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Wildfires in boreal ecoregions: Evaluating the power law assumption and intra-annual and interannual variations

Author:
  • Veiko Lehsten
  • William J. de Groot
  • Mike Flannigan
  • Charles George
  • Peter Harmand
  • Heiko Balzter
Publishing year: 2014
Language: English
Pages: 14-23
Publication/Series: Journal of Geophysical Research - Biogeosciences
Volume: 119
Issue: 1
Document type: Journal article
Publisher: American Geophysical Union (AGU)

Abstract english

Wildfires are a major driver of ecosystem development and contributor to carbon emissions in boreal forests. We analyzed the contribution of fires of different fire size classes to the total burned area and suggest a novel fire characteristic, the characteristic fire size, i.e., the fire size class with the highest contribution to the burned area, its relation to bioclimatic conditions, and intra-annual and interannual variation. We used the Canadian National Fire Database (using data from 1960 to 2010) and a novel satellite-based burned area data set (2001 to 2011). We found that the fire size distribution is best explained by a normal distribution in log space in contrast to the power law-based linear fire area relationship which has prevailed in the literature so far. We attribute the difference to previous studies in the scale invariance mainly to the large extent of the investigated ecoregion as well as to unequal binning or limiting the range at which the relationship is analyzed; in this way we also question the generality of the scale invariance for ecoregions even outside the boreal domain. The characteristic fire sizes and the burned area show a weak correlation, indicating different mechanisms behind each feature. Fire sizes are found to depend markedly on the ecoregion and have increased over the last five decades for Canada in total, being most pronounced in the early season. In the late season fire size and area decreased, indicating an earlier start of the fire season. Key Points Fire area-fire number relationship is analyzed for boreal wildfire globally The distribution does not follow a power law as previously assumed The fire size of Canadian wildfires increased strongly over the last decades

Keywords

  • Physical Geography
  • boreal wildfires
  • fire season
  • power law

Other

Published
  • ISSN: 2169-8953
E-mail: veiko [dot] lehsten [at] nateko [dot] lu [dot] se

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Dept of Physical Geography and Ecosystem Science

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Department of Physical Geography and Ecosystem Science
Lund University
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