Indirect and Long-Term Effects of Fire on the Boreal Forest Carbon Budget

Abstract

The landmark paper of Seiler and Crutzen (1980) clearly laid out the scientific rationale as to why the study of biomass burning was essential in terms of completely understanding greenhouse gases emissions from the land surface to the atmosphere. While this analysis fueled much of the fire and biomass burning-related research in the tropical biomes (forests and savannas), it turned scientific attention away from the boreal region, as one conclusion drawn from the Seiler and Crutzen analysis was that on a global scale, the amount of carbon released into the atmosphere was very small relative to other biomes. Recent research has shown that the Seiler and Crutzen estimates of carbon released into the atmosphere from fires in the boreal forests may be out by at least an order of magnitude. In addition, because fires consume organic soils which take thousands of years to form, biomass burning in the boreal forest may actually represent a direct net release of carbon to the atmosphere over intermediate time scales (hundreds of years). Finally, fires in boreal forests have significant impacts on the physical climate of the soil substrate in boreal forests, which in turn, affect soil respiration and plant growth. Thus, fires have important indirect effects on sequestration of atmospheric carbon in the boreal region.In this paper, we review the overall short- and long-term effects that fire has on exchanges of carbon between the atmosphere and boreal forest ecosystems. Using examples from recent research in the boreal forests of Alaska and elsewhere, this paper addresses the following questions: (1) how much fire occurs in the boreal forest? (2) how much biomass is consumed during fires in the boreal forest and what types and what levels of greenhouse gases are released during these fires? (3) how much carbon was released during fires in the North American boreal forests from 1970 to present? (4) how do fires influence patterns of soil respiration? and (5) how do fires influence the patterns of forest succession?KeywordsSoil RespirationBoreal ForestOrganic SoilFire SeverityForest SuccessionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.