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Global Change Effects on Fire and Fuel Management in Northern Forests

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27 diapositives · 402 Views · Oct 12, 2014

This paper discusses the impact of global change on fire dynamics and fuel management strategies in northern forests, particularly within the boreal region. It examines historical fire incidence, current trends, and the future implications of climate change on fire weather and vegetation. The authors suggest that while proactive fuel management can protect communities, it may not substantially reduce overall burned areas in these extensive ecosystems. The challenges of implementing effective fuel management practices in the face of changing climate and human influences are addressed comprehensively.

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  1. GLOBAL CHANGE EFFECTS ON FIRE AND FUEL MANAGEMENT IN NORTHERN FORESTS Brian Amiro, Brian Stocks, Marty Alexander, Mike Flannigan, and Mike Wotton Canadian Forest Service

  2. Outline • The recent past: fire history • The present • fire occurrence • magnitude of boreal fires • Fuel management at the landscape scale • The future • global change • the carbon issue

  3. Circumpolar Boreal Forest • Huge size • Fire dominated (short fire cycle) • Crown fires common • Relatively sparse settlement Ecologically, this forest needs fire!

  4. Fire History: • 1 to 3 million ha burned annually • ~8,000 fires annually • large variability • general trend upwards • uncertainty in older data • direct suppression costs ~$0.5 billion

  5. Large-Fire Database fires > 200 ha 1980 - 1994

  6. Lichen woodland Coniferous Deciduous Mixed Wood Grassland/Agriculture Non-fuel Water FUEL TYPES

  7. Fires are most common in “coniferous” fuel types in the boreal forest Fires 1980-94 Fuel Types An increasing deciduous component reduces the rate of spread and resists crowning

  8. ~ 400 x 400 km • Coniferous fuels • - Jack pine • - Black spruce • Small deciduous • component Example Area: Boreal Shield Saskatchewan 1980-1994

  9. 1988-91, 1980-82, 1983-87, 1992-94, 1995 Fuel Types lakes deciduous coniferous Scale: about 400 x 400 km

  10. Fuel Management at the Landscape/National Scale • Assume that localized fuel management can protect valued areas (e.g., communities) • But: Can proactive fuel management decrease area burned in northern forests? • Basic Options • fuel reduction (mechanical, burning) • fuel conversion (deciduous) • fuel isolation (mechanical, burning, tie into strategic fuelbreaks)

  11. Fuel Reduction • Fuel continuity & build-up greatest in areas of most fire exclusion • Wildfires are reducing fuel, but these are mostly stand-replacing crown fires • Mechanical or prescribed-fire treatments not normally used on huge scales • Prescribed fire has a narrow window • Chemical (herbicide) treatments have ecological concerns

  12. Fuel Conversion spruce • Species are limited (essentially aspen in the west) • Economic impact on species shift • Ecological/ Biodiversity impacts aspen

  13. For a 400 x 400 km area (16 million ha), to limit fire size to 1000 ha with 200m wide “breaks” would require treating about 1 million ha! Even if a “perfect” fuel treatment can limit fire size, the area required to be treated is huge! Fuel Isolation

  14. Fuel Management Summary • At large scales, the greatest potential for fuel management is in areas where a “natural” fire regime has been in place. • The greatest problems will be in areas where fire suppression has been effective, and fuel continuity and amount are above historical norms. • Without a major change in settlement and land-use, it is unlikely that fuels can be managed to reduce area burned in Canada over the next few decades.

  15. “Global” Change • Changing fire weather • Climate effects on vegetation • Human changes to the landscape • Human effects on fire

  16. Precipitation: 2xCO2/1xCO2 ratio REGIONAL CLIMATE MODEL May to Aug means Temperature: 2xCO2-1xCO2 (oC)

  17. Regional Climate Model Fire Weather Index Ratio: 2xCO2/1xCO2 Interpretation: Fire danger will increase through much of western Canada

  18. Future climate? (Hogg and Hurdle 1995 Water Air Soil Pollut.) Climate Effects on the West-Central Forest Present climate (isolines are a moisture index)

  19. aspen lowland black spruce The Carbon Issue How much carbon is lost: - during the fire? - after the fire through decomposition? When does the forest turn from a source of carbon to a sink following a fire? Regeneration same year as fire:

  20. Models estimate that Canadian forests have changed from net carbon sinks to sources, because of enhanced disturbance

  21. Modelled Carbon Losses from Fire • Direct fire carbon losses are approximated from fuel combustion • The post-fire fluxes are largely unknown • The post-fire net carbon balance needs to be quantified, to include decomposition and succession kg carbon / m2 Wong 78 Kurz & Apps Kasischke et al. 95a Seiler & Crutzen 80 Auclair & Carter 93 Kasischke et al. 95b Dixon & Krankina 93

  22. Mature jack pine Fort Providence, NWT One-year-old burn

  23. Mature pine/aspen/spruce Prince Albert National Park, SK 10-year-old burn

  24. 1989 fires At the landscape scale, it appears to take close to 30 years before the forest returns to its “pre-burn” sink condition. Daytime carbon dioxide fluxes were measured along a 500 km transect during BOREAS 1995 fires

  25. NPP in 1994. North-central Saskatchewan. (~ 130 km x 120 km area) Cree Lake

  26. Estimates of NPP following fire for 10 ecoregions

  27. Conclusions • Fire is the dominant stand-renewing agent in most of the boreal forest: ecologically, this forest needs fire. • Fuel management is unlikely to be successful at decreasing area burned, although the threat to small, valued areas (e.g., communities) can be reduced. • Landscape fragmentation is increasing, and although of ecological concern, it has had little impact on area burned to date. • A changing climate is likely to affect fire weather and vegetation types: The impact is to increase fire through much of the area: In mixed-wood areas, younger forests will burn less.