[PPT] - Fire Regimes and Fire Regimes and Pyrodiversity Pyrodiversity PowerPoint Presentation

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Fire Regimes and Fire Regimes and Pyrodiversity Pyrodiversity

ESPM 134 ESPM 134 Spring 2008 Spring 2008 Rick Everett Rick Everett

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Where we’re going today: Where we’re going today:

Start integrating previous lecture information

Start integrating previous lecture information with the effects of fire as a disturbance factor in with the effects of fire as a disturbance factor in forested ecosystems forested ecosystems – –

Revisit Fire Regimes

Pyrodiversity

Fire as a formative agent in biological systems

Set up for Prescription fires & management, Set up for Prescription fires & management, Restoration Restoration

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Fire Regimes Fire Regimes

5 Components:

5 Components:

Fire Frequency

Seasonality

Fire Severity

Dimensionality (SIZE)

Interactive Syntax

What other disturbance factors contribute to the regime?

Insects

Disease

Climate

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Fire Regimes Fire Regimes

Agee, James K. 1996. Fire Regimes and

Agee, James K. 1996. Fire Regimes and Approaches for Determining Fire History Approaches for Determining Fire History

(Attached to your handout, and on the web .ppt)

Fire Regimes

Defining using severity:

Low

Moderate

High

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Agee, continued Agee, continued

Fire Histories

Point Frequencies

Low to moderate fire frequencies

Area Frequencies

Moderate to very high fire frequencies…stand replacement events

N t

l Fi R t ti N t l Fi R t ti

Natural Fire Rotation

Fire rotation is the time required for an area equal to the entire area of

Fire rotation is the time required for an area equal to the entire area of interest to burn and is expressed in terms of years per area (125 years for interest to burn and is expressed in terms of years per area (125 years for a 40,000 ha area). a 40,000 ha area).

Fire Cycle

Average stand age of a forest whose age distribution fits a mathematical

Average stand age of a forest whose age distribution fits a mathematical distribution distribution

Usually a Weibull, non

Usually a Weibull, non-

parametric distribution

parametric distribution

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Fire Frequency Fire Frequency

# of fires per unit time in a specific area

# of fires per unit time in a specific area

Example: 10 fires in 100 ha every 100 years

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Seasonality Seasonality

Description of the time of the year that fires occur:

Description of the time of the year that fires occur: Spring, Summer, Fall Spring, Summer, Fall

Only can be an estimation of Season, not a calendar

Only can be an estimation of Season, not a calendar date… date…

Immense effect on plant ecosystem

Fire during “unexpected” period (plant hasn’t developed a life

Fire during “unexpected” period (plant hasn’t developed a life hi hi h h dl fi d i i ) hi hi h h dl fi d i i ) history which handles fire during a given season) history which handles fire during a given season)

Even holding fire intensity constant, mortality can be greatly

Even holding fire intensity constant, mortality can be greatly increased increased

Affecting:

Phenology (leafing & buds)

Water availability & uptake

Organism activity (especially arthropods)

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Fire Severity Fire Severity

Degree of alteration of vegetation & soils by fire

Degree of alteration of vegetation & soils by fire

Relative…varies by system

Relative…varies by system

Usually thought of as:

Usually thought of as:

Amount of crown scorch

Height of bark char

Amount of plant consumption (live & dead fuels)

Plant mortalities

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Low severity: unburned duff, cone, match!

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Fire Severity Fire Severity

Individual tree

Individual tree damage: damage:

Foliage & Bud

Foliage & Bud Damage Damage

Cambial kill

Cambial kill – – bole & bole & leaders leaders leaders leaders

Root Damage

Root Damage – – poorly poorly studied (mycorhizal, studied (mycorhizal, too) too)

60º C kills tissues (we

60º C kills tissues (we blister…plant vascular blister…plant vascular tissues die tissues die

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Larger Scale damage:

Soils

Heating & sterilization

Volatilization & Hydrophobicity

Bulk Density

Chemistry (Nitrogen export)

Water

Changes local water potenital

Changes local water potenital g p g p

Loss of photosynthetic crown :

Loss of photosynthetic crown : commensurate rise in commensurate rise in watertable watertable

Changes in percolation,

Changes in percolation, holding capacitance holding capacitance

Mudflows & Runoff

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Dimensions Dimensions

Size of fire (hectares or acres)

Size of fire (hectares or acres)

Another ‘Dimension’:

Another ‘Dimension’:

Unburned area within fires

Degree of ‘patchiness’

Low and moderate severity fires in coniferous non

Low and moderate severity fires in coniferous non-

d

l b bl l f i d d l b bl l f i d stand replacement systems probably left a varied stand replacement systems probably left a varied ‘patchy’ mosaic of burned & unburned areas, leading ‘patchy’ mosaic of burned & unburned areas, leading to: to:

Uneven aged stand structure

Unburned Patches:

Wildlife Refuge

Seed source

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Interactions with other disturbance Interactions with other disturbance agents agents

Insects, pathogens, drought, etc.

Before Fire

Insects, pathogens & other agents may increase mortality,

Insects, pathogens & other agents may increase mortality, leading to increased aerial & ladder fuels…increasing leading to increased aerial & ladder fuels…increasing intensity intensity

After Fire

Insects often key into dead or wounded trees

Fire

Fire-

related stresses in plants may increase pathogen

related stresses in plants may increase pathogen susceptibility susceptibility

In general: hard to predict, but large

In general: hard to predict, but large-

scale & important

scale & important

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Lake Arrowhead, SBNF July 2003

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Prehistoric Fire Intervals Prehistoric Fire Intervals

‘prehistoric’ generally refers to fire regimes seen prior to

‘prehistoric’ generally refers to fire regimes seen prior to 1850 in California 1850 in California

Reconstructed using fire

Reconstructed using fire-

scar dendrochronology

scar dendrochronology

Both season, and date, can be developed from Fire

Both season, and date, can be developed from Fire-

scar

scar dendrochronology dendrochronology Reconstructed using geomorphologically

Reconstructed using geomorphologically-

derived

derived

Carbon

Carbon-

dates

dates

Phytoliths

Generally driven by ignition sources….

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Lightning Lightning

Current theory:

High negative charge builds up in

High negative charge builds up in clouds clouds

Electrons stripped off of water & snow

Electrons stripped off of water & snow droplets as they are repeatedly lifted & droplets as they are repeatedly lifted & descend within the cloud. descend within the cloud.

‘Stepped leaders’ form every 50 meters

Ultimately seek high positive charge near

Ultimately seek high positive charge near ground ground g

Up to 2 km from flux source

Nasty:

40 Kiloamperes

Bolt Temperature: 30000º C, nearby air

Bolt Temperature: 30000º C, nearby air temperature 10000º C temperature 10000º C

1 gigavolt, 100 terwatts

So: no problem with providing a source

f ignition & ‘push’ for a fire regime
f ignition & ‘push’ for a fire regime

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North American Aboriginals North American Aboriginals

Large influences on fire regimes

Most cultures have some evidence of fire use

Major influences in most plant communities

Major influences in most plant communities except sub except sub-

alpine & alpine

alpine & alpine

Decreased intervals

Diversified & increased annual seasonality of

Diversified & increased annual seasonality of burning (lifted the lightning season limit) burning (lifted the lightning season limit)

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Vegetation Vegetation Area (ha) Area (ha) mFRI mFRI Spruce/cedar Spruce/cedar 2004 2004 100 100 Cedar/Doug fir Cedar/Doug fir 806278 806278 25 25 Mixed conifer Mixed conifer 5522676 5522676 8 8 Redwood Redwood 928102 928102 10 10 Red Fir Red Fir 761396 761396 35 35

Fire return intervals in California

Lodgepole Lodgepole 860378 860378 45 45 Pine Pine-

Cypress

Cypress 49290 49290 30 30 Ponderosa Ponderosa 678043 678043 5 5 Great Basin Pine Great Basin Pine 19636 19636 7 7 Pinyon Pinyon-

juniper

juniper 985407 985407 70 70 Juniper steppe Juniper steppe 363867 363867 70 70 Calif mixed Calif mixed evergreen evergreen 1359693 1359693 10 10

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Vegetation Vegetation Area (ha) Area (ha) mFRI mFRI Chaparral Chaparral 3400234 3400234 30 30 Montane chaparral Montane chaparral 229220 229220 30 30 Coastal sagebrush Coastal sagebrush 989414 989414 20 20

Other kind of communities

g Coastal sage Oak wd. Coastal sage Oak wd. 256470 256470 5 5 Oak Woodlands Oak Woodlands 3821807 3821807 3 3 Great Basin Great Basin Sagebrush Sagebrush 740558 740558 20 20 Fescue Oatgrass Fescue Oatgrass 351484 351484 3 3 California Steppe California Steppe 5288897 5288897 3 3 Tules Tules 743764 743764 5 5

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Fire Rotations Fire Rotations

Vegetation Vegetation Average Fire rotation Average Fire rotation Cedar Douglas fir Cedar Douglas fir 61 61 Mixed Conifer Mixed Conifer 27 27 Red Fire Red Fire 63 63 Lodgepole Lodgepole 46 46 Great Basin Pine Great Basin Pine 23 23 Chaparral Chaparral 70 70 Pinyon Pinyon-

Juniper

Juniper 440 440

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Historic Fire Intervals Historic Fire Intervals

Fire Histories based on written or oral

Fire Histories based on written or oral Eurocentric culture records Eurocentric culture records

Major decrease seen throughout western US &

Major decrease seen throughout western US & California after 1905 California after 1905 California after 1905 California after 1905

Golly! 1905: Transfer Act

Golly! 1905: Transfer Act – – Creation of modern day Creation of modern day USFS & start of aggressive fire suppression USFS & start of aggressive fire suppression

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Pyrodiversity Pyrodiversity

Prehistorically (key word: heterogeneity):

Diverse regimes

Differing sizes

Differing severities

Differing intervals

Fairly regular seasonality

Fairly regular seasonality Fairly regular seasonality Fairly regular seasonality

Variability in fire regimes : variable effects of

Variability in fire regimes : variable effects of ecosystems ecosystems

Promoted biodiversity

Broader amplitude of habitats & niches for the entire suite of

rganisms in a community
rganisms in a community

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Fire suppression policies have altered prehistoric

Fire suppression policies have altered prehistoric fire regime fire regime

This should now be familiar:

This should now be familiar:

M ll & d i d fi h b M ll & d i d fi h b

Most small & moderate sized fires have been

Most small & moderate sized fires have been suppress suppress

Now, only the most large & severe burn plant

Now, only the most large & severe burn plant communities communities

These fires do not promote biological diversity

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