On a drive home from Thanksgiving with family, a trip that took me through several eastern states, I spent a lot of time looking out the window at bad deer habitat. Acre after acre in every state lined the highways: unmanaged forests and woodlots grown up into closed-canopy, shady, mature forests of pine and low-value hardwoods. A lot of people – even hunters – call this “deer woods.” From a deer’s perspective, “deer deserts” would be a better description.
These deer deserts are what happens when fields, clearcuts, old pastures, high-graded timber, neighborhood greenspace, state parks, national forests, or any forested lands are left alone to manage themselves – while fire has been suppressed. Fast-growing, fire-intolerant tree species fill the sunlit spaces, throwing shade on anything growing beneath them. Except for unreliable acorn crops, deer will find little of value in the way of forage or cover in these shady woods choked with pines, red maples, birches, sweetgums, poplars, red cedar and many others. You can reverse the process and turn these deer deserts back into high-quality wildlife habitat through Forest Stand Improvement.
Research by Dr. Craig Harper and his students at the University of Tennessee showed FSI can increase high-quality deer forage from 100 lbs./acre in a shady desert to over 1,200 lbs./acre where 50% of the sunlight is reaching the ground. That’s up there with warm-season food plots! FSI is not difficult, and you can tackle it in small units to keep the work manageable. In short, there is no better way to create fantastic deer and wildlife habitat, and better hunting – for less money – than to revitalize those deer deserts with FSI. Let’s get started.
What is Forest Stand Improvement?
Forest Stand Improvement is a technique for reversing the process of canopy closure by selectively removing low-value and non-native trees – and even high-value native trees that are overabundant – to reintroduce sunlight between widely spaced trees selected to remain. The sunlight will drive growth of understory forage and cover that is valuable to deer. Meanwhile, mast-producing trees selected to remain can produce more mast.
What’s the difference between Timber Stand Improvement (TSI) and Forest Stand Improvement (FSI)? “Timber” Stand Improvement is primarily aimed at increasing future timber value and income. TSI can also improve wildlife habitat, but economic value is the primary goal. Dr. Craig Harper began using “Forest Stand Improvement” to identify forest management intended to improve wildlife habitat and other objectives.
There is some overlap, because TSI can improve wildlife habitat, and FSI can improve timber value. You might be able to sell the trees you remove for FSI, but deciding which trees are removed and which remain is primarily about enhancing wildlife and forest health. However, in most cases FSI involves removing low-quality trees and retaining high-value ones, so you benefit from enhanced wildlife habitat and future timber value. If long-term timber value and income is an important factor in helping you own and maintain your hunting land, talk to a licensed forester before you start killing trees.
FSI Rules: It’s About the Sunlight
We all have to get past the old idea that trees equal deer habitat. It’s what grows at ground level in the sunlight between trees that makes deer habitat. You often hear people summarize deer as “creatures of the edge.” This is a poor way to describe deer. It’s not edges deer are drawn to. It’s the food and cover that grows along edges!
Edges are where sunlight leaks from an opening into a shady forest, driving growth of broadleaf forbs – deer food. A forest can be “all edge” if trees are spaced widely enough to allow adequate sunlight through. According to the research of Dr. Craig Harper, “adequate” is 30 to 50% of the sky open to the sun. That’s what FSI does: Produce more deer food by making a forest “all edge.”
There are several do-it-yourself techniques to restore sunlight. You can easily girdle large trees with a chainsaw and inject herbicide in the cut to kill them standing. Smaller trees and shrubs can be cut down and stump-treated with herbicide or left alive to produce stump-sprout forage. We’ll get into how-to resources below.
Rule 2: Valuable Trees Can Be Overabundant
To select and remove enough trees to achieve 30 to 50% sunlight reaching the ground, you’re going to have to get used to killing trees you might think of as valuable trees for deer. Any species of tree can be overabundant. You can have too many white oaks, red oaks, persimmons or any other “good” deer tree in a space.
This could be two mature white oaks trees growing too close to each other. It could be a cluster of overcrowded persimmon saplings. We want mast producers like these to produce acorns and fruit for nutrition and hunting opportunity – and you can get more mast with fewer trees that receive more sunlight. A single white oak tree with ample space between it and other trees will produce more mast in the long run than multiple white oaks crowded together.
Rule 3: Bring the Heat
When you restore 30 to 50% or more sunlight to the ground in deer deserts, you get an explosion of understory plant growth. And that plant growth immediately begins the process of succession that gradually unravels your hard work by summoning shade. Shrubs appear. Then tree saplings. Then mature trees. In a few years, the shady desert is back.
You don’t have to wait until you can restart the process of killing trees through FSI. There’s a much easier way to hinder succession and keep understory growth in those early, valuable stages: Prescribed fire. Once you have improved a block of woods through FSI, put a firebreak around it and get ready to burn. Maintaining high-quality deer habitat with prescribed fire on a regular interval is much easier than restoring the sunlight initially with FSI.
Unfortunately, there really is no equal to prescribed fire for maintaining quality deer habitat. Prescribed fire regulations are more burdensome in some states, but very few states prohibit prescribed fire on private lands. If the regulations in your state seem like a barrier, talk to your state’s Prescribed Fire Council or state forestry agency to find the support that can help you become a practitioner.
Rule 4: Be Ready to Fight Invasives
We all have them. The species vary by region, but we all have non-native invasive grasses, vines, shrubs and trees in our woods, and their seeds are in the soil alongside seeds of native species. When you restore sunlight to the ground through FSI, the non-native invasives are going to respond also. You must expect this, and you must be prepared to knock them back down. If you don’t, they’ll take over and dominate the new open space, and most of them have little to no value for deer.
If you’re lucky enough to have a light infestation, you may be able to manually pull or cut problematic invasives, but most of us won’t be that lucky. Many non-native invasives grow back easily after being cut. Real control is going to require herbicides. Invasive trees can be killed with girdle-and-spray, or the cut stumps can be treated.
Prescribed fire will help keep these plants in young growth stages, making it easier to spot-spray them with a backpack sprayer or ATV-mounted boom sprayer. So, when your burn units begin to green up after a recent prescribed fire, it’s critical to plan a walk-through to scout for and treat re-emerging invasive plants while they’re young and small.
Rule 5: Small Units Are Easier to Tackle
If you’re imagining large areas of forest as you read about these tasks, don’t let it overwhelm you! You do not have to mount an attack on every forested acre you manage at once. It is much easier, and makes more sense, to break the job up into units.
In fact, by selecting units or blocks for FSI, you can place them strategically to enhance the “huntability” of a property. Since forested blocks treated with FSI become deer destinations due to enhanced forage and bedding cover, they become attraction and destination points. Hunting in and around FSI blocks, or between them and other destinations like food plots, can be a very successful strategy.
One of the best ways to divide a hunting property for FSI is to map out prescribed fire “burn units” based on an existing or future network of firebreaks. You may not need to conduct FSI in every burn unit, but every FSI block will eventually need to be disturbed with fire.
Next Steps
This is only a primer on FSI. You likely have many questions about what to do next. There are many resources available. For example, we have:
- An article that dives deeper into the girdle-and-spray technique for quickly killing standing trees selected for removal.
- An article that helps you decide whether to girdle, hinge, fell or leave trees based on their species.
- An article that explains firebreak establishment.
- How to divide a hunting property into burn units.
- A YouTube playlist of FSI videos, including what the results can look like when you use FSI to create bedding blocks (watch below).
To really dive into the details, I recommend Dr. Craig Harper’s booklet: Forest Stand Improvement: Implementation in Hardwood Stands of the Eastern U.S.
Don’t waste another “habitat season.” Map out your burn units now, then pick one of a reasonable size that needs FSI. Once you start studying trees, removing some, and leaving others, the work will go faster as you learn. You’ll likely find you didn’t remove enough trees on the first pass, and that’s part of increasing your FSI skills. The sooner you start, the sooner you’ll reap the many benefits of Forest Stand Improvement for wildlife.