Fuel accumulation in a high-frequency boreal wildfire regime: from wetland to upland

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 were 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 over 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 bl...