Carcaillet, C., Bergeron, Y., Richard, P.J.H., Frechette, B., Gauthier, S. and Prairie, Y.T. 2001. Change of fire frequency in eastern Canadian boreal forests during the Holocene: does vegetation composition or climate trigger the fire regime? Journal of Ecology 89: 930-946.
What was done
The authors developed high-resolution charcoal records from laminated sediment cores extracted from three small kettle lakes located within the mixed-boreal and coniferous-boreal forest region of eastern Canada, after which they determined whether vegetation change or climate change was the primary determinant of fire frequency changes, comparing their fire history with hydro-climatic reconstructions derived from ð18O and lake-level data.
What was learned
Throughout the Climatic Optimum of the mid-Holocene, between about 7000 and 3000 years ago, when it was significantly warmer than it is today, Carcaillet et al. report that "fire intervals were double those in the last 2000 years," meaning fires were only half as frequent throughout the earlier warmer period as they were during the subsequent cooler period. They also determined that "vegetation does not control the long-term fire regime in the boreal forest" but that "climate appears to be the main process triggering fire." In addition, they report that "dendroecological studies show that both frequency and size of fire decreased during the 20th century in both west (e.g. Van Wagner, 1978; Johnson et al., 1990; Larsen, 1997; Weir et al., 2000) and east Canadian coniferous forests (e.g. Cwynar, 1997; Foster, 1983; Bergeron, 1991; Bergeron et al., 2001), possibly due to a drop in drought frequency and an increase in long-term annual precipitation (Bergeron and Archambault, 1993)."
What it means
In the words of the authors, "the future warmer climate is likely to be less favorable for fire ignition and spread in the east Canadian boreal forest than over the last 2 millennia," which is good news for Canada and similar parts of the world.
Bergeron, Y. 1991. The influence of island and mainland lakeshore landscape on boreal forest fire regime. Ecology 72: 1980-1992.
Bergeron, Y. and Archambault, S. 1993. Decreasing frequency of forest fires in the southern boreal zone of Quebec and its relation to global warming since the end of the 'Little Ice Age'. The Holocene 3: 255-259.
Bergeron, Y., Gauthier, S., Kafka, V., Lefort, P. and Lesieur, D. 2001. Natural fire frequency for the eastern Canadian boreal forest: consequences for sustainable forestry. Canadian Journal of Forest Research 31: 384-391.
Cwynar, L.C. 1977. Recent history of fire of Barrow Township, Algonquin Park. Canadian Journal of Botany 55: 10-21.
Foster, D.R. 1983. The history and pattern of fire in the boreal forest of southeastern Labrador. Canadian Journal of Botany 61: 2459-2471.
Johnson, E.A., Fryer, G.I. and Heathcott, J.M. 1990. The influence of Man and climate on frequency of fire in the interior wet belt forest, British Columbia. Journal of Ecology 78: 403-412.
Larsen, C.P.S. 1997. Spatial and temporal variations in boreal forest fire frequency in northern Alberta. Journal of Biogeography 24: 663-673.
Van Wagner, C.E. 1978. Age-class distribution and the forest fire cycle. Canadian Journal of Forest Research 8: 220-227.
Weir, J.M.H., Johnson, E.A. and Miyanishi, K. 2000. Fire frequency and the spatial age mosaic of the mixed-wood boreal forest in western Canada. Ecological Applications 10: 1162-1177.
Reviewed 14 April 2004