CLASS UPDATES Office hours: Fridays 9AM-12noon (or 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 Forests NREM390 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-fir mixed conifer 6,500-8,000 ft. Ponderosa pine 5,500-6,500 ft Alpine Meadows >11,000 ft Spruce-Fir 9,000-11,000 ft Short- grass steppe <5,500 ft Fire regimes in Rocky Mountain Conifer Ecosystems

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-fir mixed conifer 6,500-8,000 ft. Ponderosa pine 5,500-6,500 ft Alpine Meadows >11,000 ft Spruce-Fir 9,000-11,000 ft Short- grass steppe <5,500 ft Fire regimes in Rocky Mountain Conifer Ecosystems

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, 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-fir mixed conifer 6,500-8,000 ft. Ponderosa pine 5,500-6,500 ft Alpine Meadows >11,000 ft Spruce-Fir 9,000-11,000 ft Short- grass steppe <5,500 ft Fire regimes in Rocky Mountain Conifer Ecosystems

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)

Lodgepole pine: fire regime Mixed severity fire regime Low-intensity surface fires, yr. –Fuel characteristics –Topography & Weather Stand-replacing fires, 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-fir mixed conifer 6,500-8,000 ft. Ponderosa pine 5,500-6,500 ft Alpine Meadows >11,000 ft Spruce-Fir 9,000-11,000 ft Short- grass steppe <5,500 ft Fire regimes in Rocky Mountain Conifer Ecosystems

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

Relatively rapid 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-fir mixed conifer

Fire regimes EcosystemSeverity class Fire intervalDriving 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 regimes EcosystemSeverity classFire intervalDriving 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 pineMixed severity Subalpine (lodgepole pine- spruce-fir) High severity> 400+ yrs Fuel load Weather, fuel load, topography Weather, fuel load, topography Weather, fuel load, topography < 60 yrs > 100yrs 4-36 yrs < 100 yrs 1-5 yrs yrs < 10 yrs < 100 yrs Low severity Low to moderate severity Low to moderate severity Mixed severity Weather yrs > 400 yrs Weather, fuel load, topography

ElevationLow (< 2,000m)High (>2,300 m) Stand age130 yr.250 yr. % serotiny65%1.9 % Fire return interval~ 180 yrs.~ 300 yrs. Pine seedling density (stems/ha) 211,000 stems/ha600 stems/ha LP regenerationHigh (> 50/m2)Low (< 10/m2) Seed viabilityHigh (ground fires, melt resin, scarify soil) Low (crown fires, serotiny) Stand developmentSimilar 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-FireYellowstone LakeCougar 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 surface fires, high survival no new regeneration, dense LP stand Probably ground fires, some mortality, new seedlings, mixed-age LP stand Mixed LP, spruce-fir, crown fire, slow regen