Silviculture is the growing and cultivation of trees.
Silviculture is the branch of forestry that addresses the art and science of controlling the establishment, growth, composition, health, and quality of forests and woodlands to meet the diverse needs and values on Indian trust lands on a sustainable basis.
Objectives of silviculture
- Production of higher volume in per unit area.
- Production of superior quality timber and wood.
- Production of valuable species.
- Introduction of exotics species.
- Protection of Site.
- Control of ecosystem.
A silviculture system is a planned series of treatments for tending, harvesting, and reestablishing a stand to meet management objectives.
These treatments are applied throughout life of the stand and the combinations of regeneration methods and stand tending, known as intermediate treatments.
1. Clearcutting – It is a method of regenerating an even-aged stand in which a cohort, new age class of seedlings, develops in a fully-exposed microenvironment after removal, in a single cutting, of all trees in the previous stand. Regeneration is from natural seeding, direct seeding, planted seedlings, and advance regeneration. Cutting may be done in groups or patches.
The management unit in which regeneration, growth and yield are regulated consists of the individual clearcut stand in the clearcutting system.
2. The seed-tree method – It is an even-aged regeneration method in which a new age class develops from seeds that germinate in virtually fully-exposed microenvironment after removal of entire stand except for a small number of widely dispersed trees.
3. The shelterwood – It is the method of regenerating an even-aged stand in which a new cohort develops in a moderated microenvironment beneath the residual trees.
The sequence of treatments include three different types of cuttings:
A. An optional preparatory cut to set the stage for the regeneration and accomplish if one or more of the following:
• Enhance conditions for seed production by releasing the future seed trees.
• Develop the wind-firmness of future seed and shelter trees.
• Provide for efficient removal of merchantable suppressed and intermediate trees thereby reducing breakage during the establishment. This is goal in high-volume old-growth stands.
B. An establishment cut or shelterwood seed cut to prepare seed bed and to create the new stands.
C. The final removal to release the established regeneration from competition with seed and shelter trees.
4. Coppice – It is a method of regenerating a stand in which all the trees in the previous stand are cut, knocked over, injured at the rootand the majority of regeneration is from stump sprouts or root suckers.
Intermediate treatments include all the cultural treatments occurring in stands that are between regeneration periods. The intermediate treatments are performed in order to ensure the desired species composition, improve stem quality, and adjust stand density to regulate growth in a developing stand.
These treatments have the primary emphasis of correcting stand defects, increasing volume, and value of usable forest products. There is no intention of establishing regeneration through the application of intermediate cut. The care must be taken during any intermediate cutting to protect the residual stand from the injury.
Classification of intermediate treatments is as follows:
Release Cuttings –
Treatments are designed to free young, target trees from undesirable, usually overtopping, competing vegetation. The emphasis is upon stand improvement and species composition, rather than growth effects, although increased the growth rates are an advantageous outcome.
Types of release treatments are –
A. Cleaning – A release treatment made in age class not past the sapling stage in order to free favored trees from less desirable tree species of comparable age. A cleaning might be applied to release the young ponderosa pine stands from competing juniper trees or the oak sprouts in the southwest, or to free white pine from overtopping by inferior hardwoods such as aspen, in the eastern region.
B. Weeding – A release treatment made in stands not past the sapling stage that eliminates or suppresses any undesirable vegetation regardless of the crown position and may include grass, vines, or shrubs. The undesirable competing vegetation in the southwest includes oak, grass, or locust and in the northwest may include the mountain and vine maple.
C. Liberation cutting – A release treatment made in a stand not past the sapling stage to free the favored trees from the competition with older, overtopping trees. This treatment differs from cleaning in that the trees removed from much older age class. This method is resemble the final removal cuttings of the seed-tree regeneration methods.
Improvement Cutting –
It is a cutting made in a stand beyond the sapling stage for the primary purpose of improving composition and quality. Trees of undesirable species, form or condition are removed from main canopy.
The need for improvement cutting is often results from a lack of an earlier application of a needed release cutting. Such cuttings are extremely important, and care should be taken to mark very best leave trees.
Thinning are cuttings made in the stand between regeneration and final harvest to reduce stand density for purpose of stimulating the growth of remaining trees to increase the yield of desired products, enhance forest health, and recover potential mortality.
Geometric Thinning –
This type of thinning trees in rows, strips, and with fixed-spacing intervals with no regard for their species, position in the canopy, vigor, and form. This is least desirable type of thinning because form, phenotypic quality, and species composition are at best neutral after the treatment. It may be justified in uniform, healthy plantations, extremely dense stands where other thinning methods are cost-effective.
Free Thinning –
This method releases selected crop trees by using of the combination of the above thinning methods. The free thin, is also known as the free selection method, is a form of uneven-aged management that recognizes the forest and each stand as a mosaic of conditions and tree groupings, and applies desired forest treatment objectives appropriately to each encountered condition and grouping.