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 and Fire Regimes in Boreal Ecosystems

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Fire ecology and fire regimes in boreal ecosystems

Fire Ecology and Fire Regimes in Boreal Ecosystems

Oct 19, 2010


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


Soil temperature moisture and fire influence vegetation types

Soil temperature, moisture, and fire influence vegetation types


Boreal region land of fire ice

Boreal region: land of fire & ice

  • 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

  • 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)


Smoldering

Smoldering?


Boreal fires high energy release rates

Boreal fires: high energy release rates


Effects of fire on boreal landscape

Effects of fire on boreal landscape

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

    temporarily

    (vegetation = insulation)

  • Replaces forest stands


Loss of protective insulation from vegetation

Loss of protective insulation from vegetation


Post fire p ermafrost thaw recycling of nutrients water

Post-fire permafrost thaw: recycling of nutrients & water


Fire creates mosaic of vegetation

Fire creates mosaic of vegetation…


A nd mosaic of stand types

and mosaic of stand types…


Human influence on boreal fires

Human influence on Boreal fires

  • 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

  • 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 in 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 and 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 ?

      CO2fertilization

      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?

TTYGroup:

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?

  • 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!


Fire ecology and fire regimes in boreal ecosystems

Sink

Source


Fire ecology and fire regimes in boreal ecosystems

CO2 fert

Climate

Fire

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 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?


Climate change effects on permafrost

Climate change effects on permafrost…


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