Document: DAV-3-87-5

The role of fire disturbance, climate, and atmospheric CO₂ in the response of historical carbon dynamics in Alaska from 1950 to 1995.

MCGUIRE, A.D.* ¹, R.A.MEIER ¹, Q.ZHUANG ¹, M.MACANDER ¹, T.S.RUPP ¹, E.KASISCHKE ², D.VERBYLA ², D.W.KICKLIGHTER ³ and J.M.MELILLO ³

University of Alaska, Fairbanks, AK 99775 USA ¹
Environmental Research Institute of Michigan, USA ²
The Ecosystems Center, Woods Hole, MA USA ³

Abstract:
To evaluate how historical C storage in Alaska may have been influenced by fire disturbance, climate variation, and rising atmospheric CO₂ between 1950 and 1995, we conducted three simulations with the Terrestrial Ecosystem Model (TEM) that included responses of C storage to: CO₂ only, CO₂ and climate, and CO₂, climate, and fire disturbance. Between 1950 and 1995, the simulations of TEM indicate that C storage in Alaska increased between 2.0 and 2.9 1012 g (Tg) C yr^-1 depending on assumptions of fire severity. The partitioning of effects indicate that rising CO₂ was responsible for an increase in C storage of 3.6 Tg C yr^-1 and that climatic variation was responsible for a loss of 0.3 Tg C yr^-1 . The simulations indicate that fire disturbance, which includes changes in C storage associated with both fire emissions and subsequent succession, was responsible for the loss of 0.4 to 1.3 Tg C yr^-1 depending on assumptions for fire severity. In contrast to the overall period, historical fire disturbance accounts for increases in C storage of between 3.1 and 10.0 Tg C yr^-1 during the 1980s for the lowest and highest assumptions of severity, respectively. This result suggests that regrowth associated with past fire disturbance was greater than losses associated with fire emissions during the 1980s, and that the strength of the regrowth effect increases with fire severity. Our analysis suggests that fire disturbance, rising CO₂ and climate variation all play substantial roles in C dynamics for Alaska, and that modeling contemporary C dynamics for boreal forests requires a temporally and spatially explicit approach that incorporates the historical effects of fire disturbance.

Keywords: Terrestrial Ecosystem Model, Carbon Dynamics, Fire Disturbance, Atmospheric Carbon Dioxide, Climate Change

This abstract is being presented at: 8:30 AM in session:
Oral Session #22: Multiple Disturbance Effects, Including Fire.