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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).

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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)
fire regimes review
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
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
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?
slide6

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.

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

slide9

Ponderosa pine: Low intensity,

frequent surface fires (historic)

Stand-replacing fires

slide10

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.

douglas fir mixed conifer ecology
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
douglas fir fire regime
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

slide13

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.

lodgepole pine ecology
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
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
slide16

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.

slide18

Relatively

  • rapid regeneration:
    • Lodgepole pine
    • Aspen
    • Spruce
    • Fir
slide19

High-Elevation

Spruce-Fir ecosystems

(10,000-11,000 ft)

slide23

Ecosystems &

fire regimes

Lodgepole pine,

Spruce-Fir

Douglas-fir

mixed conifer

Ponderosa pine

Pinyon-

Juniper

Tallgrass prairie

Short grass steppe

/ Sagebrush

fire regimes25

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

slide26

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

fire and ecosystem heterogeneity
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
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
slide29

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.