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Methane and carbon dioxide exchange in a peatland ecosystem in north central Minnesota
Abstract
Methane and carbon dioxide fluxes were measured using the eddy correlation technique in a peatland in north central Minnesota during the 1991 and 1992 seasons. The objective of the study was to quantify methane and carbon dioxide fluxes and investigate their dependence on controlling variables. The vegetation at the site was dominated by Sphagnum papillosum, Scheuchzeria palustris and Chamaedaphne calyculata. Compared to the 30-year normal, the 1991 season was warmer and drier, while the 1992 season was wetter and cooler. Methane flux (daytime average) peaked at 160 mg m$\sp{-2}$ d$\sp{-1}$ during mid July in 1991. The peak flux (190 mg m$\sp{-2}$ d$\sp{-1}$) in 1992 occurred about 3 weeks later. A low water table during most of the 1991 season resulted in higher methane oxidation and consequent decline in methane flux. Despite lower peat temperature during the later half of the 1992 season, methane flux was higher by 30-40 mg m$\sp{-2}$ d$\sp{-1}$ because of the overriding influence of the water table on methane emissions. When the water table was below the surface, peat temperature and water table depth together accounted for about 70% of the variance in the methane flux data. When the water table was above the surface, there was no consistent relationship between methane flux and water table position. Peat temperature alone accounted for about 55% of the variance in methane flux. Seasonally (mid May-mid October) integrated values of the daily net ecosystem CO$\sb2$ exchange indicated that this ecosystem was a source of atmospheric CO$\sb2,$ releasing about 71 g C m$\sp{-2}$ in 1991 when temperature was high and water table was low. However, over a similar period in 1992 when temperature was cooler and water table was high, this ecosystem was a sink for atmospheric CO$\sb2$ with a net accumulation of about 32 g C m$\sp{-2}$. Concurrently measured (midday) values of methane flux and canopy photosynthesis were examined under a variety of conditions. While the overall seasonal patterns of methane flux and photosynthesis seemed similar, the day to day variations in photosynthesis were not closely related to changes in methane flux.
Subject Area
Biogeochemistry|Biophysics
Recommended Citation
Shurpali, Narasinha J, "Methane and carbon dioxide exchange in a peatland ecosystem in north central Minnesota" (1995). ETD collection for University of Nebraska-Lincoln. AAI9528831.
https://digitalcommons.unl.edu/dissertations/AAI9528831