CLASS UPDATES Office hours: Fridays 9AM-12noon (or email me for an appointment) Powerpoints – on class website Schedule changes: thesis statement, outline,

CLASS UPDATES

• Office hours: Fridays 9AM-12noon (or email me for an appointment)

• Powerpoints – on class website

• Schedule changes: thesis statement, outline, first draft

• Exams – will be returned on Thursday

• Quiz Thursday (today’s lecture/discussion only)

Fire Ecology:Rocky Mountain Mixed

Conifer ForestsNREM390

October 5, 2010

Fire Regimes: Review

• Components of fire regimes– Extent

– Frequency

– Seasonality

– Intensity

– Duration

– Severity

• Historic vs. Modern Fire Regime?

Fire classification:severity and frequency (return interval)

• Short fire return intervals (<20 years)– Low-severity surface fires are common .– Fire tolerant herbaceous species or shrubs dominate.– Species composition often similar.

• Intermediate fire return intervals (20-75 years)– Fuel buildup and continuous in distribution– Moderate-severity fires (patchy crown fires) or some high-severity fires– Greater changes in plant composition

• Long fire return intervals (>100 years)– Very high fuel loads possible– High-severity fire commonly occur (stand-replacing crown fires)– Postfire & prefire vegetation can be very different

• Mixed-severity fires– Combination of frequent low-severity & infrequent high severity fires

How do historical (pre-settlement) and modern (current) fire regimes differ – and why?

• In ecosystems with high frequency, low intensity fire regimes (e.g., dry forests, grasslands, woodlands, savannas):– Significant changes to fire regime due to:

• Land use change (agriculture, urban)• Fire suppression and fuel accumulation• Change in vegetation type and structure

• Forests with low frequency, high severity stand-replacing fire regimes:– Much less change from historical fire regimes – Why?

Lodgepole pine(aspen, spruce-fir)8,000-9,000 ft

Douglas-firmixed conifer6,500-8,000 ft.

Ponderosa pine5,500-6,500 ft

Alpine Meadows>11,000 ft

Spruce-Fir9,000-11,000 ft

Short-grass steppe<5,500 ft

Fire regimes inRocky MountainConiferEcosystems

Ponderosa Pine: Ecology

• Shade intolerant

• Early successional

• Fire resistant – Thick bark– Seedlings > 5 yr. old

• Mast seeding (episodic)

Ponderosa pine: fire regime

• Fire frequency: 5-30 yrs.• Light surface fires• Regeneration:

– Patches of old trees crown fire & seed bed

– Mast year + fire-free period

• 1900s: grazing & fire suppression– Many seedlings survive– Fuel build up– High severity, stand-replacing fires

Ponderosa pine: Low intensity, frequent surface fires (historic)

Stand-replacing fires

Lodgepole pine(aspen, spruce-fir)8,000-9,000 ft

Douglas-firmixed conifer6,500-8,000 ft.

Ponderosa pine5,500-6,500 ft

Alpine Meadows>11,000 ft

Spruce-Fir9,000-11,000 ft

Short-grass steppe<5,500 ft

Fire regimes inRocky MountainConiferEcosystems

Douglas-fir, mixed conifer: Ecology

• Intermediate shade tolerance• Early successional

– Seedlings can establish on moist, cool sites

• Late successional– Understory of Ponderosa Pine– Understory of Lodgepole Pine

• Intermediate fire resistance – mature trees only

• Historic: Mixed fire severity– Light surface fires, 20-60 yr. – Severe stand-replacing fires, >60 yr.

• Fire suppression shade tolerant species– Douglas-fir seedlings– Hemlock, white spruce,

blue spruce (low fire resistance)

• Shift: increased mixed-conifer forests on landscape

• Favors high severity, stand-replacing fires

Douglas-fir: fire regime

Lodgepole pine(aspen, spruce-fir)8,000-9,000 ft

Douglas-firmixed conifer6,500-8,000 ft.

Ponderosa pine5,500-6,500 ft

Alpine Meadows>11,000 ft

Spruce-Fir9,000-11,000 ft

Short-grass steppe<5,500 ft

Fire regimes inRocky MountainConiferEcosystems

Lodgepole pine: Ecology• Shade intolerant• Early successional• Intermediate fire resistance• Serotiny

– Young trees – low serotiny– Old trees – low serotiny (high elevations with low fire

frequency– Intermediate age – high serotiny

• requires intense ground fires• Melt resin • Exposed mineral soil (seed bed)

http://www.cfr.washington.edu/Classes.esc.202/LPBarkBFireRot.htm

Lodgepole pine: fire regime• Mixed severity fire regime• Low-intensity surface fires, 50-100 yr.

– Fuel characteristics– Topography & Weather

• Stand-replacing fires, 100-400 yr. – Climate driven – drought, winds

• Fire suppression– Understory: spruce, fire

(low fire resistance)– Low impact on fire dynamics

• Altitudinal gradient: Rockies– Moisture, temperature– Biomass accumulation

Lodgepole pine(aspen, spruce-fir)8,000-9,000 ft

Douglas-firmixed conifer6,500-8,000 ft.

Ponderosa pine5,500-6,500 ft

Alpine Meadows>11,000 ft

Spruce-Fir9,000-11,000 ft

Short-grass steppe<5,500 ft

Fire regimes inRocky MountainConiferEcosystems

Mid-Elevation Lodgepole pine ecosystems (8,000-9,000 ft)

Relativelyrapid regeneration:

- Lodgepole pine- Aspen- Spruce- Fir

High-Elevation Spruce-Fir ecosystems (10,000-11,000 ft)

Slow regeneration process

Alpine meadows and tundra forest

Lodgepole pine, Spruce-Fir

Short grass steppe/ Sagebrush

Ecosystems &fire regimes

Pinyon-Juniper

Tallgrass prairie

Ponderosa pine

Douglas-firmixed conifer

Fire regimesEcosystem Severity

classFire interval Driving factor

Tallgrass prairie

Short Grass Steppe /Sagebrush

Pinyon-juniper

(savannas, woodlands)

Ponderosa Pine

Mixed conifer (Ponderosa pine, Douglas fir, white fir, larch)

Lodgepole pine

Subalpine (lodgepole pine-spruce-fir)

Fire regimesEcosystem Severity class Fire interval Driving factor

Tallgrass prairie

Short Grass Steppe /Sagebrush

Pinyon-juniper

(savannas, woodlands, forests)

Ponderosa pine

Mixed conifer (Ponderosa pine, Douglas fir, grand fir, western larch)

Lodgepole pine Mixed severity

Subalpine (lodgepole pine-spruce-fir)

High severity > 400+ yrs

Fuel load

Fuel load

Weather, fuelload, topography

Weather, fuel load,

topography

Weather, fuelload, topography

< 60 yrs> 100yrs

4-36 yrs< 100 yrs

1-5 yrs

20-50 yrs

< 10 yrs< 100 yrs

Low severity

Low severity

Low to moderateseverity

Low to moderateseverity

Mixed severity

Weather

50-100 yrs> 400 yrs

Weather, fuel load,

topography

Elevation Low (< 2,000m) High (>2,300 m)

Stand age 130 yr. 250 yr.

% serotiny 65% 1.9 %

Fire return interval ~ 180 yrs. ~ 300 yrs.

Pine seedling density

(stems/ha)

211,000 stems/ha 600 stems/ha

LP regeneration High (> 50/m2) Low (< 10/m2)

Seed viability High (ground fires, melt resin, scarify soil)

Low (crown fires, serotiny)

Stand development Similar to unburned forests

High herbaceous density, Slow forest recovery

* Effect of patch size on LP regeneration: Large > Small* Effect of fire severity on LP regeneration: ground fires > crown & surface

Post-Fire

Pre-Fire Yellowstone Lake Cougar Creek

Lodgepole Pine regeneration after the 1988 Yellowstone Fires

Fire and Ecosystem Heterogeneity• Mosaic pattern – “patchiness”

– Fire intensity – Burned area

• Microclimate variation– Light– Moisture– Nutrients

• Species composition & diversity– Different microclimate requirements– Different regeneration strategies

• Ecosystem diversity– Successional communities– Dynamic equilibrium (landscape scale)

Other examples of post-fire heterogeneity• Herbaceous vegetation

– Light (larger patches)– Seed dispersal high

• Aspen – Root suckering (low fire intensity)– Regeneration by seed (woody debris – elk browse)

• Spruce-fir – Distance to seed trees– Shade, moisture

• Wildlife– Mosaic of different habitats– Increased abundance of food

Initial vegetation cover: Lodgepole pine

No fire until 300 yrs.

Fire every ~40-50 yrs.

Fire every ~100 yrs.

Probably surfacefires, high survivalno new regeneration,dense LP stand

Probably ground fires,some mortality,new seedlings,mixed-age LP stand

Mixed LP,spruce-fir,crown fire,slow regen