Rebirth in Fire


STUDENTS: Module 4: Forces in the Environment

Fire icon. Rebirth in Fire Introduces the role of fire in revitalizing native plants and maintaining a healthy forest environment.

Illustration: matches...caution advised.Wildland fire is a natural process in the environment. In some areas, forest managers use prescribed burns to maintain the healthy forest environment. In order for people to appreciate the role of fire as a technique for resource management, they must understand that fire can be beneficial under the right conditions.
For fire to occur, three elements must be present: heat, oxygen, and fuel. These three elements form a ?fire triangle.?
Illustration: Fire Triangle
    Fuel + Heat + Oxygen = Combustion




Photo: Interview with a firefighter. Heat can be transferred in three ways:
1. Radiation - heat is transferred by means of short energy waves.
2. Convection - heat is transferred through liquids and gases by means of up-and-down movements called convection currents.
3. Conduction - heat is transferred by direct contact of molecules.


Characteristics of Fuel:
1. Moisture - how well a fuel will ignite and burn is dependent upon its moisture content or chemical composition.
2. Size and shape - light fuels such as shrubs, grasses, leaves and pine needles burn rapidly but are easily extinguished. Heavy fuels such as logs and limbs burn more slowly.
3. Fuel loading - the quantity of fuels in an area which is available for combustion
4. Horizontal continuity and vertical arrangement - the manner in which fuels are spread over a certain area.


Characteristics of Weather:
1. Temperature - fuel and ground temperatures are primarily due to direct radiation from the sun
2. Wind - encourages combustion and the spread of fire
3. Relative Humidity - low humidity takes moisture from fuels; fuels, in turn, take moisture from the air when humidity is high
4. Precipitation - fuel moisture is affected by the amount of precipitation.


Characteristics of Topography:
1. Aspect - the direction in which a slope faces relative to the sun
2. Slope - the degree of incline of a hillside. The steeper the slope, the faster the fire burns up or down (depending on wind direction)
3. The shape of the country ? box canyons, narrow canyons, and other rugged topographic features can influence the wind?s speed and direction.




It is essential that the public understand appropriate fire management policies, and that fire is a necessary part of ecological succession in many forested areas.

The objectives of prescribed burning are:
1. fuel reductionPhoto: Prescribed burn.
2. preparation of seedbeds for regeneration of wind-disseminated species which become established most readily on bare mineral soil
3. control of competing vegetation
4. improvement of grazing
5. management of wildlife by allowing species that they feed on to grow
6. recreation management to maintain a park-like appearance
7. thinning of saplings
8. control of pests

The key idea that needs to be understood is that often it is most efficient to ?fight fire with fire;? that is, allow the proper authorities to set fires deliberately so as to avoid larger and more destructive fires in later years.
fuel
heat
oxygen
fire triangle
radiation
convection
conduction
Photo: Shooting an interview.
temperature
humidity
precipitation
burn
prescribed burn
aspect
slope
regeneration
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