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

Camilo Rey-Sanchez, Gil Bohrer, Julie Slater, Yueh Fen Li, Roger Grau-Andrés, Yushan Hao, Virginia I Rich, G. Matt Davies

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

Peatlands are a large source of methane (<span classCombining double low line"inline-formula">CH4</span>) to the atmosphere, yet the uncertainty around the estimates of <span classCombining double low line"inline-formula">CH4</span> flux from peatlands is large. To better understand the spatial heterogeneity in temperate peatland <span classCombining double low line"inline-formula">CH4</span> emissions and their response to physical and biological drivers, we studied <span classCombining double low line"inline-formula">CH4</span> 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), <span classCombining double low line"inline-formula">CH4</span> pore-water concentration at different peat depths, <span classCombining double low line"inline-formula">CH4</span> fluxes from the ground and from representative plant species using chambers, and microbial community composition with a focus here on known methanogens and methanotrophs. Integrated <span classCombining double low line"inline-formula">CH4</span> emissions for the growing season were estimated as <span classCombining double low line"inline-formula">315.4±166</span>&thinsp;<span classCombining double low line"inline-formula"><math xmlnsCombining double low line"http://www.w3.org/1998/Math/MathML" idCombining double low line"M9" displayCombining double low line"inline" overflowCombining double low line"scroll" dspmathCombining double low line"mathml"><mrow classCombining double low line"unit"><mi mathvariantCombining double low line"normal">mg</mi><mspace widthCombining double low line"0.125em" linebreakCombining double low line"nobreak"/><msub><mi mathvariantCombining double low line"normal">CH</mi><mn mathvariantCombining double low line"normal">4</mn></msub><mspace widthCombining double low line"0.125em" linebreakCombining double low line"nobreak"/><msup><mi mathvariantCombining double low line"normal">m</mi><mrow><mo>-</mo><mn mathvariantCombining double low line"normal">2</mn></mrow></msup><mspace widthCombining double low line"0.125em" linebreakCombining double low line"nobreak"/><msup><mi mathvariantCombining double low line"normal">d</mi><mrow><mo>-</mo><mn mathvariantCombining double low line"normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svgCombining double low line"http://www.w3.org/2000/svg" widthCombining double low line"78pt" heightCombining double low line"16pt" classCombining double low line"svg-formula" dspmathCombining double low line"mathimg" md5hashCombining double low line"ef20001b32af2721b2dc95616d9bbffd"><svg:image xmlns:xlinkCombining double low line"http://www.w3.org/1999/xlink" xlink:hrefCombining double low line"bg-16-3207-2019-ie00001.svg" widthCombining double low line"78pt" heightCombining double low line"16pt" srcCombining double low line"bg-16-3207-2019-ie00001.png"/></svg:svg></span></span> in 2017 and <span classCombining double low line"inline-formula">362.3±687</span>&thinsp;<span classCombining double low line"inline-formula"><math xmlnsCombining double low line"http://www.w3.org/1998/Math/MathML" idCombining double low line"M11" displayCombining double low line"inline" overflowCombining double low line"scroll" dspmathCombining double low line"mathml"><mrow classCombining double low line"unit"><mi mathvariantCombining double low line"normal">mg</mi><mspace widthCombining double low line"0.125em" linebreakCombining double low line"nobreak"/><msub><mi mathvariantCombining double low line"normal">CH</mi><mn mathvariantCombining double low line"normal">4</mn></msub><mspace linebreakCombining double low line"nobreak" widthCombining double low line"0.125em"/><msup><mi mathvariantCombining double low line"normal">m</mi><mrow><mo>-</mo><mn mathvariantCombining double low line"normal">2</mn></mrow></msup><mspace linebreakCombining double low line"nobreak" widthCombining double low line"0.125em"/><msup><mi mathvariantCombining double low line"normal">d</mi><mrow><mo>-</mo><mn mathvariantCombining double low line"normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svgCombining double low line"http://www.w3.org/2000/svg" widthCombining double low line"78pt" heightCombining double low line"16pt" classCombining double low line"svg-formula" dspmathCombining double low line"mathimg" md5hashCombining double low line"76b89e953aa6d4e973a65484dea0a34b"><svg:image xmlns:xlinkCombining double low line"http://www.w3.org/1999/xlink" xlink:hrefCombining double low line"bg-16-3207-2019-ie00002.svg" widthCombining double low line"78pt" heightCombining double low line"16pt" srcCombining double low line"bg-16-3207-2019-ie00002.png"/></svg:svg></span></span> in 2018. Median <span classCombining double low line"inline-formula">CH4</span> emission was highest in the open water, then it decreased and became more variable through the concentric vegetation zones as the WL dropped, with extreme emission hotspots observed in the tamarack mixed woodlands (Tamarack) and low emissions in the restored zone (18.8-30.3&thinsp;<span classCombining double low line"inline-formula"><math xmlnsCombining double low line"http://www.w3.org/1998/Math/MathML" idCombining double low line"M13" displayCombining double low line"inline" overflowCombining double low line"scroll" dspmathCombining double low line"mathml"><mrow classCombining double low line"unit"><mi mathvariantCombining double low line"normal">mg</mi><mspace linebreakCombining double low line"nobreak" widthCombining double low line"0.125em"/><msub><mi mathvariantCombining double low line"normal">CH</mi><mn mathvariantCombining double low line"normal">4</mn></msub><mspace linebreakCombining double low line"nobreak" widthCombining double low line"0.125em"/><msup><mi mathvariantCombining double low line"normal">m</mi><mrow><mo>-</mo><mn mathvariantCombining double low line"normal">2</mn></mrow></msup><mspace linebreakCombining double low line"nobreak" widthCombining double low line"0.125em"/><msup><mi mathvariantCombining double low line"normal">d</mi><mrow><mo>-</mo><mn mathvariantCombining double low line"normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svgCombining double low line"http://www.w3.org/2000/svg" widthCombining double low line"78pt" heightCombining double low line"16pt" classCombining double low line"svg-formula" dspmathCombining double low line"mathimg" md5hashCombining double low line"22bd542194aabf3918bdd58dbd499748"><svg:image xmlns:xlinkCombining double low line"http://www.w3.org/1999/xlink" xlink:hrefCombining double low line"bg-16-3207-2019-ie00003.svg" widthCombining double low line"78pt" heightCombining double low line"16pt" srcCombining double low line"bg-16-3207-2019-ie00003.png"/></svg:svg></span></span>). Generally, <span classCombining double low line"inline-formula">CH4</span> flux from above-ground vegetation was negligible compared to ground flux (<span classCombining double low line"inline-formula">&lt;0.4</span>&thinsp;%), although blueberry plants were a small <span classCombining double low line"inline-formula">CH4</span> sink. Pore-water <span classCombining double low line"inline-formula">CH4</span> concentrations varied significantly among zones, with the highest values in the Tamarack zone, close to saturation, and the lowest values in the restored zone. While the <span classCombining double low line"inline-formula">CH4</span> 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 <span classCombining double low line"inline-formula">CH4</span> transfer velocity (the <span classCombining double low line"inline-formula">CH4</span> flux divided by the difference in <span classCombining double low line"inline-formula">CH4</span> pore-water concentration between the top of the peat profile and the concentration in equilibrium with the atmosphere). Since ebullition and plant-mediated transport were not important sources of <span classCombining double low line"inline-formula">CH4</span> and the peat structure and porosity were similar across the different zones in the bog, we conclude that the differences in <span classCombining double low line"inline-formula">CH4</span> transfer velocities, and thus the flux, are driven by the ratio of methanogen to methanotroph relative abundance close to the surface. This study illustrates the importance of the interactions between water-level and microbial composition to better understand <span classCombining double low line"inline-formula">CH4</span> fluxes from bogs and wetlands in general.

Original languageEnglish (US)
Pages (from-to)3207-3231
Number of pages25
JournalBiogeosciences
Volume16
Issue number16
DOIs
StatePublished - Aug 29 2019

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Earth-Surface Processes

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