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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
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