Prescribed burns taking place at the ArboretumMONDAY, MARCH 3, 2008
Each spring and fall the Arboretum conducts “prescribed burns,” controlled fires conducted when a set of conditions fall within specified criteria, making conditions optimal for a safe and effective burn.
The following frequently asked questions and answers clarify our use of fire as a land managemet tool.
Q: What is a prescribed burn?
A: A prescribed burn is a controlled fire that is conducted only when a set of land management and safety standards can be met. These standards (or prescriptions) describe: 1) the land management goals that will be achieved by burning, 2) the time of year the burn will be conducted, 3) the personnel and equipment needed, and 4) a set of weather conditions that will ensure the safety of the fire crew and any nearby people and properties.
Each year the Arboretum Ecologist determines which areas will be burned according to research needs and various land care goals. The Arboretum Land Care Manager writes prescriptions for these various units and the Arboretum Field Staff follows these guidelines as they burn the Arboretum’s fire-tolerant or fire-dependent prairies, savannas, oak woodlands and wetlands.
Each year, the Arboretum applies for, and receives, a “permit to burn” from the City of Madison Fire Department.
Q: Why does the Arboretum conduct prescribed burns?
A: The Arboretum relies on fire as one of its primary management tools for restoring and maintaining some of its plant and animal communities.
In fact, staff at the Arboretum did pioneering research work in the late 1940s that found fire was essential to the restoration of tallgrass prairies.
Fire is a necessary disturbance in prairies and other fire-dependent communities because it removes plant litter, changes the soil chemistry, helps control woody plants in prairies, and favors native species over invasive exotic plants.
Today’s prescribed fires are a substitute for human-set or lightning-set fire that occurred prior to the settlement of Wisconsin by Europeans, some 150 years ago.
Q: What factors does the Arboretum Field Staff consider when deciding whether or not to burn?
A: They look at the fuel moisture conditions, because when the fuel moisture is too high, the grass and other fuels will not burn efficiently, and when it is too low, the fuels become very flammable and the intensity of the fire increases.
They also closely monitor the weather conditions. They look at wind direction to determine which sites can be safely burned. For example, they must wait for a day with a south or west wind—one that carries smoke away the Beltline—in order to burn Curtis Prairie. In addition, they check wind speed, relative humidity and ambient air temperature. Once they have made a decision to burn, the staff notifies the local fire departments.
Q: What type of equipment does the Arboretum use to control its prescribed burns?
A: The Arboretum has three heavy-duty 4WD pickup trucks that are equipped with water tanks, pumpers, and 100-foot, high-pressure hoses. We also have an ATV that is equipped with a foam spray unit that we use to smother smoldering woody material and to create firebreaks.
Some members of the Field Staff are equipped with Indian Pump backpack sprayers, which they can use to spray water on a fire. We also have fire rakes and flappers. The fire crew uses two-way radios to communicate with one another, the Arboretum office, and the Dane County 911 dispatch office. The crew also wears Nomex fire-retardant clothing for their protection.
Q: How does the Arboretum start, control and stop a fire?
A: Burning within the prescription and burn plan assures us that the fire can be controlled. We start and stop fires at established fire breaks—fire lanes, bodies of water, pavement, grassed lawns. We use water to extinguish the flames at the fire breaks.
In the area selected for the prescribed burn, a back fire is started facing the wind using a drip torch. Once the back fire is moving, we set side fires which burn roughly perpendicular to the wind.
A head fire is ignited after the other fire lines have burned in toward the center of the burn area. It burns with the wind – making it faster-burning and potentially more dangerous.
The idea is to burn around the edges of an area so that the flames will travel toward the middle. When the walls of flame meet, the fire is over.
As a general rule, this is how the typical prescribed fire is conducted, but each fire is different and there are endless variations on the theme. For example, sometimes no head fire is set, and the entire burn is conducted with a back burn. This provides for slower-moving flames that do a better job of killing woody plants.
Q: What time of year does the Arboretum conduct its prescribed burns?
A: The Arboretum does its prescribed burning in either spring or fall, although most burns are in the spring. The spring burn season runs from late March through April into early May. The fall burn season is in October and November, at a time when most plants have gone dormant.
Q: What time of day does the Field Staff start the prescribed burns?
A: Most burns are started in mid-morning because it typically takes that long for the humidity levels to fall into the range defined by the prescription.
Q: How long does a prescribed burn last?
A: Prescribed burns vary in length depending on the size of the unit being burned, the nature of the material being burned, and whether any backburning is required to protect research plots or other designated areas within the burn unit. Prairie burns at the Arboretum commonly last about one hour, while burns in savannas and oak woodlands last longer because of the extra time it takes to make sure that all smoldering woody material is out.
Q: Can I watch a prescribed burn at the Arboretum?
A: Yes, if you keep a safe distance of 50 to 100 yards from the burn perimeter and do not distract or interfere with the burn crew.
Q: Do you ever notify the public about an impending prescribed burn?
A: No, there generally isn’t time. Once we make the decision to burn, we only have an hour or so to complete all the preparations necessary before we light the fire. If you are really interested in seeing a prescribed burn, you should come out to the Arboretum on those spring or fall days when you think conditions are good for a burn.
Q: Does the Arboretum use volunteers on their prescribed burns?
A: No. The Arboretum has its own trained staff to conduct the prescribed burns. The use of fire, even in controlled situations, is dangerous work that requires training and experience in order to ensure the safety of the crew and the environment. All members of our burn crew have received extensive training, including the federal wildland fire management training course.
Q: How can I learn more about prescribed burns?
A: A good source of information is the booklet, “How to Manage Small Prairie Fires” by Wayne Pauly, naturalist with the Dane County Parks Department. It is for sale in the Arboretum Bookstore.