A dynamic soil layer model for assessing the effects of wildfire on high latitude terrestrial ecosystems
Shuhua
S.
Yi, University of Alaska Fairbanks, ffsy@uaf.edu
A.
David
McGuire, University of Alaska Fairbanks, ffadm@uaf.edu
(Presenting)
Eric
S.
Kasischke, University of Maryland, ekasisch@mail.umd.edu
Wildfire is considered an important disturbance to boreal ecosystems in North America. It can affect carbon dynamics directly through combustion emissions, and indirectly through vegetation succession and removal of the surface organic layer, which might accelerate the degradation of permafrost and hence the release of soil carbon. At the regional scale, the direct effects of fire have received a lot of attention, but the evaluation of the indirect effects has been more limited because the appropriate tools have not yet developed for application at the regional scale. In this study, we developed a dynamic soil layer model (DSLM) used in the Terrestrial Ecosystem Model (TEM) to investigate the effects of changes of surface organic layer on soil temperature, moisture, and carbon dynamics. The DSLM consists of (1) a simultaneous heat and water transfer scheme, in which a Two-Directional Stefan Algorithm was used to provide a stable and efficient simulation of soil thermal dynamics in both seasonal frost and permafrost regions; (2) an explicit vertical distribution of soil carbon; (3) a conceptual model of removal of organic layer by wildfire; (4) and a conceptual model of recovery of organic layer after wildfire. DSLM-TEM was calibrated for black spruce, white spruce, deciduous and tundra vegetation types. DSLM-TEM was first tested on a tundra burn site and two black spruce fire chronosequences for its performance on soil temperature and moisture simulation. Several sensitivity tests have then been performed to investigate the effects of different schemes of organic layer removal and recovery on permafrost and carbon dynamics. Initial results showed that: (1) soil temperatures and soil moistures were well simulated; (2) active layer depth was sensitive to the thickness of the organic layer; and (3) the simulated organic layer thickness can reasonably represent the dynamics of soil organic layer development after fire disturbance.
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