Effects of fires on carbon cycling in North American boreal peatlands

Abstract

Boreal peatlands occupy about 1.14 x 106 km2 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 km2) can be expected to burn annually, but the surface peat layer is expected to burn only in a small portion of this area (1160 km2). Carbon losses from aboveground combustion, in the form of CO2, CO, CH4, 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 CO2 but decreased CH4 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.

Peatland dynamics in a complex landscape: Development of a fen-bog complex in the Sporadic Discontinuous Permafrost zone of northern Alberta, Canada

“…-Hummock sphagna and P. mariana are prerequisites for permafrost initiation in the southern parts of the discontinuous zone (Kuhry 1998;Zoltai et al 1998;Camill 2000;Robinson & Moore 2000). Early layers containing these taxa date to 6800 (core 8) and 5400 (core 3) cal.…”

“…3B), a pattern consistent with decreasing accumulation over time. Because of high surficial decay rates and high sensitivity to fire (Kuhry 1994;Zoltai et al 1998;Robinson & Moore 2000), permafrost peatlands usually accumulate OM more slowly than non-permafrost sites (Bhiry et al 2007;Turetsky et al 2007;Sannel & Kuhry 2009). Two of the three peat plateau cores show a decrease in apparent accumulation in upper core sections (from 49 to 30 g m À2 a À1 and from 42 to 31 g m À2 a À1 in cores 8 and 3, respectively), and shallow plateau cores have low accumulation rates (13-20 g m À2 a À1 ).…”

Overstory vegetation influence nitrogen and dissolved organic carbon flux from the atmosphere to the forest floor: Boreal Plain, Canada

“…The climate is sub-humid (Zoltai et al, 1998) and precipitation is temporally and spatially variable (Pelster et al, 2008). Annual precipitation from 1978 to 2008 ranged from 394 to 777 mm, with a mean of 577 mm (Environment Canada, 2008a).…”

Modelling Soil Moisture Deficit and Moisture Content of Ground Vegetation: Progress Towards Development of a Fire Weather Index System Appropriate to the UK

“…and significant quantities of carbon may be released [18]. The results presented here are therefore important in both the local and the global context.…”