ESPM 134
Scott Stephens
Introduction to Fire Science
1) What is required for fire to occur?
The combustion triangle
- Fuels
- Oxygen
- Ignition
2) Where do fuels come from?
Photosynthesis - the biological factory
-constantly operating
Net primary production: 115 billion dry tones/year on land
- this represents a capture and storage of less than 1/2 of 1% of the total
solar energy
3) Where do ignitions come from?
Arson - becoming more of a problem each year, unpredictable
Lightning - very common in the western mountain ranges, southwest, southeast
Volcano's - important in some areas of the west, Hawaii
Accidents - campgrounds, off road vehicles, power lines, vehicle collisions
Prescribed fire - burning wildlands under a prescription for desired objectives
(management goal)
4) Pre-historic disturbance regimes (very diverse in forested landscapes, many interact)
- insects
- disease
-volcanic
- fire
- climate
- avalanche
5) Native Americans use of fire in North America
Management of the landscape
- open vistas to prevent attack
- herding game animals
Vegetation management
- desired species - oaks, wood rose, big leaf maple, dogwood, willow, etc.
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6) The great debate: What is natural?
Are humans part of the "system"? YES
- Native people increased the number of fires throughout North America,
for at least the last 3000-8000 years.
How do we know this?
- Historic evidence - fire scar analysis
- Vegetation structure
- Historical accounts
7) Current National Park policy
Native Americans management practices not "natural", beginning to change
Don't try to manage lands as native Americans did, park believes this would be
difficult to do
8) Fire ecology
The interaction between fire and the ecosystem
- fires effect the vegetation, and subsequent vegetation effects future fires
- Yosemite example
- Plants adaptations to fire?
- chaparral adapted to hot/dry climates, small evergreen leaves that
burn easily
9) Fire regimes: frequency, area, severity, season, and synergy of fires
Each vegetation type has a particular fire regime
Examples
- Sierra Nevada ponderosa pine/mixed conifer
- Yellowstone lodgepole pine/subalpine fir
10) Ecological imbalance
Examples
- giant sequoia-mixed conifer forest
- much higher tree density today, many ladder fuels present that
did not occur 100
years ago, much higher fuel loading
11) Wildfire acreage in 1994
2% of all fires on USFS jurisdiction lands required large scale suppression efforts
- very efficient at suppressing low and moderate intensity wildfires
94% of area burned was from 2% of the fires
- remaining fires occur in extreme conditions, almost impossible to
suppress
- reduced pyrodiversity, only most severe fires currently occurring
National federal wildfire suppression costs approached or exceeded 1 Billion dollars in
1994, 1996, 2000, 2002.
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12) US Forest Service response
Comprehensive fire strategy developed in 1995
Policy sets goal of increasing area treated in fire dependent ecosystems to
3,000,000 acres annually by 2005
Both prescribed fire and mechanical methods will be used
Objective is to increase ecosystem sustainability
President Bush’s healthy forest initiative. Proposes to reduce hazard primarily with
mechanical methods on 7 millions acres of forest in 2003.
13) Newer fires: Euro-Americans
100 + years of fire suppression
Origin of the U.S. Forest Service
- Smokey the Bear, the single most successful ad campaign in the history
of our country
- today there are more high intensity (don't say hot) crown fires, less low
intensity (don't say cool) surface fires, far less pyrodiversity.
Suppression is important, but we must begin to manage the ecosystem to produce
sustainable forests -forests that can incorporate "natural" disturbances (fire, insects,
disease) without a biological catastrophe. New fire policy out of the Washington DC
headquarters of the Forest Service, Department of Fire and Aviation Management.
Prescribe burn or mechanically treat 3,000,000 acres/year by 2005 in fire dependent
ecosystems. 50-75% of new employees in forest system must be trained in fire
management (already in region 8, southeast).
15) Future fires
Large, high intensity wildfires will continue to occur each summer and fall
- can't suppress all fires, only the low and medium intensity fires
- fires that occur in high fuel loads with low humidifies and high
temperature cannot be suppressed, you have to get out of the way and wait
until the weather change.
References
Agee, J. K. 1993. Fire ecology of pacific northwest forests. Island Press. 493 pp.
Biswell, H. H. 1989. Prescribed burning in California wildlands vegetation management. University of
California Press. 255 pp.
Pyne, S.J., P.L. Andrews, and R.D. Laven. 1996. Introduction to wildland Fire. 2nd Edition. John Wiley & Sons.
Toronto, Ontario. 769 pp.
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