Carbon exchange over four growing seasons for a subarctic sedge fen in northern Manitoba, Canada

Net ecosystem exchange of carbon (NEE) was measured using eddy covariance for four growing seasons at a subarctic hummocky fen in northern Manitoba, Canada. Over a 115-day measurement period each year, cumulative NEE ranged from a gain of 49 g C m-2 to a loss of 16 g C m-2 with a mean loss of 6 g C m-2 from the fen, with an uncertainty of about Âą34 g C m-2. Ecosystem respiration decreased with higher water tables (r2=0.3), especially in one summer when flooding occurred to 0.12 m above the peat surface. Additional methane emissions previously documented for the site of 4 to 5.7 g C m-2 y-1 added to the carbon loss. Carbon loss was measured from this same fen in the 1990s and it is likely that the carbon gain (peat accumulation) during past centuries has not continued in recent decades. Scaling to annual greenhouse gas emissions as a 100-year global warming potential showed that this fen is currently a source of 192 to 490 g CO2-equivalents m-2 y-1 based on both carbon dioxide and methane flux measurements, indicating that peat is decomposing.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author