Monday, August 3, 2009 - 2:30 PM

OOS 1-4: Consequences of an altered fire regime on climate and carbon storage in arctic tundra

Adrian Rocha, Marine Biological Laboratory, Mark Flanner, National Center for Atmospheric Research,, Michelle C. Mack, University of Florida, and Gaius R. Shaver, Marine Biological Laboratory.


Fires are currently rare in arctic tundra because both ignition sources and vegetation flammability are low.  Changing climatic conditions may favor an altered fire regime in the arctic, but the affect of this change on climate is poorly understood.  We used a combination of modeling, remote sensing, literature reviews, and CO2 and energy flux observations from historical fires in the tundra biome to gain a better understanding of fire impacts on arctic ecosystems and climate.  Literature reviews and satellite data allowed us to determine how quickly albedo and LAI recovered to preburned levels.  CO2 and energy exchange observations were obtained with eddy covariance towers across a burn severity gradient (i.e. Severe, Moderate, and Unburned) during the 2008 growing season from the Anaktuvuk River Fire (AR fire).  The Anaktuvuk River fire burned a 1000 km2 area during the late 2007 growing season and created a mosaic of patches that differed in burn severity.  We compiled satellite data, values from the literature, and data from the three eddy covariance towers with modeling efforts with a radiative transfer model to calculate the radiative forcing of arctic fires under different fire regimes. 


Arctic fires had a substantial affect on surface properties that influence mass and energy exchanges.  Our literature review and remote sensing observations demonstrate that arctic fires substantially decreased albedo for several years.  Burn severity influenced the recovery of vegetation, and energy and mass exchanges.  Net radiation and soil heat flux increased with burn severity, whereas CO2 uptake decreased with burn severity.  Arctic fires also were associated with increases in thaw depth and a depletion of terrestrial carbon pools.  The slow recovery of terrestrial carbon pools combined with the decreases in albedo suggests that increasing arctic fires could result in a positive forcing on climate.  Our analyses also demonstrate that the climatic impact of an altered fire regime will depend on the size and severity of fires, the recovery of vegetation, and changes in the plant functional type (i.e. shrubs vs. tussocks) of recovering vegetation.