Abstract
The global boreal forests comprise large stocks of organic carbon that vary with climate and fire regimes. Global warming is likely to influence several aspects of fire and cause shifts in carbon sequestration patterns. Fire severity or forest floor depth of burn is one important aspect that influences both carbon emission during combustion as well as post-fire ecosystem regeneration. Numerous publications on projections of future area burned exist, whereas scenarios on twenty-first century fire severity are more scarce, and the stand-typical response to severe fire weather is rarely taken into account. This paper aims to synthesize knowledge on boreal forest carbon stocks in relation to changes in fire severity for Quebec, Canada. Besides warming, this region may be subjected to an important increase in future precipitation. Future fire severity and area burned may well increase as fire weather will be drier, especially near the end of the twenty-first century. Moreover, the fire season peak may shift towards the late summer. Intense burning will favour tree cover development while the forest floor carbon stock may become less important. As a result, total Quebec boreal carbon sequestration may diminish. The development of dynamic vegetation models may improve scenarios on twenty-first century changes in carbon sequestration driven by climate change and fire severity and frequency effects.
Highlights
The boreal forest ecosystems contain approximately 882 Pg of carbon (C) in living biomass, detritus, and soils (Apps et al 1993), representing 49 % to 64 % of global forest C (Kasischke 2000, Lal 2005)
Wildland fire intensity is highest in the northern boreal regions (Bergeron et al 2004b), whereas insect outbreaks are concentrated in the southern mixedwood region (Gray 2008)
As we aimed to evaluate the effect on forest floor C stocks, we used the definition by Payette (1992), who considered fire severity as an indication of the proportion of the forest floor affected by fire as well as the ecological effects of fire on plant community and habitat
Summary
The boreal forest ecosystems (boreal forest, peatlands, and tundra) contain approximately 882 Pg of carbon (C) in living biomass, detritus, and soils (Apps et al 1993), representing 49 % to 64 % of global forest C (Kasischke 2000, Lal 2005) Due to these important quantities, boreal ecosystems possess a potential to influence atmospheric composition by release of carbon dioxide (CO2) and methane (CH4) (Bonan et al 1995). Rates of sequestration are directly linked to four processes: 1) the rate of plant growth, including trees, shrubs and moss layer; 2) the rate of decomposition of organic matter; 3) permafrost formation; 4) fire frequency and severity (i.e., depth of burning) (Kasischke et al 1995) These processes are influenced by climate and local landscape and soil factors in the long term, whereas other factors such as fires, insect outbreaks, diseases, droughts, and ice storms may alter C dynamics almost instantly.
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