Thinning

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Apples thinning: before (at left) after (at right) Abans d'aclarirPICT1233-horz.jpg
Apples thinning: before (at left) after (at right)

Thinning is a term used in agricultural sciences to mean the removal of some plants, or parts of plants, to make room for the growth of others. Selective removal of parts of a plant such as branches, buds, or roots is typically known as pruning.

Contents

In forestry, thinning is the selective removal of trees, primarily undertaken to improve the growth rate or health of the remaining trees. Overcrowded trees are under competitive stress from their neighbors. Thinning may be done to increase the resistance of the stand to environmental stress such as drought, insect infestation, extreme temperature, or wildfire. [1] [2]

In forestry

Thinning in the Umatilla National Forest Umatilla National Forest, salvage thinning Badger TS (36044553064).jpg
Thinning in the Umatilla National Forest

Tree thinning may be practised in forestry to make a stand more profitable in an upcoming final felling, or to advance ecological goals such as increasing biodiversity or accelerating the development of desired structural attributes such as large diameter trees with long tree crowns.

Early thinning, eg. after 20 years, rather than late thinning, eg. after 50 years, has different effects on the trees thinned. An early thinning would encourage trees to develop wider crowns, increase trunk diameter and be more stable against threats like snow breakage or windthrow. Too much thinning too early in their lifespan could cause a site to overgrow with shrubs and prevent an understory from regenerating efficiently. Alternatively, thinning an area later would mean that trees will grow tall and slender; although the trees would gain value incrementally with time, they may be less marketable as thinness reduces said value. Epicormic shooting is a risk when thinning is carried out tardily, which can lead to tree branchiness and the presence of knots in the resultant timber harvest, again reducing value.

Traditionally, thinning has been performed to create a desired balance between individual tree attributes (such as tree diameter) and area-relative attributes such as volume. [3] It has been, and often still is, applied with the desire to create uniform stands. As a result, thinning treatments are often described in terms of number of trees per area to remain or average spacing between trees. It is also necessary when too many trees were initially planted or survived through the seedling phase. Planting less and thinning less saves money in commercial forestry; thinning is carried out in a balanced manner, dependent on site qualities as well as planting régimes.

There is no certain outcome from thinning nor standard timing for it. Individual site conditions and responses of individual or mixed species on sites may vary considerably and thus responses to thinnings likewise are inconsistent. Norway spruce on a suitable site have responded well in terms of growth increment, to late thinnings (after 50 years) [4] whereas other species have not for example slash pine. [5]

Due to such variability it is better to talk about a thinning régime rather than one particular method of thinning taking place in a stand.

Thinning methods

Ecological thinning

A thinning in which the trees removed have little or no economic value is called a pre-commercial thinning. Ecological thinning is a variant of this being studied for use in forest conservation. The primary aim of forest thinning is to increase growth of selected trees, but ecological thinning is done to favor development of wildlife habitat (such as hollows) rather than focusing on increased timber yields. Thinning may also reduce the risk of wildfire by increasing availability of groundwater as well as reducing fuel for wildfires. [2]

Chemical thinning is a form of non-commercial thinning in which the trees are killed while they stand by injecting a chemical such as glyphosate (Round Up) into a cut made in the stem. This reduces the number of live stems remaining, providing a benefit to those that remain and may be undertaken where the cost of a traditional thin is high. It can also be done on very exposed sites where breaking the canopy through a traditional thinning operation would expose the stand to a high risk of windthrow.

Another type of thinning is called variable density thinning. In this type of thinning, the intent is to manage various portions of the stand in different ways to create structural and spatial heterogeneity. The intent is often to increase biodiversity or wildlife habitat. In variable density thinning, some portions of the stand may not be entered. These unentered areas, sometimes called reserves, leave islands, or skips (as they are skipped over) help retain a large range of tree diameters, serve as a future source of competition-related mortality, and may preserve snags, down wood, and understory plants.

Other portions of a stand could be heavily thinned or gaps or openings could be created. These areas accelerate the growth rates of trees in the open areas or on their perimeter and help retain or develop long crowns with live branches. Another portion of the stand, sometimes referred to as the matrix, is thinned to result in residual trees densities which area in between the other extremes. Over the whole area, a wide variety of trees with different diameters and species are retained.[ citation needed ]

Virtual thinning in marteloscopes

Timber marking - selecting the trees to be cut in a forest stand by marking them - is a crucial task for a forest manager. Because of the irreversible character of cutting trees, tools were developed to virtually practice tree selection. A marteloscope is a forest site (typically a one hectare rectangular site) where all trees are numbered, mapped and recorded. This information can then be visualised through an application on a hand-held device such as a tablet. [8]

In agriculture

Sugar beets thinning Sugar beets thinning.jpg
Sugar beets thinning

In agriculture and gardening, thinning is the selective removal of flowers, fruits, shoots, and seedlings or young plants to allow adequate space for the remaining organs/plants to grow efficiently. In large-scale farming, techniques like precision seeding and transplanting can eliminate the need for thinning by starting plants at their optimum spacing. On a smaller scale, such as a home vegetable garden, thinning can be used as a way to make maximum use of space for certain crops. For example, beets, carrots, green onions and others can be planted densely, and then thinned to make room for continued growth of the plants left in the soil, and also as a harvest of baby vegetables (beet greens, baby carrots, baby onions). Also thinning is used in post harvesting.[ citation needed ]

See also

Related Research Articles

<span class="mw-page-title-main">Logging</span> Process of cutting, processing, and moving trees

Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidding, on-site processing, and loading of trees or logs onto trucks or skeleton cars. In forestry, the term logging is sometimes used narrowly to describe the logistics of moving wood from the stump to somewhere outside the forest, usually a sawmill or a lumber yard. In common usage, however, the term may cover a range of forestry or silviculture activities.

<span class="mw-page-title-main">Coppicing</span> Method of woodland management

Coppicing is the traditional method in woodland management of cutting down a tree to a stump, which in many species encourages new shoots to grow from the stump or roots, thus ultimately regrowing the tree. A forest or grove that has been subject to coppicing is called a copse or coppice, in which young tree stems are repeatedly cut down to near ground level. The resulting living stumps are called stools. New growth emerges, and after a number of years, the coppiced trees are harvested, and the cycle begins anew. Pollarding is a similar process carried out at a higher level on the tree in order to prevent grazing animals from eating new shoots. Daisugi, is a similar Japanese technique.

<span class="mw-page-title-main">Arboriculture</span> Management and study of trees and other woody plants

Arboriculture is the cultivation, management, and study of individual trees, shrubs, vines, and other perennial woody plants. The science of arboriculture studies how these plants grow and respond to cultural practices and to their environment. The practice of arboriculture includes cultural techniques such as selection, planting, training, fertilization, pest and pathogen control, pruning, shaping, and removal.

<span class="mw-page-title-main">Pruning</span> Selective removal of parts of a plant

Pruning is a horticultural, arboricultural, and silvicultural practice involving the selective removal of certain parts of a plant, such as branches, buds, or roots.

Silviculture is the practice of controlling the growth, composition/structure, as well as quality of forests to meet values and needs, specifically timber production.

<span class="mw-page-title-main">Clearcutting</span> Forestry/logging practice in which most or all trees in an area are uniformly cut down

Clearcutting, clearfelling or clearcut logging is a forestry/logging practice in which most or all trees in an area are uniformly cut down. Along with shelterwood and seed tree harvests, it is used by foresters to create certain types of forest ecosystems and to promote select species that require an abundance of sunlight or grow in large, even-age stands. Logging companies and forest-worker unions in some countries support the practice for scientific, safety and economic reasons, while detractors consider it a form of deforestation that destroys natural habitats and contributes to climate change. Environmentalists, traditional owners, local residents and others have regularly campaigned against clearcutting, including through the use of blockades and nonviolent direct action.

<i>Picea rubens</i> Species of plant

Picea rubens, commonly known as red spruce, is a species of spruce native to eastern North America, ranging from eastern Quebec and Nova Scotia, west to the Adirondack Mountains and south through New England along the Appalachians to western North Carolina. This species is also known as yellow spruce, West Virginia spruce, eastern spruce, and he-balsam. Red spruce is the provincial tree of Nova Scotia.

<span class="mw-page-title-main">Windthrow</span> Trees uprooted by wind

In forestry, windthrow refers to trees uprooted by wind. Breakage of the tree bole (trunk) instead of uprooting is called windsnap. Blowdown refers to both windthrow and windsnap.

In forestry, fishing and mining, high grading refers to the selective harvesting of goods to keep only the most valuable items. The term is frequently associated with fraud, especially in mining.

Articles on forestry topics include:.

<span class="mw-page-title-main">Ecological thinning</span>

Ecological thinning is a silvicultural technique used in forest management that involves cutting trees to improve functions of a forest other than timber production.

<span class="mw-page-title-main">Selection cutting</span> Forestry practice

Selection cutting, also known as selection system, is the silvicultural practice of harvesting trees in a way that moves a forest stand towards an uneven-aged or all-aged condition, or 'structure'. Using stocking models derived from the study of old growth forests, selection cutting, also known as 'selection system', or 'selection silviculture', manages the establishment, continued growth and final harvest of multiple age classes of trees within a stand. A closely related approach to forest management is Continuous Cover Forestry (CCF), which makes use of selection systems to achieve a permanently irregular stand structure.

The following outline is provided as an overview of and guide to forestry:

Salvage logging is the practice of logging trees in forest areas that have been damaged by wildfire, flood, severe wind, disease, insect infestation, or other natural disturbance in order to recover economic value that would otherwise be lost.

<span class="mw-page-title-main">Shelterwood cutting</span>

Shelterwood cutting is the progression of forest cuttings leading to the establishment of a new generation of seedlings of a particular species or group of species without planting. This silvicultural system is normally implemented in forests that are considered mature, often after several thinnings. The desired species are usually long-lived and their seedlings would naturally tend to start under partial shade. The shelterwood system gives enough light for the desired species to establish without giving enough light for the weeds that are adapted to full sun. Once the desired species is established, subsequent cuttings give the new seedlings more light and the growing space is fully passed to the new generation.

<span class="mw-page-title-main">Even-aged timber management</span>

Even-aged timber management is a group of forest management practices employed to achieve a nearly coeval cohort group of forest trees. The practice of even-aged management is often pursued to minimize costs to loggers. In some cases, the practices of even aged timber management are frequently implicated in biodiversity loss and other ecological damage. Even-aged timber management can also be beneficial to restoring natural native species succession.

<span class="mw-page-title-main">Close to nature forestry</span>

Close to nature forestry is a management approach treating forest as an ecological system (ecosystem) performing multiple functions. It is developing in the peri-alpine coutries of Europe for more than 70 years, based on certain sustainable forest management practices from the late 19th century. Close to nature silviculture tries to achieve the management objectives with minimum necessary human intervention aimed at accelerating the processes that nature would do by itself more slowly. It works with natural populations of trees, ongoing processes and existing structures using cognitive approach, as in the case of so called selection forest or other types of uneven-aged forests. Its theory and practice takes forest as a self regulating ecosystem and manages it as such.

<span class="mw-page-title-main">Forestry mulching</span> Soil improvement and conservation methodologies

Forestry mulching is a land clearing method that uses a single machine to cut, grind, and clear vegetation.

<span class="mw-page-title-main">Continuous cover forestry</span> Approach to sustainable forest management

Continuous cover forestry is an approach to the sustainable management of forests whereby forest stands are maintained in a permanently irregular structure, which is created and sustained through the selection and harvesting of individual trees. The term "continuous cover forestry" does not equate exactly to any one particular silvicultural system, but is typified by selection systems. For example, coppice with standards and Reiniger's target diameter harvesting are also continuous cover forestry. Different existing forest stands may require different silvicultural interventions to achieve a continuously productive irregular structure. Crucially, clearcutting and other rotational forest management systems are avoided.

<span class="mw-page-title-main">Tree plantation</span>

A tree plantation, forest plantation, plantation forest, timber plantation or tree farm is a forest planted for high volume production of wood, usually by planting one type of tree as a monoculture forest. The term tree farm also is used to refer to tree nurseries and Christmas tree farms.

References

  1. "Ecological Restoration vs. Thinning". Northern Arizona University. Archived from the original on September 1, 2006.
  2. 1 2 "In California's forests, removing small trees leaves water for bigger ones and for dwindling reservoirs". The Economist. 2016-12-17. ISSN   0013-0613 . Retrieved 2016-12-19.
  3. Smith et al. 1997
  4. Responses from thinning a 50 year old Norway spruce plantation in central New York, SUNY Coll. Enviro. Sci. & Forestry Sch. Tech. Publication No. 1 (ESF 85-002) Drew, AP 1985
  5. Thinning practices in short-rotation stands. In A.B. Crow (Ed.), Advancement in management of Southern pines pg 50-60 10th Ann Forerst Symposium Baton Rouge LA. State UniPress 1961
  6. Baker, Frederick. Theory and Practice of Silviculture. First Edition. New York: McGraw-Hill, 1934. Print.
  7. Silviculture Concepts and Applications, Ralph D. Nyland 2002 Chapter 18 Methods of Thinning
  8. "Marteloscopes and data". iplus.efi.int/. Informar. Retrieved 10 March 2020.