What weather conditions are important to consider when planning and conducting a prescribed fire?
The primary weather conditions to consider when planning and conducting a prescribed fire are relative humidity, wind speed and direction, temperature, and mixing height. Most prescribed fires are conducted with relative humidity between 30–50%. Burning with relative humidity below 25% can be tricky as spotfires are likely and suppression becomes challenging. Burning with relative humidity above 50% is often ineffective because of high fine fuel moisture content. Forecast wind speed is for winds 20 feet above surrounding obstructions. The actual wind speed at ground level is usually less. Wind speeds of 2-15 miles per hour are common for most prescriptions. Winds greater than 15 miles per hour can create containment challenges in the event of an escape or spotfire. Mixing height is the distance aboveground where smoke is mixed with the atmosphere. The mixing height and transport wind speeds at that elevation influence smoke dispersal. A mixing height of at least 1,700 feet is recommended for most prescriptions.
Will fire kill my hardwoods?
This is a common question regarding burning in hardwood forests in the eastern U.S. The short answer is yes, fire can kill hardwoods, but fire can also kill pine trees or any other type of tree. The key to hardwood tree mortality is fire intensity and duration. Low-intensity fire with flame lengths of 6-12 inches typically will not harm upland hardwood species unless woody debris has accumulated at the base of the tree. Use a conservative prescription, on the first burn in particular, to limit fire intensity and duration. Before burning your forest or woodland for the first time, walk through the area you intend to burn and remove any slash or accumulated woody debris from around the trunks of high-value trees, whether for wildlife or timber. Accumulated woody debris, when ignited, may retain heat long enough to damage the cambium (inner bark layer) and injure or stress the tree. Unless there has been a recent windstorm, ice storm, or other such event, most trees will be clear of debris and clearing can be done fairly quickly.
How often should I burn my fields?
When managing fields or openings for wildlife that use herbaceous openings, burn frequently enough to prevent plant succession and not allow woody species to dominate the area. This may be every 1-3 years. However, many wildlife species use woody or brushy cover. When managing for these species, the fire-return interval will be longer to maintain desirable woody plant composition and structure. Burning every 4-7 years in the eastern US with low to moderate fire intensity will usually maintain a woodland mosaic with scattered trees, shrubs, brambles, and a herbaceous understory. These intervals are recommended if annual precipitation is greater than 30 inches. In more arid regions, the interval will be longer. For more general information, see “How often should I conduct a prescribed fire?”
What is the best fuel mixture to use in my drip torch?
Gasoline, diesel, and kerosene are the fuels most often used in drip torches. Recommended mixture ratios depend on personal preference and ambient temperatures. A common mixture is 60% diesel or kerosene and 40% gasoline when temperatures exceed 75ºF. When temperatures are below 75ºF, a 50:50 ratio may be used. Exceeding 50% gasoline is not recommended because of increased volatility. Greater diesel/kerosene mixtures may be useful under high fuel moisture conditions.
Can prescribed fire be used to manage Japangrass/stiltgrass/Japanese stiltgrass?
Japangrass (Microstegium vimineum) is a nonnative, invasive annual grass that is capable of overtaking forest understories in eastern U.S. forests. Fire is one tool that can be used to manage Japangrass. Fire prescriptions to control Japangrass include burning in early spring just after Japangrass germinates, but before overstory trees have leafed out, or burning during August and September before Japangrass has seeded. Burning during mid-summer is difficult because of high litter moisture as a result of overstory forest shading. Japangrass can also be managed using a variety of herbicides, including grass-selective herbicides at relatively low application rates.
Is successful completion of a course or class required before conducting a prescribed fire?
Generally speaking as it relates to state laws and regulations for private individuals, there are no courses or classes that are required before conducting a prescribed fire. However, classroom instruction as well as on-the-ground experience is recommended before organizing and conducting your first prescribed burn. Contact your county Extension agent, state prescribed burn association, or state forestry department for information about prescribed fire classes and training.
Why do you want the wind blowing when you conduct a prescribed burn?
On days winds are light they are also variable in direction. This creates a situation where fire and smoke are going in multiple and unpredictable directions. A steady wind direction allows the ability to predict the direction of fire and smoke. A wind of at least 4 miles per hour out of a constant direction is the best for safety, smoke dissipation, and fire crew efficiency.
Where can I get help developing a prescribed fire plan?
There are numerous private organizations as well as state and federal agencies that may be willing to assist landowners with writing prescribed fire plans. For example, check with the local county Cooperative Extension office, state forestry department, state wildlife or conservation department, the regional Natural Resource Conservation Service office, or a local, state or national conservation group. There are also many well qualified private consultants that can provide custom made prescribed fire plans to fit any situation. Check with your state prescribed fire council for additional guidance (Coalition of Prescribed Fire Councils).
Does fire occur in wetlands?
Yes, many wetlands do periodically burn, both from wildfire and prescribed fire. Many wetlands are only seasonally wet, so they are susceptible to fire during the dry period. Fire can be used to alter the structure of vegetation in a wetland to meet certain management objectives. A specific example includes burning cattail mashes in the Northern Great Plains to benefit waterfowl. Also, periodic wildfire in the Everglades is important to remove accumulated peat from wetlands which allow for greater water depth during wet periods. These deep water areas are important for certain wildlife species such as the American alligator.