ALTERNATIVES TO FIRE FOR FUEL REDUCTION
AT CALIFORNIA’S FOREST-URBAN INTERFACE
R.F. Powers, D.H. Young, M.D. Busse,
E.E. Knapp, G.O. Fiddler, W.R. Horwath
CALIFORNIA...
A Land of Pavement
People
And That’s The Problem…
People live in the bush
Prescribing fire to
reduce fuel buildup
is not panacea.
CONSEQUENCES OF BRUSHY UNDERSTORIES
AT THE FOREST-URBAN INTERFACE
The ponderosa pine/shrub community
at the forest/urban interface has the
shortest fire return cycle (5-10 yrs)
of any forest type in the Sierra Nevada
(Skinner and Chang 1996)
It’s the nexus
of high fuel loadings, severe drought,
high population density,
and high property values.
What to do about it?
FUELS CAN BE HARVESTED
Sometimes the revenues from
chips will cover
the cost of
treatment.
~ a billion Btu’s
per ha = $?
Ladder fuels
removed.
Organic C lost.
FUELS CAN BE MASTICATED
1A Residues can
be retained
as a surface
mulch.
Ladder fuels
reduced.
Organic C
retained.
FUELS CAN BE MASTICATED
1B Residues can be retained, then
tilled into the surface soil
as an incorporated mulch.
INCORPORATION
Respiration
O Horizon
Mineral soil
Added Carbon:
Humification
Where does it go?
Does it immobilize N?
What happens to other soil properties?
Alternative Methods
of Fuel Reduction
at the Forest/Urban
Interface
OBJECTIVES
1. Reduce fire risk
2. Evaluate impacts on:
•
•
•
•
Residual trees
Soil properties
Returning understory
Carbon cycle
STEP 1. Choose forested sites
with shrub understories
spanning the range of
forest-urban interface
conditions
Challenge
Alternative Methods
of Fuel Reduction
at the Forest/Urban
Interface
Elev. 790 m, 1725 mm ppt
Challenge Series
fine, mixed mesic Typic Palexerults
Whitmore
Alternative Methods
of Fuel Reduction
at the Forest/Urban
Interface
Elev. 730, 1140 mm ppt
Aiken Series
clayey, mesic Xeric Haplohumults
Mt. Shasta
Alternative Methods
of Fuel Reduction
at the Forest/Urban
Interface
Elev. 1,350 m, 940 mm ppt
Ponto Series
medial, mesic, Andic Xerochrepts
Sierraville
Alternative Methods
of Fuel Reduction
at the Forest/Urban
Interface
Elev. 2,000 m, 890 mm ppt
Jorge Series and Tahoma Series variant
loamy-skeletal & fine-loamy, mixed, frigid Ultic Haploxeralfs
STEP 2. Thoroughly characterize
each site for biomass
and nutrient content
before treatment
200 Permanently
referenced
points per site
0
10
1mD
All Veg.
Clipped
2mD
All Veg.
Tallied
Ground line
20
30 cm
Diagnostic horizons
Forest Floor
(0.25 m2)
Sierraville
Alternative Methods
of Fuel Reduction
at the Forest/Urban
Interface
PRETREATMENT BIOMASS
OF ALL POTENTIAL FUELS
BIOMASS (Mg ha -1)
120
100
80
60
40
20
0
Sierraville
Mt. Shasta
Sierraville
Alternative Methods
of Fuel Reduction
at the Forest/Urban
Interface
PRETREATMENT BIOMASS
OF ALL POTENTIAL FUELS
BIOMASS (Mg ha -1)
120
100
80
60
40
20
0
Sierraville
Mt. Shasta
Mt. Shasta
Whitmore
Sierraville
Alternative Methods
of Fuel Reduction
at the Forest/Urban
Interface
PRETREATMENT BIOMASS
OF ALL POTENTIAL FUELS
BIOMASS (Mg ha -1)
120
100
80
60
40
20
0
Sierraville
Mt. Shasta
Whitmore
Mt. Shasta
Whitmore
Sierraville
PRETREATMENT BIOMASS
OF ALL POTENTIAL FUELS
120
BIOMASS (Mg ha-1)
Challenge
Alternative Methods
of Fuel Reduction
at the Forest/Urban
Interface
100
80
60
40
20
0
Sierraville
Mt. Shasta
Whitmore
Challenge
Mt. Shasta
Whitmore
Sierraville
PRETREATMENT BIOMASS
OF ALL POTENTIAL FUELS
120
1 x 109
BTU
BIOMASS (Mg ha-1)
Challenge
Alternative Methods
of Fuel Reduction
at the Forest/Urban
Interface
1.3 x 109
BTU
100
80
0.6 x 109
BTU
60
40
0.3 x 109
BTU
20
0
Sierraville
Mt. Shasta
Whitmore
Challenge
STEP 3. Impose a range of fuel
treatments that reduce
ladder fuels and affect
the carbon cycle
Selected treatments applied in a
randomized block design
1. Control
2. Manual removal
3. Mastication
4. Masticate and incorporate
5. Local BMP
Control
Fuel Reduction Alternatives
Challenge Exptl. Forest
Manual
removal
Control
Fuel Reduction Alternatives
Challenge Exptl. Forest
Manual
removal
Control
Fuel Reduction Alternatives
Challenge Exptl. Forest
Masticate
Manual
removal
Control
Fuel Reduction Alternatives
Challenge Exptl. Forest
Masticate
Incorporate
GENERALIZED TREATMENTS
CONTROL
MASTICATE
+ ROTOTILL
MANUAL
RELEASE
MASTICATE
LOCAL BEST
MANAGEMENT
PRACTICE
EARLY RESULTS
•
•
•
•
Relative costs
Carbon changes
Treatment effectiveness
Introducing fire
RELATIVE COST
RELATIVE COSTS OF ALTERNATIVE
FUEL TREATMENTS
8
6
2000
4
2
0
te
a
tic
s
Ma
RELATIVE COST
RELATIVE COSTS OF ALTERNATIVE
FUEL TREATMENTS
8
6
2000
4
2
0
te
e
a
t
c
i
ca
t
i
t
s re
s
a
a
M Fi
M
+
RELATIVE COST
RELATIVE COSTS OF ALTERNATIVE
FUEL TREATMENTS
8
6
2000
4
2
0
te
e
te e
a
t
a
a
c
i
c rat
c
i
t
i
t
t
s
s
e
s
a rpo
Ma Fir
Ma
M
o
+
c
n
+I
RELATIVE COST
RELATIVE COSTS OF ALTERNATIVE
FUEL TREATMENTS
8
6
2000
4
2
0
te
e
te e
a
t
a
d l
a
c
i
c
t
n
c
i
t
i
a
t
a va
s re
r
s
st
a
o
H
a
a
o
p
M Fi
M
M
r
m
o
+
e
c
R
n
+I
RELATIVE COST
RELATIVE COSTS OF ALTERNATIVE
FUEL TREATMENTS
8
6
2000
4
2
0
g
te
e
te e
a
t
n
a
d
i
a
c
i
c rat
n al
c
i
h
t
i
t
t
t
a
s
v
s
e
s
o
a
H o
a rpo
M Fir
N
Ma
M
m
o
o
+
e
D
R
nc
I
+
HOW MUCH GOES OFF AS CO2?
0 cm
1.25 cm
2.5 cm
5.0 cm
10.0 cm
Residue
thickness
6.0
2
/s
SIZE MATTERS
WHEN IT
COMES TO
RESIDUES
4.0
μ
2.0
0.0
0
20
40
60
80
Time (days)
Chips (1-2 cm diam.)
/2
Chunks (1-5 cm diam.)
mol/m
μ
SURFACE CO2 EFFLUX
0 cm
1.25 cm
2.5 cm
5.0 cm
10.0 cm
Residue
thickness
µmol/m2/s
8.0
2
/s
SIZE MATTERS
WHEN IT
COMES TO
RESIDUES
CHIPS
(1-2 cm)
6.0
4.0
μ
2.0
0.0
0
20
40
Time (days)
60
80
/2
mol/m
μ
SURFACE CO2 EFFLUX
0 cm
1.25 cm
2.5 cm
5.0 cm
10.0 cm
Residue
thickness
µmol/m2/s
8.0
2
/s
CHIPS
(1-2 cm)
6.0
4.0
μ
2.0
0.0
0
20
40
60
80
60
80
Time (days)
8.0
CHUNKS
(1-5 cm)
6.0
/2
µmol/m2/s
SIZE MATTERS
WHEN IT
COMES TO
RESIDUES
4.0
mol/m
μ
2.0
0.0
0
20
40
Time (days)
Mt. Shasta
Whitmore
Sierraville
POTENTIAL
SOIL
CARBON
LOADINGS
PRESENT
SOIL
CARBON
LOADINGS
WITH INCORPORATION
160
Understory Fuels
-1
Mg Mg
Carbon
ha-1
CARBON ha
Challenge
Alternative Methods
of Fuel Reduction
at the Forest/Urban
Interface
120
Soil 0-30 cm
80
40
0
Sierraville
Sierraville
Mt.
Mt. Shasta
Shasta
Whitmore
Whitmore
Challenge
Challenge
Mt. Shasta
Whitmore
Sierraville
POTENTIAL SOIL CARBON LOADINGS
WITH INCORPORATION
160
Understory Fuels
-1
Mg Mg
Carbon
ha-1
CARBON ha
Challenge
Alternative Methods
of Fuel Reduction
at the Forest/Urban
Interface
120
Soil 0-30 cm
80
40
0
Sierraville
Sierraville
Mt.
Mt. Shasta
Shasta
Whitmore
Whitmore
Challenge
Challenge
SOIL C COMPARISIONS AFTER 1 YEAR
CONCENTRTION ORGANIC C (g kg-1)
100
80
Control
0-10 cm
Surface Chips
60
Incorporated Chips
40
20
0
100
80
Control
10-20 cm
Surface Chips
60
Incorporated Chips
40
20
0
CHALLENGE
SOIL C COMPARISIONS AFTER 1 YEAR
CONCENTRTION ORGANIC C (g kg-1)
100
80
Control
0-10 cm
Surface Chips
60
Incorporated Chips
40
20
0
100
80
Control
10-20 cm
Surface Chips
60
Incorporated Chips
40
20
0
WHITMORE
CHALLENGE
MANUAL REMOVAL
UNDERSTORIES REBUILD
1st Spring
16 Months
1st Spring
16 Months
1st Spring
16 Months
MASTICATE
MANUAL REMOVAL
UNDERSTORIES REBUILD
FOLLOW-UP TREATMENTS
SPLIT-PLOT CHEMICAL CONTROL
CONTROL
MANUAL
RELEASE
MASTICATE
+ ROTOTILL
MASTICATE
MASTICATE
+
UNDERBURN
FOLLOW-UP TREATMENTS
SPLIT-PLOT CHEMICAL CONTROL
FOLLOW-UP TREATMENTS
SPLIT-PLOT CHEMICAL CONTROL
FOLLOW-UP TREATMENTS
SPLIT-PLOT CHEMICAL CONTROL
FATE OF HERBICIDES
MOBILIZED IN THE SOIL
SOLUTION
SOIL PROFILE
0 cm
20 cm
Zone of most
intensive
biological activity
High alumina
ceramic samplers
50 cm
Beyond region
of most fine roots
FOLLOW-UP TREATMENTS
UNDERBURNING
MASTICATE
+ BURN
FOLLOW-UP TREATMENTS
Heat Impacts on Soil?
Impacts on Trees?
MASTICATE
+ BURN
CHIPS ARE NOT DISTRIBUTED UNIFORMLY
Depth
(cm)
0 - 2.5
2.5 - 7.5
7.5 - 12.5
> 12.5
WHITMORE
60
60
48
48
DISTANCE (m)
DISTANCE (m)
CHALLENGE
35
24
35
24
12
12
0
0
0
12
24
36
DISTANCE (m)
48
60
0
12
24
36
DISTANCE (m)
48
60
CHIPS ARE NOT DISTRIBUTED UNIFORMLY
Depth
(cm)
0 - 2.5
2.5 - 7.5
7.5 - 12.5
> 12.5
WHAT WILL THIS MEAN
IF WE REINTRODUCE
FIRE?
WHITMORE
60
60
48
48
DISTANCE (m)
DISTANCE (m)
CHALLENGE
35
24
35
24
12
12
0
0
0
12
24
36
DISTANCE (m)
48
60
0
12
24
36
DISTANCE (m)
48
60
DOES RESIDUE CONDITION
AFFECT FIRE INTENSITY?
Preliminary Trial
Instrument and ignite
Reconstruct field
soil at two
moisture contents
Add residues at
successive
thicknesses
Mulch layer (0, 2.5, 7.5, and 12.5 cm)
Metal barrier
Surface
0
2.5
5
10
Soil
0.9 m
Thermocouple
wires
Mineral soil depth (cm)
0.0
2.5
5.0
10
Dry soil
(2%)
500
Moist soil
500
400
400
TEMPERATURE (°C)
0 cm mulch
0 cm mulch
300
300
200
200
100
100
0
0
400
400
2.5 cm mulch
2.5 cm mulch
300
300
200
200
100
100
0
0
400
7.5 cm mulch
400
300
300
200
200
100
100
0
0
400
7.5 cm mulch
400
12.5 cm mulch
12.5 cm mulch
300
300
200
200
100
100
0
0
0
2
4
6
8
10
HEAT DURATION (h)
12
0
2
4
6
8
10
HEAT DURATION (h)
12
Mineral soil depth (cm)
0.0
2.5
5.0
10
Dry soil
(2%)
500
Moist soil
500
400
400
TEMPERATURE (°C)
0 cm mulch
0 cm mulch
300
300
200
~250
C
200
100
100
0
0
400
400
2.5 cm mulch
2.5 cm mulch
300
300
200
200
100
100
0
0
400
7.5 cm mulch
400
300
300
200
200
100
100
0
0
400
400
7.5 cm mulch
~450 C
12.5 cm mulch
12.5 cm mulch
300
300
200
200
100
100
0
0
0
2
4
6
8
10
HEAT DURATION (h)
12
0
2
4
6
8
10
HEAT DURATION (h)
12
Mineral soil depth (cm)
0.0
2.5
5.0
10
Dry soil
(2%)
500
Moist soil
(16%)
500
400
400
TEMPERATURE (°C)
0 cm mulch
0 cm mulch
300
300
200
200
100
100
0
0
400
400
2.5 cm mulch
2.5 cm mulch
300
300
200
200
100
100
0
0
400
7.5 cm mulch
400
300
300
200
200
100
100
0
0
400
7.5 cm mulch
400
12.5 cm mulch
12.5 cm mulch
300
300
200
200
100
100
0
0
0
2
4
6
8
10
HEAT DURATION (h)
12
0
2
4
6
8
10
HEAT DURATION (h)
12
Mineral soil depth (cm)
0.0
2.5
5.0
10
Dry soil
500
Moist soil
500
400
400
TEMPERATURE (°C)
0 cm mulch
0 cm mulch
300
300
200
200
100
100
0
0
400
400
2.5 cm mulch
2.5 cm mulch
300
300
200
200
100
100
Root injury
0
0
400
7.5 cm mulch
400
300
300
200
200
100
100
0
0
7.5 cm mulch
Root injury
400
400
12.5 cm mulch
12.5 cm mulch
300
300
200
200
100
100
0
0
Root injury
0
2
4
6
8
10
HEAT DURATION (h)
12
0
2
4
6
8
10
HEAT DURATION (h)
12
Mineral soil depth (cm)
0.0
2.5
5.0
10
Dry soil
500
Moist soil
500
400
400
TEMPERATURE (°C)
0 cm mulch
0 cm mulch
300
300
200
200
100
100
0
0
400
400
2.5 cm mulch
2.5 cm mulch
300
300
200
200
100
100
Root injury
0
0
400
7.5 cm mulch
400
300
300
200
200
100
Microbial death 100
0
0
7.5 cm mulch
Root injury
400
400
12.5 cm mulch
12.5 cm mulch
300
300
200
200
100
100
0
Microbial death
Root injury
0
0
2
4
6
8
10
HEAT DURATION (h)
12
0
2
4
6
8
10
HEAT DURATION (h)
12
Mineral soil depth (cm)
0.0
2.5
5.0
10
Dry soil
500
Moist soil
500
400
400
TEMPERATURE (°C)
0 cm mulch
0 cm mulch
300
300
200
200
100
100
0
0
400
400
2.5 cm mulch
2.5 cm mulch
300
300
200
200
100
100
Root injury
0
0
400
7.5 cm mulch
400
300
300
200
200
100
Microbial death 100
0
0
7.5 cm mulch
Root injury
400
400
12.5 cm mulch
12.5 cm mulch
300
300
200
200
100
100
0
Soil carbon loss
Microbial death
Root injury
0
0
2
4
6
8
10
HEAT DURATION (h)
12
0
2
4
6
8
10
HEAT DURATION (h)
12
PRELIMINARY CONCLUSIONS
•
Residue thickness makes a difference.
Surface temps exceed 300 C with as little as
1-inch of mulch, 400 C with 5 inches if soils
are dry.
•
Soil moisture makes a difference. Max
subsurface temps typically 100 C lower.
•
Regardless of moisture, residue thickness
> 5 inches produced lethal temps in rooting
zone.
•
Lethal soil temps can last up to 10 hours in
dry soil, 5 hours in moist.
DEPTH OF RESIDUES
Thickness
(cm)
0 - 2.5
2.5 - 7.5
7.5 - 12.5
> 12.5
WHITMORE
60
60
48
48
DISTANCE (m)
DISTANCE (m)
CHALLENGE
35
24
35
24
12
12
0
0
0
12
24
36
DISTANCE (m)
48
60
0
12
24
36
DISTANCE (m)
48
60
POTENTIAL SOIL HEATING
Thickness
(cm)
0 - 2.5
2.5 - 7.5
7.5 - 12.5
> 12.5
Max, soil temp.
@ 10 cm (Cº)
< 40
40 - 60
60 - 90
> 90
WHITMORE
60
60
48
48
DISTANCE (m)
DISTANCE (m)
CHALLENGE
35
24
35
24
12
12
0
0
0
12
24
36
DISTANCE (m)
48
60
0
12
24
36
DISTANCE (m)
48
60
FIELD
VALIDATION
Before
After
BehavePlus 2.0 Fire Model
(Run with typical summer temperature and fuel moisture
conditions for west slope Sierra Nevada, elev. 1,000 m)
40
No treatment
Slash/ cut only
Masticated
30
20
10
0
0
10
20
30
40
Wind speed (km/hr)
Flame length
8
meters
meters/ minute
Rate of fire spread
6
4
2
0
0
10
20
30
Wind speed (km/hr)
40
Fuel loading:
86 Mg/ha
(38 tons/acre)
Ponderosa pine
DBH 25 cm
Height 14.5 m
Live crown ratio 60%
BehavePlus 2.0 Fire Model
(Run with typical summer temperature and fuel moisture
conditions for west slope Sierra Nevada, elev. 1,000 m)
40
No treatment
Slash/ cut only
Masticated
30
20
10
Expected tree mortality
100
80
0
10
20
30
40
Wind speed (km/hr)
Flame length
%
0
60
40
20
0
8
meters
meters/ minute
Rate of fire spread
0
6
10
20
30
40
Wind speed (km/hr)
4
2
0
0
10
20
30
Wind speed (km/hr)
40
Fuel loading:
86 Mg/ha
(38 tons/acre)
Ponderosa pine
DBH 25 cm
Height 14.5 m
Live crown ratio 60%
FIELD
VALIDATION
SOIL THERMOCOUPLES
SAP FLOW MEASUREMENTS
DUFF PINS
SUMMARIZING…
•
Targets fuel problems in zone of greatest risk.
One not covered by Nat. Fire Surrogate Study.
SUMMARIZING…
•
Targets fuel problems in zone of greatest risk.
One not covered by Nat. Fire Surrogate Study.
•
Tackles applied (fuel reduction, herbicide mobility)
and fundamental (carbon sequestration) issues
of major significance.
3
ps
Chi
CO2
Soil Respiration
rpo
inco
d
rate
2
e
Chips on surfac
1
0
1
Control
2
5
6
7
TIME
8
9
13
SUMMARIZING…
•
Targets fuel problems in zone of greatest risk.
One not covered by Nat. Fire Surrogate Study.
•
Tackles applied (fuel reduction, herbicide mobility)
and fundamental (carbon sequestration) issues
of major significance.
•
Establishes a replicated, large-scale experiment with
staying power and strong contrasts:
Mt. Shasta
Manual
removal
Control
Whitmore
Challenge
Fuel Reduction Alternatives
Challenge Exptl. Forest
Masticate
Incorporate
Sierraville
SUMMARIZING…
•
Targets fuel problems in zone of greatest risk.
One not covered by Nat. Fire Surrogate Study.
•
Tackles applied (fuel reduction, herbicide mobility)
and fundamental (carbon sequestration) issues
of major significance.
•
Establishes a replicated, large-scale experiment with
staying power and strong contrasts:
•
Creates opportunities (collaboration, grants, technical
transfer to an unusually broad audience).
SUMMARIZING…
•
Targets fuel problems in zone of greatest risk.
One not covered by Nat. Fire Surrogate Study.
•
Tackles applied (fuel reduction, herbicide mobility)
and fundamental (carbon sequestration) issues
of major significance.
•
Establishes a replicated, large-scale experiment with
staying power and strong contrasts:
•
Creates opportunities (collaboration, grants, technical
transfer to an unusually broad audience).
•
Offers a scientific basis for evaluating options.
Bottom Line:
All active options
carry costs.
Bottom Line:
All active options
carry costs.
The option of Doing
Nothing carries the
greatest cost of all.
CALIFORNIA...
A Land of Pavement and People
The ponderosa pine/shrub community
at the forest/urban interface has the
shortest fire return cycle (5-10 yrs)
of any forest type in the Sierra Nevada
(Skinner and Chang 1996)
The ponderosa pine/shrub community
at the forest/urban interface has the
shortest fire return cycle (5-10 yrs)
of any forest type in the Sierra Nevada
(Skinner and Chang 1996)
It’s the nexus
of high fuel loadings, severe drought,
high population density
and high property values
The ponderosa pine/shrub community
at the forest/urban interface has the
shortest fire return cycle (5-10 yrs)
of any forest type in the Sierra Nevada
(Skinner and Chang 1996)
It’s the nexus
of high fuel loadings, severe drought,
high population density
and high property values
What to do about it?