Fuels Management
"Decades of fire suppression have often produced overcrowded vegetation in our forest, weakening trees and rendering them more susceptible to pests, diseases, and displacement by invasive species. Too often, the result is soil erosion and habitat degradation especially in sensitive areas such as stream, lakes, and wetlands."
Dale Bosworth, Former Chief of the Forest Service, September 2001
To protect the homes and improve the health of the forest, we must reduce the fuels.
Right now many places on the forest are set up for an intense wildland fire. There is extreme fuel loading, a greater density of dead and dying trees, and more structures in the forest. We have a hot, dry windy climate, steep topography and numerous fire starts, both human and natural. Climate and topography we cannot change. Fuels we can modify and we can educate the public on fire safety. In turn, firefighter safety will increase and the loss of structures will decrease.
What are "fuels"?
Any combustible material in the forest. Needles, shrubs, downed trees, grass, trees, brush, etc. are all fuels. Light fuels; such as, grass burns quickly and spreads rapidly. Heavy fuels; such as, downed logs take longer to ignite and burn up.
What is "ladder fuel" and why is it a problem?
Vegetation that allows the fire to move from lower fuels into higher fuel layers is called ladder fuel. Flames from the fuels at the ground level, such as pine needles, can be carried into taller fuels, such as a shrub, which can ignite still taller fuels, such as tree branches. You need to reduce the ladder fuels and reduce the accumulation of surface and ground fuels to decrease the intensity of a wildland fire. The benefits of reducing the fuel include a reduced competition for light, moisture, and nutrients. A decreased mortality to the remaining larger older trees and a decrease of insects and disease due to the maintained or increase growth in the healthy trees.
Fuel Reduction Projects
All projects are designed to change vegetation conditions to modify fire behavior and reduce the potential for wildfire by altering three primary fuel conditions as necessary: surface fuels, ladder fuels, and overstory crown densities. This is accomplished through the implementation of a variety of treatments, commonly using more than one treatment type on the same piece of ground to achieve the desired condition.
It is important to note that the vegetation conditions that pose a fuels hazard are dynamic, with continued growth, needle-cast, litter-fall, and new growth of understory vegetation continually occurring. As such, future treatments will need to occur over time on the same area to sustain the benefits of the previous treatments.
How do we reduce fuels?
Which treatment strategy to use depends upon cost effectiveness, availability of implementation resources, the size and type of vegetation to be removed, and site-specific resource protection needs. Typically, fuels reduction is a 2 step process. The first process is a mechanical treatment using timber sales, and project crews to remove the excess trees. Prescribed fire is the 2nd step which will clean up the small fuels, brush and reduce the duff layer by consuming these fuels at a lower temperature converting them to nutrients. The primary treatments used in the Eldorado National Forest include:
- Thinning (hand and ground-based mechanical)
- Prescribed burning (pile and understory burning)
- Mastication and chipping
Mechanical and hand thinning are used to reduce the number of trees, which affects crown fire potential and decreases the competition for limited resources for the remaining trees. Mechanical thinning is generally more cost effective than hand thinning for removal of large trees (trees greater than 16 inches diameter), and allows removal of larger trees to achieve spacing objectives.
- Ground-based mechanical thinning is generally prohibited on slopes more than 30 percent and on sensitive areas, such as stream environment zones.
- Aerial-based mechanical thinning uses helicopter or cable-based systems to remove trees on slopes greater than 30 percent.
- Hand thinning is generally limited to the removal of trees less than 16 inches diameter on steeper slopes, and in sensitive areas. Hand thinning may also involve pruning, which removes lower branches on trees, increasing the crown-base height (the distance from surface fuels to tree crowns). Because it is labor-intensive, pruning is generally limited to project areas in the defense zone.
Mechanical treatments are designed to remove or rearrange fuels, prepare areas for future fire applications by removing excessive ladder and surface fuels, and can be especially useful in sensitive areas. Smoke emissions and the fire intensity in a wildfire situation are reduced through the use of mechanical equipment: mastication, biomass removal, shredding, chipping, and handcut removal.
Prescribed fire is a planned fire designed to replicate natural fire but under controlled conditions. It reduces surface fuels using pile burning or understory burning. Pile burning is used on steep slopes where machines are prohibited and adjacent to developed areas where machines cannot process or otherwise remove material. Understory burning may be used to remove slash created by machine thinning and as an additional treatment in previously treated areas, or to restore forest health and to mimic the historic process of low-intensity fire.
Exact fire prescriptions for a project area are developed by fire managers before burning is allowed. These fire prescriptions are based on weather, moisture content of the fuels, topography, time of year, air quality, and how the fire can be lighted (ignition patterns). There may only be 50 days in an entire year when an area meets the prescription.
Mastication and chipping are used to reduce ladder and surface fuels. Masticators consist of a mastication head on the end of an articulated arm that moves through the forest on a tracked or rubber-tired machine or mounted on a small loader-type machine with rubber tracks. Fuels are ground up into irregular-shaped chunks and left on the ground. The irregular-shapes allow air and water to seep between them, hastening decomposition.
Chips are created when material is fed into a chipper and either removed from the site as biomass or spread on site. Chipping creates uniform-sized chips that can form an interlocking mat that decomposes very slowly and inhibits regeneration of shrubs and grasses.
We must use all our tools to communicate the issues and options to reduce the fuel. Doing nothing can have severe consequences on public and private land. Insect, disease, and wildland fires do not recognize property lines.