The Role of Silviculture in
Restoring Fire-Adapted
Ecosystems
James K. Agee
University of Washington
Fire Scar Cross Section
1842
1774
Cle Elum, WA
• Each fire kills several cm
of cambium
• Subsequent annual
growth begins to cover
scar
• Next fire repeats process
• Fires about every 10
years on this sample
between 1600-1900
Historic Character
Fires Self-buffer
The “Light Burning” Controversy
• These fires maintained
ecosystem stability
• BUT killed small trees,
• “the future of American
forestry”
• Fire defined as
incompatible with forest
management
Fire Exclusion Wins!
• Forest Industry fights
for fire
• Forest Service fights
against it
• “Light Burn
Committee”
concludes in favor of
fire exclusion
Pine Forest - 1908
Pine Forest - 1928
Pine Forest - 1938
The Fire Problem in 2005
• “Enormous areas are growing up in dense,
even-aged stands…of reproduction”
• “Fire hazard has increased tremendously”
• “Fires, when they do occur, are exceedingly hot
and destructive and are turning extensive areas
of forest into brush fields”
• “We must depend on either replacing fire as a
natural silvicultural agent or use it as a
silvicultural tool”
Harold Weaver
• All quotes are from
Journal of Forestry 1943
• Bookended by disclaimers
• Prefaced by BIA saying it did not represent
their position
• Followed by SAF saying we don’t know
enough do until research is done, so we
don’t have to do anything
Pine Forest - 1948
Logging removes the most
fire-tolerant trees
The Glory Days of Livestock
Changes in Fire Regimes
Historical
H
L
Now
L
H
M
M
Adapted from
Forest Service Regions 1-6 – FRCC 2000 – All Cover Types
Forest Restoration
• Stand-level Principles
• The Silvicultural Tools
–Fire
–Chain saw
• The Landscape
Firesafe Principles at the
Stand Level
• Reduce surface fuels
• Reduce ladder fuels
• Keep the large trees
• Reduce crown density
Reduce Fuel and Fire
Behavior
More Open Crowns=
No Crown Fire
Fewer Ladder fuels =
No Torching
Lower surface fuels =
Low Flame Length
Leave Big trees =
Tall Crowns/Thick Bark
Fire-resistant
Surface Fuels
• Prescribed fire consumes
fuels
• Limits flame length of
later wildfire
• Pile burn or Manual
treatment possible but
usually more expensive
Pile Burning Effective, too
Single Prescribed Fire Creates
Fuel
4 Yrs
Post-fire
Surface
fuels
At least as
high as
before
Increase in
height to
live crown
Blacks Mtn Experimental Forest, California
Ladder Fuels
• Carry fire from surface to crown
• A function of height to live crown, foliar
moisture and surface fire flame length
• So…
– Reduce surface fire flame length
– Keep live crown as high as possible
Flame lengths needed to initiate
torching
Flame lengths in meters
Prescribed Fire and Ladder
Fuels
3 Months After Fire • Surface Fuels are Reduced
• Height to Live Crown
Increased
• Green surface fuels
increase and less
flammable
Raises
Height to Live Crown
Tyee Fire, Washington, 1994
2 mos
8 yrs
This stand had only ladder fuels
removed and surface fuels reduced
• 1994 - 80,000 ha
Tyee fire Washington State
• Stands Where
Prescribed fire and
thinning occur survive
• Crown fires become
surface fires
Megram Fire, California 1999
Fueled by Windsnap-Windthrow Event 1995-96
Limited fuelbreak creation followed the event
Fuelbreak left Dense Crown
Surface and Ladder Fuels Treated
Untreated
Treated
Reduce Crown Density
• Important to address once surface fire and
torching are addressed
• DON’T START HERE!!!!!
• Active crown fire a function of rate of spread and
canopy bulk density [CBD]) which produce a
“mass flow rate”
• Thinning reduces crown mass and therefore
mass flow rate, usually below a critical level so
that active crowning doesn’t occur
Unmerchantable Small
Trees
Lower
Merchantable
limit
• So stand is thinned
from below, but…
• Very small
unmerchantable
material left
Removed
• Result: no effect on
height to live crown
Yarding Affects Surface Fuels
YARDING METHOD
SURFACE FUEL
AMOUNT/DEPTH
Feller-buncher or cable – whole tree
NE/NE
Feller-buncher or cable – lop/scatter
I/I
Harvester-forwarder
I/NE or I/I
Helicopter
I/I
NE = NO EFFECT I = INCREASE D = DECREASE
Effect of Thinning and Burning
• Simulation using NEXUS and FOFEM
• Mixed-conifer forest w/trees to 100 cm
diameter (40 inches)
• Thin from 34 to 14 sq m per ha (60 sq
ft/ac)
• Total of 8 treatments simulated in same
stand:
– 4 thinning treatments w/ or w/out prescribed
fire
Treatments
• No treatment
• Low thin until 14 sq m BA target reached
• Low thin but start at 15 cm dbh tree (comm’l
limit)
• Selection thin, largest down until 14 sq m BA
target reached
• Then, either prescribed fire or no prescribed fire
applied with flame length 0.6 m (2 ft)
• Finally , a late summer wildfire was applied
Increasing survival
UM = Unmanaged
ST = Selection thin
LT = Low thin
CL= Commercial limit
PF = Prescribed fire
Agee and Skinner 2005
For. Eco. and Manage.
211 (1-2): 83-96
Take-Home Points
• No action is a disaster
• Thinning from above is a disaster
• Low thinning is the best thinning
method
• Prescribed fire is helpful, but
may have to be applied twice as
fire-killed trees fall
Tyee Fuelbreak Survives
• Fuelbreaks are linear
treated areas where
“firesafe “ principles
applied:
Crown fire
Fuelbreak
Crown
fire
• Surface fuels reduced
• Ladder fuels reduced
• Crowns of trees
thinned
Tyee Fuelbreak Edge
Green
Brown
Fuelbreak
Edge
Fire Direction
Surface fire
becomes
Crown Fire
• 25 Year Old Fuelbreak
• Thinned trees grew faster
- More Resistant
• No ladder fuels
• Immediately adjacent
area burns with crown fire
Cone Fire – Edge of Treatment
180o Views
Fire Went Out
Thin and Burn – 2 yr Old
Untreated
B&B Fire, Oregon
Deschutes National Forest
B&B Fire, Oregon
Deschutes National Forest
B&B Fire, Oregon
Deschutes National Forest
B&B Fire, Oregon
Deschutes National Forest
What Tool to Use?
• Prescribed Fire +++++:
– Surface fuel reduction
– Increased CBH
– Little effect on CBD
• Prescribed Fire - - - -:
– Creates as well as consumes dead fuel
– Smoke and escapes
– These latter two are deal-breakers
What Tool to Use?
• Thinning +++++++++
– Reduces CBD
– More selective than fire
– No smoke!
• Thinning - - - - - - - - – Many dry forest stands don’t need CBD reduction
– Thinning creates a lot of fine dead fuel
– Unmerchantable understory may be left, so no effect
on CBH
Need a Market for “Fuel”
•
•
•
•
Co-generation for power
Portable methanol production
Post-pole markets (limited)
Small dimension mills
• All require a sustained raw material supply
• Raw material supply requires public trust
Scaling up to Landscape Levels
“Where no man has gone before….”
Historical Fire Regimes
High Priority
Low Priority
A Regular Pattern of SPLATS
Finney, M. 2001.
Forest Science 47(2): 219-228.
• Fires slow within
“SPLATs” –
Strategically Placed
LAndscape
Treatments
• Move faster between
SPLATS
• What configuration is
best?
Effect of SPLAT Spatial Location
• “a” = no bricks
• “b-d” = 19% of
landscape covered
but with different
pattern
• Fire moving from
bottom to top
• What about left to
right? (“d” best).
Assumes spread rate in bricks 10% of pre-treatment
Fireshed
•
•
•
•
Technical tool using FARSITE
Places SPLATS defined by use groups
Simulates outcomes
Terrific communication tool to get people
speaking the same language
FARSITE in Utah Woodland
Stratton, R. 2004 J. Forestry
Fuel modification knocks back fire by 1,500 acres, or 18%,
at 85 percentile fire weather, but only 6% at 95 percentile weather
A Real Question
• If we are going to be there with crews
when the fire is burning, reduction in
spread/intensity will help control
• Or will we be WUI-willies?
• Current political pressure forcing Federal $
to WUI for fuel treatment and suppression
– coalition of environmental groups and
Western Governor’s Association
Between Rock and Hard Place
• If the latter, wider landscape-level
treatments are probably needed if we
expect forest survival – another
landscape-level decision that needs to go
into the mix.
• But no dollars available – will these
treatments pay for themselves? Only with
harvest.
We Need Real Applications
Applications will Occur in a
Changing Global Climate
The West
greens up
– more
carbon to
deal with
Green
means increase in
vegetation density
5-9 degree F
increase
18-22% ppt
Increase, mostly
in winter
Conclusions
• Restoration can’t be done with fire alone
• Harvest is a key
• Harvest can’t be done without public trust
– Restoration of sustainable forest condition
– NOT driven by output quotas
• Public trust will come if we do the “right
thing”