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Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ......

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Fire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service Pacific Southwest Research Station Redding, CA PSW
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Page 1: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Fire Intensity & Scale

Carl N. SkinnerProject Leader

USDA Forest Service

Pacific Southwest Research Station

Redding, CA

PSW

Page 2: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Intensity vs. Severity

• Intensity = A measure of the rate of heat (energy) released by a fire.

Fire intensity is directly proportional to the fuel condition, amount and rate of fuel consumed. Thus, fuels, weather, and topography are very important in determining the rate of heat released by a fire.

• Severity = Degree to which a site has been altered or changed by fire.

Loosely, a product of fire intensity, vegetation susceptibility, and residence time.

Page 3: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Young Trees Under Old

Only Young Trees

Fire with <4 ft flames in both stands.

Fire severity class = Low

Fire severity class = High

Young trees killed by scorch in both stands.

Severity vs. Intensity

Page 4: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Fire Severity Distribution

Sources: Weatherspoon & Skinner 1995, Taylor & Skinner 1998, USDA Forest Service 2003

Low

High

Mod

Page 5: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Fire

Severity

Patterns

~Hancock

Fire

2006

Page 6: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Fire

Severity

Patterns

~Biscuit Fire

2002

Page 7: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Fire & Climate Change:

Where are we headed?

• Fire season getting longer.

• Fuels keep growing.

• Greater probability of intense fires.

Fuel

Fire

Triangle

Page 8: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Mediterranean Climate

• Cool/wet Wintersvegetation/fuel

• Warm/dry Summerannual fire season

• Lightning

Page 9: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Fire Climate - Precipitation PatternsFrom: Schroeder & Buck 1970, p. 203.

J

F

M

A

M

J

J

A

S

O

N

D

0

1

2

3

4

Inches

Prescott, AZ - Avg. 20.7"

J

F

M

A

M

J

J

A

S

O

N

D

0

1

2

3

Inches

Toronto, Canada - Avg. 32.1

J

F

M

A

M

J

J

A

S

O

N

D

0

1

2

3

Inches

North Platte, NB - Avg. 18.2"

J

F

M

A

M

J

J

A

S

O

N

D

0

1

2

3

4

5

6

7

Inches

Sonora, CA - Avg. 32.2"

Page 10: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

20th Century Fire Trends

Sierra Nevada

Area Burned

0

100

200

300

400

500

600

700

800

1910-51 1952-93

Area

1000s of Acres

Weatherspoon & Skinner 1996

Page 11: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

20th Century Fire Trends

Sierra Nevada

Area Burned

0

100

200

300

400

500

600

700

800

1910-51 1952-93

Lightning

Human

1000s of Acres

Weatherspoon & Skinner 1996

Page 12: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

20th Century Fire Trends

Sierra Nevada

Max Fire Size

0

10

20

30

40

50

60

1910-51 1952-93

Area

1000s of Acres

Weatherspoon & Skinner 1996

Page 13: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

20th Century Fire Trends

Sierra Nevada

Max Fire Size

0

10

20

30

40

50

60

70

80

1910-51 1952-93

Lightning

Human

1000s of Acres

Weatherspoon & Skinner 1996

Page 14: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits
Page 15: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Red dots =

Lightning Caused Fires

Blue dots =

Human Caused Fires

Page 16: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

From: Jones et al. 2001 Science 292: 662-667

Much colder than 20th or 21st Century.

Tree-ring Based Fire Histories

Mostly cover the period of

~1600 to 1900

Page 17: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Climate Change & Fire

Regimes?

• TemperatureFire Frequency

• MoistureFire Extent

Climate Variation?

Swetnam 1993

Chang 1999

Miller 2003

Page 18: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Climate Change & Fire?

Hasn’t Climate Warmed Before?

Never

when accompanied by

50-100 Yrs of

fire suppression!

Page 19: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Restoration???

Page 20: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Resilience

“…the capacity of a system to absorb

disturbance and reorganize while

undergoing change so as to retain

essentially the same function,

structure, identity, and feedbacks…”

Folke, C. and others 2004. Regime shifts, resilience, and

biodiversity in ecosystem management. Annual Review of

Ecology, Evolution, and Systematics 35: 557-581.

Page 21: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Resilience

Forested systems characterized by fire

regimes of frequent, mostly low-

moderate intensity fires, dominated

by large, long-lived trees, are

considered resilient if the forested

landscape exhibits a generally

forested condition, including larger

trees, shortly following a disturbing

event such as fire.

Page 22: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Hancock Fire 2006

Biscuit Fire 2002

Page 23: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Scale of Effects

Page 24: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Fire:

A Catalyst for

Change

Page 25: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits
Page 26: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Severity Patterns – Alternative Pathways

Page 27: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits
Page 28: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Stanislaus NF - 1929

“The virgin forest is uneven-aged, or at best even-aged by small groups,

and is patchy and broken; hence it is fairly immune from extensive

devastating crown fires.”

“fire creates a patchy scattered distribution of reproduction”

(Show and Kotok 1924)

Page 29: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Climate Change…

Where are we headed?

• Fire season getting longer.

• Fuels keep growing.

• Greater probability of intense fires.

Fuel

Fire

Triangle

Page 30: Fire Intensity & ScaleFire Intensity & Scale Carl N. Skinner Project Leader USDA Forest Service ... by large, long-lived trees, are considered resilient if the forested landscape exhibits

Thank You!


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