What dictates fire behavior–the fire behavior triangle. Why do ecologists care?

1. What dictates fire behavior–the fire behavior triangle. Why do ecologists care? 1. Weather 2. Fuels 3. Topography Fire behavior largely determines fire effects!

3. Fuel Types- 4 Categories: where it is located Fire behavior is largely determined by which fuel strata is carrying the fire: • Ground • Surface • Ladder • Crown/ aerial

4. Fuel Types • Ground Fuels • Duff (partially decomposed) • Peat • Roots • Stumps litter fermentation layer Duff humus mineral soil

5. Fuel Types • Surface Fuels • Grasses • Shrubs • Litter (leaves) • Woody debris

6. SURFACE AND GROUND FUELS

9. Fuels • Aerial/ canopy Fuels • Crown or canopy of overstory • Ladder Fuels (located between crown and surface fuels) • Smaller trees • Vines

16. For each fire type: Fuel Characteristics influence fire behavior • Fuel Loading • Size and shape • Compaction • Chemistry • Arrangement • Vertical • Composition • Continuity • horizontal

17. Fuel Loading

18. Fuel loading- do we just weigh everything that can burn? • Fuel loading is simplified by categorizing fuels into similar groups • All fuels are characterized by their size category, called “timelag fuel class”. This is related to their capacity to absorb and lose water in relation to their environment. • The most important factor associated with fuel size is its surface area to volume ratio…why?

20. Timelag Fuel Class • EMC = equilibrium moisture content: the watever vapor pressure of the fuel is in equilibrium with the wvp of air. • Given a stable air mass, the “timelag” is time it takes for a particle of fuel to reach 63% of the difference between its initial moisture content and the equilibrium moisture content. • It is NOT how long the fuel will burn

21. Timelag= approaching equilibrium • It takes 5 timelags for 95% of the change to occur • But most of the change happens within the first timelag Difference http://stream2.cma.gov.cn/pub/comet/FireWeather/S290Unit10FuelMoisture/comet/fire/s290/unit10/print.htm#page_2.2.0

22. Larger fuels lose and absorb water less quickly http://stream2.cma.gov.cn/pub/comet/FireWeather/S290Unit10FuelMoisture/comet/fire/s290/unit10/print.htm#page_2.2.0

23. Timelag categories (know these!) • Size of fuel (diameter, inched) Timelag Class • 0” to ¼” 1 hour • ¼” to 1” 1o hour • 1” to 3” 100 hour • > 3” 1000 hour

24. Three ways to assess fuel loading • Fuel models • Photo series • Measure it

25. Fuel Loading – what do you include? Timber Brush

26. Fuel models use 4 fuel groupings- based on proportion in each timelag class Anderson, 1982 Fuel Models and Fire Behavior Prediction

27. The 13 fuel models

28. Example BEHAVE outputs: Rate of spread Rate of Spread for Fuel models at 5 mph wind

29. FUEL MODEL 13: HEAVY LOGGING SLASH

30. 6-10 tons/ acre FUEL MODEL 7: SOUTHERN ROUGH

31. 3-5 tons/acre FUEL MODEL 8: CLOSED TIMBER LITTER

32. 1-3 tons/acre FUEL MODEL 3: TALL GRASS

33. Photo series • Hundreds of field plots measured= averaged = photo series fuel loading values. • Digital photo series (USFS) • http://depts.washington.edu/nwfire/dps/

34. MEASURE IT: Today’s Lab! • Brown’s Planar Intercept