Introduction to Physical Control – Prescribed Burning
Prescribed burning is a practice where fire is intentionally applied to a site under specific conditions to accomplish specific restoration objectives. Control of woody invasive species may be one of the objectives of a prescribed fire program. Prescribed burning impacts all fire-susceptible species within the burn area and therefore is generally only practiced in the management of fire-adapted ecosystems such as prairies, grasslands, savannas and barrens, and certain forest types.
Prescribed burning is often effective at controlling invasive woody species seedlings, though it can also trigger germination of invasive plant seeds in the soil. Depending on fire intensity and species susceptibility, prescribed fire may also kill or girdle the above ground portions of mature invasive woody plants. However, it will not kill root systems and regrowth should be expected. Frequent repeated application of prescribed fire can be used to suppress woody invasive species, especially in ecosystems that are suited to frequent fire. While a single instance of prescribed burning does not provide long-term control, it can be effective for improving access to dense infestations for follow-up treatment.
How it works
Fire is ignited and managed according to a burn plan for the site and corresponding burn permits. Once ignited, fire spreads over the intended burn area, consuming dry fuel. This may include the above-ground growth of woody invasive plants.
Methodology in Detail
A prescribed burn should always be conducted according to a burn plan. The contents and requirements of burn plans vary, but they generally include a detailed site description, objectives of burning, environmental and weather conditions that must be in place to meet the objectives, personnel and equipment needs, safety considerations, smoke management plans, and emergency plans. States and provinces generally require special training and certification for managers developing burn plans and implementing prescribed fires. Additionally, state, provincial and/or local permits are often required to implement a prescribed burn.
Woody species vary considerably in their tolerance of fire. On the extreme end of the spectrum, certain woody species depend on fire to complete their life cycles. For example, pitch pine and jack pine, both native to parts of the Great Lakes basin, produce cones that are tightly bound shut with sap (pitch). Exposure to very high temperature is necessary to open these cones and release seed. Unsurprisingly, these fire dependent species tend to occur in dry ecosystems where fires would be frequent if not suppressed by humans. Examples of these ecosystems include savannas, barrens, and xeric (dry) upland forests.
While none of the woody invasive species considered by WIGL are fire dependent, many of them exhibit adaptations that allow them to survive fire. Most woody invasive species, particularly shrubs, will be able to regrow from the root system following a prescribed burn. In certain species, damage to the main stem of mature plants triggers an especially aggressive root response where plants regrow both from the damaged stem and from the entire root system. Black locust is an example of a woody invasive species that often invades fire-dependent ecosystems and responds to prescribed fire by suckering from the roots and with increased seedling germination (Stone 2009). Similarly, stem densities of Oriental bittersweet can increase dramatically following prescribed burning due to vegetative regrowth (Pavlovic et al. 2012). Thick barked species, such as mature Amur cork tree, may also be exceptionally resistant to fire damage.
Extreme caution must be used if mature vines are growing into the canopy of trees on a proposed burn site. These vines such as Oriental bittersweet, Japanese honeysuckle and wintercreeper can act as ladder fuels, carrying fire into the tree canopy, potentially leading to a dangerous canopy fire (Fryer 2011).
Prescribed fire is usually practiced on both ends of the growing season in the Midwest. In the Great Lakes Region, this is typically mid-March through mid-April and mid-October through mid-November. Richburg et al. (2004) noted that prescribed fire is likely to have the most impact on woody invasive species when conducted during the growing season, after leaf out when root resources are diminished. However, the use of prescribed fire should be timed based on comprehensive goals for the site and consideration of potential impacts on desirable vegetation and wildlife. Similarly, the fire return interval required to prevent woody invasive species maturation may not be the same as the return interval required to meet other site goals. In these cases, additional management techniques for control of woody invasives should be considered.
Any invasive species treatment needs to be monitored in the years following treatment. Regrowth should be anticipated following top-killing of mature invasive woody plants by fire. Managers should also monitor seedbank response.
Jurisdictional and regional prescribed fire councils and consortia offer a wealth of information about land management using prescribed burning.
Regional Groups: Lake States Fire Science Consortium
Tallgrass Prairie and Oak Savanna Fire Science Consortium
- Brooks, M and M Lusk. 2008. Fire management and invasive plants: a handbook. U.S. Fish and Wildlife Service, Arlington, VA.
- Fryer, JL. 2011. Celastrus orbiculatus. In: Fire Effects Information System. U.S. Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.
- Pavlovic, NB, Leicht-Young, SA, Grundel, R, Weyenburg, SA and N Mulconrey. 2012. To burn or not to burn Oriental bittersweet: a fire manager’s conundrum. Joint Fire Science Program Research Project Report 9.
- Rice, PM. 2005. Fire as a tool for controlling non-native invasive plants. University of Montana, Bozeman, MT.
- Richburg, JA, Patterson III, WA, and M Ohman. 2004. Fire management options for controlling woody invasive plants in the Northeastern and Mid-Atlantic U.S. Joint Fire Science Program Report, Project 00-1-2-06.
- Stone, KR. 2009. Robinia pseudoacacia. In: Fire Effects Information System. U.S. Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.
- U.S. Fish and Wildlife Service. 2009. Prescribed burning in practice. In: Managing Invasive Plants – Concepts, Principles, and Practices.
Photo Credit: Chris Hoving via flickr.com