Aspect: The compass direction in which a slope predominantly faces.

Canopy: The continuous layer of foliage from adjacent trees in a stand.

Capturing mortality: Harvesting and using timber from trees that would die and degrade from competition or other natural causes if left alone. (Frequently used in the context of thinnings or timber stand improvement treatments.)

Clearcut: A harvest in which all of the trees on a site are harvested. Clearcut harvests favor regeneration of shade intolerant species. (Learn more at the North Central Forest Management Guides site)

Commercial thinning: Any type of thinning producing merchantable material at least equal to the value of the direct costs of harvesting. (Helms)

Conifer: A tree species that produces seeds in cones.

Crop tree: Any tree selected to be a component of a future commercial harvest. (Often referring to high-value trees left in the forest to increase value for a future harvest.)

Crown: The portion of a tree composed of living foliage and the branches that support it.

Crown class: A category of tree based on its crown position relative to those of adjacent trees. (Helms) [Learn more on our how trees grow page]

Codominant ’Äì A tree whose crown helps to form the general level of the main canopy’Äîreceiving direct sunlight from above but little from the sides.

Dominant ’Äì A tree whose crown extends above the general level of the main canopy’Äîreceiving direct sunlight from above and partly from the sides.

Emergent ’Äì A tree whose crown is completely above the general level of the main canopy’Äîreceiving full sunlight from above and from the sides.

Intermediate ’Äì A tree whose crown extends into the lower portion of the main canopy’Äîreceiving little direct sunlight from above and none from the sides.

Suppressed (overtopped) ’Äì A tree whose crown is completely overtopped by the crowns of one or more neighboring trees.

Early successional: An ecological community that typically colonizes an area relatively quickly after a major disturbance. Young aspen is a common early successional community in northern Minnesota. [See also succession]

Forest health: A general term referring to the forest's vigor and, in general, the absence of major insect or disease outbreaks.

Hardwood: Tree species in the angiosperm group (the flowering plants, that produce seeds enclosed in a fruit). Hardwood trees are characterized by broad leaves (as opposed to needles) and are usually deciduous.

Hazard tree: Any tree that presents a danger. The classic example is a tree with a large dead branch (’Äúwidowmaker’Äù) overhanging a heavily used trail.

Highgrading: The removal of only the most commercially valuable trees (high-grade trees), often leaving a residual stand composed of trees of poor condition or of undesirable species. (Helms)

Intermediate treatment: Any treatment (such as a thinning) designed to enhance growth, quality, vigor, and composition of the stand after establishment or regeneration and prior to final harvest.

Live crown ratio (LCR): The ratio of crown length to total tree height. LCR is one indicator of a stand's need for thinning: Small LCRs (tall trees with small crowns) generally indicate the need to thin the stand.

Landing: The area in which harvested logs are stacked and sorted for transportation off site.

Natural disturbance: A general class of ecological disturbance that results from natural forces. Common Minnesota examples include windstorms, lightning-ignited fires, and outbreaks of native forest pests such as forest tent caterpillars.

Precommercial thinning: A thinning, TSI, or other treatment in which the harvested products cannot be sold for profit. Precommercial treatments cost the landowner money to implement.

Regeneration: Seedlings or saplings existing in a forest stand. (v. ’ÄìEstablishment of new tree seedlings. Regeneration can be natural (from seed or vegetative sources) or artificial (planted). (Helms)

Advance regeneration ’Äì Seedlings or saplings that develop or are present in the understory, prior to a silvicultural treatment.

Rotation: In even-aged systems, the number of years between stand regeneration and final harvest.

Seed-tree: A silvicultural system in which most trees on a site are harvested but seed trees are left on-site to regenerate the stand. (Learn more at the North Central Forest Management Guides site)

Self-thinning: The natural process by which dense stands thin themselves through tree mortality. A classic Minnesota example is the gradual process of young aspen stands self-thinning from several thousand stems per acre (’Äúdog-hair’Äù aspen) down to a lower density as the stand matures.

Serotinous: A pinecone that requires heat from a fire to open and release the seed.

Shade tolerance: A measure of a species' ability to thrive under low light conditions, such as under a dense forest canopy. Different tree species have different levels of shade tolerance. For example, trembling aspen and tamarack are highly shade intolerant (they require full light to thrive), while balsam fir and sugar maple are highly shade tolerant.

Shelterwood: A silvicultural system relying on a series of partial harvests to promote advanced regeneration prior to the final harvest. (Learn more at the North Central Forest Management Guides site)

Silviculture: The art and science of controlling the establishment, growth, composition, health, and quality of forests and woodlands to meet the diverse needs and values of landowners and society on a sustainable basis. (Helms) (Learn more at the North Central Forest Management Guides site)

Slash: Residual branches, tops, and other woody material left on the ground as a result of storm, fire, or timber harvest activities.

Skid road: A temporary forest road used to move logs from the stump to the landing.

Stand: A contiguous group of trees sufficiently uniform in age-class distribution, composition, and structure, and growing on a site of sufficiently uniform quality, to be a distinguishable unit. The stand is generally the unit on which forest management activities occur. (Helms)

Stumpage: The value of timber as it stands uncut in the woods (on the stump).

Stump sprouts: A young tree developed directly from the base, stump, or root of another tree.

Succession: The gradual supplanting of one community of plants by another.

Thinning: Removing some trees from a stand in order to reduce stand density of trees primarily to improve growth, enhance forest health, or capture mortality (Learn more at our thinning page.)

Timber stand improvement (TSI): Improving the quality of a stand through pruning, girdling or removing undesirable species, applying herbicide, or other treatments. TSI treatments are generally precommercial.

Windthrow: Trees uprooted by excessive wind. Shallow-rooted trees (i.e. white pine and birch) are almost always affected.

Sources:

Helms, J.A. 1998. The Dictionary of Forestry. Washington, DC: Society of American Foresters.

Smith, D.M. et al. 1997. The Practice of Silviculture. New York: J. Wiley & Sons.