1. Fire regimes and the World’s biomes 23 September 2010

2. What is a fire regime? Characterization of the features of the historic (“natural”) fires for a particular ecosystem or ecoregion.

3. Fire Regime Components: Examples…? Extent (size) Frequency Seasonality Duration Intensity Severity Magnitude

4. Extent Range of burned area Can influence seed dispersal from neighboring systems. Barriers to spread?

5. Fire Frequency – Data sources Dendrochronology (tree scars from non-lethal fires, cross-dating) Paleoecology (charcoal in lake & soil sediments; wounds on tree boles) Data bases: reports, aerial photos, maps, atlases, satellite images, remote sensing

6. Fire frequency: Fire return interval The number of fire events at a point or within a specific area. Short fire return intervals –< 25 years Intermediate fire return intervals –25-100 years Long fire return intervals –>100 years

7. Seasonality How likely fire might occur during each time of year Affects plant survival and flowering

8. Duration The length of time a fire burns within a particular area For example… –Fast-moving prairie fires –Slow moving ground fires Important effect on intensity and severity…

9. Intensity Burned Area Direction of spread One Foot Flame depth

10. Severity Effect of fire on the ecosystem Some measures of severity… –% of organic biomass consumed by fire –% soil organic matter consumed –Mortality of plants and animals –Depth of heat penetration into the soil –Change in color of ash and soil –Description of fire behavior (surface, ground, crown) Most common measure of severity –Mortality in overstory vegetation

11. Fire classification: severity and frequency (return interval) Short fire return intervals (<20 years) –Low-severity surface fires are common. –Fire tolerant herbaceous species or shrubs dominate. –Species composition often similar. Intermediate fire return intervals (20-75 years) –Fuel buildup and continuous in distribution –Moderate-severity fires (patchy crown fires) or some high-severity fires –Greater changes in plant composition Long fire return intervals (>100 years) –Very high fuel loads possible –High-severity fire commonly occur (stand-replacing crown fires) –Postfire & prefire vegetation can be very different Mixed-severity fires –Combination of frequent low-severity & infrequent high severity fires

12. How do historical (pre-settlement) and modern (current) fire regimes differ – and why? In ecosystems with high frequency, low intensity fire regimes (e.g., dry forests, grasslands, woodlands, savannas), significant changes due to: –Land use change (agriculture, urban) –Fire suppression and fuel accumulation –Change in vegetation type and structure Forests with low frequency, high severity stand- replacing fire regimes: –Much less change from historical fire regimes – Why?

13. Fire Regime Exercise Brief description of several major ecosystems in the world TTYP: describe the fire regime for each ecosystem

15. Northern boreal forests Boreal forests and tundra Long winters, short summers Lots of biomass

16. Mediterranean shrublands Generally shrublands, also trees and grass Wet, mild winters / hot, dry summers Fire adapted biota

17. Tropical rainforests High biomass Ever-wet with occasional droughts

18. Tropical savannas (Africa) Cyclic wet/ dry periods Grazing x fire interactions Shifting grasslands – savannas – forests

19. Brazilian cerrado Fire-adapted grasses & shrubs Dry winters Summer rains

20. Ponderosa pine – Douglas fir Mountains in the West/Southwest Dry summers, but also cooler and moister at high elevations Without fire, D-fir establishes in understory of Ponderosa pine