Climate change may lead to larger fires, greater area burned, and more reburning across interior Alaska

Abstract

Boreal forests are experiencing rapid warming, altering fire regimes and vegetation dynamics. However, projecting future fire activity remains challenging given complex interactions among climate, vegetation, and landscape features. We used the LANDIS-II forest landscape simulation model to simulate wildfires across 8.7 million hectares of interior Alaska boreal forest under three climate scenarios: historical climate (NCAR-CCSM4) and two RCP 8.5 climate change scenarios (GCMs NCAR-CCSM4 (moderate warming) and GFDL-CM3 (warmer and wetter conditions)). We quantified differences in fire size, area burned, and fire frequency trends among scenarios and characterized areas that experienced different fire frequencies. Maximum annual area burned was greater under climate change and fire rotation was shorter. Reburning increased more rapidly under future climates and reburned areas were spatially clustered. We explored differences in fuels, topography, and climate among fire frequencies and found that reburn hotspots were characterized by lower pre-fire biomass, fine fuels, and lower conifer fraction, reflecting shortened fire return intervals. Warmer mean annual temperatures and steeper slopes were also associated with more fires. Our results suggest climate change will amplify extreme fire years and reburning in interior Alaska forests, with reduced fuel biomass, lower conifer fraction, and steeper terrain most consistently characterizing frequently burned areas.