Soil microbes are key drivers of ecosystem processes, yet their role in regulating landscape-scale vegetation change is not known. Comprehensive studies of treeline position have noted that ectomycorrhizal fungi may be an important factor delineating the boundary between forest and tundra. Yet, these critical plant-fungal symbioses are sensitive to wildfires. Fire is the primary landscape-scale disturbance in the boreal forest and increasingly important in tundra. Fire, an indirect effect of climate warming, may overshadow the direct effects of climate change on species distribution and migration. We know that fire affects seedling establishment, fungal communities, and soil parameters; however, the influence of fire on mycorrhizal seedling establishment and the importance of these symbioses to seedling survivorship and performance post-fire are not well understood. My research will investigate potential for fire-induced biome shifts at the boreal/tundra interface by addressing several factors: 1) Is there fungal limitation to seedling establishment post-fire? 2) Do different fungal taxa result in differential seedling performance? 3) Could fire induced changes in plant-fungal interactions at ecotones result in landcover shifts? Preliminary results from a growth chamber study indicate there may be fungal limitation to seedling establishment post-fire beyond treeline. Mycosymbiont limitation may be linked to seedling biomass and growth patterns. A treeline biome shift would alter climate feedbacks (carbon storage and energy exchange) and availability of ecosystem services integral to the subsistence-based economies in Alaskan communities. This research is a cross-site project connecting post-fire boreal and tundra seedling establishment to treeline dynamics.