The effects of fire on the thermal stability of permafrost in lowland and upland black spruce forests of interior Alaska in a changing climate

Elchin E Jafarov, NSIDC, CU Boulder, elchin@nsidc.org (Presenter)
Vladimir E Romanovsky, GI, UAF, veromanovsky@alaska.edu
Helene Genet, IAB, UAF, hgenet@alaska.edu
Dave A McGuire, IAB, UAF, admcguire@alaska.edu
Sergei S Marchenko, GI, UAF, ssmarchenko@alaska.edu

Fire is an important factor controlling the composition and thickness of the organic layer in the black spruce forest ecosystems of Interior Alaska. Fire that burns the organic layer can trigger dramatic changes in the underlying permafrost, leading to accelerated ground thawing within a relatively short time. In this study, we addressed the following questions: (1) which factors determine the post-fire ground temperature dynamics in lowland and upland black spruce forests? and (2) what level of burn severity will cause irreversible permafrost degradation in these ecosystems?

We evaluated these questions in a transient modeling-sensitivity analysis framework in order to assess the sensitivity of permafrost to climate, burn severity, soil organic layer thickness, and soil moisture content in lowland (thick organic layers) and upland (thin organic layers) black spruce ecosystems. The results indicate that climate warming accompanied by fire disturbances could significantly accelerate permafrost degradation. Permafrost in upland black spruce environments under a stable climate with an organic soil layer up to 30 cm thick could completely degrade in an 18 m soil column within 120 years of a severe fire. In contrast, permafrost in a lowland black spruce environment with an 80 cm thick soil organic layer is capable of being sustained under different scenarios of burn severity and climate warming.

Presentation Type:  Poster

Session:  Poster Session 2-B   (Wed 4:30 PM)

Associated Project(s): 

• Related Activity or Previously Funded TE Activity

Poster Location ID: 48