Canadian Forest Service Publications
Fuel accumulation in a high-frequency boreal wildfire regime: from wetland to upland. 2017. Thompson, D.K.; Parisien, M.-A.; Morin, J.; Millard, K.; Larsen, C.P.S.; Simpson, B. Canadian Journal of Forest Research 47(7):957-964.
Issued by: Northern Forestry Centre
Catalog ID: 38304
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Although it is increasingly accepted that young (e.g., ≤30 years) stands originating from wildfire are considerably less flammable than older stands in the boreal forest of North America, the role of fuel availability and structure in this phenomenon has not been thoroughly investigated. As a regional study in a high-frequency fire regime, detailed wildfire fuel loading and structure was measured in 66 sites including both wetlands and uplands in the Boreal Plains landscape of Wood Buffalo National Park, in northwestern Canada. Overall, a significant increase in total flammable biomass occurred in upland sites after 97 years but this increase was not consistently observed in wetlands, except where there was dense tree cover. Fuel accumulation was highly moderated by canopy fuels, as surface fuels were relatively constant across differing site types and time since fire, averaging 0.4 kg m-2. Significant but gradual canopy fuel accumulation was observed in moist conifer upland forests dominated by mature black spruce (Picea mariana) or white spruce (Picea glauca) over 100 years since fire. Outside of these mature moist conifer uplands, there was no difference in total fuel loading between other upland forest and across the gradient of treed to open wetlands.
Plain Language Summary
Understanding wildfire risk is a vital part of community wildfire preparedness. Along with weather and topography, one of the main factors is “fuel load,” the sum of live and dead vegetation in a given area. While fuel loads in pine and spruce forests are generally well understood, fuel loads in wetlands in the boreal forest remain poorly documented. In this study, the researchers compared fuel load in dry upland forest and wetlands in Wood Buffalo National Park in northeastern Alberta between 2012 and 2014. The researchers also determined time since the previous wildfire from maps of previous fires or from tree ring data. They found that dry forests and wetlands have similar total fuel loads, with the greatest fuel loads found in wet spruce forests on the edge of wetlands. Wetlands dominated by grasses were found to have far greater fuel load than current estimates used for wildfire management in Canada. This helps explain why so much grass wetland area is burned in northern Canada during drought years. The study also showed that these grass-dominated boreal wetlands also recover their fuel load within around four years after a fire, compared with 30 or more years for other ecosystems such as pine forests. This information will help us better understand wildfire risk and prevention.