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CLASS UPDATES

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).

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CLASS UPDATES

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  1. 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)

  2. Fire Ecology:Rocky Mountain Mixed Conifer Forests NREM390 October 5, 2010

  3. Fire Regimes: Review • Components of fire regimes • Extent • Frequency • Seasonality • Intensity • Duration • Severity • Historic vs. Modern Fire Regime?

  4. 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

  5. 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?

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

  7. Ponderosa Pine: Ecology • Shade intolerant • Early successional • Fire resistant • Thick bark • Seedlings > 5 yr. old • Mast seeding (episodic)

  8. 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

  9. Ponderosa pine: Low intensity, frequent surface fires (historic) Stand-replacing fires

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

  11. 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

  12. Douglas-fir: fire regime • 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

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

  14. 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

  15. 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

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

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

  18. Relatively • rapid regeneration: • Lodgepole pine • Aspen • Spruce • Fir

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

  20. Slow regeneration process

  21. Alpine meadows and tundra forest

  22. Ecosystems & fire regimes Lodgepole pine, Spruce-Fir Douglas-fir mixed conifer Ponderosa pine Pinyon- Juniper Tallgrass prairie Short grass steppe / Sagebrush

  23. Fire regimes

  24. Low severity Low severity Low to moderate severity Low to moderate severity Mixed severity Fuel load • < 60 yrs • > 100yrs • 50-100 yrs • > 400 yrs 4-36 yrs < 100 yrs 1-5 yrs Fuel load 20-50 yrs Weather, fuel load, topography < 10 yrs < 100 yrs Weather, fuel load, topography Weather, fuel load, topography Fire regimes Weather, fuel load, topography Weather

  25. Lodgepole Pine regeneration after the 1988 Yellowstone Fires Pre-Fire Cougar Creek Yellowstone Lake Post-Fire * Effect of patch size on LP regeneration: Large > Small * Effect of fire severity on LP regeneration: ground fires > crown & surface

  26. 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)

  27. 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

  28. Initial vegetation cover: Lodgepole pine Probably ground fires, some mortality, new seedlings, mixed-age LP stand No fire until 300 yrs. Mixed LP, spruce-fir, crown fire, slow regen Fire every ~100 yrs. Probably surface fires, high survival no new regeneration, dense LP stand Fire every ~40-50 yrs.

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