COS 178-2 - Vegetation shifts, permafrost thaw, and hydrologic dynamics in the boreal forests of Alaska under future climate and wildfire

Abstract: Harboring an estimated 30 percent of the forested area on Earth, the boreal pan-arctic region exists as an extensive reservoir of ecologically important landscapes containing legacies of permafrost, belowground carbon, and coniferous-dominant forests. The resilience of these forests and their vital ecosystem services such as carbon sequestration as well as provisioning conditions and habitat are paramount to the wellbeing of both humans and wildlife alike. Warming at almost three times the global average, the structure and composition of the boreal forest are threatened by increasing wildfire and climate-related changes to a degree that inhibits their ecosystem recovery. Regions such as interior Alaska have seen an increase in fire size and frequency contributing to multi-scale feedbacks concerning shifts from conifer-dominant vegetation, permafrost thaw, and hydrologic changes. To explore future landscape-level trajectories, we used the spatially explicit model, LANDIS-II. Dynamic attributes of wildfire, soil moisture, permafrost, and forest succession, built into the modeling framework and its extensions, are modeled over a 100-year simulation period and 8,695,760-hectare (4-hectare resolution) landscape under historic and future climate (RCP 8.5) forcings. We found spatial variability of increased depths to the active permafrost layer and decreases in soil moisture associated with climatic changes and increased disturbances are compared through the simulation period. Moreover, related shifts in forest composition from a conifer-dominate landscape were driven by vegetation and wildfire feedbacks favoring deciduous trees/shrubs, a process exacerbated by increased warming, interconnected to both permafrost thaw and the lowering levels of soil moisture. This study’s quantification of dynamics changes in boreal forest reliance outlines the importance of landscape modeling to reflect future changes in climate and disturbance regimes in boreal forest ecosystems.