CLIMATE SPACE OF FIRE REGIMES
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Journal of Biogeography
SUPPORTING INFORMATION
The climate space of fire regimes in north-western North America
Ellen Whitman, Enric Batllori, Marc-André Parisien, Carol Miller, Jonathan D. Coop, Meg A. Krawchuk,
Geneva W. Chong and Sandra L. Haire
Appendix S1 Supplementary figures and data.
Figure S1 Map of the database of 1879 large (≥ 385 ha) fires that burned in the study area within the
1984–2011 study timeline. The fire perimeters in this database were consolidated from the Canadian
National Fire Database and the Monitoring Trends in Burn Severity project, producing a consistent, transboundary set of fires. Fires for which the differenced normalized burn ratio (dNBR) was calculated for
use in analysis of burn severity are represented in red, whereas other fire perimeters without dNBR data
are included in black. Fires without dNBR data were nonetheless included in the analyses of other fireregime component characteristics (i.e. fire size, frequency, season, cause).
CLIMATE SPACE OF FIRE REGIMES
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Table S1 The units and range of the fire-regime components within the climate domains (CDs). Ranges
are presented for the 33 CDs where fires occurred, as well as the 24 CDs where ≥ 5 fires occurred, which
were used for regression analysis. Frequency is the burned area-weighted number of fires in a CD. Size is
the mean fire size in ha. Severity is the mean 90th percentile differenced normalized burn ratio within a
CD and season is the median Julian day of fire ignition. Cause is represented by the percentage of all
ignitions within the CD caused by lightning. Human footprint index (HFI; Sanderson et al., 2002),
although not a fire-regime component, is the mean HFI within the area of a CD.
Fire-regime component
Frequency
Size
Severity
Season
Cause
Human footprint index
Climate domains with
fires
Min
Max
0.0
0.5
447.5
6069.9
74.8
701
195
265
0
100
0
78
Climate domains
≥ 5 fires
Min
Max
0.0
0.5
877.9
6069.9
74.8
664.4
196
265
0
92
4.4
35.4
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Figure S2 The coefficient of variation (CV) within a climate domain (CD) for fire-regime components of
(a) fire size, (b) severity and (c) season. CV within a CD is represented by asterisk size, where larger
asterisks indicate more variation within a CD and smaller asterisks indicate a fairly homogenous range of
values. Fire size varies substantially within CDs, whereas fire severity and season are more consistent.
CDs where < 5 fires occurred during the study timeline are represented in white, and CDs with no fires
are represented in grey.
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Appendix S2 Regressions fitted to climate gradients and fire-regime components.
Figure S3 Scatterplots with fitted regressions and deviance explained (DE) for fire-regime components
and the dominant climate gradients of the study area. The primary climate gradient of the study area of
temperature and summer precipitation is represented as rotated component 1 (RC1) and the secondary
climate gradient of continentality and winter precipitation is represented as rotated component 2 (RC2).
All regressions presented here are significant at a P ≤ 0.05 level. Units of measurement are average fireregime components within a climate domain, where a climate domain had ≥ 5 fires in 1984–2011.
Relationships are: (a) fire frequency as a function of RC1, (b) fire season as a function of RC1, (c) burn
severity as a function of RC1, (d) burn severity as a function of RC2, (e) fire cause as a function of RC1,
(f) fire cause as a function of RC2, (g) human footprint index (HFI) as a function of RC1 and (h) HFI as a
function of RC2.
CLIMATE SPACE OF FIRE REGIMES
Figure S4 The deviance explained in bivariate regressions between fire-regime components and the fireregime driver of human footprint index (HFI), and the two environmental gradients rotated component 1
(RC1) and rotated component 2 (RC2). RC1 is a gradient of temperature and summer precipitation,
whereas RC2 is a gradient of continentality and winter precipitation. The fire-regime components of fire
cause and burn severity are strongly predicted by environmental gradients, as is HFI. Fire frequency
(Freq), size and season are less driven by the climate gradients in the study area.
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