title: Resistance of the boreal forest to high burn rates.
abstract: Boreal ecosystems and their large carbon stocks are strongly shaped by extensive wildfires. Coupling climate projections with records of area burned during the last 3 decades across the North American boreal zone suggests that area burned will increase by 30-500% by the end of the 21st century, with a cascading effect on ecosystem dynamics and on the boreal carbon balance. Fire size and the frequency of large-fire years are both expected to increase. However, how fire size and time since previous fire will influence future burn rates is poorly understood, mostly because of incomplete records of past fire overlaps. Here, we reconstruct the length of overlapping fires along a 190-km-long transect during the last 200 y in one of the most fire-prone boreal regions of North America to document how fire size and time since previous fire will influence future fire recurrence. We provide direct field evidence that extreme burn rates can be sustained by a few occasional droughts triggering immense fires. However, we also show that the most fire-prone areas of the North American boreal forest are resistant to high burn rates because of overabundant young forest stands, thereby creating a fuel-mediated negative feedback on fire activity. These findings will help refine projections of fire effect on boreal ecosystems and their large carbon stocks.
authors.affiliation: Département de biologie, chimie et géographie, Centre d'études nordiques, Université du Québec à Rimouski, Rimouski, QC, Canada G5L 3A1; and.
authors.forename: Jessie
authors.initials: J
authors.lastname: Héon
authors.affiliation: Département de biologie, chimie et géographie, Centre d'études nordiques, Université du Québec à Rimouski, Rimouski, QC, Canada G5L 3A1; and dominique_arseneault@uqar.ca.
authors.forename: Dominique
authors.initials: D
authors.lastname: Arseneault
authors.affiliation: Northern Forestry Centre, Canadian Forest Service, Natural Resources Canada, Edmonton, AB, Canada T6H 3S5.
authors.forename: Marc-André
authors.initials: MA
authors.lastname: Parisien
mesh_terms: D002244:Carbon / Q000378:metabolism; D005390:Fires; D065928:Forests; D009656:North America
chemical_list: D002244:Carbon
keywords: climate change; fire-free intervals; fuel feedback; probability of burning; tree ring dating