RMRS
Relation to Severity
and Forest Structure
The Results
Theresa B. Jain
Russell T. Graham
2003 National Silviculture Workshop in Granby,
Colorado
Introduced this study, its design, data collection
methods, challenges we were facing, preliminary
results
Today
Background information for context
No detailed methods
Concentrate on “real” results
Trust Me
Identify a Simple Relationship
Within a Broad Scope Under Extreme Fire
Events
As a Function of
Pre-Fire Forest
Structure
Predict Burn Severity
Unique Feature: Sampling Design
For a Particular Fire
Physical
Setting
Weather
Forest Structure
Randomized Stands
Pre-fire forest structure
Slope: Physical setting
Burning index (weather)
Probability sampling
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Fire Behavior
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Burn Severity
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Bitterroot Fires
Forests as
Vegetation and Fuel
Crown fires
A. Canopy
Plants B. Ladder
C. Shrub
Surface fires
D. Low vegetation
Soils E. Woody fuel
F. Ground fuels
Dead Smoldering fires
E. Woody
Wood
F. Ground
A
A
B
C
D
E
E
F
D
Scope and Applicability
• 78 fire events 2000, 2001,
2002, 2003 Montana, Idaho,
Colorado, Utah, Oregon,
Arizona
• Data sources
Retrospective study
Collaboration
FIA
Wilderness Institute
David Pilliod
Results
As a Function of
Pre-Fire Forest
Structure
Burn Severity
Quantifying Burn Severity Classification
Issues:
• Intensity, fire severity, burn severity definitions are
inconsistent
• Lumpers, splitters, selectors
• No rational for a severity classification
• No precedence is set for a consistent way to communicate
severity
Revisiting and Revising Severity
Definitions
Severity classes to:
• Applicable to management
• Synthesize the science
• Lumped, split, or selected
• Simple to quantify and describe
• Visualize
Fire Disturbance Continuum
Similar to a Silviculture System
Pre-Fire
Environment
Environmental
characteristics
before the fire
Current
Condition
Fire Environment
Post-Fire
Response
Environment
Environmental
characteristics during the
fire
Environmental
characteristics
after the fire
“Fire Intensity”
(Fire characteristics)
“Burn Severity”
What is left
“Fire Severity”
(Direct effects from
combustion process)
“First-order fire effects”
Disturbance
Desired
Future
Condition
The biological
and physical
response to the
environment
“Second-order
fire effects”
Response
Soil Burn Severity
Pre-Fire
Environment
Physical
setting
PVT
Soils
Surface dead
Climate
Productivity
Erosion
potential
Time of year
Fire Environment
Post-Fire
Environment
Heat Pulse
0 C
C
O
N
0 - 100
S
0 - 177 U
M
P
50 - 177
T
177 - 400 I
O
N
> 400
CHAR
Response
Microbes
Proportion
CHAR
Erosion
Soil Burn Severity Definition and Classification
Levels
1 > 85 surface organic, all char classes
2 40-85% surface organic, all char classes
3 < 40% surface organic, black soil
4 < 40% surface organic, gray/orange soil
5 No surface organic, black soil
Dry Forest (PP/DF)
100%
6 No surface organic, Cover
80%
gray to orange
60%
40%
20%
0%
1
Rock
Mineral Black
Humus Unburned
2
3
4
Severity Levels
Mineral Orange
Mineral Unburned
Litter Charred
5
6
Mineral Gray/white
Humus Charred
Litter Unburned
Tree Burn Severity
Pre-Fire
Environment
Tree
species
Crown ratio
Size
Surface fuels
Live
Dead
Physical
setting
PVT
Time of year
Climate
Fire Environment
Flame Length
Feet
0-2
2-4
4-8
S
C
O
R
C
H
8 - 12 Crown
Bole
> 12 Dead
Post-Fire
Environment
Response
Green crown
Bole alive
Vertical
Horizontal
Harvest
Mortality
Beetle
Needle
input
Habitat
Hydrologic
Beetle
Tree Burn Severity and Classification
• Green: needles
present and green
• Mixed: partial green
crowns
• Brown: Needles
present but brown
• Black: no needles left
Plot Dist.
100%
Black
80%
Brown
60%
Mixed
40%
20%
Green
0%
Dry
Mixed Severity: most of the observations
Fire and silviculture science
> 30 % residual crown ratio alive
< 30 % residual crown ratio alive
Moist
Forest Type
Cold
5 Levels of Tree
Burn Severity
40%
20%
0%
Dry
Green
> 30% crown ratio
Cold
< 30% crown ratio
< 30% crown ratio
Brown
80
Green
> 30% crown ratio
< 30% crown ratio
Brown
Black
80
60
60
40
40
20
20
0
0
Dry
Moist
Forest Type
Cold
Black
Low Bole Scorch Height
Height
(feet)
100
> 30% crown ratio
Moist
Forest Type
Post-Fire Crown Ratio Left Alive
Green
80%
60%
Green
Mixed Green > 30%
Mixed Brown < 30%
Brown
Black
% Crown
Ratio
Plot Dist.
100%
Dry
Moist
Forest Type
Cold
Results
As a Function of
Pre-Fire Forest
Structure
Burn Severity
Components Used in Predicting Burn
Severity as a Function of Forest Structure
• Soil severity: lumped 6 levels into 3.
1: Levels 1 and 2 (litter cover > 40%)
2: levels 3 and 4 (litter cover < 40%)
3: levels 5 and 6 (no litter)
• Tree Severity:
1: Green
2: Mixed green
3: Lumped mixed brown and brown
4: Black
Forest Structure and Physical Setting
• Forest Structure
Summarize to a patch, stand, or plot level
Readily available and supported - FFE-FVS
Use tree list - FVS output
Added canopy base height, cover
• Physical setting
All soil and tree burn severities occurred on all aspect,
slope, elevation, etc.
Particular fire - location
Dry, moist, or cold forest type
• Weather – simulation (not today)
Classification Tree
Interactions
More Important
Fire
Canopy Base Ht
Green
Surface
Mixed Green
Brown
Density
Green
Less Important
Black
Structure Characteristics Related to Burn
Severity in Order of Importance
1) Place – Particular fire or fires
Reflected vegetation classification
(Potential vegetation type)
2) Relative stand age
3) Pre-fire crown ratio or crown base height
4) Surface fuels
5) Density
Value of an Interaction
Soil Burn Severity
• Set of fires (Northern Rocky Mountains)
• Crown ratio (>35 %)
canopy base heights (15 to 23 feet)
• Set of fires
• Cover (> 96 %)
> 40% organic horizons mineral
soil dominated by black char
“low soil burn severity”
0.61 probability of being correct
Stem Exclusion
Vegetation Structural
Stage
Soil Burn Severity
No. of Obs.
30
> 40% litter
20
< 40 % litter
No litter
10
0
Dry
Moist
Cold
Forest Type
Tree Burn Severity
No. of Obs.
25
Green
Mixed green
Mixed brown
Brown
Black
20
15
Combination of Effects
Soil Burn Severity
10
5
0
Dry
Moist
Forest Type
Cold
Soil Burn Severity – High
No litter, gray mineral soils
0.70 probability of being correct
• < 30 % cover
• Large Trees (>70 ft)
• Canopy Base Ht >
30 feet
Douglas-fir/Ninebark
Canopy Base Height
Green Tree Burn Severity
0.79 probability of being correct
•
•
•
•
Set of fires
Canopy Base Height < 5.3 feet
Had some tall trees
Up to 450 to 2000 trees per acre
GF PVT
Kootenai NF, MT
Density and Canopy Base Heights
Black Tree Burn Severity
0.49 probability of being correct
• Set of fires
• Canopy Base Height
> 3.8 feet
5.8 ft CBH
58% avg. cover
• Some observations:
Hayman Fire
No. of Obs.
- Open grown trees have low
crown base heights
- Grass or shrubs grow
underneath
60
Green
Mixed green
Mixed brown
Brown
Black
50
40
30
20
10
0
Dry
Moist
Forest Type
Cold
Key Points
• Not all fires burn the same
• Fuels are live vegetation
• Consider all forest characteristics
Canopy base heights
Surface fuels
Density
• Stand dynamics and development
Silviculture System
• Desired future condition – after a wildfire
occurs, what do you want the forest to look
like
• PVT – growth and development
• Integrate all vegetation – not just trees
• Disciplines are equal
• We can provide scientific results
• But the ART of Silviculture will make the
difference