Lesson 13: Fire and Forest Protection

 

 

Fire that is destructive and burning out of control is known as wildfire. Of the 4 million acres of forestland lost to wildfire each year, about 3,000 acres belong to Maryland. Nationally, less than 10 percent of these fires are of natural cause. The rest are set by humans as a result of burning debris, smoking, unattended campfires, or—most often—arson.

Wildfire destroys the forest in many ways. Even when trees are not killed outright, fire scars can later provide entry to disease organisms and insects, and devalue the wood. Fire destroys wildlife habitat, limits forest recreation, and reduces aesthetic values. Fire can burn through the soil’s organic layer, removing nutrients and reducing the soil’s water-holding capacity. With this blanket of organic matter removed, rain quickly runs off the site, washing soil into streams, degrading water quality, and destroying fish habitat.

In the United States during the late 1800s, a series of forest fires burned millions of acres and took thousands of lives. These devastating fires prompted state and Federal forestry agencies to begin serious efforts to control wildfires. Since that time, yearly losses from fire have decreased by as much as 80 percent since the early 1900s. Fire control is both a state and Federal effort. In addition, many forest industries employ professionally trained fire crews who are kept on alert during fire season. Maryland’s three fire seasons occur during spring, right before leaves appear on trees; during summer when it is dry; and during fall, as trees lose their leaves and after the leaves have fallen.

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The Fire Triangle

Fire is the result of a process that occurs when three elements - heat, fuel, and air - are brought together in the right combination to support combustion. The three elements make up the fire triangle. Heat is required to start the fire and keep it going. The igniting heat raises the temperature of the fuel to the point where it will burst into flames somewhere between 400 and 700 degrees Fahrenheit. Heat to keep the fire burning comes from fuel, the flammable materials in the forest. Oxygen supplies the necessary oxygen to support combustion. Remove any one of the three elements and the fire is extinguished.

 

 

 

 

 

 

 

The Rate and Spread of Fire

Fires, which vary greatly in behavior and burning characteristics, are influenced by fuels, weather, and topography.

The type and condition of the fuel affects both the intensity of the fire and its rate of spreading. Forest fuels are classified into four groups: flash fuels, heavy fuels, green fuels, and ladder fuels. Flash fuels, or “fast” fuels, such as brush, dry grass, and dry leaves, burn quickly: they dry rapidly and are easily ignited. Generally, these fires are not difficult to extinguish. Heavy fuels, or “slow” fuels, include logs, stumps, and large trees, which tend to stay wet and will seldom ignite without the aid of flash fuels. Once they start burning, however, heavy fuels give off more heat, burn longer, and are more difficult to extinguish than flash fuels. Green fuels are the growing vegetation in the forest, such as grasses, herbaceous growth, bushes, and leaves. Although this vegetation is not flammable, fire will dry it out and cause it to burn. Some green fuels, such as pine needles, contain flammable oils that burst into flame under intense heat. Ladder fuels refer to the dead limbs, persistent cones (those that stay on limbs for a long time), or vegetation such as Spanish moss that “pull” the fire up into the crown of the stand. The seasonal growing cycle affects the moisture content of most forest fuels, as does the weather.

Weather conditions at the time of the fire, as well as during the preceding weeks or even months, influence its intensity and rate of spreading. Conditions include precipitation, temperature, winds, and relative humidity. Wildfire is more likely to break out after long periods of hot weather and low humidity, when fuels are warm, dry, and easy to ignite. High winds are especially dangerous, causing fire to spread fast and unevenly and to burn more intensely. Winds blow the fire’s heat forward, drying and preheating fuels, blowing sparks into new areas, which then ignite. Large fires often generate their own winds.

A site’s topography influences fire speed and direction. Drawn upward by convection, fires burn intensely and rapidly in mountainous areas. Slopes facing south and west tend to burn faster: they are warmer and drier from greater exposure to the sun. When fighting fires in these areas, firefighters need to gauge wind patterns—how winds flow through gaps and valleys—and be aware of any burning debris rolling down slopes.

 

 

Fighting a Fire

Early detection and response is critical. Time is required for notification, crew assembly, travel, and the actual fire fighting. In the past, lookouts in fire towers were responsible for detecting forest fires. Today, aircraft and satellites offer the primary means of detection.

Because fighting forest fires is hot, dangerous work, crew safety is top priority. First, the crew must carefully evaluate the situation—by observing type of fuels present, fire direction and rate of spread, size of fire, lay of the land, and the weather. It is important to identify a line of retreat and chain of command, as well.

The two general methods for controlling forest fires are direct attack and indirect attack. Direct attack is useful for light or slow-burning fires, in which firefighters can work close to the blaze. They approach the fire at the head, either digging a firebreak or fighting the fire directly with water or dirt. Sometimes, aircraft drops water from above. Firefighters employ the indirect attack for fighting intense, rapidly burning fires, when conditions are too dangerous for direct attack. The indirect approach requires constructing a fire line along a course that parallels the edge of the fire. Firefighters dig away all leaves, grass, twigs, roots, or other flammable material down to the mineral soil, to a width of approximately 2 feet, often using mechanized equipment, such as the fire plow. They then set a backfire to burn out the area between the constructed line and the wildfire, to remove the fuel. Roads, streams, and cultivated fields also serve as firebreaks.

 

Figure 13-2: CalFire firefighters make a firebreak as they fight a fire from the Lightning complex fire in Boulder Creek, CA, in 2020. Photo by Nhat V. Meyer/Bay Area News Group; https://www.mercurynews.com/2020/08/27/california-fires-what-exactly-does-containment-mean Links to an external site.

 

 

Figure 13-3: Nicole Allen, Jackson Hotshots crew member, uses a driptorch to create a backfire during the Schneider Springs fire near Naches WA in 2021. Photo by Evan Abell/Yakima Herald-Republic. https://www.yakimaherald.com/news/local/experts-call-for-expanded-wildfire-prevention-tactics-as-fire-seasons-become-more-extreme/article_5ff9f141-1260-5bc9-9ad7-e0b35fe4aca3.html Links to an external site.

 

The job of controlling a fire is not complete until it is “mopped up.” Mopping up involves searching through the burned-over area, felling snags, trenching logs or covering them with dirt, removing roots growing under the fire line, and extinguishing smoldering debris.

Maryland’s forests, a mixture of hardwoods and pines, are not as likely to burn as the coniferous forests in the West and South. Maryland’s forest tracts are small in comparison, and more accessible to firefighters. However, there are times, particularly during the spring and fall fire seasons, when leaf litter and ground vegetation in Maryland turn dangerously dry. The state’s Department of Natural Resources Forest Service monitors the potential for fire hazard and limits recreational use during times of extreme hazard. During these periods, it is important to exercise extreme caution with all types of fire.

Maryland’s Forest Service trains and assists local fire departments in preventing and suppressing forest fires. It also promotes fire prevention through educational programs, such as “Smokey Bear.” (See Appendix 28. Links to an external site.)

 

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Prescribed Fire

Uncontrolled wildfire is devastating. Fire, however, is a natural part of forest ecology and can act as a valuable, yet inexpensive, management tool. Native Americans used fire to clear land for creating and maintaining pasture, to improve forage for wildlife, and to open the way for travel. European settlers adopted these practices; prescribed fire is the result.

Under the right conditions, which include the approval and supervision of your local state forestry office, a prescribed fire suppresses undesirable vegetation, releases nutrients, and removes the buildup of flammable debris which, in turn, lessens the severity of wildfires.

Prescribed fire, which controls certain pine diseases and can improve forest accessibility, is also helpful in changing or maintaining various types of forests. Fire set in summer, for example, prepares a site for pine seedlings, benefiting the shade-intolerant species by removing hardwood competition. Prescribed burns—performed most often in winter—are used for managing wildlife as well. Clearing the understory and promoting lush, succulent new growth the following spring, prescribed burns increase wildlife cover and food such as insects and seeds. Certain species of plants and animals have evolved to withstand periodic light fires and, in fact, often require them for successful growth and reproduction.

Prescribed burns are planned to coincide with proper environmental conditions; control measures, such as fire lines, ditches, and access roads, are prepared in advance. Fire properly prescribed and applied does not burn through the litter layer and damage tree roots. Prescribed burns do not trap wildlife like wildfires do, either, if burns are kept small and slow moving. Because they burn less fuel and usually burn only a few hours under ideal atmospheric conditions, prescribed burns release fewer air pollutants than a typical wildfire. Many areas, however, restrict the use of prescribed burning because of increased development, road expansion, and air quality concerns.

 

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Fire and Our Ecosystem

Not only is an occasional fire a natural event for a forest, it is often a healthy one. Where fire is normal and recurring, habitats adapt, and recovery tends to be relatively quick.

The jack pine forests of Michigan, the pitch pine–oak forests of Cape Cod, and the longleaf pine forests of the South all rely on fire to perpetuate themselves. With their fire-resistant bark and serotinous cones, which need the heat of fire to open, pines are better able to survive fire than the less resistant hardwoods.

Exclude natural fires from a forest and vegetation changes. Insect populations, diseases, and natural cycles such as nutrient recycling and plant succession are disrupted. And as noted above, frequent low-intensity burns reduce the chance for large, catastrophic fires later on.

Fire has played an important role in shaping the state’s forests. On Maryland’s Coastal Plain, natural fires once maintained a forest of loblolly pine, a subclimax forest type. The loblolly pine is intolerant of shade, requires bare mineral soil to germinate, and is replaced by oaks and other hardwoods once the forest canopy closes. However, the loblolly pine is well adapted for withstanding low-intensity fires, which often kill less tolerant hardwoods. Today, prescribed burning and forest harvest operations maintain the loblolly pine forest.

Fire has also helped shape Maryland’s interior—and highly desirable—hardwood forests. Fires set back succession and allow trees such as tulip poplar, hickory, and oak to reproduce. However, because of good fire control, wildfires are fewer now than in the past and, therefore, no longer play the large role they once did in shaping the natural system of the forest. The challenge foresters face is how to manage these forests now that fire’s role has been reduced.

 

 

References

• Alban, L.M., J. Riley, E.C. Schwaab, R. Rabaglia, and K.E. Miller. 1995. "Maryland's Forests: A Health Report." Maryland Department of Natural Resources Forest Service.
• American Forest and Paper Association. 1996. Forests Facts and Figures 1995. Washington, D.C.
• Kricher, J.C., and G. Morrison. 1988. A Field Guide to Eastern Forests. Peterson Field Guide Series. Boston: Houghton Mifflin Co.
• National Wildfire Coordinating Group. 1980. "Wildfire Prevention Handbook." Seattle, WA: Outdoor Empire Publishing, Inc.
• Rader, Terry D. 1977. Forest Fire Protection. Penn State Cooperative Extension. Pennsylvania Forest Resources Number 48.
• U.S. Dept. of Agriculture Forest Service. 1984. Manual for Forest Fire Fighters. Northeastern State and Private Forestry.
• U.S. Dept. of Agriculture Forest Service. 1973. Water Versus Fire.
• U.S. Fire Administration. 2008. "Total Wildland Fires and Acres (1997-2006)." Cited 11 June 2008 from http://www.usfa.fema.gov/statistics/estimates/wildfire/shtml.
• Vodak, M.C., and M. Ferrell. 1990. "Prescribed Burning in New Jersey Woodlands." Rutgers Cooperative Extension Service. FS367.

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Assignment

Read:

Fazio, James R. The Woodland Steward: A Practical Guide to the Management of Small Private Forests. Pages 71—77.