Canadian Forest Service Publications
Holocene fire disturbance in the boreal forest of central Sweden. 2013. Brown, K.J.; Giesecke, T. Boreas 43(3):639-651.
Issued by: Northern Forestry Centre
Catalog ID: 35747
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Holocene fire disturbance and vegetation history were reconstructed using macroscopic charcoal and pollen accumulation rates from two lake sediment records (Holtjärnen and Klotjärnen) collected in the boreal forest of central Sweden. The records were used to examine the potential drivers associated with changes in fire regime. Climate, vegetation and human activity were all identified as factors variously influencing the fire regime. In the early Holocene, near bicentennial fire return intervals were regionally widespread, suggesting that fire disturbance was largely regulated by climate at that time. In the mid- and late Holocene, vegetation exerted an important control on the fire regime. During the mid-Holocene, the expansion of thermophilous broadleaf vegetation offset the influence of warmer climate by altering the local microclimate and by changing the structure and flammability of the available fuels. During the transition to the late Holocene, thermophilous vegetation decreased in abundance and Pinus increased, resulting in a more flammable forest even though the climate was cooling and moistening. Fire disturbance correspondingly increased. The modern boreal forest was established in the late Holocene as Picea expanded regionally as the climate cooled, moistened, and became increasingly continental. Although no change in the frequency of fire was apparent at this time, increased stand densities likely facilitated greater fuel consumption in subsequent fires. Within the last millennium, human action markedly modified the forested landscape, altering the fire regime.
Plain Language Summary
This study looked at fire dynamics in the boreal forest. We examined long-term interaction between fire disturbance, climate, fuel, and human activity as drivers of change in fire patterns. Using records of fire disturbance, we could estimate when and how frequently fire occurred and compare that data to plant life and climate records. The key findings suggest that climate was an important regulator of fire in early Recent times. In contrast, the influence of plant life is more evident later on as warm climatic conditions became associated with less fire and cool, humid conditions with more fire. A marked increase in charcoal deposition characterizes the boreal forest we know today, as more fuel is consumed during fire events. In a future warmer climate, the expansion of broadleaf plants into the boreal forest could actually offset changes to the fire regime that have been brought about by climate change.