Spatiotemporal variability in peatland subsurface methane dynamics

Strack, Maria; Waddington, J. M.

doi:10.1029/2007jg000472

Cited by 47 publications

(58 citation statements)

References 45 publications

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“…Although these concentrations are far below the solubility limit of methane (i.e., about 2,000 lM at 10°C), we cannot exclude that some methane might be entrapped as bubbles in the rhizosphere. Strack and Waddington (2008) estimated that more than 50% of the subsurface methane stock can be entrapped in bubbles. Third, we have no detailed data on the development of the vegetation from June to September and therefore we cannot assess of whether the plant mediated transport of methane has an impact on the shape of the profiles and the amount of methane in the subsurface.…”

Section: Methane Fluxes and Profilesmentioning

confidence: 99%

“…Northern peatlands store between 370 and 455 Gt of carbon (Gorham 1991;Turunen et al 2002). Methane release from these peatlands is highly variable seasonally and at spatial scales ranging from microtopographic to regional (e.g., Bartlett et al 1992; Morrissey and Livingston 1992;Shannon and White 1994;Bubier et al 1995;Christensen et al 1995;Moore and Roulet 1991;Bellisario et al 1999;Joabsson and Christensen 2001;Kutzbach et al 2004;Whalen 2005;Strack and Waddington 2008).…”

Section: Introductionmentioning

confidence: 99%

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Methane emissions from an alpine fen in central Switzerland

2011

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Methane emissions and below ground methane pore water concentrations were determined in an alpine fen at 1,915 m a.s.l. in central Switzerland. The fen represented an acidic (pH 4.5-4.9), nutrient-poor to mesotrophic habitat dominated by Carex limosa, Carex rostrata, Trichophorum caespitosum and Sphagnum species. From late fall to late spring the fen was snow-covered. Throughout winter the temperatures never dropped below 0°C at 5 cm below the vegetation surface. Methane emissions in June, July, August and September were in the range of 125 (±26)-313 (±71) mg CH 4 m -2 day -1 with a tendency to decrease along the summer season. Mean methane pore water concentrations at a depth of 20-40 cm below the vegetation surface were 526 (±32) lM in June and in the range of 144 (±10)-233 (±7) lM in July, August and September. At a depth of 0-20 cm the mean methane pore water concentrations dropped back to \20 lM with an almost linear decrease between 0 and 15 cm. Oxygen pore water concentrations were close to air saturation in the first few centimeters and dropped back below detection limit at a depth of 20 cm. In July and August the pore water concentrations of dissolved organic carbon (DOC) were in the range of 7.2-10.1 mg C l -1 at all depths. The pore water concentrations of acetate, formate and oxalate were in the range of 2.0-8.2 lM at all depths. Methanotrophic and methanogenic communities were quantified using pmoA and mcrA, respectively, as marker genes. The abundances of both communities showed a distinct peak at a depth of 10-15 cm below the vegetation surface.

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Section: Methane Fluxes and Profilesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Methane emissions from an alpine fen in central Switzerland

2011

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“…About 6-16% of total non-anthropogenic methane emission is thought to be contributed by lakes (Bastviken et al, 2004). It is estimated that 33-88% of the total methane in the sediment is in the gas-phase (Tokida et al, 2005a;Strack and Waddington, 2008). Since methane is continuously produced in lake sediment and is relatively insoluble in water, methane-containing bubbles are formed in pore water (Boudreau et al, 2005;Laing et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Intense methane ebullition from open water area of a shallow peatland lake on the eastern Tibetan Plateau

Zhu

Chen

et al. 2016

Science of The Total Environment

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“…When specific within-site sampling locations were considered, all the sites showed the same trend of sealed pore-water samplers having higher CH 4 concentrations than open samplers. However, this difference was only significant (Mann-Whitney, p < 0Ð05) at the floating mat site at SCB and at the marl site at FCE (Figure 1 Strack and Waddington, 2008), and CH 4 flux ranged from 123 to …”

Section: Pore-water Ch 4 Concentrationsmentioning

confidence: 88%

Evidence that piezometers vent gas from peat soils and implications for pore‐water pressure and hydraulic conductivity measurements

Waddington¹,

Ketcheson²,

Kellner³

et al. 2009

Hydrological Processes

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Entrapped gas bubbles in peat can alter the buoyancy, storativity, void ratio and expansion/contraction properties of the peat. Moreover, when gas bubbles block water-conducting pores they can significantly reduce saturated hydraulic conductivity and create zones of over-pressuring, perhaps leading to an alteration in the magnitude and direction of groundwater flow and solute transport. Some previous researches have demonstrated that these zones of over-pressuring are not observed by the measurements of pore-water pressures using open-pipe piezometers in peat; rather, they are only observed with pressure transducers sealed in the peat. In has been hypothesized that open-pipe piezometers vent entrapped CH 4 to the atmosphere and thereby do not permit the natural development of zones of entrapped gas. Here we present findings of the study to investigate whether piezometers vent subsurface CH 4 to the atmosphere and whether the presence of piezometers alters the subsurface concentration of dissolved CH 4 . We measured the flux of methane venting from the piezometers and also determined changes in pore-water CH 4 concentration at a rich fen in southern Ontario and a poor fen in southern Quebec, in the summer of 2004. Seasonally averaged CH 4 flux from piezometers was 1450 and 37·8-mg CH 4 m −2 d −1 at the southern Ontario site and Quebec site, respectively. The flux at the Ontario site was two orders of magnitude greater than the diffusive flux at the site. CH 4 pore-water concentrations were significantly lower in open piezometers than in water taken from sealed samplers at both the Ontario and Quebec sites. The flux of CH 4 from piezometers decreased throughout the season suggesting that CH 4 venting through the piezometer exceeded the rate of methanogenesis in the peat. Consequently we conclude that piezometers may alter the gas dynamics of some peatlands. We suggest that less-invasive techniques (e.g. buried pressure transducers, tracer experiments) are needed for the accurate measurement of porewater pressures and hydraulic conductivity in peatlands with a large entrapped gas component. Furthermore, we argue that caution must be made in interpreting results from previous peatland hydrology studies that use these traditional methods.

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Spatiotemporal variability in peatland subsurface methane dynamics

Cited by 47 publications

References 45 publications

Methane emissions from an alpine fen in central Switzerland

Methane emissions from an alpine fen in central Switzerland

Intense methane ebullition from open water area of a shallow peatland lake on the eastern Tibetan Plateau

Evidence that piezometers vent gas from peat soils and implications for pore‐water pressure and hydraulic conductivity measurements

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