Reintroduction of fire in
regenerating dry forests following
stand-replacing wildfire
David Peterson1, Paul Hessburg1, Brion
Salter1, Kevin James1, Matt Dahlgreen2, and
John Barnes2
1 Pacific
Northwest Research Station, Wenatchee
2 Okanogan-Wenatchee National Forest
We’ve talked about…
„ Changes in forest
structure and fuels due
to decades of fire
exclusion.
„ The need for restoration
to manage future fire
behavior.
„ Methods for achieving
these goals in different
forest types and at
varying spatial scales.
When bad things happen to good
forests…
„ Often, large, stand-
replacing wildfires don’t
wait for fuel treatments
to be completed and we
end up with lots of dead
trees.
„ What do we do now?
What do we do now?
„ Declare victory and go home.
„ Fire has reintroduced itself to the ecosystem.
„ Repair fire suppression damage and walk away.
„ Let Nature take care of things.
„ Accept defeat and move on to greener forests.
„ Fire destroyed the forest we wanted to save.
„ Do basic post-fire rehabilitation and restoration work.
„ Focus on restoring the remaining green forests.
„ Start planning for the next fire.
Why work to restore fire-resistant conditions
in regenerating forests?
„ These are our future forests.
„ The fuels problem has
„
„
„
„
probably gotten worse.
There is another fire coming;
we just don’t know when.
We have lots of acres in this
condition and more on the
way.
Opportunity to modify future
fire behavior on landscape.
Funding for reforestation and
TSI is limited, so we need to
use strategic thinking and
low cost methods.
Principles for restoring fire-resistant
forests after stand-replacing fire
„ Mature forests
„ Reduce surface fuels
„ Increase height to live
crown
„ Reduce crown density
„ Keep big trees of
resistant species
„ Regenerating forests
„ Reduce surface fuels
„ Increase height to live
crown
„ Reduce crown density
„ Encourage development
of large trees of resistant
species
Adapted from Agee and Skinner, 2005. Forest Ecology and Management
Preston Creek Prescribed Fire Study
„ Entiat River Basin, north-central Washington
„ Dry forests – ponderosa pine, Douglas-fir,
and grand fir
„ History of stand-replacing fires in Entiat Basin
Tyee Fire (1994) – 95,000 acres
„ Dinkelman Fire (1988) – 51,000 acres
„ Entiat Fire (1970) – 61,000 acres
„
Preston-Fox Management Area
„ Management area is within a
„
„
„
„
34,000 acre contiguous
block of the 1970 Entiat fire.
Contains the Entiat
Experimental Forest
Structurally and
compositionally
homogeneous stands
Window for effective thinning
still open, but not for long
Landscape patterns driven
mostly by geology/soils, with
few relict forest stands
Management objectives
„ Reduce short-term (0-30 years) risks of
severe disturbances from fire and insects.
„ Take advantage of thinning window, and
attempt to extend it.
„ Put landscape and component stands on a
trajectory toward conditions closer to natural
range of variability.
„ Restore fire as a key ecosystem process.
Methods / Approach
„ Approach
„
„
Apply spring prescribed fire to mostly south-facing pine
stands.
Apply fall prescribed fire to mostly north-facing stands
with Douglas-fir and pines (ponderosa and lodgepole)
„ Methods
„
„
„
„
No mechanical pretreatment
Burned about 250 acres shortly after snowmelt in 2004.
Snow on higher elevations and adjacent north-facing slopes
protected against fire escape or spotting.
Burned a couple of units in October 2004. First attempts
were disappointing, but we are hopeful…
Partnership with PNW Research to monitor results.
Spatial variability in fire effects
„ Established 264
monitoring plots on a
grid; about 1 plot/acre
„ At each plot, we
assessed percentage of
surface area burned
„ Grouped plots by area
burned
„
„
„
None (0%)
Partial (5-95%)
Complete (100%)
Fire heterogeneity within
prescribed fire perimeter.
Complete (118)
Partial (72)
None (74)
Tree density (trees/acre)
600
500
Prefire 2004
Postfire 2004
Postfire 2005
400
300
200
100
0
Tree basal area (ft2/acre)
Changes in density and basal area
by burn class
80
60
Prefire 2004
Postfire 2004
Postfire 2005
40
20
0
No fire
Partial Complete
Fire Class
No fire
Partial Complete
Fire Class
Changes in tree size distributions
Partial fire (5-95%)
„ Prescribed fire killed
Tree density
(stems/acre)
80
60
40
20
0
Complete fire (100%)
100
Tree density
(stems/acre)
mostly smaller trees
(less than 4” dbh)
„ Resulting distribution is
unimodal with mean of
4-5” dbh
„ Fire is basically thinning
from below and favoring
large trees over small
trees.
100
80
60
40
20
0
0 1 2 3 4 5 6 7 8 9 10 11 12
Tree size class (inches)
Changes in height to live crown
Height to Live Crown (ft)
16
14
No fire
Partial fire
12
10
8
6
4
2
0
No Fire
Partial Complete
Fire Class
Back to basics… How did we do?
„ Reduce surface fuels
Yes, but follow-up fires
will probably be needed.
„ Increase live crown height
„ Yes, in many places.
„ Decrease crown density
„ Yes, although not as
much as we wanted.
„ Promote development of
large trees
„ Hopefully. We’ll see.
„
Future concerns to be addressed…
„ Fire effects on bark
beetle and mistletoe
activity.
„ Potential adverse
effects of spring fire on
tree roots, understory
vegetation, and soil
biota.
„ Changes is landscape
spatial patterns.
Where do we go from here?
„ Continue monitoring sites for changes in fuels, stand
structure, understory vegetation.
„ Work out prescriptions and methods for applying
prescribed fire in mixed-conifer stands on northfacing slopes.
„ Deal with the problem of residual coarse woody
debris after fires
„
„
„
Can we use prescribed fire with huge fuel loads?
What are the patterns and rates of fuel succession?
How does heat production vary with decay state?
„ Work on reforestation methods that encourage rapid
development of fire resistance.
Comments and feedback are welcome.
Principles for restoring fire-resistant
forests
„ Reduce surface fuels
„ Increase height to live
crown
„ Decrease crown density
„ Keep big trees of fireresistant species
Source: Agee and Skinner, 2005