Canadian Forest Service Publications
Fuel load, structure, and potential fire behaviour in black spruce bogs. 2015. Johnston, D.C.; Turetsky, M.R.; Benscoter, B.W.; Wotton, B.M. Canadian Journal of Forest Research 45:888-899.
Issued by: Great Lakes Forestry Centre
Catalog ID: 36132
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Boreal peatlands in Canada comprise a substantial store of soil organic carbon (peat), and this peat is vulnerable to extensive burning during periods of extended drying. Increased frequency of extreme weather events in boreal regions is expected with future climate change, and the conditions that would support sustained smouldering peat combustion within peatlands may be more common. Organic soils tend to burn by smouldering combustion, a very slow-moving process in fuels such as those found in peatlands. Thus the most extreme conditions for carbon loss to the atmosphere due to the burning of peat likely occur when widespread propagation of flaming combustion leads to widespread initiation of smouldering. To investigate the potential for large-scale, high-intensity fire spread across forested bogs, we examined the fuel conditions in forested bogs necessary to support active crown fire. We measured surface and canopy fine fuels (those available to contribute to the propagating energy flux of the main flaming front) across a postfire chronosequence of forested boreal bog from central Alberta, Canada. We found that fuel load of fine surface material remained relatively constant across the chronosequence and at levels large enough to support crown fire initiation. Black spruce (Picea mariana (Mill.) B.S.P.) regeneration begins to fill in the crown space with increasing time since disturbance and achieves crown bulk densities similar to black spruce upland forests. We estimated that after about 80 years, the black spruce canopy has developed enough available fuel to support active crown fire on between 10% to 40% of days in a typical fire season in central Alberta, Canada. Broad-scale propagation of high-intensity fire across a peatland when coincident with drought-induced lower moisture in deep peatland layers has the potential to lead to a substantial release of stored terrestrial carbon.
Plain Language Summary
Boreal peatlands in Canada comprise a substantial store of soil organic carbon that is vulnerable to extensive burning during periods of drought. Under future climate change conditions, peat combustion may become more common. The most extreme conditions for carbon loss to the atmosphere will likely occur when high intensity crown fires burn across the surface of large peatlands which can then lead to extensive smouldering of peat. We measured surface and canopy fine fuels in forested bogs in central Alberta to evaluate the conditions necessary to support active crown fires that would lead to extensive peat smouldering. We estimate that after about 80 years, a black spruce canopy develops enough available fuel to support active crown fire on 10 - 40 % of days in a typical fire season. Broad scale, high intensity fires across peatlands, particularly when deep layers are dry, has the potential to lead to a substantial release of stored terrestrial carbon.