Reburns (3 fires) were associated with greater shifts in conifer-dominant areas to broadleaf-deciduous than single burns (1 fire), which climate change accelerated.
In interior Alaska, increasing wildfire activity associated with climate change is projected to continue, potentially altering regional forest composition. Conifers are emblematic of boreal forest; however, greater frequency and severity of wildfires has been found to favor broadleaf-deciduous species in numerous studies. This study examines potential shifts in forest type in interior Alaska and how shifts may be impacted by recurring wildfires under future climate change. A spatially-explicit forest landscape model, LANDIS-II, was used to simulate forest succession and wildfire over a 380,400-hectare landscape under historic and future (RCP 8.5) climate. Wildfire was modeled using the SCRPPLE fire extension and vegetation growth, belowground carbon, hydrologic, and permafrost dynamics were modeled with the DGS succession extension. The relative importance of drivers of forest type change away from black spruce was quantified using random forest models for areas on the landscape experiencing different numbers of wildfires. Greater frequencies of fire activity were associated with shifts in conifer-dominant areas to broadleaf-deciduous, which climate change accelerated. Vegetation transitions were most strongly influenced by percent tree mortality from the most recent wildfire. Starting deciduous fraction and proximity of mature black spruce to a site pre-fire were also influential, indicating pre-fire composition and context.