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Timber Stand Improvement

Southern forestlands are currently not producing up to their potential. This low productivity is especially severe on 5 million acres of privately owned forestland where very poor trees are growing on space that is needed by better trees. On the average, undesirable or cull trees occupy one-third of the total growing space in pine-hardwood and hardwood stands of the South. Timber stand improvement practices are needed to remove trees of undesirable form, quality, condition, growth rate, or species. Removal of poor trees will stimulate the growth of better trees and will increase profits to private, non-industrial forestland owners. It is very likely that your timberlands need timber stand improvement practices.

What Is TSI

Timber stand improvement, or TSI, is a term used to identify forest management practices which improve the vigor, stocking, composition, productivity, and quality of forest stands. The improvement is accomplished by removing poor trees and allowing crop trees to fully use the growing space. The chief aim of TSI is continued production of more and better timber products. TSI practices can be used to convert assorted hardwood and pine stands into productive forests of desirable species. TSI can speed up the growth and improve the quality of the trees in your forest.

Different TSI practices may be needed at different times during the life of an established stand -- from the start of a new crop of trees until the final harvest. Here are some basic TSI practices:

Prescribed burning in pine stands to remove undesirable hardwoods, to prepare seedbeds, and to reduce the potential for wildfires.
Cull tree removal to make growing space available on areas occupied by deformed, defective, and undesirable trees. Some cull trees may be cut and sold; however, most must be killed with herbicides.
Thinning to relieve overcrowding and increase the growth rate of crop trees. Precommercial thinning in young, unmerchantable stands is a cost practice. Intermediate thinnings or improvement cuts in older stands produce some income for the landowner.
Sanitation cutting to remove trees that have been damaged by insects, diseases, wind or ice.
Release of young, vigorous crop trees for faster growth and better quality by removing overtopping and competing trees.

Trees To Remove In TSI

In pine, mixed pine-hardwood, and hardwood stands, remove trees that are financially mature or that interfere with the growth and development of more valuable trees. You will want to remove trees such as these:
  • suppressed trees that will not live until the next thinning.
  • trees too crooked, forked, or limby to make a No. 2 sawlog.
  • trees with fire scars and injuries from insects, disease, wind, or ice.
  • trees on the wrong site (such as a water oak growing on a ridge).
  • trees that are mature and slow growing.
  • any tree that will not contribute to the net value of the stand before the next thinning.
  • wolf trees with large crowns that occupy too much growing space or shade out more desirable species.
You will want to leave these trees in your timber stand:
  • high quality trees.
  • fast growing trees.
  • some mast producing and den trees for wildlife.
  • trees located so that all available growing space is used efficiently.
Most people think TSI practices always involve out-of-pocket costs for the landowner. However, some TSI practices can produce immediate income. Thinning is a TSI practice that can produce income if the trees can be sold. Research has shown that volume growth and financial returns will increase with each additional TSI treatment, if costs are reasonable and adequate markets are available. For example, a prescribed burn before the harvest of an old pine stand can increase volume growth in the new stand. Prescribed burning plus removal of large hardwoods in a young pine stand can also yield a good investment return.

Ask a forester to assist you in choosing the right TSI practices that will produce the desired forest management results at the least cost. Some TSI practices are quite cheap, and some, such as thinning, will produce immediate income. All TSI practices will increase future incomes. TSI doesn't cost -- it pays!

Prescribed Burning

Fire, if properly used, can be a very effective TSI practice for forest improvement, maintenance, and protection of pine stands. It is the cheapest management tool available to a landowner. Prescribed fire can be used for these purposes:
  • remove undesirable hardwoods in pine stands.
  • reduce the hazard of wildfire by controlling fuel build-up on the forest floor.
  • expose the mineral soil seedbed for natural seedfall and improved germination.
  • remove brush and debris before planting seedlings.
  • improve wildlife habitat by promoting growth of annual legumes and desirable browse, by increasing the nutrient content of food plants, and by eliminating heavy brush on the forest floor.
  • control brown spot disease on young longleaf pine seedlings.
Prescribed fire is usually not recommended for hardwood stands. Hardwoods have thin bark that is easily damaged by fire. Pines have a thick bark that insulates the cambium (layer of growth cells under the bark) from heat damage. If you are interested in learning more about the use of prescribed fire, contact your county agent or county forester. Never attempt to use fire in your timber stands without the help of a forester. Fire is a management tool that must be applied regularly, at certain times of the year, during the right weather, and with proper equipment. A professional forester can assist you in developing a prescribed burning program for your timber stands.

Cull Tree Removal

Cull tree removal involves cutting or killing undesirable weed trees or culls. A cull is any tree, pine or hardwood, whose quality is so poor that you cannot sell it. Cull trees grow larger, but no better in quality. They take up needed growing space, shade desirable trees, and harbor insects and disease. You will make more money if you remove them to make room for better trees. Occasionally, a poor tree may be left because of its wildlife value. Some poor quality trees may be used for firewood and low value products, but most culls must be killed by chemical or mechanical means. Methods of cull tree removal include these:
  • cutting and selling or using trees for firewood
  • injecting herbicides with:
    tree injectors
    hypo-hatchet
    hatchet and squirt bottle ("hack and squirt")
  • basal spraying
  • thin-line application
  • stump treatment to prevent sprouting
  • foliar sprays
    ground application
    aerial application
  • soil applications
    dry pellets (by hand or air)
    liquids ("spot gun" application)
Tree kill will vary with the herbicide used, size of the tree, time of the year, species, and other factors.

These species are usually easy to kill:

  • basswood
  • birch
  • blackgum
  • box-elder
  • cherry
  • elm
  • ironwood
  • oak
  • plum
  • sassafras
  • sumac
  • sweetgum
  • willow
These species are usually hard to kill:
  • ash
  • beech
  • cedar
  • privet
  • dogwood
  • hackberry
  • sugarberry
  • hickory
  • holly
  • maple
  • poison ivy
  • honeysuckle
  • kudzu

Thinning

Thinning overcrowded stands increases diameter growth of remaining trees and decreases loss from natural mortality. Larger diameter trees are more valuable as sawtimber, plywood, and veneer than are smaller trees that are used for pulpwood or fence posts. Thinning does not increase the total volume or fiber yield of a stand, but it substantially increases the yield of lumber, plywood, and poles and decreases the loss of trees from natural mortality.

Marking Trees For Thinning

You can learn how to mark your own pine stands for thinning. All you need is help from a forester, a thinning guide that gives the number and spacing of trees at various ages, and practice. Your county agent has a publication on "leave-tree" marking of pine stands. Selective marking of hardwood stands requires the expertise of an experienced forester.

Precommercial thinning is cutting in young, dense stands where the trees are too small to sell as wood products. This type thinning produces no immediate income for the landowner, but the cost can be justified by the value of increased future growth. The purpose of precommercial thinning is to reduce the competition and improve the growth rate of the remaining trees. Unwanted trees can be removed with herbicides, mechanical equipment, or by cutting. Thinning can sometimes be delayed until trees are large enough to make fenceposts if a market is available. The growth loss from delayed thinning will probably be greater than the income received for low-value products. Precommercial thinning plus cull tree removal of large hardwoods can result in an investment return of 10 to 20 percent in young pine stands.

Commercial thinning of merchantable size trees produces some income for the landowner, depending upon the number, size, and quality of trees being removed. A commercial thinning is often referred to as an improvement cut if the very poor quality trees being removed are marketable. From a marketing standpoint, there should be sufficient volume to justify a harvesting operation by the buyer. The money a landowner receives for his standing trees, called stumpage, decreases as the cost of harvesting increases. Harvesting cost decreases as tree size, quality, and volume per acre increase. You may want to delay thinning until trees are large enough to make an economical harvest, even though increased growth of crop trees will also be delayed.

Pine Beetle Prevention

You can reduce the likelihood of southern pine beetle attack in your pine timber by thinning. Overstocked stands are more susceptible to beetle attack. Overcrowding weakens the ability of trees to repel insect penetration. Healthy trees can often "pitch out" a beetle with increased resin flow. Also, cutting slow-growing, over mature trees during thinning operations reduces the chance of beetle attack. Some remaining crop trees damaged during thinning may be killed by black turpentine beetles, but the potential danger of southern pine beetle infestation in an overcrowded stand far exceeds the loss of some isolated trees to black turpentine beetles.

Sanitation Cutting

Sanitation cutting is normally done during thinning so that trees damaged by insects, disease, fire, wind, or ice can be sold along with good trees. Sanitation cutting is included in the practice of "thinning from below" where trees with damaged or deformed stems are cut first regardless of their crown position. You must decide whether or not to remove each deformed tree by its condition and whether you think the tree will live until the next scheduled thinning. Some good healthy trees may also be cut to achieve the desired spacing of their crowns (thinning from above) from the crop trees left. Sanitation cutting may not be economical unless it is done during a commercial thinning operation. If you cut only deformed trees, you may have difficulty selling them. If the trees cannot be sold, use the cheapest means of cull tree removal rather than sanitation cutting. Sanitation cutting alone is profitable only after a natural disaster, such as a hurricane, wind, or ice storm, where valuable trees are damaged.

Release

Release is a TSI practice you can use to regulate species composition and improve the quality and growth of your very young stands of trees. A new crop of trees can become established by natural seeding or sprouting under a canopy of overtopping trees. Unless these new trees are released from shading, they will not survive. The overtopping trees may be of desirable species, or they may be low-quality or culls. Undesirable, competing species may also be growing among the young trees. Cut overtopping and competing trees if they can be sold, or kill them with a herbicide if they are culls. You can inject or aerially spray hardwoods growing over young pine trees. Some herbicides can be used to kill hardwoods in established pine stands if the pines are five years or older. Use care when releasing desirable hardwood trees in hardwood stands because herbicide sprays will kill both desirable and undesirable hardwoods. Some injected herbicides can be translocated through root grafts to adjoining crop trees. Get professional help from a forester before using herbicides for overstory or understory release of young trees.

Tax Considerations

Timber stand improvement practices may qualify for deduction as annual expenses from your ordinary income. Keep good records of your TSI costs. Contact your county agent for more information on forest taxation, management, marketing, and multiple use.

For more information and publications on forest management, marketing and protection, contact your county Extension office.

More Information

The following publications provide more detailed information on topics related to timber stand improvement. Copies are available from your county Extension office.
Information Sheet 1573 Tree Injection with Reduced Labor
Publication 1588 Direct Seeding
Publication 1612 Forestry/Wildlife Myths and Misconceptions
Publication 1618 Natural Regeneration Using Seed Trees
Publication 1834 Evaluating High-Graded Hardwood Stands
Publication 2004 Bottomland Hardwood Management
Also:  
Publication 1532 Weed Control Guidelines for Mississippi
(See Woody Plants Section)

Also, check out our Extension Forestry Site.

By Dr. Thomas A. Monaghan, Leader, Extension Forestry

Mississippi State University does not discriminate on the basis of race, color, religion, national origin, sex, age, disability, or veteran status.

Publication 1281
Extension Service of Mississippi State University, cooperating with U.S. Department of Agriculture. Published in furtherance of Acts of Congress, May 8 and June 30, 1914. Ronald A. Brown, Director

Copyright by Mississippi State University. All rights reserved.

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