Pyrogenic carbon emission from a large wildfire in Oregon, United States

Abstract

We used a ground‐based approach to compute the pyrogenic carbon emissions from the Biscuit Fire, an exceptionally large wildfire, which in 2002 burned over 200,000 ha of mixed conifer forest in southwestern Oregon. A combination of federal inventory data and supplementary ground measurements afforded the estimation of preburn densities for 25 separate carbon pools at 180 independent locations in the burn area. Average combustion factors for each of these pools were then compiled from the postburn assessment of thousands of individual trees, shrubs, and parcels of surface and ground fuel. Combustion factors were highest for litter, duff, and foliage, lowest for live woody pools. Combustion factors also increased with burn severity as independently assessed from remote imagery, endorsing the use of such imagery in scaling emissions to fire area. We estimate the total pyrogenic carbon emissions from the Biscuit Fire to be between 3.5 and 4.4 Tg C (17 and 22 Mg C ha−1) depending on uncertainty in our ability to estimate preburn litter pools and mineral soil combustion with a central estimate of 3.8 Tg C (19 Mg C ha−1). We estimate that this flux is approximately 16 times the annual net ecosystem production of this landscape prior to the wildfire and may have reduced mean net biome production across the state of Oregon by nearly half in the year 2002.