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Long-term fire frequency variability in the eastern Canadian boreal forest: the influences of climate vs. local factors

Authors

  • ADAM A. ALI,

    1. Chaire industrielle CRSNG-UQAT-UQAM en aménagement forestier durable, Université du Québec en Abitibi-Témiscamingue, 445 boul. de l'Université, Rouyn-Noranda (QC), Canada J9X 5E4,
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    • 1Present address: Centre for Bio-Archeology and Ecology (UMR5059 CNRS), Université Montpellier 2, 163 rue Auguste Broussonet, F-34090 Montpellier, France.

  • CHRISTOPHER CARCAILLET,

    1. Centre for Bio-Archeology and Ecology (UMR5059 CNRS), Université Montpellier 2, 163 rue Auguste Broussonet, F-34090 Montpellier, France,
    2. Paleoenvironnements and Chronoecology (PALECO-EPHE), Ecole Pratique des Hautes Etudes, Institut de Botanique, 163 rue Auguste Broussonet, F-34090 Montpellier, France
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  • YVES BERGERON

    1. Chaire industrielle CRSNG-UQAT-UQAM en aménagement forestier durable, Université du Québec en Abitibi-Témiscamingue, 445 boul. de l'Université, Rouyn-Noranda (QC), Canada J9X 5E4,
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Adam A. Ali, e-mail: adam.ali@uqat.ca

Abstract

The influence of climatic and local nonclimatic factors on the fire regime of the eastern Canadian boreal forest over the last 8000 years is investigated by examining charred particles preserved in four lacustrine deposits. Herein, we compare the distribution of fire-free intervals (FFIs) and the synchronicity of fire events among sites, using Ripley's K-function to determine the extent of the role of local-scale vs. large-scale processes with respect to fire control. Between 8000 and 5800 cal. bp (calibrated years before present) the climatic and ecological conditions were less conducive to fire events than after this date. After 5800 cal. bp, the number of fires per 1000 years (fire frequency) progressively increased, reaching a maximum ca. 3400 cal. bp. There was a sharp decrease in fire frequency during the last 800 years. Between 8000 and 4000 cal. bp, comparable FFIs and synchronous fire episodes were determined for the study sites. During this period, the fire frequency was predominantly controlled by climate. After 4000 cal. bp, two sites displayed independent fire histories (different FFI distributions or asynchronous fire events), underlining the important influence of local factors, including short-term fuel wetness, characteristics of the watershed and landscape connectivity, in determining fire occurrence. We conclude that climatic changes occurred during the last 4000 years that induced a rise in the water table; this may explain the high spatial heterogeneity in fire history. Current and projected global climatic changes may cause similar spatial variability in fire frequency.

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