Timber Stand Improvement: What It Is and Why Your Forest Needs It

What Is Timber Stand Improvement?

Timber Stand Improvement (TSI) is a forestry practice that selectively removes undesirable trees to improve the growth, health, and value of the remaining stand. It is one of the most impactful — and most underutilized — tools available to private forest landowners in the Southeast.

In its simplest form, TSI answers a straightforward question: which trees on your property are helping, and which ones are hurting? The ones that are helping — your crop trees, your mast producers, your longleaf pines, your high-value hardwoods — get more growing space, more sunlight, more water, and more nutrients. The ones that are hurting — the suppressed, defective, low-value, or invasive stems crowding out the good trees — are removed.

NRCS defines TSI under Conservation Practice Standard Code 666 — Forest Stand Improvement. This practice code covers a range of activities including thinning, liberation cutting, improvement cutting, sanitation cutting, and mid-story removal. The common thread is that all of these activities selectively remove trees to benefit the remaining stand.

For landowners in Central Florida and across the Southeast, TSI is particularly important because decades of fire suppression have allowed shade-tolerant hardwoods to invade pine stands — the process known as mesophication. These hardwoods compete directly with desirable pines for light, water, and nutrients. TSI removes them, simultaneously improving timber growth, forest health, and wildlife habitat.

Why Your Forest Needs TSI

The Competition Problem

Trees compete with each other for three essential resources: sunlight, water, and soil nutrients. In an unmanaged forest, this competition results in a stand that is overcrowded, stressed, and underperforming.

Consider a typical acre of fire-suppressed pine-hardwood forest in Central Florida:

• Total basal area: 120+ square feet per acre (far above the optimal 50–70 for a managed pine stand)
• Pine basal area: 50–60 square feet per acre
• Hardwood basal area: 60–80 square feet per acre (the problem)
• Understory light: Less than 10% of full sunlight (severely limiting groundcover)

In this scenario, the pine trees are spending half their energy competing with hardwoods that have no commercial value and degrade the site for wildlife. Removing the hardwood component frees those resources for the pines, resulting in dramatically improved growth rates.

The Research

The benefits of TSI are extensively documented:

• Pine diameter growth increases 20–40% after mid-story hardwood removal, according to research from Auburn University, the University of Florida, and USDA Forest Service Southern Research Station.
• Pine volume growth increases 15–30% over the decade following TSI treatment.
• Timber quality improves because reduced competition allows trees to maintain live crown ratio (the proportion of the trunk with living branches), which drives diameter growth and produces higher-quality sawlogs.
• Tree mortality decreases because reduced competition for water makes trees more resilient to drought, insects, and disease.
• Groundcover diversity increases immediately after mid-story removal, as sunlight reaches the forest floor and activates the native seed bank.

The Triple Benefit

TSI is one of the rare forestry practices that simultaneously benefits three landowner objectives:

1. Timber value: Remaining pines grow faster, producing more board-feet per acre per year and reaching merchantable size sooner. The timber you are growing becomes more valuable.

2. Wildlife habitat: Mid-story removal restores sunlight to the forest floor, stimulating native groundcover that feeds and shelters deer, turkey, quail, and dozens of other species. See our guide on managing for deer, turkey, and quail.

3. Forest health: Reduced competition improves tree vigor, making the stand more resistant to drought, pine bark beetles, and disease. Removing diseased or defective trees (sanitation cutting) directly reduces pathogen and pest pressure.

Types of TSI

Mid-Story Hardwood Removal

The most common TSI practice in the Southeast is removal of the hardwood mid-story — the layer of shade-tolerant hardwoods that has developed in pine stands due to fire suppression. This mid-story typically consists of:

• Sweetgum (2–8 inches DBH)
• Water oak, laurel oak (2–10 inches DBH)
• Red maple (2–6 inches DBH)
• American holly, wax myrtle, and other evergreen shrubs/small trees
• Various invasive species (Chinese privet, Chinese tallow)

Mid-story removal is most efficiently accomplished through forestry mulching, which can grind the entire mid-story layer in a single pass while navigating around marked retention pines.

Thinning

Thinning reduces the overall density of the stand by removing a portion of the trees. In planted pine plantations, where trees were established at uniform spacing (typically 6x10 or 8x10 feet), thinning removes every other row (row thinning) or selects individual stems for removal based on form and vigor (selective thinning).

Thinning is typically a commercial operation — the removed trees have merchantable value as pulpwood or small sawlogs. The revenue from thinning can offset or exceed the cost of the operation.

First thin timing: Planted pine stands in the Southeast are typically first thinned at age 12–18, when the stand has reached a basal area of 100–150 square feet per acre and individual trees are large enough to sell as pulpwood.

Subsequent thins: Additional thinnings may be performed every 5–10 years to maintain optimal growing space as the stand matures.

Liberation Cutting

Liberation cutting is the removal of overtopping or competing trees that are suppressing desirable young trees. This is common in natural regeneration situations where longleaf pine seedlings or other desirable species need to be “liberated” from competition.

For example, on a site where longleaf pine seedlings have established beneath a canopy of off-site loblolly or slash pine, liberation cutting removes the loblolly/slash canopy to give the longleaf seedlings full sunlight.

Improvement Cutting

Improvement cutting removes undesirable trees from a mature or maturing stand to improve the quality and composition of the remaining stand. This might include removing:

• Defective trees (forked, crooked, damaged)
• Diseased trees
• Low-value species
• Wolf trees (very large, short-boled trees with spreading crowns that occupy excessive growing space)

Sanitation Cutting

Sanitation cutting specifically targets trees that are infested with insects or disease, or that are likely to become infested. In the Southeast, pine bark beetle infestations are a significant concern, and sanitation cutting can remove beetle-infested trees before the beetles emerge and spread to adjacent healthy trees.

How TSI Is Performed

Assessment and Marking

Before any cutting begins, a forester or land manager walks the stand and identifies which trees will be removed and which will be retained. In some cases, trees to be cut are marked with paint or flagging. In other cases (particularly mid-story removal), the prescription is defined by species and size class: “remove all hardwood stems less than 10 inches DBH.”

The marking process considers:

• Species: Which species are desirable (retain) and which are undesirable (remove)?
• Size: What size classes should be targeted for removal?
• Spacing: After removal, will the remaining trees have adequate growing space?
• Timber value: Are any of the trees being removed large enough to sell?
• Wildlife considerations: Are there mast-producing trees, cavity trees, or den trees that should be retained regardless of species?

Mechanical Treatment

For most TSI applications in the Southeast — particularly mid-story hardwood removal — forestry mulching is the treatment method of choice.

Advantages of mulching for TSI:

• Processes small to medium hardwoods (2–10 inches) efficiently
• Navigates around retention trees with precision
• Leaves a mulch layer that protects soil and suppresses weeds
• No need for skidding, piling, or burning debris
• Single-machine operation minimizes site disturbance

Limitations:

• Trees larger than 12–14 inches DBH may be more efficiently handled by chainsaw felling
• Cannot capture timber value from removed trees (they are ground into mulch)

For stands where the removed trees have merchantable value, a conventional logging operation may be more appropriate for the larger stems, with forestry mulching handling the residual small-diameter material.

Chemical Treatment

Herbicide is an important component of many TSI prescriptions:

• Cut-stump treatment: Applied to freshly cut stumps of species that resprout (sweetgum, Chinese tallow, Chinese privet). Critical for preventing the mid-story from regenerating.
• Hack-and-squirt: Herbicide (typically imazapyr or triclopyr) is applied into cuts made in the bark of standing trees. The tree dies in place over several months. This method is useful for scattered mid-story trees that are not dense enough to justify a mulcher.
• Basal bark: Herbicide in an oil carrier is applied to the bark around the base of small trees. The herbicide penetrates the bark and kills the tree. Effective on stems up to about 4–6 inches in diameter.

Prescribed Fire

In fire-adapted southeastern forests, prescribed fire is the long-term maintenance tool that keeps the mid-story from returning after initial mechanical TSI. A 2–3 year burn rotation kills hardwood seedlings and sprouts before they can grow into the mid-story, maintaining the open conditions created by the initial TSI treatment.

Without follow-up fire, the mid-story hardwoods will reestablish within 5–10 years, and the TSI investment will be partially or fully lost.

TSI Cost and Economics

Treatment Costs

TSI costs vary depending on the method and the density of material being removed:

Return on Investment

The financial return on TSI comes from multiple sources:

Increased timber growth: If TSI increases pine growth by 25% (a conservative estimate based on research), a stand growing 1 cord per acre per year before treatment would produce 1.25 cords per year after treatment. At $25 per cord stumpage, that is $6.25 per acre per year in additional growth — compounding annually over the remaining rotation.

Improved timber quality: Faster-growing, well-spaced pines produce higher-quality sawlogs with more clear wood and fewer defects. The value difference between pulpwood and sawtimber is substantial — $25 per cord for pulp versus $200+ per MBF for sawtimber.

Hunting lease revenue: Properties with improved wildlife habitat command higher hunting lease rates. In the Southeast, well-managed properties can earn $5–$15 per acre per year in lease income above what unmanaged properties receive.

EQIP cost-share: Forest Stand Improvement (Code 666) is one of the most commonly funded EQIP practices in the Southeast. Payment rates of $150–$450 per acre can cover 50–75% of the cost of TSI, dramatically improving the economics. See our EQIP guide for application details.

Property value: A well-managed forest with clear sight lines, healthy timber, and abundant wildlife is worth more per acre than a closed-canopy, overstocked, mesophied stand. For properties being sold or appraised, TSI investment can directly increase market value.

The Break-Even Timeline

For a TSI treatment costing $2,000 per acre with 50% EQIP cost-share (landowner cost: $1,000 per acre), the combined returns from increased timber growth, hunting lease improvement, and property value appreciation typically recover the investment within 5–10 years — with benefits continuing to accrue for the remainder of the timber rotation.

When to Schedule TSI

Seasonal Considerations

TSI can be performed year-round in the Southeast, but some seasonal considerations apply:

• Summer (June–August): Hot, humid conditions are hardest on equipment and operators, but summer treatment has the advantage of treating hardwoods during active growth, when cut-stump herbicide is most effective.
• Fall (September–November): Comfortable working conditions, hardwoods are beginning dormancy. Good timing for TSI if prescribed fire is planned for the following winter/spring.
• Winter (December–February): Cool conditions are easiest on equipment. Hardwoods are dormant, which reduces herbicide effectiveness somewhat but allows easier identification of evergreen invasive species.
• Spring (March–May): Good working conditions. Avoid ground-nesting bird season (April–July) on properties with known nesting activity. Spring TSI provides immediate growing-season benefit to retained pines.

Stand Readiness

TSI should be considered when:

• Hardwood basal area exceeds 30 square feet per acre in a pine stand
• The mid-story is blocking more than 50% of available sunlight to the forest floor
• Pine growth rates have plateaued or declined due to competition
• Wildlife habitat quality has degraded due to canopy closure
• The stand is being prepared for prescribed fire reintroduction
• EQIP funding is available to offset treatment costs

TSI in the Context of Total Forest Management

TSI is not a standalone practice — it is one component of a comprehensive forest management strategy. The land management process integrates TSI with:

• Prescribed fire: To maintain the open conditions created by TSI
• Invasive species management: To prevent invasive plants from colonizing the newly opened understory
• Regeneration planning: To ensure the next generation of desirable trees is establishing
• Wildlife habitat management: To create the mosaic of open forest, dense cover, and edge habitat that supports diverse wildlife populations

TreeShop provides timber stand improvement services across Central Florida and the Southeast, integrating mechanical mulching, herbicide treatment, and prescribed fire preparation into a complete TSI program. Our approach ensures that the investment in TSI produces lasting results rather than a temporary improvement that is overwhelmed by regrowth within a few years.

Frequently Asked Questions

Is TSI the same as logging?

No. Logging (timber harvesting) removes trees primarily for their commercial value — the logs are sold as pulpwood, sawtimber, or other forest products. TSI removes trees primarily to benefit the remaining stand, regardless of whether the removed trees have commercial value. In some cases, TSI involves removing trees that do have value (commercial thinning), but the purpose is stand improvement, not timber harvest.

Will TSI hurt my property?

When properly planned and executed, TSI improves your property in every measurable way — faster timber growth, better wildlife habitat, higher property value, reduced fire risk, and improved aesthetics. The only risk is poor execution: removing the wrong trees, damaging retention trees, or failing to follow up with herbicide and fire. This is why working with an experienced land manager is important.

How often does TSI need to be done?

The initial TSI treatment — removing the hardwood mid-story that has accumulated over decades of fire suppression — is a one-time event. After the initial treatment, prescribed fire on a 2–3 year rotation can maintain the open conditions indefinitely. Periodic maintenance mulching (every 5–10 years) may be needed for hardwood sprouts that escape fire, but this is far less intensive and expensive than the initial treatment.

Can I do TSI in a hardwood stand?

Yes. TSI applies to any forest type. In hardwood stands, TSI typically involves removing low-value or defective stems to release higher-value crop trees (red oak, white oak, walnut, yellow poplar). The principles are the same — reduce competition to improve the growth and value of the best trees.

What is the difference between TSI and thinning?

Thinning is one type of TSI. TSI is the broader category that includes any selective tree removal aimed at improving the remaining stand — this includes thinning (reducing overall density), improvement cutting (removing low-quality stems), liberation cutting (releasing young trees from overtopping competition), sanitation cutting (removing diseased trees), and mid-story removal. In practice, most TSI prescriptions in the Southeast combine elements of two or more of these approaches.