Prescribed burning for hardwoods
by
Michael Foster
Within the past couple of months I have released a couple of articles concerning wildlife management and improving the quality of a timber stand. In continuation with that theme this week’s article will focus on the use of prescribed fire for hardwood forests. Whether ignited through natural forces or human induced, the historical use of fire in hardwood forests—especially oak/hickory dominated forests and hardwood savannahs—is well documented. Research has shown that fire occurred in hardwood stands every 2-24 years with the average fire occurring on a 4-6 year rotation. While burns occurred during all seasons, the majority of hardwood fires occurred in the dormant season: these fires were most often lit by Native Americans and early European settlers to take advantage of the benefits provided by periodic fires.
The benefits provided by prescribed fire in a hardwood forest are basically the same as those you would see in a pine dominated forest: increased vegetative diversity, structural diversity, reduced fuel loads, and nutrient recycling. The use of fire has a significant impact on succession of plant and animal communities. Fire sets back succession: with this comes greater diversity and increased quality in wildlife habitat. By burning different sections of a property in and alternating pattern, multiple successional stages can be created and diversity can be maximized. To realize the benefits of burning in hardwood forests while minimizes damage to valuable timber the timing and intensity of fires have to be at the forefront of a manager’s mind.
Most timber managers and landowners are leery about using fire in hardwoods due to the potential to reduce timber value. While it is true that hardwood species are not as resilient to fire as most pines, it is important to remember that any tree can be damaged or killed due to fire; it all depends on the timing and intensity of the fire. To minimize damage to hardwoods it is important to burn with low intensity fires that have flame lengths of 6-18 inches. This is best achieved by burning during the mid to late winter on cool days with low to moderately low humidity—between 30 and 55%. It is also critical to remove any large debris away from the bases of high quality trees; smoldering logs at the base of trees effectively cook the cambium layer just below the surface of the bark, opening the tree up to insect and disease invasion.
Protecting valuable timber when using prescribed burning is crucial to preserving the quality of the wood it can produce. However, depending on the objectives of the property some trees may need to die. Using a moderate to high intensity fire can have a similar effect as timber stand improvements using hack-and-squirt; however, it is far less selective in relation to trees that are killed. Therefore, only utilize fire in this situation if timber production is not a primary objective for that particular property.
It is important to realize that fire without thinning will not produce the results that a property manager may be looking for. If sunlight cannot reach the forest floor the vegetative diversity that can be created utilizing fire will not be realized. Only in reducing the amount of canopy closure will stimulation of understory growth occur, thereby increasing browse species and soft mast production. It is also important to note that the diversity of vegetative species created by thinning a hardwood forest can only be maintained through periodic disturbance. Prescribed burning, when used correctly, is a great way to create this disturbance with minimal labor and financial cost. However, it is critical to take into consideration the primary objective of the property and protect valuable hardwoods when needed.