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FOREST MANAGEMENT WORKSHOP MANUAL

GROWING TREES

It takes a lot of faith to look ahead sixty to eighty years to grow sawtimber. But that is what growing trees is all about. Every time a tree is planted, it's care is trusted to future generations. This points out the need for the public to be better informed regarding the necessity for managing our forest lands and the techniques involved.

Fortunately, our forests have endured over the years because trees are renewable. This basic fact means that we can continue to enjoy the benefits from forests - and the growing forests themselves - if we manage them properly.

The average forested tract in Kentucky consists of about 24 acres and is a community of small, intermediate and large-size trees, trees of all ages, which under natural growing conditions, grow too close together for maximum growth.

In some respects, this average tract is like a field of tobacco - you can not grow good tobacco unless the plants are properly spaced and some weeding is done. The same holds true with trees. When working with trees, an individual should think in terms of imporving the quality and growing conditions of the crop trees if a good crop is expected. This is what management attempts to do. With these considerations in mind, let's look briefly at some management practices and what they are designed to achieve.

Establishing a Timber Stand

On abandoned fields or harvested sites, the landowner's first consideration should be to establish a new stand of trees for the next crop. This should be accomplished as economically and quickly as possible with desirable species adapted to the site. Several methods of reproducing a stand of trees are worth consideration.
Natural Reproduction
All trees produce seed. When a stand is harvested, a large number of seeds will usually be available in the soil to germinate if conditions are right. The proportions of different species which make up a stand are dependent on the amount of seed present, soil conditions, amount of sunlight, moisture, and competition between plants. When properly done, this is the most economical method of reproduction and usually results in the most productive stands.
Planting
Planting of tree seedlings is necessary when a seed source of desirable species is unavailable, such as on abandoned fields or when converting from one tree species to another. Trees need to be properly spaced to minimize cultural practices and expenses and selected on the basis of use and adaptation to soils and climate of the area. (See Appendix, "Tree Planting").
Seeding
Direct seeding involves the sowing of seed on the ground where it germinates and grows. Usually the practice is accomplished with a plane, helicopter or hydroseeder. In Kentucky, most direct seeding is done with a hydroseeder to establish grasses and legumes on difficult sites as mine spoil or road banks. Extensive direct seeding of tree species hasn't proven to be a very successful practice.
Coppice
Coppice reproduction of a stand is by sprouts from either stumps or roots of cut trees. The primary advantage of this method is the rapid sprout growth from the already developed root systems. Disadvantages include decay as the sprouts grow and development of multiple stems. Coppice reproduction is often a major component of any naturally occurring hardwood stand.
Site Preparation
In reproducing a stand, best survival and growth is obtained under optimum growing conditions. To achieve this degree of success requires that undesirable competing growth be controlled. Site preparation may consist of controlling brush and herbaceous species by manual, chemical or mechanical means, usually before and just after a stand is reproduced. Under unfavorable conditions, site preparation can be a major cost of reproduction.

Intermediate Cutting Practices

Cleaning
A cutting made in a stand of trees in the age range of 1 to 20 years, to free the best trees from undesirable individuals of the same age which are or may overtop them. The principal purpose of this practice is to regulate species composition with emphasis on the better species. Unwanted trees can be removed chemically or by cutting. This practice is frequently unnecessary.
Release Cutting
A cutting made in a stand of trees between the ages of 1 to 20 years, to reduce competition of older overtopping trees. Older trees may be good species but of poor form. The purpose of this practice then is to release the new crop from the unfavorable influence of older trees. Trees can be eliminated by cutting, girdling, or chemical treatment. This practice is frequently unnecessary.
Thinning
A cutting made in an immature stand of trees to reduce the excessive number of trees per acre. This practice stimulates tree growth while concentrating wood production on a limited number of selected trees. The frequence of thinnings during the life of a stand of trees depends on the tree species being grown and site productivity. Yellow-poplar trees growing on a good site may have a cutting cycle of 8-12 years. Upland oak species growing on a good site might have a cutting cycle of 6-9 years.

There are several types of thinnings including selection thinning, crown thinning, etc., which we will not discuss in this selection.

Improvement Cutting
A cutting in a stand of trees which are 20 years of age or older. The purpose of the practice is to improve tree composition and tree quality by removing trees of undesirable species, form, or condition, from the main canopy. This practices oftentimes includes grapevine removal. Trees may be harvested if a market exists or merely cut or chemically treated and left standing. One improvement cutting may be sufficient to put the stand into condition or several cuttings over a period of years may be required. Improvements cuttings should precede a harvest cut by at least 10 years so the full benefit can be obtained from the release of the better trees.
Pruning
Branches of trees are removed to increase the quality of the wood. Trees usually pruned are pine species and black walnut. Normally in pruning pine species, at least 30% of the total tree height needs to be left in live crown to maintain maximum growth. With walnut trees, at least 50% of the total height should be left in live crown. Prune trees when they are young. It is recommended that crop trees be selected and pruned when 5 or 6 inches in diameter. Remove limbs flush with the tree trunk. Once the wound has healed over, new growth is clear and of higher value.

Biological and Financial Maturity

The practices we have looked at so far are carried out during the life of a stand. When a tree or stand of trees reaches maturity, then harvesting practices must be considered.

But first let's look at maturity of a tree. Maturity varies with tree species, site productivity, climate conditions, and the product to be grown. Let's consider two types of maturity - financial and biological. Financial maturity requires that the landowner attaches a dollar value to growing trees. If the expected value increase of a tree no longer equals or exceeds the desired rate of return, then the tree should be removed and replaced with a younger tree.

Biological maturity is the age a tree reaches before beginning to deteriorate. Evidence of decline includes dead tops, insect damage, rot, etc. The economic maturity of Yellow- poplar on a good site may be 72 years, yet its biological maturity may be 200-250 years. Most tree species in Kentucky reach their economic maturity between 35-81 years. The higher the interest rate desired, the shorter the rotation.

Harvesting Practices

Now let's look briefly at harvesting practices.
Selection Cutting
Involves the harvesting of scattered mature trees in an all- aged stand on a periodic basis. This practice affords a high degree of protection to the site during and after logging and is aesthetically pleasing. Disadvantages to the practice include higher logging costs due to the scattered trees. Also it is difficult to prevent injury to immature trees during logging operations. The practice favors reproduction of shade tolerant species such as maple, oak, and hickory rather than the intolerant species. Reproduction comes from seed in the soil and sprouts from stumps and roots.
Clear Cutting
Is a regeneration cutting and is used when a stand of trees reaches maturity or when a stand consists of mostly poor quality trees which need to be removed and replaced with quality trees.

After the merchantable trees are removed, all young growth 2" in diameter or larger which remain must be cut or chemically treated to allow for sunlight on the site.

Regeneration of the site may be by natural means or by aritficial means. Natural regeneration results from seed in the soil and sprouting from stumps and roots of cut trees (coppice). Artificial regeneration would consist of planting the area with seedlings raised in a nursery or direct seeding the area.

This practice has the advantages of reducing logging costs due to concentrated logging on a small area, and is simple and easy to apply. The new tree crop develops in full sunlight, favoring intolerant species such as yellow-poplar, walnut, and ash. The new stand is even-aged. Disadvantages of this practice include temporary removal of forest cover resulting in increased runoff and a change in the micro-climate of the area. However, soil erosion is not increased beyond what would occur under other cutting methods. Aesthetically, this practice is the least desirable and it cannot be used effectively unless the wood market will absorb all the material on the area.

Shelterwood
Involves the gradual removal of an entire stand in a series of partial cuttings over a period of years of not less than 10 nor more than 20. Natural reproduction from seed and sprouts starts under the protection of the older stand and is finally released when able to endure exposure. Approximately 10-30% of the tree volume is removed in each preparatory cutting. The fundamental characteristics of the shelterwood method is the establishment of a new crop of trees before completion of the preceding rotation.

This practice is not normally used in Kentucky and results in an even-aged stand or forest. The main disadvantages to the practice is the damage to the young trees during the removal of older ones.

Seed Tree
The area is cut clear except for scattered trees called seed trees left standing singly or in groups for the purpose of furnishing seed to restock the area. Less than 10% of the original volume is left standing in seed trees. After the new crop is established, seed trees may be removed in a second cutting or left indefinitely.

The number of seed trees left on an area range from 1 to 10 per acre depending on the tree species, tree size, type of seed, etc.

This practice creates an even-aged stand or forest. It concentrates logging on a relatively small area, tending to keep costs down. It is simple and easy to use.

The disadvantages of the practice include complete exposure of the site following logging. The practice isn't aesthetically pleasing and is restricted to windfirm species having wind dispersed seed such as pine.

Salvage Cutting
A cutting made for the purpose of removing trees killed or damaged by insects, disease, wind, etc. It may involve complete or partial removal of a stand.

Protection

All trees have their enemies. In many private holdings, fire and domestic animals lower the productivity of the woodland more than insects and disease.

Fire causes damage to trees, some of which is not easily recognized. Fire may kill young trees in a forest and damage older trees, leaving fire scars where rot may enter. Fire weakened trees may be attacked by insects and diseases or more easily felled by wind. The composition of a forest may be changed by fire, in time becoming a scrubby growth of inferior species. A woodland owner may suffer losses in his cash-crop trees even though the fire actually kills very few of them.

Insects and Disease
Insects and diseases may kill trees, retard growth, or mar wood and tree form. The annual toll of timber killed or ruined by diseases alone in the U.S. is 40 percent as much as timber cut. Farm woodlots are especially susceptible to diseases, especially if grazed or burned frequently. Much of this problem may be eliminated by removing infected trees or those likely to become defective in early life, such as scarlet oak.
Grazing
Most landowners are not aware of the problems created by allowing livestock to graze hardwood forests. Hardwood forests will tolerate only light grazing. Higher concentration of cattle will damage surface feeder roots and compact the soil, reducing its absorptive capacity. In general, the farmer who uses the farm woodlot as a pasture is creating a loss for himself and the livestock. Forage grown in a forest is poorer in quantity and quality than open pasture. Research has shown that an improved grass-legume pasture can produce 11 times the yield by dry matter as compared to forage in a forest or woodlot.
Erosion
The home of tree roots is the soil, and the growth of the tree and the productivity of the forest are directly affected by the quantity, quality and location of the soil. Man's activities in the forest do cause an increase in soil disturbance. A harvesting operation, access roads, grazing or even a hiking trail may be a source of soil erosion if poor judgement or a bad practice is applied. Soil loss from erosion in turn affects soil productivity and tree growth. Through good planning and application of preventative practices, erosion can be minimized.

Conclusion

Because of what man has learned about growing trees, there should be no problem in supplying our present and future needs from the forests we have - except that man hasn't yet put all of what he knows into practice.


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Last revised August 14, 1995.

Please send comments to: Duane Bristow (72711.1414@compuserve.com)