Evaluating Flammability of Reburns in the Boreal Forests of Interior Alaska
Dr. Brian Buma and Katherine Hayes, University of Denver
Temperatures in high-latitude environments are rising quickly, leading to increases in the frequency and intensity of wildfires. This trend is especially important in the boreal where fire return intervals have shrunk from between 100-300 years to often less than 20. Shortening fire intervals have led to an increased presence of early to mid-successional deciduous species, with birch (Betula neoalaskana), alder (Alnus crispa), aspen (Populus tremuloides) and willow (Salix spp.) becoming dominant in stands previously dominated by black spruce (Picea mariana). The presence of deciduous species has been invoked as a landscape management solution to arctic and boreal warming, based on paleoecological evidence of declining fire activity found alongside increases in the presence of birch. However, historical forest compositions were slightly different: past boreal environments were dominated by birch alone, while recent studies have found alder, aspen, and even willow in dominant quantities. Preliminary work demonstrates that fuel structures change dramatically across a 1-3 short interval fire gradient, with three burns resulting in more open, shrubby structure with increased willow. In this introductory talk, we will describe our plan to ask two fundamental questions: 1) How does fuel structure change with repeat burning, including repeat, short interval fires in deciduous dominated stands, and 2) How does fire behavior change if those landscapes are to reburn yet again? Data has been collected on biomass and species composition (summer 2019); fuel structure data collection and high resolution fire modeling will take place in summer 2020 with results available in fall/winter 2020. The benefits to this work include quantification of the flammability of this emerging and apparently novel forest structure. Insights gained from this research will contribute directly to fire management: by knowing the relative flammability of different forest structures and compositions in reburned boreal forest, managers can better make decisions about restoration via prescribed fire, wildfire suppression and the dynamics of fire and vegetation.