Fire ecology and fire regimes in boreal ecosystems
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Fire Ecology and Fire Regimes in Boreal Ecosystems. Oct 19, 2010. Fire ecology of boreal region. Black spruce ( Picea mariana ) serotinous cones, highly flamable Early successional White spruce ( Picea glauca ) Non serotinous cones Late successional

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Fire ecology of boreal region
Fire ecology of boreal region

  • Black spruce (Piceamariana)

    • serotinouscones, highly flamable

    • Early successional

  • White spruce (Piceaglauca)

    • Non serotinous cones

    • Late successional

  • Other species: larch, birch, alder, willow, aspen

Boreal region land of fire ice
Boreal region: land of fire & ice types

  • Vegetation shaped by fire and permafrost

    • Heat and cold

    • Aridity and moisture

  • Permafrost: permanently frozen ground

    • Impermeable boundary between surface and ground waters

    • Active layer (thaw zone) – allows for shallow soil, rooted vegetation

  • Dynamic equilibrium between vegetation and permafrost determined by fire

Boreal forests fire regime
Boreal Forests Fire Regime types

  • Wildfires are episodic

    Some years very large wildfires

  • Relatively frequent fires

    Continuous layer of fuels:

    grasses, moss, shrubs, black spruce

    (~ lodgepole pine *)

  • Dry summers

    Lightning, long days (midnight sun)

  • Mixed fire-regime

    high intensity stand-replacing crown fires +

    ground fires (smoldering in deep organic layers)

Natural fire cycles: ~50-200 years

After human use/protection:

<100 years in remote regions to >500 in heavily protected

(Beniston 2003)

Effects of fire on boreal landscape
Effects of fire on boreal landscape types

Fire is the dominant disturbance in boreal forests

  • Allows for massive decomposition and recycling of water and nutrients

  • Fires cause active zone of

    permafrost to increase


    (vegetation = insulation)

  • Replaces forest stands

Post fire p ermafrost thaw recycling of nutrients water
Post-fire typespermafrost thaw: recycling of nutrients & water

A nd mosaic of stand types
a typesnd mosaic of stand types…

Human influence on boreal fires
Human influence on Boreal fires types

  • Fires deliberately set by Native Americans and settlers

    • Signal fires, campfires, hunting (ring of fire – moose, caribou), mosquito control

    • Gold rush in 1896 – “epidemic of forest fires”

      • Railroad construction

      • Expose mine deposits

      • Create/improve pasture

  • After railroad completed

    (1923) – new emphasis

    on fire suppression and control

Fire management in alaska
Fire management in Alaska types

  • 1930-1950’s – emphasis on fire control

    • Patrols and strong military presence

  • 1950’s = enormous fires, mostly lightening caused (5 mill acres burned in 1957)

    • Smoke shut down “the state” for 2 weeks

  • 1960’s and 70’s fire control in Alaska reached similar levels as the lower 48 (under BLM)

    • Emphasis on aircraft, helicopters, smokejumpers

  • 17% of land is designated for fire suppression: “valued areas” (proximity to communities and roads)

  • 83% of land (interior Alaska) under a natural fire regime.

Fire and climate change in the boreal region
Fire and Climate Change typesin the Boreal Region

  • TTYGroup on potential general impacts of CC on fire dynamics:

  • What has been predicted for temperature and precipitation due to climate change in North American boreal region?

  • What does this mean for the fire weather of the N. A. boreal region?

  • What are the direct effects of climate change on the vegetation composition of boreal forests?

  • What does this mean for fire behavior?

Relationship between climate change and fire in boreal regions 1
Relationship between climate change typesand fire in Boreal regions (1)

  • Climate change increases fire activity:

    • Warmer and drier climate (Higher T, lower PP) = drier fuels

    • Longer fire season

    • Increased lightening

  • More fire = positive feedback on global warming

    • Increased greenhouse gas emissions enhancing warming.

    • Increased CO2 = greater biomass production, more fuel (controversial)

Relationship between climate change and fire in boreal regions 2
Relationship between climate change and fire in Boreal regions (2)

  • Indirect effects of climate change

    • More fuel loads ?


      insect outbreaks

      tree line expansion into tundra

    • Less fuel loads / different fuel loads? = negative feedback

      Deciduous vs. coniferous

    • Longer fire season = drier forest floor = potential to alter depth of burn + deeper thaw of permafrost

Boreal forests carbon sink or source
Boreal forests: Carbon sink or source? regions (2)


1. What factors determine whether a region (or ecosystem) is a “sink” or “source,” and why?

2. What does it mean to refer to the boreal region as a “carbon sink” or a “carbon source”?

Boreal forests carbon sink or source1
Boreal forests: Carbon sink or source? regions (2)

  • Forests sequester carbon via photosynthesis

    • Carbon stored in biomass

    • Long-term carbon storage: soil, permafrost, peat

  • Carbon released to atmosphere by:

    • Respiration

    • Fire

    • Decomposition of soil organic matter, melting of permafrost

  • Downward carbon flux: carbon sequestration

  • Upward carbon flux: carbon emission

  • Net carbon flux: sink or source

Balance between CO2 sequestration and emissions = complex!

Sink regions (2)


CO2 regions (2)fert



CO2, Climate, fire

Effects of post fire succession and human activities on future fire regimes in the boreal region
Effects of post-fire succession and human activities regions (2)on future fire regimes in the boreal region?

  • Rate of biomass recovery

  • Species composition (deciduous vs. coniferous)

  • Tree line expansion into tundra

  • Fire severity – depth of burn, permafrost – feedbacks

  • Fire suppression efforts – successful?

  • Insects and disease – increase with warming?