Climate-induced Shifts in Fire Frequency, and
Resulting Effects on Stand Composition
Carissa D. Brown
Northern Biogeography Lab
Department of Geography, Memorial University
Black spruce (Picea mariana)
Fire drives secondary succession and species
distribution in boreal forests
Fire drives secondary succession and species distribution in boreal forests
Short window
of opportunity
Temperature trends (1960-2009)
Burrows et al. 2011 Science; Chapin et al. 2005 Science
Climate-fire regimes
Ratio of 3xCO2 / 1xCO2
area burned:
Flannigan et al. 2005
Climate-fire-succession
Balshi et al. 2009
Kasischke and Turetsky 2006
Fire drives secondary succession and species distribution in boreal forests
What happens if fire regimes change?
How will changes in fire-climate
interactions effect black spruce
distribution?
1991
1990
1991
2005
1990
longinterval
fire
shortinterval
fire
mature
forest
mature forest
long-interval fire
short-interval fire
Post-fire colonisation: is seed available?
mature forest
long-interval burn
short-interval burn
Seed availability
Number of viable seeds/m2/year
8
6
4
2
0
mature
forest
long
interval
LI
Fire history
short
interval
SI
Brown and Johnstone, 2012, For. Ecol. Man.
Will seed germinate and survive?
Number of emerged seedlings
Black spruce emergence
Fire history
Brown and Johnstone, 2012, For. Ecol. Man.
Closely timed fires short-circuit
regeneration cycles
long
fire
return
interval
seed
availability
establishment
short
seed
growth
and
survival
A failure in two parts
1. Lack of seed
2. Unsuitable substrate
A failure in two parts
Long-term disruption
Indirect climate effects caused by a
change to the disturbance regime may
initiate vegetation shifts of a larger
magnitude or opposite direction than
would happen due to climate alone
mammal
Carbon storage
organic horizon
1990/91
2005
wood
mature forest
long-interval burn
Fire history
short-interval burn
How will shifting fire regimes
influence tree distributions in the
boreal forest?
If serotiny loses its advantage (ecosystems
become less resilient), what will succeed?
The prediction
Regions that have experienced a novel
disturbance regime will become more suitable
for alternative tree species dominance
Black spruce ecosystems
Eagle Plains, Yukon
Dalton Complex, Alaska
Taylor Complex, Alaska
Boundary Fire, Alaska
Future scenarios for successional shifts
historic regime
black spruce
self-replacement
severity
frequency
BS seed
severity
frequency
In the absence of seed limitation
BS seed
moisture
Current distributions
Black spruce
Current distributions
Black spruce
White spruce
Current distributions
Black spruce
White spruce
Paper birch
Black spruce
White spruce
Paper birch
50 km
Shifting regimes in Labrador
ACKNOWLEDGEMENTS
Dr. Jill Johnstone, University of Saskatchewan
…and many, many field assistants, labmates, and colleagues.
Threshold
for recovery:
50 –
150 years
Thresholds
for stand
recovery
5
High severity fire
(good post-fire seedbed)
Seedling density . m2
4
3
Range of seed
requirements
2
Low severity fire
(poor post-fire seedbed)
1
Stand recovery to
4000 trees/ha
0
0
50
100
150
200
250
Mean stand age
Viglas, Brown, et al. in review, Can. J. Forest Research
Patterns between species: Alaska
Alaskan birch
Number of seedlings
Black spruce
Soil moisture (%)
Species-specific optimal seed bed conditions