Prescribed fire is the most effective and efficient tool to manage and improve deer habitat in most areas. Fire can be used to improve food and cover in ways that other practices cannot, and fire is relatively inexpensive to apply at a large scale. More deer habitat managers are using fire today than ever before. However, if you have never used fire, getting started can be daunting. And for those who have started using fire, they typically have many questions, especially when and how often they should use fire.
There are many managers who have used fire for decades, especially in the South. However, many of them are not getting the results they would like, and they find themselves stuck in a rut implementing fire the same way they have for 30-plus years. Fortunately, more research on the effects of fire is being conducted today than ever before, and we have information that can help guide both novice and experienced burners to better achieve their deer habitat objectives.
Fire Effects On Deer Habitat
Practices to improve deer habitat modify either food or cover resources, and fire can have strong effects on both. When managing for increased food resources, we often focus on providing better nutrition to deer during the growing season when does are lactating and bucks are growing antlers. Spring and summer is the time when deer are growing, and it is the time when maximum amounts of high-quality forage are needed to grow larger deer. Acorns and corn available in fall and winter cannot do that. Forages with greater concentrations of crude protein and phosphorus are required in spring and summer, and forbs (broadleaf, herbaceous plants) provide the greatest nutrition overall to deer. Thus, we use fire to shift plant composition toward more forbs and fewer grasses, woody plants, and vines to improve nutrition.
Fire also can make some plants more nutritious to deer by causing them to resprout. Younger leaves from a particular species are more digestible and nutritious to deer than older leaves, and we can promote young, resprouting leaves with fire. For example, stump sprouts of red maple or winged elm that have been top-killed by fire are highly nutritious and strongly selected by deer. These sprouts have elevated levels of several important minerals, which led Drs. Bronson Strickland and Marcus Lashley to call them “mineral stumps.” Similar effects are seen with shrubs, vines, and brambles (such as blackberry) after they are top killed. It’s important to remember that the effects of fire on resprouting plants is fairly short-lived, but we’ll circle back to that later.
Managers also use fire to influence vegetation structure, which includes the height and density of vegetation. We typically focus on managing structure from the ground up to approximately 6 feet tall for deer. Deer select areas with more dense vegetation for loafing and bedding, as this cover helps them avoid predators – including hunters! It is desirable to have well-dispersed cover approximately 4- to 6-feet tall, which makes deer feel more secure and promote more daylight activity. Several years ago, we began recommending creation of areas with denser cover over approximately 2 to 15 acres to serve as “bedding blocks” where deer would spend much of the day as a strategy to hold more deer on your property and better predict their location during the hunting season. Prescribed fire is the primary tool we use to manipulate woody stem density and visibility in these bedding blocks, but the frequency of fire in these areas is much less than in areas where we are promoting forbs for nutritious forage.
Prescribed Fire Planning
Most managers who use prescribed fire understand the importance of having a burn plan that outlines appropriate conditions to meet objectives while minimizing smoke impacts and fire-escape risk. A burn plan for an individual fire is important, but having a property management plan that includes a comprehensive strategy for fire across the property over time is equally important. Comprehensive fire plans should delineate burn units based on existing firebreaks or those to be constructed, as well as whether a particular unit is meant primarily to provide food or cover. Desired conditions within each unit then guide how often and when you might burn a particular unit to promote resources for deer.
Creating a comprehensive fire plan solves several important issues.
- First, it helps ensure food and cover are distributed across your property rather than being limited to a single area within a given year because you burned too much (or too little) on a section of your property.
- Second, a fire plan allows for accurate prescriptions that promote diverse conditions as opposed to a simpler prescription, such as burning a third of your property every year or burning one particular field or pine stand every year.
- Finally, fire planning allows you to begin considering the fire regime rather than individual burn treatments. Fire shouldn’t be considered an event, but rather a practice that needs to be applied on a rotation across a property with an understanding that multiple fire events on a given unit often are necessary to greatly change the vegetation.
Prescribed Fire Frequency
“On the vast majority of properties managed for deer that we have visited, fire is not used as frequently as needed to meet management objectives.”
Several factors influence the effects of fire on deer habitat, including frequency, intensity, timing, sunlight entering a given stand, and scale. It can be difficult to disentangle the effects of these factors as they interact and are related. Frequency often is considered to have the strongest effect on vegetation response, and it should be the primary factor considered when establishing a fire management plan for a property. Fire frequency refers to how often a particular area is burned and is referred to as a fire-return interval. For example, an area burned every year has a 1-year fire-return interval, whereas an area burned every four years has a 4-year fire-return interval. Common fire-return interval prescriptions for deer habitat management in the eastern United States range from 1 to 6 years.
- Shorter return intervals, especially 1- and 2-year, tend to promote herbaceous plants, such as forbs and grasses.
- Longer return intervals promote more understory trees, vines, and shrubs in areas with sufficient annual rainfall to support these plants.
The effect of return interval varies with location, as return intervals can be lengthened in areas with shorter growing seasons, reduced precipitation, or on sites with low-productivity soils where succession is naturally slower than in areas with more productive soils. That said, on the vast majority of properties managed for deer that we have visited, fire is not used as frequently as needed to meet management objectives. Generic, outdated prescriptions to “burn every 3–5 years for deer habitat” are pervasive, but more-frequent fire is needed to maximize availability of high-quality forage.
Prescribed Fire Timing
The timing (or seasonality) of prescribed fire considers the time of year that an area is burned. Historically and even today, the vast majority of managers apply fire during the dormant season, which generally is regarded as winter, prior to spring green-up. This timing is understandable as winter is the easiest time to burn when there are relatively dry conditions, blue skies, a light steady wind, and no leaves on the trees to cast shade and dampen fire intensity. With new information, many managers now are beginning to use fire during the growing season, but there are important differences in fire timing during the growing season.
We typically break the growing season into three distinct periods: early, mid-, and late growing season. The early growing season is relatively soon after leaf-out, and this period is when most managers conduct growing-season burns. The mid-growing season generally includes late spring through mid-summer, and the late-growing season includes late summer into fall prior to frost.
Burns conducted during winter often are relatively complete, meaning there aren’t many areas within a burn unit where fire did not spread. Measures of fire intensity, including maximum temperature of the fire and flame lengths, often are greatest in the dormant season compared to burns conducted using similar firing techniques at other times of the year.
Dormant-season fire can increase forb coverage, but it is less effective at decreasing coverage of understory trees, vines, brambles, and shrubs than fire during portions of the growing season because the vast majority of those plants resprout following fire at this time of year. Dormant-season fire can be very effective at top-killing woody plants, however, so it is a great time to burn if you need to set-back a woody thicket and maintain dense resprouting vegetation for loafing or bedding. Woody plants resprouting after dormant-season fire provide high-quality forage, but the nutritional pulse they provide is earlier in the spring than peak nutritional demands. Finally, there generally is less visibility and taller cover for deer present the fall following a dormant-season burn compared to growing-season fire because the vegetation has a full growing season to recover.
There has been increased interest in growing-season fire recently because burning during the growing season increases the number of available burn days, and the effect on the plant community differs from dormant-season burning. With equal conditions, growing-season fire is less intense and complete than dormant-season fire because shade of trees and green fuels dampen fire intensity. Early growing-season burns generally are more intense than mid- or late growing-season burns because leaves may not have fully developed. Grass and pine litter can be burned effectively on many days throughout the growing-season, but hardwood stands are difficult to burn in the growing season unless the canopy has been thinned to allow at least 30 to 50% sunlight, and even then relatively dry conditions with a steady wind of about 2 to 8 mph often are needed for a complete burn and to achieve intensity hot enough to top-kill small-diameter woody stems.
In general, burning during any portion of the growing season is more effective at decreasing coverage of woody vegetation compared to burning during the dormant season. However, fire intensity and coverage must be sufficient to top kill woody plants, which can be more difficult to achieve, especially during the mid-growing season. Grass coverage may decrease following mid- and late-growing season burns, and forb coverage increases most following late-growing season fire. Prescribed fire during the early and mid-growing seasons provide a nutritional pulse during the summer from resprouting woody plants, and deer are attracted to burned units for approximately 2 months after the fire. Prescribed fire during the growing season results in more open conditions with greater visibility in the fall because the vegetation consumed or top-killed by the fire has not had time to regrow to the height it would if dormant-season fire had been used.
Specific Prescriptions
We recommend using prescribed fire at different times of the year within a given management unit that contains multiple stands or fields, especially when a unit is being managed to increase forage availability. In general, we recommend using frequent fire (every 1 to 2 years) where increased nutrition is desired, and we use fire through the year in different stands and fields to promote a continual nutritional pulse of high-quality forage from forbs and fresh woody resprouts. We then designate other units for loafing and bedding cover that we burn less frequently (typically 4 to 5 years). We typically burn these areas during the dormant season when it is relatively easy to get fire intensity hot enough to kill woody stems 1 to 3 inches in diameter. This approach, of course, will vary depending on location and limiting resources for deer, but it is a good starting point. In all cases, there are benefits to incorporating fire throughout the year and with different frequencies to provide greater diversity in vegetation composition and structure.
It’s worth noting that prescribed fire shouldn’t be expected to replace other habitat management tools. We usually don’t recommend using fire to reduce overstory canopy coverage, as either commercial timber harvest or noncommercial Forest Stand Improvement can achieve this objective faster and with selectivity to retain oaks and other mast producers important to deer and other species. Similarly, if an area has either dense grass or thick woody stems that you wish to reduce, fire should be paired with other tools, such as an herbicide application or mechanical disturbance, to achieve desired results.
Using Fire to Improve Hunting
Prescribed fire can be used creatively to help improve the predictability of deer movement on your property. As discussed, deer are readily attracted to the young forage that is produced soon after a growing-season fire. Thus, burning an area in July to August where you plan to bowhunt in September can be an effective strategy to attract deer. However, be aware that if in the woods, sufficient sunlight is necessary to stimulate germinating or resprouting plants, so some canopy reduction by killing some undesirable trees is usually necessary.
Conversely, there may be areas around main access trails where you would rather avoid spooking deer during the hunting season. Several outdoor personalities have recommended the creation of “dead zones” by limiting habitat improvements to avoid attracting deer around access trails or downwind of stand locations. Instead of creating unproductive acreage, consider burning these areas frequently (perhaps annually) during the late-growing season. Vegetation regrowth will be limited before the hunting season to limit cover that would hold deer, but these areas will provide high-quality forage during summer. Don’t hesitate to experiment with fire prescriptions and see how deer respond!
Promoting Diverse Conditions
One approach to promote habitat diversity is a slight change in how the primary “fire season” is viewed. A benefit to using fire throughout the year is the increased number of burn days. As mentioned previously, most properties are not burning enough acreage or often enough! Burning during nontraditional windows allows managers to increase fire implementation to better improve conditions for deer, and a creative approach can maximize those benefits. And if you are relatively new to using prescribed fire, burning during the growing season provides the least risk because of the relatively moist fuels.
Rather than starting to plan for burning right after the deer season ends, consider starting your annual burn program during the late growing season. Take advantage of available burn days during the fall, but it isn’t necessary (or desirable) to burn everything during this time. If you don’t quite get all of the units burned in the fall that you would like, simply burn them during the dormant season.
Fuels are most flammable during the dormant season, and on many properties most fire will be applied during this period. There’s nothing wrong with trying to get most burning done in the winter, but reserving some units for fire during the early- and mid-growing season can help provide fresh, resprouting vegetation to meet lactation and antler growth demands. After conducting those burns, it’s time to start planning for the next round of late-growing season fire. Always keep firebreaks maintained so you are ready to burn at any time. Every day is a potential burn day!
There are plenty of different approaches to plan for fire, but this strategy allows for flexibility with the exact season while maintaining an appropriate frequency. We don’t recommend “saving” a unit for fire during a particular season if that results in a decreased fire frequency, as it’s generally much more desirable to get the area burned outside of the season you assigned than to let the frequency decrease. Woody thickets develop quickly, especially if you don’t burn an area for a couple of years just because you wanted to use a mid-growing season fire in that unit.
Conclusion
Fire is a flexible tool that managers should use throughout the year to promote diverse food and cover conditions for deer. Instead of getting stuck in a rut with a single, generic burn prescription, consider burning at different times and frequencies across your property to better meet your deer management objectives.