Webinar presented by Torre Jorgenson, Alaska Ecoscience, Fairbanks, AK
Fire, ecosystems, and permafrost interact to greatly modify landscapes across boreal Alaska.
Fires affect ecosystems by causing varying levels of disturbance that alter above ground
vegetation and surface soils, but fire affects vary across vegetation types and landscapes. After
disturbance, ecosystem structure and processes evolve through successional development,
leading to organic-matter accumulation and colder, wetter, nutrient-poor soils that favor
permafrost formation. Boreal ecosystems that develop on permafrost are dominated by a limited
suite of ecotypes, yet they are widespread across boreal uplands and lowlands. These permafrost-
affected ecosystems support slowing-growing, stress-adapted, herbivore-resistant species that are
more prone to fire, resulting in shorter fire-return intervals. Once ignited by lightning or humans,
fire alters the surface microclimate and often initiates permafrost degradation. But permafrost
responses vary across soil landscapes, ranging from rapid thaw in rocky uplands to long-term
persistence in peatlands. These fire-ecosystem-permafrost interactions, however, need to be
evaluated with the context of other drivers of permafrost thaw, especially climate change and
hydrology.