HARVEST TYPES

 Intermediate Cutting

Thinnings

Cuttings made in immature stands in order to stimulate the growth of the trees that remain and to increase the total yield of useful material from the stand.

Low Thinning - sometimes called thinning from below. Trees are removed from the lower crown classes.

Crown Thinning - trees are removed from the upper crown classes in order to open up the canopy and favor the development of the most promising trees in these same classes.

Selection Thinning - Dominant trees are removed to stimulate the growth of the trees in the lower crown classes.

Mechanical Thinning - the trees to be cut or retained are chosen on the basis of a predetermined spacing or pattern with little or no regard for their position in the crown canopy.

Free Thinning - cutting designed to release crop trees regardless of their position in the crown canopy. Combines several of the other thinning methods; most often needed in stands that are irregular in composition, age or density.

Commercial Thinning – a general term used to describe any intermediate harvest that makes money, as opposed to precommercial thinning, which does not.

Release Cuttings

The act of freeing a young stand of desirable trees, not past the sapling stage, from the competition of undesirable trees that threaten to suppress them.

Cleaning - a cut made in a stand, not past sapling stage, in order to free the best trees from undesirable individuals of the same age which overtop them or are likely to do so.

Weeding - the removal of all plants competing with the crop species, regardless of whether their crowns are above, beside, or below those of the desired trees.

Herbicide use is considered a release treatment.

Precommercial thinning (PCT) - is a weeding.

Improvement Cuttings

Improvement cuttings are made in stands past the sapling stage for the purpose of improving composition and quality by removing trees of undesirable species, form, or condition from the main canopy.

A cutting designed to free good trees from the competition of older, undesirable trees is clearly an improvement cutting.

Improvement cuttings are often conducted simultaneously with true thinnings or reproduction cuttings. It should be understood that improvement cuttings are strictly preliminary operations designed to set the stage for systematic thinnings or reproduction cuttings. They are not carried out continuously throughout a rotation and should not be regarded as substitutes for the standard methods of cutting.

Salvage Cuttings

Salvage cuttings are made for the primary purpose of removing trees that have been or are in imminent danger of being killed by insects or disease, rather than competition between trees. 

Presalvage cuttings - designed to anticipate damage by removing highly vulnerable trees.

Sanitation Cutting - elimination of trees that have been attacked in order to prevent the pests from spreading to other trees.

Even-Aged Stands

Clearcutting method - removal of the entire stand in one cutting with regeneration coming from natural seeding or artificially.

Shelterwood method - removal of the mature timber in a series of cuttings, which extend over a relatively short portion of the rotation, encouraging the establishment of essentially even-aged reproduction under the partial shelter of the overstory. All but the final cut in this series are sometimes known as Shelterwood preparatory cuts; the final cut as a shelterwood removal cut or Overstory Removal.

Uneven-aged Stands

Selection method - removal of the mature timber either as scattered individuals or in small groups at relatively short intervals, repeated indefinitely, encouraging the continuous establishment of reproduction and maintaining an uneven-aged stand.

Silvicultural Systems

A planned program of silvicultural treatment during the whole life of the stand; it includes not only the reproduction cuttings but also any intermediate cuttings. The reproduction methods used have such a decisive influence on the form and treatment of the stand that the name of the method is commonly applied to the silvicultural system; the shelterwood system, for example, leads to reproduction by means of the shelterwood method of cutting.

A silvicultural system consists of a number of steps in a logical sequence. In the application of the shelterwood system there might be some early cleanings in established reproduction, followed a thinning(s), and a one or two stage final harvest cutting.

Note: these definitions and descriptions have been taken from The Practice of Silviculture, by David M. Smith.