Effects of fires on carbon cycling in North American boreal peatlands

• Published in: Environmental Reviews
• Main Authors: Zoltai, S C, Morrissey, L A, Livingston, G P, Groot, W J
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1998
• Subjects: permafrost; Subarctic
• Online Access: http://dx.doi.org/10.1139/a98-002; http://www.nrcresearchpress.com/doi/pdf/10.1139/a98-002

Boreal peatlands occupy about 1.14 x 10 6 km 2 in North America. Fires can spread into peatlands, burning the biomass, and if moisture conditions permit, burning into the surface peat. Charred layers in peat sections reveal that historically bogs in the subhumid continental regions and permafrost peatlands of the subarctic regions have been the most susceptible to fires. Fire return periods were estimated from the numbers and ages of the charred peat layers. Based on average moisture conditions of the surface, about 0.5% of the peatlands (6420 km 2 ) can be expected to burn annually, but the surface peat layer is expected to burn only in a small portion of this area (1160 km 2 ). Carbon losses from aboveground combustion, in the form of CO 2 , CO, CH 4 , and nonmethane hydrocarbons, are the highest in forested swamps at 2.03 Tg C ·year -1 . Carbon losses due to combustion of surface peat is the highest in the driest peatlands (e.g., raised bogs underlain by permafrost) at 5.82 Tg C ·year -1 . The total estimated carbon release due to aboveground combustion is 2.92 Tg C ·year -1 and due to belowground peat combustion is 6.72 Tg C ·year -1 . These estimates of direct carbon emissions to the atmosphere due to wildfires suggest a globally significant, but relatively small source in contrast with emissions from wildfires in uplands. The effects of a possible climate change are expected to be most prominent in the continental and northern parts of North America. A lower water table would result in increased CO 2 but decreased CH 4 emissions from the peatlands. A drier climate may mean increased fire frequency and intensity, resulting in more fires in peatlands and an increased probability of the fires consuming part of the peat.Key words: fire, peatlands, carbon, boreal, permafrost, gas flux.