the uncertainty around the estimates of CH4 flux from peatlands is large. To better understand the spatial heterogeneity in temperate peatland CH4 emissions and their response to physical and biological drivers, we studied CH4 dynamics throughout the growing seasons of 2017 and 2018 in Flatiron Lake Bog, a kettle-hole peat bog in Ohio. The site is composed of six different hydro-biological zones: an open water zone, four concentric vegetation zones surrounding the open water, and a restored zone connected to the main bog by a narrow channel. At each of these locations, we monitored water level (WL), CH4 pore-water concentration at different peat depths, CH4 fluxes from the ground and from representative plant species using chambers, and microbial community composition with focus here on known methanogens and methanotrophs. Integrated CH4 emissions for the growing season were estimated as 315.4 ± 166 mg CH4 m−2 d−1 in 2017, and 362.3 ± 687 mg CH4 m−2 d−1 in 2018. Median CH4 emission was highest in the open water, then decreased and became more variable through the concentric vegetation zones as the WL dropped, with extreme emission hotspots observed in the Tamarack mixed woodlands (TMW), and low emissions in the restored zone (18.8–30.3 mg CH4 m−2 d−1). Generally, CH4 flux from above-ground vegetation was negligible compared to ground flux (< 0.4 %), although blueberry plants were a small CH4 sink. Pore-water CH4 concentrations varied significantly among zones, with the highest values in the TMW, close to saturation, and the lowest values in the restored zone. While the CH4 fluxes and pore-water concentrations were not correlated with methanogen relative abundance, the ratio of methanogens to methanotrophs in the upper portion of the peat was significantly correlated to CH4 exchange velocity (here defined as the ratio between pore-water concentration of CH4 in the top of the peat profile and CH4 flux). This study illustrates the importance of the interactions between water level and microbial composition to better understand CH4 fluxes from bogs, and wetlands in general.

Camilo Rey-Sanchez et al.
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Camilo Rey-Sanchez et al.
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Short summary
It is estimated that natural wetlands emit approximately 30% of all the methane released to the atmosphere, yet, these estimates are highly uncertain due to the complexity of biological, chemical and physical processes controlling methane emissions. In this study, we explore how some of these key processes drive methane emissions in a temperate peat bog. We show that the composition of microbial methane cyclers in the upper portion of the peat drives the velocity of methane release to the air.
It is estimated that natural wetlands emit approximately 30% of all the methane released to the...
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