Prescribed burns |
| Prescribed or controlled burns are important management
tools in natural area restoration. Lightning-caused fire was a regular natural
feature in woods, savannas, and prairies even before the land was settled
by humans. Later, Native Americans used fire extensively, and after European
settlement this practice was continued by farmers. Early in the 20th century
intentionally set fires became discouraged by foresters and government agencies,
and by the 1950s were no longer carried out. As a result, natural areas
became overrun with invasive shrubs, to their great detriment. Prescribed fire was first reintroduced into the Upper Midwest in the 1940s by John Curtis and associates during their work on the establishment of new prairies at the University of Wisconsin-Madison Arboretum. The demonstration of fire’s utility led to a gradual increase in the use of prescribed burns throughout the region. In Wisconsin, prescribed fire is now a critical management tool for organizations such as The Nature Conservancy, The Prairie Enthusiasts, and the Wisconsin Department of Natural Resources. Many private landowners also use fire on a regular basis. What is a prescribed burn? The term “prescribed burn” refers to a fire that has been determined to be critical for the management of a specific natural area. All fire is potentially dangerous, and those conducting a prescribed burn have the responsibility for insuring that the fire is under control at all times. The burn is done according to a written and approved plan, the prescription. The plan describes the objectives of the burn and the expected results. The burn plan specifies, either in words or by a map, the parcel of land to be burned, the landowner(s), and owners of adjacent land not included in the burn. Any considerations of smoke management will be identified. The burn plan specifies the required governmental permits, and lists those who must be notified on the day the burn is to take place. The locations and characteristics of all fire breaks are given, as well as strategies for containment of fire within the burn unit. Any preparations of the burn unit needed before the burn can take place should be indicated, including a list of fire sensitive elements within or near the burn unit that must be protected. The burn plan should state the personnel needed, as well as their qualifications and duties. The burn plan also lists the equipment needed to conduct the burn. Smoke management is another factor that must be clearly spelled out in the written burn plan. The expected progress of the burn should be stated, and a contingency plan identified for a burn not proceeding as expected. Requirements for containment of the site after the burn is completed (mop-up) should be listed. After the burn is completed, a written evaluation of the burn should be made and included as part of the final documentation for each prescribed burn. Approval of a prescribed burn Regulation of prescribed burns in Wisconsin depends upon the location of the burn. In the forested regions of the state, permission to carry out a daytime prescribed burn must be obtained from the Department of Forestry of the Wisconsin Department of Natural Resources. Exact requirements depend upon the part of the state and the time of year. In nonforested regions of the state, permission to carry out daytime prescribed burns is granted by the local municipality. In some of these locations, the local fire department may be involved. In all regions, the local fire department should be notified before the burn begins. Burn unit The burn prescription specifies the precise area to be burned. Before the burn can be carried out, adequate fire breaks must be created that completely surround the burn area. Roads and waterways often serve as breaks, but in many areas, fire breaks must be constructed. In grassy areas, fire breaks are generally wide mowed areas, usually broad enough for passage of a truck or all-terrain vehicle. In wooded areas, fire breaks are created by removing all litter in a wide zone down to the mineral soil. It should be emphasized that although they are called fire breaks, mowed strips are not safe lines across which the fire will not cross. What does provide safety is a wide burned area (called a “black line”) adjacent to and inside the fire break. Because the black area has already burned, there is no fuel available to carry a fire. The first step in conducting a prescribed burn is to create a black line around the burn unit. Deciding to burn. Weather and other conditions needed for the prescribed burn are monitored, and when conditions are suitable, and needed personnel are available, the burn is scheduled. The decision to perform the burn is made by the person who is to be in charge of the burn, the burn boss. Due to changing weather, the determination to burn can only be done one or two days before the burn. Sudden changes in weather or other factors may require that a scheduled burn be cancelled at the last minute. The critical weather elements are relative humidity, temperature, wind speed, and wind direction. |
| On the day of the burn. On the day of the burn, all personnel assemble at the site well in advance of the time of lighting. Burn crew members should have fire-resistant outer clothing, leather shoes, and leather gloves. An orientation meeting is conducted at which the details of the prescribed burn are reviewed by the burn boss. The weather is reviewed, and weather variables that might change (such as wind speed or direction) are identified. If necessary, crew members will familiarize themselves with the burn unit by walking the whole periphery. At this time, the burn boss will point out particular items that might need attention. The members of the two separate burn lines are identified at this time. Each burn line has a line boss, who supervises the fire on that particular line. Each line has at least one crew member responsible for lighting, and crew members with water. The line boss directs the crew members, and maintains communication with the burn boss. Usually the two burn teams start at a single point and move in opposite directions. Communication between crew members during the burn is vital. For most burns, two-way radios are essential. Before the burn begins, all radios should be tuned to the same channel and checked. |  |
| Equipment for prescribed burns: A reliable supply of water is essential, with proper equipment for spraying water on fires. The simplest equipment is the backpack sprayer with hand pump, which can be used to spray water directly on a fire. Rakes, shovels, and flappers can also be used to put out small fires. Even a foot can be used to stamp out a tiny fire, but for a fire of any significant size, water is essential. |  |
| High-pressure spraying equipment mounted on four-wheel drive pickup trucks or all-terrain vehicles is usually used when large areas are being burned. These spray units are equipped with high-pressure pumps, and have 100-300 feet of high-pressure hose. |  |
| Kinds of running fires Three kinds of running fires are recognized. The “head fire” is one that is running with the wind. Depending on the wind speed and other weather factors, the flames of a head fire can be a few feet to 20-30 feet high. A head fire is potentially dangerous and should only be allowed when it is running towards an area that has already been completely fire proofed. |  |
| The “backfire” is one that is running against the wind. Because the wind is tending to push the fire back, toward the area already burned, the backfire is a low-intensity fire, hugging the ground, and moving slowly toward the wind. Depending on the nature of the fuel, the backfire may burn to greater or lesser intensity. The “flanking” fire is one that is sideways with the wind. Depending on constancy of the wind direction, a flanking fire may burn slowly or more rapidly. |  |
| Conducting the burn. Before the burn is started, a weather check is made to determine wind speed and direction, temperature, and relative humidity. Assuming conditions are favorable, a small test fire is first done to determine how the fuel burns. Lighting is done with a drip torch. This is a hand-held device consisting of a fuel reservoir, a burner arm, and an igniter, and is used for dripping burning liquid fuel onto materials to be burned. Each fire line has at least one drip torch. The fire is always started at a good fire break on the downwind side of the burn unit, and allowed to burn as a backfire along the inner edge in order to create a substantial black line. Water is used to ensure that the backfire does not jump the break and burn outside the burn unit. Careful attention must be taken to ensure that the blackline along the downwind side of the burn unit is wide and thoroughly black. Crew members with water packs monitor the fire to ensure that it remains within the burn unit. A spot fire is a small fire that has become started downwind of the burn unit, usually from flying sparks or embers. It is important that at least one crew member with a water pack be stationed in the downwind zone where spotting might occur, to monitor and control spotting. |  |
| Completing the burn Once the downwind black line and corners have been secured, the burn lines move in opposite directions around the flanks of the burn unit. In some cases, interior lighting may also be necessary to ensure that the whole unit is burned or to widen out the blackline. Second drip torches are sent into the interior to light as directed by the line boss. It is important that wide blacklines are present on both the downwind side and the flanks of the unit, before the upwind side is lighted. Depending on wind speed, temperature, and humidity, the headfire may move at a rapid rate. The flame height of the headfire can often be quite high, but as soon as the fire reaches already blackened areas it will die out. Once the unit has been completely burned, it is time for mop-up. Before the burn unit can be left, it must be made safe. Burning material well within the unit can be left as long as the smoke is not too bad, but burning wood or brush along or near the control line must be extinguished. |  |
| Kinds of prescribed burns In restoration work, prescribed
burns are used for prairies, savannas, woodlands, and wetlands. Each type
of habitat must be handled differently. Prairie fires, generally in grass,
are the easiest types of burns to carry out, although they often burn with
great intensity. The fuel in savanna burns consists of mixtures of grass
and leaves. Savanna burns are more difficult to carry out than prairie burns
because of variable fuels, and because of downed timber that may check the
spread of flames. The fuel of woodland burns consists of leaves, sticks,
and timber. Woodland burns are not commonly done, although they can be very
useful in restoration work. Wetland burns are the most complicated to run
because of the problems of access. The fuel of wetland burns consists of
mixtures of grasses, sedges, cattails, and other herbaceous vegetation.
Although sedges and cattails can burn at great intensity, standing water
within the unit may result in a highly variable burn distribution. Caution Although the prescribed burn is one of the most useful tools in ecological restoration, it must be carried out by trained personnel, and based on a precisely written burn plan. Fire should not be used casually or without proper thought and direction. |
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