A Multi-Year Record of Methane Flux at the Mer Bleue Bog, Southern CanadaAbstractIntroductionMaterials and MethodsSite DescriptionField MeasurementsLaboratory MeasurementsResultsCH4 Fluxes and Concentrations, Vegetation and Peat CH4 Production/Oxidation PotentialsRelationship Between CH4 Flux and Environmental VariablesDiscussionConclusionsAcknowledgementsReferencesA Multi-Year Record of MethaneFlux at the Mer Bleue Bog, SouthernCanadaTim R. Moore,1* Allison De Young,1Jill L. Bubier,2Elyn R. Humphreys,3Peter M. Lafleur,4and Nigel T. Roulet11Department of Geography, and Global Environmental & Climate Change Centre, McGill University, 805 Sherbrooke St. W, Montreal,Quebec H3A2K6, Canada;2Mount Holyoke College, 50 College Street, South Hadley, Massachusetts 01075, USA;3Department ofGeography and Environmental Studies, Carleton University, Ottawa, Ontario K1S 5B6, Canada;4Department of Geography,Trent University, Peterborough, Ontario K9J7B8, CanadaABSTRACTThe Mer Bleue peatland is a large ombrotrophicbog with hummock-lawn microtopography, poorfen sections and beaver ponds at the margin.Average growing-season (May–October) fluxes ofmethane (CH4) measured in 2002–2003 across thebog ranged from less than 5 mg m-2d-1in hum-mocks, to greater than 100 mg m-2d-1in lawnsand ponds. The average position of the water tableexplained about half of the variation in the seasonaverage CH4fluxes, similar to that observed inmany other peatlands in Canada and elsewhere.The flux varied most when the water table positionranged between -15 and -40 cm. To betterestablish the factors that influence this variability,we measured CH4flux at approximately weeklyintervals from May to November for 5 years (2004–2008) at 12 collars representing the water table andvegetation variations typical of the peatland. Overthe snow-free season, peat temperature is thedominant correlate and the difference among thecollars’ seasonal average CH4flux is partiallydependent on water table position. A third impor-tant correlate on CH4flux is vegetation, particularlythe presence of Eriophorum vaginatum, which in-creases CH4flux, as well as differences in the po-tential of the peat profile to produce and consumeCH4under anaerobic and aerobic conditions. Thecombination of peat temperature and water tableposition with vegetation cover was able to explainapproximately 44% of the variation in daily CH4flux, based on 1097 individual measurements.There was considerable inter-annual variation influxes, associated with varying peat thermal andwater table regimes in response to variations inweather, but also by variations in the water level inperipheral ponds, associated with beaver damactivity. Raised water level in the beaver ponds ledto higher water tables and increased CH4emissionin the peatland.Key words: greenhouse gases; peatlands; wet-lands; water table; Eriophorum vaginatum; Castorcanadensis.INTRODUCTIONSince the early studies (for example, Clymo andReddaway 1971; Svensson 1980; Harriss and others1982), over 1100 papers have been published onthe exchange of methane (CH4) between peatlandsReceived 21 October 2010; accepted 10 March 2011;published online 6 April 2011Author Contributions: TRM conceived and directed the study; ADYcollected and analyzed much of the data; JLB, ERH, PML and NTR con-tributed data to the study and aided in the interpretation of the results; allsix wrote the paper.*Corresponding author; e-mail: [email protected] (2011) 14: 646–657DOI: 10.1007/s10021-011-9435-9 2011 Springer Science+Business Media, LLC646and the atmosphere (ISI Web of Science). Througha combination of field and laboratory studies, thescientific community has been able to define therange of fluxes, with their high spatial variability(several orders of magnitude over short distances)and strong seasonal variability, which helps con-strain models (for example Walter and Heimann2000) and the spatial and temporal contribution ofwetlands to atmospheric CH4. Major controls onfluxes include microbial rates of CH4productionand consumption, temperature and water tableposition and vegetation, as well as processes ofdiffusion, ebullition and transport through theaerenchyma of plants (see Whalen 2005).Harriss and others (1982) noted almost 30 yearsago ‘… the potential complexity of the problem ofquantitatively determining long-term net flux ofCH4from a wetland system to the atmosphere’ andthis complexity remains. In particular, many fieldcampaigns have been run over short periods, for 1or 2 years, and there is little knowledge of theinterannual variability in CH4emission rates (withthe exception of the decadal record at Sallie’s Fen,NH, U.S.A., see Treat and others 2007). In addition,many studies focus on only one or two factorscontrolling the rates and do not address the highdegree of small-scale spatial variability that influ-ences scaling-up attempts (see Baird and others2009).At large temporal and spatial scales, water tableposition exerts an important control on CH4emis-sion rates, through its control on the distribution ofoxic and anoxic parts of the peat profile, and indi-rectly through vegetation and substrate quality. Atthe Mer Bleue peatland in south central Canada, wemeasured the May to October 2002–2003 emissionof CH4from a series of collars, representing themajor range of vegetation and water table positionin the peatland, from hummock-lawn-hollow bogthrough poor fen to beaver ponds. Overall, therewas a strong correlation between the seasonalaverage CH4flux and the average water table po-sition (Figure 1A). This pattern has been repeatedin many other studies, as illustrated in Figure 1B,where the slopes of the regression betweenlog10CH4flux and water table depth are similar, butthe intercepts vary. Within any of these relation-ships, however, there is considerable variationaround the best-fit line, showing that factors otherthan water table depth play an important role,particularly in the intermediate water table depths(at Mer Bleue between -15 and -40 cm).In this paper, we report on CH4fluxes measuredat 12 permanent locations in the bog section of MerBleue, to better identify the correlates on fluxes.Measurements were made at 1–2 week intervalsfrom May to November over 5 years (2004–2008),to establish the interannual variability in CH4Mer BleueueM1101001000Water table position (cm)Average CH4 flux (mg m-2 d-1)log10CH4 = 1.71 + 0.028WTr2 = 0.48, p < 0.001, n = 48 A0.11101001000-75 -50 -25 0 25 -60 -50