How to Conduct a Prescribed Burn
Burning, grazing, and rest are generally the most powerful tools for managing local wildlife habitats. Yes, usually more powerful than planting, feeding, and tillage. It may seem simple to light a match, stock some cattle, or erect a fence, but accomplishing specific habitat management goals with these tools requires considerable study and management. Each has the potential to harm or benefit wildlife habitat. Appropriate results depend upon the proper application of these tools. This article addresses only some basics of prescribed burning.
Study should be the first step in using prescribed fire. A person considering prescribed fire should learn about fire behavior, fire and smoke management, burning laws, plant responses, animal needs, and animal responses. People who use fire should continually strive to learn about it there is much to learn. No one should attempt to conduct a prescribed burn until he or she has intensively studied burning and gained burning experience by assisting educated and experienced burn managers.
Qualified burn managers include some ranchers, farmers, forestry or wildlife agency personnel, state agricultural extension personnel, Nature Conservancy and Ducks Unlimited land management personnel, Natural Resource Conservation Service (NRCS) personnel, and Noble Foundation wildlife or forage specialists. This list omits some sources of qualified burn managers. With a little initiative, anyone should be able to gain adequate experience because there are multiple opportunities.
Establish goals and a plan for each burn. Goals and site characteristics should dictate the prescription for a burn. Plan every aspect of a burn well in advance to develop an adequate fuel load (usually grass or tree leaves), prepare fireguards, gather and repair equipment, organize labor, and obtain permits. Since future weather is uncertain, an individual burn and its associated equipment and labor should be scheduled for about three dates. Equipment and labor needs for prescribed burning are further discussed in a February 1995 Ag News and Views article.
The overriding theme in prescribed burning should be safety and control. Do not conduct a burn when either is questionable. Fireguards are important to help control a fire. There are many types of fireguards including streams, water impoundments, bluffs, thin plant communities, cool season grasses, bare soils (usually bladed or tilled), roads, burned areas, and mowed vegetation that is wetted. A burn manager should be familiar with various fireguards and their limits. Most fireguards should provide uninterrupted access around the burn perimeter for firefighting equipment. Where possible, avoid acute angles, or those less than 90 degrees, along fireguards. Some fireguards, such as green fireguards, require management several months or years before a burn. Green fireguards are discussed in a July 1996 Ag News and Views article.
Move heavy fuels such as logs, snags, and brush piles away from a fireguard on the burn side. Move them well inside or outside the burn area because they burn for extended periods, emitting sparks that create wildfire hazards. Juniper trees adjacent to narrow fireguards in backfired areas should be removed because they throw many embers when burning. When blading or mowing fireguards, move the fuel to the side of the fireguard away from the burn. Windrows of vegetation on the burn side of a fireguard create wildfire hazards because they tend to burn for extended periods. Fuel near a fireguard should burn completely and cease burning relatively quickly, allowing a burn crew to proceed with a burn.
Gather adequate weather information the day before and the day of a burn. Fuel will not burn when wet and often will not burn adequately when relative humidity is too high. Fire control becomes difficult when relative humidity is too low; i.e., below 25 percent. Do not conduct a burn when wind is forecast to change direction. Most burn prescriptions require 5- to 15-mile-per-hour winds from a consistent direction. Absence of wind makes fire unpredictable. Light and variable winds create poor burning conditions. Winds above 20 miles per hour make fire control difficult. However, some management goals necessitate burns during weather that makes fire control more difficult. For example, burn prescriptions for controlling relatively mature woody plants often require low relative humidities, high temperatures, and substantial winds. Such reclamation burns are relatively dangerous and only very skilled burn managers should undertake them.
Local fire departments, neighbors, and, depending on property location, some state agencies should be notified the day of a burn. In certain locations, state agencies must approve a burn plan before the day of a burn. In eastern Oklahoma, notify Oklahoma Forestry Services before a burn. In Texas, notify the Texas Natural Resources Conservation Commission. Tell fire departments and state agencies the name of the fire boss, the person in charge of a burn, who will request assistance should a problem develop. The fire boss decides when and how a burn is conducted.
Consider the impact of smoke on surrounding areas. Do not burn an area if smoke will envelop a highway, airport, hospital, nursing home, school in session, or residential area. Generally, burns should be conducted only during the day because nighttime temperature inversions frequently hold and spread smoke along the ground. Visibility is usually near zero in smoke, creating a severe traffic hazard. Smoke can kill people with respiratory problems when they cannot quickly escape it.
Conducting a burn is frequently simpler than planning and preparing for it. A typical burn begins with lighting a backfire along the downwind perimeter of a burn. A backfire moves slowly and with relatively low flames because it burns into the wind. When the backfired portion of the burn is safe, flank fires are generally lit beginning at the backfire along burn perimeters parallel with the wind. Flank fires have moderate flame heights and speed because they move perpendicular to the wind. When the back and flank portions of the fire are safe, a head fire is typically lit to quickly consume the remaining fuel. A head fire moves relatively fast with longer flames because it burns with the wind. Usually, fires that burn uphill act as head fires and those that burn downhill act as backfires, regardless of wind direction.
The burn manager and most, if not all, of the crew should stay with a burn until it is completely safe. The crew should patrol the perimeter to monitor adjacent areas for signs of wildfire and move or extinguish burning fuels near the perimeter, paying particular attention to burning dung, wood rat middens, logs, snags, and trees. Burning trees and snags can send sparks long distances with the wind, up to 100 yards. Monitor the burn area for at least one day after the last smoke is visible, because sometimes a hidden ember can reignite fuel near the perimeter.
Management is not always finished after a burn is extinguished. Subsequent grazing distribution, stocking rate, graze periods, and rest periods should be managed to obtain desired plant responses. When burned areas are managed improperly, livestock often concentrate on and overgraze them because the forage regrowth is more palatable than forage in unburned areas.
Additional bits of information about prescribed burning are available in February 1984, February 1986, March 1989, December 1990, May 1996, December 1996, and May 1998 Ag News and Views articles as well as in How Much Does It Cost to Burn? (Stevens et al., Ardmore, Okla.: The Samuel Roberts Noble Foundation, NF-FOR-99-01).