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
  • 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)

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
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!

slide20

Sink

Source

slide21

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?
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