Methane Efflux from Emergent Vegetation in Peatlands

Shannon, R. D.; White, Jeffrey R.; Lawson, Joan E.; Gilmour, Bradley S.

doi:10.2307/2261359

Cited by 192 publications

(156 citation statements)

References 34 publications

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“…Although contrary to much of the current literature which suggests the presence of aerenchyma containing vegetation (i.e. rushes and sedges) increases emissions (Shannon et al, 1996;Yu et al, 1997;Greenup et al, 2000), a similar result to that observed here was found in an earlier study with mesocosms collected from Auchencorth Moss (Dinsmore et al, in press). As well as providing a source of readily available organic substrate, plants containing aerenchymous tissue can provide a direct pathway for many greenhouse gases to the atmosphere, bypassing the aerobic surface horizon and therefore reducing the potential for oxidation (Bartlett and Harriss, 1993;Minkkinen and Laine, 2006).…”

Section: Controls On Spatial Variationcontrasting

confidence: 98%

Spatial and temporal variability in CH4 and N2O fluxes from a Scottish ombrotrophic peatland: Implications for modelling and up-scaling

Dinsmore

Skiba

Billett

et al. 2009

Soil Biology and Biochemistry

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Peatlands typically exhibit significant spatial heterogeneity which can lead to large uncertainties when catchment scale greenhouse gas fluxes are extrapolated from chamber measurements (generally <1 m 2 ). Here we examined the underlying environmental and vegetation characteristics which led to within-site variability in both CH 4 and N 2 O emissions and the importance of such variability in up-scaling. We also consider within-site variation in the controls of temporal dynamics. Net annual emissions (and coefficients of variation) for CH 4 and N 2 O were 1.06 kg ha -1 y -1 (300%) and 0.02 kg ha -1 y -1 (410%), respectively. The riparian zone was a significant CH 4 hotspot contributing ~12% of the total catchment emissions whilst covering only ~0.5% of the catchment area. In contrast to many other studies we found smaller CH 4 emissions and greater uptake in chambers containing either sedges or rushes. We also found clear differences in the drivers of temporal CH 4 dynamics across the site, e.g.water table was important only in chambers which did not contain aerenchymous plants. We suggest that depending on the heterogeneity of the site, flux models could be improved by incorporating a number of spatially distinct sub-models, rather than a single model parameterized using whole-catchment averages.

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Section: Controls On Spatial Variationcontrasting

confidence: 98%

Spatial and temporal variability in CH4 and N2O fluxes from a Scottish ombrotrophic peatland: Implications for modelling and up-scaling

Dinsmore

Skiba

Billett

et al. 2009

Soil Biology and Biochemistry

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show abstract

“…These low CH 4 fluxes are consistent with observations from other forest riparian areas, where much of the CH 4 produced deeper in the soil is oxidized before reaching the soil surface (humid tropics: Teh et al, 2005;floodplain wetland: Batson et al, 2015;seasonally dry ecosystems: von Fischer and Hedin, 2002;Castaldi et al, 2006;riparian area: Vidon et al, 2015). The few large fluxes observed might be due to limited sampling when gas wells were inundated (potentially missing ebullition events); low temperatures and diffusivity; fluxes of dissolved CH 4 through the groundwater to the stream channel (Itoh et al, 2007); recalcitrance of organic matter (Valentine et al, 1994;Updegraff et al, 1995); or lack of sampling of fluxes from riparian vegetation, which can be an important transport process in wetlands (Whiting and Chanton, 1993;Shannon et al, 1996;Bridgham et al, 2013). Given these caveats, 115 samples over 13 weeks of sampling show that, although riparian areas can be locations of high rates of biogeochemical cycling, large net emissions of CH 4 were not common among the riparian sites sampled at TCEF.…”

Section: Discussionmentioning

confidence: 99%

Landscape analysis of soil methane flux across complex terrain

2018

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Abstract. Relationships between methane (CH 4 ) fluxes and environmental conditions have been extensively explored in saturated soils, while research has been less prevalent in aerated soils because of the relatively small magnitudes of CH 4 fluxes that occur in dry soils. Our study builds on previous carbon cycle research at Tenderfoot Creek Experimental Forest, Montana, to identify how environmental conditions reflected by topographic metrics can be leveraged to estimate watershed scale CH 4 fluxes from point scale measurements. Here, we measured soil CH 4 concentrations and fluxes across a range of landscape positions (7 riparian, 25 upland), utilizing topographic and seasonal (29 May-12 September) gradients to examine the relationships between environmental variables, hydrologic dynamics, and CH 4 emission and uptake. Riparian areas emitted small fluxes of CH 4 throughout the study (median: 0.186 µg CH 4 -C m −2 h −1 ) and uplands increased in sink strength with dry-down of the watershed (median: −22.9 µg CH 4 -C m −2 h −1 ). Locations with volumetric water content (VWC) below 38 % were methane sinks, and uptake increased with decreasing VWC. Above 43 % VWC, net CH 4 efflux occurred, and at intermediate VWC net fluxes were near zero. Riparian sites had nearneutral cumulative seasonal flux, and cumulative uptake of CH 4 in the uplands was significantly related to topographic indices. These relationships were used to model the net seasonal CH 4 flux of the upper Stringer Creek watershed (−1.75 kg CH 4 -C ha −1 ). This spatially distributed estimate was 111 % larger than that obtained by simply extrapolating the mean CH 4 flux to the entire watershed area. Our results highlight the importance of quantifying the space-time variability of net CH 4 fluxes as predicted by the frequency distribution of landscape positions when assessing watershed scale greenhouse gas balances.

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“…It seems likely that the peak emissions from the floating mat were caused by an optimum of wet conditions in the peat, favoring methanogenesis and impeding methane oxidation, presence of some Carex aquatilis providing for conduit transport of the gas, and potentially by a release of methane from groundwater entering the land-water interface. CH 4 flux through plants with aerenchymatic tissues can be responsible for 50 to 97 % of the total CH 4 flux in peatlands because the aerenchyma link the anaerobic zone of CH 4 production with the atmosphere (Kelker and Chanton, 1997;Kutzbach et al, 2004;Shannon et al, 1996). Kutzbach et al (2004) found a strong positive correlation between the density of C. aquatilis culms and CH 4 fluxes, as well as a contribution of 66 ± 20 % of the plant-mediated CH 4 flux through C. aquatilis to the total flux in wet polygonal tundra.…”

Section: Spatial Pattern Of Ch 4 and Co 2 Fluxesmentioning

confidence: 99%

Summer fluxes of methane and carbon dioxide from a pond and floating mat in a continental Canadian peatland

et al. 2016

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Abstract. Ponds smaller than 10 000 m2 likely account for about one-third of the global lake perimeter. The release of methane (CH4) and carbon dioxide (CO2) from these ponds is often high and significant on the landscape scale. We measured CO2 and CH4 fluxes in a temperate peatland in southern Ontario, Canada, in summer 2014 along a transect from the open water of a small pond (847 m2) towards the surrounding floating mat (5993 m2) and in a peatland reference area. We used a high-frequency closed chamber technique and distinguished between diffusive and ebullitive CH4 fluxes. CH4 fluxes and CH4 bubble frequency increased from a median of 0.14 (0.00 to 0.43) mmol m−2 h−1 and 4 events m−2 h−1 on the open water to a median of 0.80 (0.20 to 14.97) mmol m−2 h−1 and 168 events m−2 h−1 on the floating mat. The mat was a summer hot spot of CH4 emissions. Fluxes were 1 order of magnitude higher than at an adjacent peatland site. During daytime the pond was a net source of CO2 equivalents to the atmosphere amounting to 0.13 (−0.02 to 1.06) g CO2 equivalents m−2 h−1, whereas the adjacent peatland site acted as a sink of −0.78 (−1.54 to 0.29) g CO2 equivalents m−2 h−1. The photosynthetic CO2 uptake on the floating mat did not counterbalance the high CH4 emissions, which turned the floating mat into a strong net source of 0.21 (−0.11 to 2.12) g CO2 equivalents m−2 h−1. This study highlights the large small-scale variability of CH4 fluxes and CH4 bubble frequency at the peatland–pond interface and the importance of the often large ecotone areas surrounding small ponds as a source of greenhouse gases to the atmosphere.

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Methane Efflux from Emergent Vegetation in Peatlands

Cited by 192 publications

References 34 publications

Spatial and temporal variability in CH4 and N2O fluxes from a Scottish ombrotrophic peatland: Implications for modelling and up-scaling

Spatial and temporal variability in CH4 and N2O fluxes from a Scottish ombrotrophic peatland: Implications for modelling and up-scaling

Landscape analysis of soil methane flux across complex terrain

Summer fluxes of methane and carbon dioxide from a pond and floating mat in a continental Canadian peatland

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