Prescribed fire: Not just for pine forests

Prescribed fire is one of the best tools when it comes to managing properties for wild turkeys. Thousands of public and private land managers employ fire annually to improve habitat. Fire can help promote new growth of herbaceous plants. It can also be used to kill undesirable saplings or other unwanted vegetation.

Unfortunately, many land managers limit fire to fields and pine forests. They avoid burning in hardwood forests for fear of damaging trees, but fire can be safely used to improve upland hardwood stands for turkeys and other wildlife species.

Hardwood stands are valued for acorn production, even though acorns are only available for a few months of the year. Protecting those hard mast trees is a priority, so managers worry about fire. Surprisingly, though, many oaks in the eastern and midwestern United States are “fire-adapted” species, meaning they can tolerate low-intensity prescribed fire. In fact, keeping fire from these hardwood stands can reduce oak regeneration in these regions.

The seedlings of many oak species develop their root systems before they begin growing vertically. Species such as white oak and southern red oak are adapted to grow their root system first and may be outcompeted without fire by species such as red maple and sweetgum. When it comes to more mature trees, upland species such as white oak, post oak and southern red oak all produce leaves that burn readily, and their trunks have relatively thick bark that can tolerate fire.

Fire alone cannot increase coverage of herbaceous plants that turkeys use for forage and cover. Hardwood stands should have at least 30% sunlight reaching the ground to increase forb and grass coverage. This means managers may need to thin some trees before burning. Removing trees, especially non-mast-bearing varieties, reduces competition for the remaining oaks and lets growth-producing sunlight bathe the forest floor. Commercial timber harvest or applying noncommercial forest stand improvements using a chainsaw or a hatchet and some herbicide (in a hack/squirt application) can get that job done.

There are a few other nuances to consider before you apply the drip torch to an upland hardwood stand.

First, the fuels in hardwoods differ from most pine stands and fields, often requiring slightly dryer conditions to burn. A longer, rain-free period and slightly lower humidity may be needed. This can vary based on the dominant fuels, which is often leaf litter. Even then, all oak stands are not equal when it comes to fire. For example, stands dominated by water oaks will typically not burn as easily as those dominated by white oaks. Why? Bottomland species like water oaks produce leaves that do not burn as well as leaves from upland species. Waiting for the correct conditions allows fire to be used in most upland hardwood stands. 

Travis Sumner, NWTF Hunting Heritage Center and habitat manager, said burning should only occur on days with humidity in the range of 20 to 40%.

“When humidity is below 20%, fire will burn hotter and run more intensely,” Sumner said. “This can damage hardwoods, particularly the roots.”

Firebreaks that deter the spread of a fire beyond its desired boundaries are critical before burning. These can be existing roads, bulldozed firebreaks, or even cleared lanes created with a backpack leaf blower.

To prevent damage to residual, desirable trees, take care to remove any large limbs touching the base of the tree you don’t want to damage. Low-intensity backing, flanking or strip-heading fires are unlikely to damage mature oaks, but large branches in contact with a tree’s base can smolder for a long time, damaging the cambium of residual trees.

 “Only mature stands should be burned – stands age 20 or older,” Sumner said, adding, “burning these stands should be done on a 2- to 4-year basis if needed.” Some hardwood stands may be left unburned based on landowner objectives.

Beware of hardwood trees with a cavity or hollow spot near the base. These should be fully cleared of surrounding leaf debris prior to the burn and monitored during the burn. Sumner said fire can creep inside and start burning inside the tree. Also, clear old hardwood snags. Trees with cavities at the base and dead snags can cause problems if allowed to catch fire. They can pitch hot embers into areas you don’t want to burn, causing a wildfire. Plus, trees that are on fire for days must be monitored.

Fire has wide-ranging benefits but successfully and safely applying it takes training and experience. No matter where you plan to burn, and especially for hardwood stands, consulting a professional who has experience in your region is always advisable. Properly applied, fire will improve cover and forage for turkeys while retaining or even boosting acorn production. I cannot think of a place I would rather sit on opening day than an open, freshly burned hardwood stand!

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