Cutover peatlands: A persistent source of atmospheric CO2

Peatlands represent an important component of the global carbon cycle, storing 23 g C m −2 yr −1 . Peatland mining eliminates the carbon sink function of the peatland. In this paper we measure the total ecosystem respiration in a natural, 2 and 3 year (young) and 7 and 8 year (old) postcutover peatland near Sainte‐Marguerite‐Marie, Québec, during the summers of 1998 and 1999. Although the natural site was a source of CO 2 during the dry 1998 study season (138 g C m −2 ), CO 2 emissions were between 260 and 290% higher in the cutover sites (363 and 399 g C m −2 for young and old, respectively). Cutover site CO 2 emissions were only 88 and 112 g CO 2 ‐C m −2 at the young and old sites during the wet 1999 study season. Total ecosystem respiration was more dependent on the water table position than on changes in the thermal regime or the labile carbon of the peat in a dry summer, but the opposite was the case in a wet summer. CO 2 emissions increased with postharvest time regardless of a decrease in labile carbon, demonstrating that cutover peatlands are a large persistent source of atmospheric CO 2 . Direct measurement of the net ecosystem CO 2 exchange in cutover peatlands, as opposed to determining the loss of carbon from bulk density determinations, provides a better understanding of how peat drainage and harvesting operations affect the carbon balance in peatlands.