The 2007 Anaktuvuk River Fire was an order of magnitude larger than the average fire sizein the historic record for northern Alaska and indices of severity were substantially higherthan for other recorded tundra burns. An interdisciplinary team assessed fire effectsincluding burn severity, potential plant community shifts, and effects on permafrost andactive layers. Observers monumented, photographed, and measured 24 burned and 17unburned reference transects, starting the year after the fire, and spanning the range ofvegetation types and burn severities. Three independent ocular estimates of burn severityat varying scales were made, two ground-based indices and one aerial index. Remotelysensed data and indices were compared to ocular estimates. Landsat imagery and field datawere used to prepare a burn severity map, which showed that 80% of the fire burned withmoderate-to-high severity. Consumption of plant biomass and organic soils was estimatedusing direct measurements of plants and soils in burned plots and allometric scalingdeveloped from unburned comparison plots. Active layer, pH, temperature, residualorganic duff depth and other soil characteristics were recorded and vegetation and organiclayers were destructively sampled for laboratory analysis of fire fuel biomass and density offuel layers. Regrowth of vegetation was rapid for some species (Eriophorum vaginatum[cottongrass]) and lush stands of fire mosses and liverworts developed after the first yearon severely burned areas. Graminoid cover, primarily E. vaginatum, increased from 11% to63% between 2008 and 2011. Shrubs were recovering more slowly by the 4th year afterburning and other species were declining (Sphagnum mosses) or virtually absent (lichens:0.1%). Shifts in community species composition seem likely for many years to come in theburn area. A dietary analysis on caribou scat collected from the area showed approximately50% lichen composition in the fall/winter diet, uncorrected for digestibility. Since lichensare absent for some years post-fire, the fire has reduced forage availability for caribou.Foraging conditions for some microtines and their predators may have improved. Data onfire effects and vegetation recovery are important for assessing the impacts of increasingtemperatures on tundra fire regimes and the implications of increased fire in the Arctic forwildlife and ecosystem processes.
