Methane flux from Minnesota Peatlands

Abstract

Northern (>40°N) wetlands have been suggested as the largest natural source of methane (CH4) to the troposphere. To refine our estimates of source strengths from this region and to investigate climatic controls on the process, fluxes were measured from a variety of Minnesota peatlands during May, June, and August 1986. Sites included forested and unforested ombrotrophic bogs and minerotrophic fens in and near the U.S. Department of Agriculture Marcell Experimental Forest and the Red Lake peatlands. Late spring and summer fluxes ranged from 11 to 866 mg CH4 m−2 d−1, averaging 207 mg CH4 m−2 d−1 overall. At Marcell Forest, forested bogs and fen sites had lower fluxes (averages of 77 ± 21 mg CH4 m−2 d−1 and 142 ± 19 mg CH4 m−2 d−1) than open bogs (average of 294 ± 30 mg CH4 m−2 d−1). In the Red Lake peatland, circumneutral fens, with standing water above the peat surface, produced more methane than acid bog sites in which the water table was beneath the moss surface (325 ± 31 and 102 ± 13 mg CH4 m−2 d−1, respectively). Peat temperature was an important control. Methane flux increased in response to increasing soil temperature. For example, the open bog in the Marcell Forest with the highest CH4 flux exhibited a 74‐fold increase in flux over a three‐fold increase in temperature. We estimate that the methane flux from all peatlands north of 40° may be on the order of 70 to 90 Tg/yr though estimates of this sort are plagued by uncertainties in the areal extent of peatlands, length of the CH4 producing season, and the spatial and temporal variability of the flux.

Methane Emissions from Wetlands in the Midboreal Region of Northern Ontario, Canada

“…However, thicket swamps, which were a large source of CH4 emission in southern Ontario, were not measured in this study. The large range of fluxes for bogs, fens, and conifer swamps in this study encompass the range of fluxes for most other boreal wetlands (reviewed in Roulet et al 1992), although fluxes from Minnesota bogs are consistently higher (e.g., Harriss et al 1985, Crill et al 1988, Dise 1993. Since the range of fluxes in this study was correlated with mean water table depth, hydrology may explain different fluxes from other boreal wetlands as well.…”

Northern fens: methane flux and climatic change

“…These crude, simplistic calculations suggest that the methane-climate feedback for subarctic fens is very sensitive to small changes in the physical Crill et al (1988), Harriss et al (1982Harriss et al ( , 1988Harriss et al ( , 1985, Knowles (1989, 1990), , Sebacher et al ( 1986 ), Svensson and Rosswall ( 1984 ), Whalen and Reeburgh ( 1988 ), Wilson et al ( 1989 ). The solid line indicates the best fit (CH 4 = 116.7e 0 · 096 w'; r 2 = 0.38; Sy= 0.71) developed from the Schefferville data for the Capricorn fen .…”

“…Mid-to high-latitude regions contain the largest area of wetlands, particularly latitudes between 50 and 70°N (Aselmann and Crutzen, 1989). Measurements of methane flux from northern boreal and subarctic wetlands reveal that annual em1ss1on rates can range from < 0.5 to > 10 g CH 4 m -2 yr-1 (e.g., Crill et al, 1988;Knowles, 1987, 1990;Sebacher et al, 1986;Svensson, 1980;Whalen and Reeburgh, 1988). Major controls on these emission rates are temperature, water table position and soil and plants, as they influence the microbiological processes of methane production and oxidation.…”

Modelling CH&lt;sub&gt;4&lt;/sub&gt; emissions from arctic wetlands: effects of hydrological parameterization

“…The largest CH 4 atmospheric mixing ratios are north of 40 • N (Steele et al, 1987). This distribution coincides with the concentration of wetlands in the northern hemisphere and suggests that wetlands in this area may make a significant contribution to the global CH 4 budget (Moore and Knowles, 1990;Aselmann and Crutzen, 1989;Crill et al, 1988;Matthews and Fung, 1987).…”