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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. 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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  1. Fire Ecology and Fire Regimes in Boreal Ecosystems Oct 19, 2010

  2. 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

  3. Soil temperature, moisture, and fire influence vegetation types

  4. 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

  5. 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)

  6. Smoldering?

  7. Boreal fires: high energy release rates

  8. 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

  9. Loss of protective insulation from vegetation

  10. Post-fire permafrost thaw: recycling of nutrients & water

  11. Fire creates mosaic of vegetation…

  12. and mosaic of stand types…

  13. 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

  14. 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.

  15. 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?

  16. 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)

  17. 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

  18. 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”?

  19. 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!

  20. Sink Source

  21. CO2 fert Climate Fire CO2, Climate, fire

  22. 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?

  23. Climate change effects on permafrost…

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