Climate Change and Fire Ecology in Northern Boreal Forests

Boreal forests comprise one third of the forested area of the entire Earth, including parts of Canada, Alaska, Russia, Siberia, Finland, Sweden, and Norway (3). This biome is characterized by acidic soils and dominance of coniferous vegetation. Tree species include white spruce, black spruce, white pine, fir, aspen, and birch (6). The boreal zone is characterized by its harsh climate and short growing season. In addition to covering such a vast portion of the land surface, boreal forests also contain approximately 12-42% of the global soil carbon pool (3). Therefore, any natural or anthropogenic process affecting boreal forests has the potential to make a significant impact on the cycling of carbon on the global scale. The release of carbon from soil organic matter into the atmosphere may contribute to increasing concentrations of greenhouse gases and future climate change.

Climate change in the northern high latitudes has occurred at a rate and magnitude exceeding the global average. In general, changes in this region are characterized by increasing temperatures, which in turn can affect the health and productivity of individual trees within the boreal forest, as well as the ecosystem as a whole (8). Increasing temperatures may lead to a longer growing season, increased soil respiration, and more severe heat stress for species currently existing at their upper thermal limit. Climate change will also have an impact on extreme weather events and disturbances in the boreal zone, including drought, hurricanes, and wind and ice storms (8). One of the most ecologically important disturbance regimes in boreal ecosystems is fire (7). Fire and climate are intimately linked; changing climate conditions may increase or decrease the frequency and intensity of fire, while fire has the potential to impact climate through the release of stored carbon, ash, and aerosols, as well as changing the albedo of the boreal zone.