1. Prescribed Fire for Site Preparation

2. Prescribed Fire for Site Preparation
Primary Uses
Reduce slash, debris, and undecomposed litter, and release nutrients in accumulated organic materials
Kill interfering vegetation or reduce understory plants to alter visual qualities in a stand
Influence plant succession or increase ecological diversity by perpetuating fire-dependant plant communities
Reduce accumulation of hazardous fuels
Reduce the thickness of forest floor or expose mineral soil

3. Uses of Burning for Site Preparation
Secondary Uses
Open cone and other fruiting structures to release seeds
Species with seratonous cones (e.g., jack pine and lodgepole pine)
Increase water yields by altering the kind and size of vegetation and reducing transpiration
Induce sprouting of surviving vegetation to improve cover, browse or forage production

4. Effects of Burning for Site Preparation
Effects will depend on:
Amount and nature of fuel
Pine litter more flammable than hardwood litter
Size of vegetation to be killed {poor top kill if >3" diameter}
Number of sproutable rootstocks (maximum kill for one burn usually around 20%, less for a winter burn)
Timing of burn
most kill in growing season (optimum just after leaf out), least in dormant season;
best consumption with least green or living vegetation, i.e., in fall/winter or after herbicide browning
higher erosion potential with fall/early winter burn (soil stays bare all winter)
late spring burn will impact ground nesting birds (e.g., wild turkeys)

5. Fire Behavior and Prescribed Fire

6. Oxygen Heat Fuel Fire Triangle
Fire needs all three to sustain combustion.
What are we removing when we construct a fire line?
What are we removing when we put water on a fire?
Both dirt and foam also help remove the oxygen as well as heat from a fire
Fuel

7. Three Principal Environmental Elements Affecting Wildland Fire Behavior

8. Fuels Fuel Type Fuel Moisture Size and Shape Fuel Loading
Horizontal Continuity
Vertical Arrangement
Radiation: heat generated from burning object affecting adjacient object.
Convection: Hot gases rising from fire. Dries out fuels and also can carry hot embers to start spot fires.
Conduction: Heat energy transferred within an object; metal rod in a camp fire. Wildland fuels are NOT a good conductor of heat

9. Fuel Moisture
The amount of water in a fuel expressed as a percentage of the oven-dry weight of that fuel
Radiation: heat generated from burning object affecting adjacient object.
Convection: Hot gases rising from fire. Dries out fuels and also can carry hot embers to start spot fires.
Conduction: Heat energy transferred within an object; metal rod in a camp fire. Wildland fuels are NOT a good conductor of heat

10. Fuel Types Nonburnable Fuel Type Models (NB)
Grass Fuel Type Models (GR)
Grass-Shrub Fuel Type Models (GS)
Shrub Fuel Type Models (SH)
Timber-Understory Fuel Type Models (TU)
Timber Litter Fuel Type Models (TL)
Slash-Blowdown Fuel Type Models (SB)
Radiation: heat generated from burning object affecting adjacient object.
Convection: Hot gases rising from fire. Dries out fuels and also can carry hot embers to start spot fires.
Conduction: Heat energy transferred within an object; metal rod in a camp fire. Wildland fuels are NOT a good conductor of heat

11. Fuel Size Time lag Fuel diameter
1-hour (fine fuels) <¼ inch (twigs, dead grass, leaves, needles)
10-hour ¼-1 inch (twigs, small branches, cones)
100-hour inch (branches, tops)
1000-hour >3 inch (large branches, tops, logs)
Fuel moisture time lags: (Time it takes for a fuel to lose 63% of its moisture)

12. Fuel Loading The quantity of fuels in an area
Generally expressed in tons per acre
Radiation: heat generated from burning object affecting adjacient object.
Convection: Hot gases rising from fire. Dries out fuels and also can carry hot embers to start spot fires.
Conduction: Heat energy transferred within an object; metal rod in a camp fire. Wildland fuels are NOT a good conductor of heat

14. Horizontal Continuity: Uniform vs Patchy
Vertical Arrangement
Ground
Surface
Aerial
Horizontal - self explanatory
Vertical arrangement on following slides

15. Ground Fuels
All combustible materials lying beneath the surface including deep duff, roots, rotten buried logs, and other organic material
Usually called a “PEAT FIRE”
Best called underground fire.
Ground fires usually only a problem in drought situatuions

16. Surface Fuels
All materials lying on or immediately above the ground including needles or leaves, grass, downed logs, stumps, large limbs and low shrubs.
99% of all fires.

17. Aerial Fuels
All green and dead materials located in the upper forest canopy including tree branches and crowns, snags, moss, and high shrubs.
Namely a crown fire!
Most difficult and dangerous to contain.
Can burn independent of surface fire.

18. Weather Temperature Wind Speed and Direction
Increases supply of oxygen
Drives convective heat into adjacent fuels
Influences spread direction and spotting
Carries moist air away replacing it with drier air
Dries fuels
Raises fuel moisture if the air contains moisture
Radiation: heat generated from burning object affecting adjacient object.
Convection: Hot gases rising from fire. Dries out fuels and also can carry hot embers to start spot fires.
Conduction: Heat energy transferred within an object; metal rod in a camp fire. Wildland fuels are NOT a good conductor of heat

19. Weather Relative Humidity (RH) Precipitation
As RH increases, fuel moisture increases
Precipitation
Increase fuel moisture
Radiation: heat generated from burning object affecting adjacient object.
Convection: Hot gases rising from fire. Dries out fuels and also can carry hot embers to start spot fires.
Conduction: Heat energy transferred within an object; metal rod in a camp fire. Wildland fuels are NOT a good conductor of heat

20. Topography Aspect Slope Position of Fire Shape of Country Elevation
Relates to curing of fuels, precipitation, length of fire season, etc.

21. Aspect

22. Steep Slopes Cause Rapid Fire Spread

23. Slope Affects Fire Behavior
Burning Material Rolling Downslope
Preheating
Draft
Faster Ignition and Spread

24. Position of Fire on Slope

25. Box Canyon & Chimney Effect

26. Radiant Heat Across Narrow Canyon

27. Spotting Across Narrow Canyon

28. Mountains Cause Channeling of Wind

29. Elevation

30. Characteristics of Fire Behavior
Fire Intensity: Heat release per unit time (BTUs)
Fire intensity affected by
Fuel loading
Fuel moisture content
Compactness or arrangement of fuels

31. Flame Length: The distance measured from the average flame tip to the middle of the flaming zone at the base of the flame

32. Rate of Spread (ROS): The distance a fire travels during a given period of time

33. Primary factors affecting rate of spread?
Rate of spread = distance/time
Burned Area
Primary factors affecting
rate of spread?
BTUs, KJs
Increased fire intensity
Windspeed
Steepness of slope

34. Slope Reversal

35. Types of Fire Behavior Running – spreading quickly Creeping
– spreading slowly with low flames
Smoldering
– burns without flames; barely spreading
Spotting
– sparks/embers carried by wind or
combustion column or moved by gravity
Spot fires
– new ignition points
Fire brand
– a piece of burning material

36. Types of Extreme Fire Behavior
Torching
– surface fire moves into crowns of individual trees
Crowning
– spreads from tree crown to tree crown
(dependent, active, or independent)
Flareup
– sudden acceleration of fire spread or intensity
(short duration, for portion of fire)
Blowup
– dramatic change in the behavior of the whole fire
(rapid transition to a severe fire)
Fire Whirls
– vortex (gas mass with rotational motion)

37. Fire Effects

49. Prescribed Fire

50. Prescribe Fire Plan * Day before & day of burn
Burn prescription written
Pre-burn site treatments completed
Equipment designated & ready
Personnel identified & trained
Approvals & permits in hand
Authorities & interested parties identified & notified*
Latest forecasts checked*
* Day before & day of burn

51. Potential problems in using prescribed burning
Scheduling: need proper fuel conditions, weather, and available manpower
Requires experienced supervision for planning and implementation
Smoke management problems
Containment issues and liability
Fire may damage or kill residual trees

52. Smoke Management

53. Principles of smoke management
Have clear, defensible objectives
Comply with local pollution regulations
Notify local fire & law enforcement officials, nearby residents, & adjacent landowners
Obtain the best available weather forecasts
Don’t burn under highly stable conditions
Burn during midday; avoid night burns
Use caution near, upwind, or up-drainage of smoke sensitive areas

54. Principles of smoke management (continued)
Use test fire to estimate smoke output & behavior
Use backing fires if feasible
Burn in small blocks if dispersion marginal
Do not burn when fuel moisture high
Don’t burn organic soils
Mop-up along roads first
Have an emergency plan!

55. Ignition Devices Hand-held/ground-based Drip torch Propane torch
Fire fuse (flare)
Flame thrower

56. Drip torch fuel:
3:1 or 3:2
Diesel/gasoline

60. Ignition Devices Aerial Helitorch
Delayed aerial ignition device (“ping-pong balls”)

61. Helitorch

62. Delayed aerial ignition device

63. Ignition Devices
Lightning

64. Ignition Techniques Backfire (backing fire)
Least intense & most predictable
Short flame lengths
Narrow burning zone
Slow rate of spread
Low smoke output

65. Backing Fire

66. Headfire (heading fire)
Most intense and unpredictable
Long flame lengths
Wide burning zone
Fast rate of spread
High smoke output

67. Strip-heading Fire
Distance between strips controls intensity

68. Spotfire
Intensity intermediate between back & head fires
Useful in shifting winds
Spots merge to form a strip head fire
What you get using a DAID

69. Spotfire
Distance between spots controls intensity

70. Flankfire (flanking fire)
Intensity intermediate between back & head fires
Fire spreads at right angle to wind
Limited to steady wind conditions
Requires careful crew coordination
Used primarily for securing flanks of back or head fires

71. Flanking Fire

72. Wind
Headfire
Backfire
Flankfire