title: Control of the multimillennial wildfire size in boreal North America by spring climatic conditions.
abstract: Wildfire activity in North American boreal forests increased during the last decades of the 20th century, partly owing to ongoing human-caused climatic changes. How these changes affect regional fire regimes (annual area burned, seasonality, and number, size, and severity of fires) remains uncertain as data available to explore fire-climate-vegetation interactions have limited temporal depth. Here we present a Holocene reconstruction of fire regime, combining lacustrine charcoal analyses with past drought and fire-season length simulations to elucidate the mechanisms linking long-term fire regime and climatic changes. We decomposed fire regime into fire frequency (FF) and biomass burned (BB) and recombined these into a new index to assess fire size (FS) fluctuations. Results indicated that an earlier termination of the fire season, due to decreasing summer radiative insolation and increasing precipitation over the last 7.0 ky, induced a sharp decrease in FF and BB ca. 3.0 kyBP toward the present. In contrast, a progressive increase of FS was recorded, which is most likely related to a gradual increase in temperatures during the spring fire season. Continuing climatic warming could lead to a change in the fire regime toward larger spring wildfires in eastern boreal North America.
authors.affiliation: Centre de Bio-Archéologie et d'Ecologie, Unité Mixte de Recherche, 5059 Centre National de la Recherche Scientifique, Université Montpellier 2, Institut de Botanique, F-34090 Montpellier, France. ali@univ-montp2.fr
authors.forename: Adam A
authors.initials: AA
authors.lastname: Ali
authors.forename: Olivier
authors.initials: O
authors.lastname: Blarquez
authors.forename: Martin P
authors.initials: MP
authors.lastname: Girardin
authors.forename: Christelle
authors.initials: C
authors.lastname: Hély
authors.forename: Fabien
authors.initials: F
authors.lastname: Tinquaut
authors.forename: Ahmed
authors.initials: A
authors.lastname: El Guellab
authors.forename: Verushka
authors.initials: V
authors.lastname: Valsecchi
authors.forename: Aurélie
authors.initials: A
authors.lastname: Terrier
authors.forename: Laurent
authors.initials: L
authors.lastname: Bremond
authors.forename: Aurélie
authors.initials: A
authors.lastname: Genries
authors.forename: Sylvie
authors.initials: S
authors.lastname: Gauthier
authors.forename: Yves
authors.initials: Y
authors.lastname: Bergeron
mesh_terms: D018533:Biomass; D002170:Canada; D002980:Climate; D003198:Computer Simulation; D017753:Ecosystem; D005390:Fires; D060106:Lakes; D015233:Models, Statistical; D016011:Normal Distribution; D009656:North America; D011058:Pollen; D012621:Seasons; D013696:Temperature; D014197:Trees