SILVICULTURE TERMINOLOGY

As prepared by the Silviculture Instructors Subgroup, Silviculture Working Group (D2), Society of American Foresters and published in The Dictionary of Forestry (1998, Society of American Foresters) with additional terms

Terminology Committee: David L. Adams (Univ. Idaho), John D. Hodges (Mississippi State Univ.), David L. Loftis (USDA FS), James N. Long (Utah State Univ.), Robert S. Seymour (Univ. Maine), John A. Helms, Chair (Univ. California). Reviewed by membership of Silviculture Working Group

This project was conceived by Prof. Clair Merritt (Purdue Univ.) who served as the committee's initial chair. Others contributing to earlier drafts included Al Alm (Univ. Minnesota), Ted Daniel (Utah State Univ.), and Ralph Griffen (Univ. Maine).

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Advance Regeneration (Reproduction) syn. Advance Growth

Seedlings or saplings that development or are present in the understory

Afforestation

Establishment of a forest or stand in an area where the preceding vegetation or land use was not forest

Age class (Cohort)

1. One of the intervals into which the range of trees is divided for classification or use. 2. A distinct aggregation of trees originating from a single natural event or regeneration activity, or a grouping of trees, e.g. 10-year age class, as used in inventory or management.

All-aged Stand

A stand with trees of all or almost all age classes, including those of exploitable age (see Stand, Two-aged Stand, Uneven-aged Stand)

Allogenic

Originating external to a system

Autogenic

Originating from within a system

Artificial Regeneration (Reproduction)

A group or stand of young trees created by direct seeding or by planting seedlings or cuttings.

Basal Area

1. The cross-sectional area of a single stem, including the bark, measured at breast height (4.5 feet or 1.37 m above the ground). 2. The cross-sectional area of all stems of a species or all stems in a stand measured at breast height and expressed per unit of land area

Best Management Practices (BMP)

A practice or usually a combination of practices that are determined by a state or a designated planning agency to be the most effective and practicable means (including technological, economic, and institutional considerations) of controlling point and nonpoint source pollutants at levels compatible with environmental quality goals --note BMPs were conceptualized in the 1972 US Federal Water Pollution Control Act

Biome

A regional ecosystem with distinct assemblage of vegetation, animals, microbes, and physical environment often reflecting a certain climate and soil

Breast Height

A standard height from ground level for recording diameter, girth, or basal area of a tree, generally 4.5 feet (1.37 m).

Broadcast

To spread or apply seed, fertilizer, or pesticides more or less evenly over an entire area

Broadcast Burn

A prescribed fire allowed to burn over a designated area within well-defined boundaries to achieve some land management objective

Brush

Shrubby vegetation that does not produce timber

Canopy

The foliar cover in a forest stand consisting of one or several layers.

Canopy Closure

See Crown Cover

Character

A distinctive and usually variable feature (e.g., color, size, performance) exhibited by all individuals of a group capable of being described or measured

Chopper (Drum Chopper)

A large cylindrical drum, which may be partially filled with water, with cutting blades mounted parallel to its axis and drawn by a tractor or skidder across a site to break up slash or crush scrubby vegetation prior to (usually) burning and planting (see Site Preparation)

Clearcutting

(see Regeneration Method)

Cleaning

A release treatment made in an age class not past the sapling stage in order to free the favored trees from less desirable individuals of the same age class which overtop them or are likely to do so (see Improvement Cutting, Liberating, Weeding).

Climax

The culminating stage of plant succession for a given environment; the vegetation conceived as having reached a highly stable condition

Codominant

(see Crown Class)

Cohort

see Age Class

Competition

The extent to which each organism maximizes fitness by both appropriating contested resources from a pool not sufficient for all, and adapting to the environment altered by all participants --note competition among individuals of the same species is termed intraspecific competition; competition between different species is termed interspecific competition

Composition

The proportion of each tree species in a stand expressed as a percentage of either the total number, basal area, or volume of all tree species in the stand.

Coppice

(see Regeneration Method)

Crop Tree

Any tree that is selected to become a component of a future commercial harvest.

Crown

The part of a tree or woody plant bearing live branches and foliage.

Crown Class

A category of tree based on its crown position relative to the crowns of adjacent trees.

Emergent

Trees with crowns completely above the general level of the main canopy receiving full light from above and from all sides.

Dominant

Trees with crowns extending above the general level of the main canopy of even-aged stands or, in uneven-aged stands, above the crowns of the tree's immediate neighbors, and receiving full light from above and partly from the sides.

Codominant

Trees with crowns forming the general level of the main canopy in even-aged stands or, in uneven-aged stands, the main canopy of the tree's immediate neighbor's, receiving full light from above and comparatively little from the sides.

Intermediate

Trees with crowns extending into the lower portion of the main canopy of even-aged stands or, in uneven-aged stands, into the lower portion of the canopy formed by the tree's immediate neighbors, but shorter in height than the codominants. They receive little direct light from above and none from the sides.

Overtopped (Suppressed)

Trees of the varying levels of vigor that have the crowns completely overtopped by the crowns of one or more neighboring trees.

Crown Cover

The ground area covered by the crowns of trees or woody vegetation as delimited by the vertical projection of crown perimeters and commonly expressed as a percent of total ground area (syn. Canopy Cover).

Crown Density

The amount and compactness of foliage of the crowns of trees and shrubs.

Culmination of Mean Annual Increment (CMAI)

The age in the growth cycle of a tree or stand at which the mean annual increment (MAI) for height, diameter, basal area, or volume is at a maximum

Current Annual Increment (CAI)

The growth observed in a tree or stand in a specific one-year period (see Mean Annual Increment (MAI), Periodic Annual Increment (PAI))

Cutting Cycle

The planning interval between partial harvests in an uneven-aged stand (see Thinning Interval)

Density Management

The cutting or killing of trees to increase spacing and accelerate growth of remaining trees --note density management is used to improve forest health of stands, to open the forest canopy for selected species, to maintain understory vegetation, to accelerate growth to maintain desired seral condition, or to attain later-successional characteristics for biological diversity

Disk

A plow drawn by a tractor or skidder having one or more heavy, round concave, sharpened, freely rotating steel disks angled to cut and turn a furrow

Disturbance

Any relatively discrete event in time that disrupts ecosystem, community, or population structure and changes resources, substrate availability, or the physical environment

Dominant

(see Crown Class)

Ecosystem

A spatially explicit, relatively homogeneous unit of earth that includes all interacting organisms and components of the abiotic environment within its boundaries -- note an ecosystem can be of any size

Ecosystem Management

Management guided by explicit goals, executed by policies, protocols, and practices, and made adaptable by monitoring and research based on the best understanding of ecological interactions and processes necessary to sustain ecosystem composition, structure, and function over the long term --note the term was initially introduced by the USDA Forest Service

Emergent

(see Crown Class)

Emulsifier

A chemical that allow another substance to form an emulsion or to stabilize in water --note an emulsifier is commonly added to oil-based pesticides to allow them to mix with water (see Surfactant)

Even-Aged Stand

A stand of trees containing a single age class in which the range of tree ages is usually less than 20 percent of rotation.

Forb

Any broad-leafed, herbaceous plant other than those in the Poaceae (Gramineae), Cyperaceae, and Juncaceae

Fertilization

The addition of nutrient elements to increase growth rate or overcome a nutrient deficiency in the soil.

Forest

An ecosystem characterized by a more or less dense and extensive tree cover, often consisting of stands varying in characteristics such as species, composition, structure, age class, and associated processes, and commonly including meadows, streams, fish, and wildlife

Forest Health

The perceived condition of a forest derived from concerns about such factors as its age, structure, composition, function, vigor, presence of unusual levels of insects or disease, and resilience to disturbance

Forest Management

The practical application of biological, physical, quantitative, managerial, economic, social, and policy principles to the regeneration, management, utilization, and conservation of forests to meet specified goals and objectives while maintaining the productivity of the forest

Forestry

The profession embracing the science, art, and practice of creating, managing, using, and conserving forests and associated resources for human benefit and in a sustainable manner to meet desired goals, needs, and values

Forest Tree Improvement (Forest Tree Breeding)

The practice of tree breeding in combination with cultural practices

Genotype

An individual's hereditary (genetic) constitution as distinguished from its physical appearance or phenotype.

Goal

The end state, aspiration, or purpose that reflects what a decision maker hopes to accomplish normally expressed in broad, general terms

Grass

A member of the family Poaceae (Gramineae). See Forb, Herb

Green Tree Retention

see Reserve Trees

Group Selection

(see Regeneration Methods)

Gross Primary Production

The total assimilation of energy and nutrients by an organism or a plant community per unit of time

Growing Space

1. The physical area available to and utilized by a tree 2. That portion of the resources of the site (light, nutrients, etc.) Available to and utilized by a tree -- note growing space is not usually directly measurable but often represented from crown projection or leaf area or as an area allocation obtained using various mathematical techniques

Growing Stock

All the trees growing in a forest or in a specified part of it, usually commercial species, meeting specified standards of size, quality, and vigor, and generally expressed in terms of number or volume

Growth-and-Yield Model

A set of relationships, usually expressed as equations and embodied in a computer program, that provides estimates of future stand development given initial stand conditions and a specified management regime --note growth-and-yield models are used to generate managed-stand yield tables, predict future stand conditions for management planning, update inventories, and compare predicted results of alternative management regimes

Grub

To remove stumps or shrubs from the ground by hand or machine, typically prior to road building or regeneration (see Scalp, Site Preparation)

Harvesting Method (Cutting Method)

A cutting method by which a stand is logged; emphasis is on meeting logging requirements while concurrently attaining Silvicultural objectives (see Regeneration Method)

Herb

A nonwoody, vascular plant such as a grass, a grasslike plant, a fern, or a forb -- see Herbaceous --note herbs are collectively termed herbage

Herbaceous

A class of vegetation dominated by nonwoody plants known as herbs

High Forest

A stand of trees, generally of seedling origin, that normally develop a high, closed canopy

High Grading

The removal of the most commercially valuable trees (high-grade trees), often leaving a residual stand composed of trees of poor condition or species composition

Improvement cutting

The removal of less desirable trees of any species in a stand of poles or larger trees, primarily to improve composition and quality (see Cleaning, Liberating, and Weeding).

Industrial Forest

Forest land owned by a company or individual operating a primary wood-using plant and managed primarily for wood products

Ingrowth

The volume, basal area, or number of those trees in a stand that were smaller than a prescribed minimum diameter or height limit at the beginning of any growth-determining that during a specified period have grown past an arbitrary lower limit of (usually) diameter or height. Ingrowth is usually measured as basal area or volume per unit area.

Intermediate

(see Crown Class)

Intermediate Treatments (Tending)

Any treatment or tending designed to enhance growth, quality, vigor, and composition of the stand after establishment or regeneration and prior to final harvest (see Tending, Stand Improvement).

Juvenile

Distinguishable from adults by external characters but less than breeding age

Juvenile Phase

The period during the life of a tree before flowering or before a mature type of foliage appears

Juvenile Wood

The xylem formed in the first 10 to 15 rings nearest the pith, which is strongly controlled by growth regulators from the crown and which, in softwoods, has lower specific gravity.

Leaf Area Index (LAI)

The sum of all the upper or all-sided leaf surface area projected downward per unit of ground beneath the canopy

Leave Strip

A narrow band of forest trees left between cutting units or adjacent to a road or stream (also buffer strip, green strip, streamside management zone)

Leave Tree

A tree (marked to be) left standing for wildlife, seed production, etc., in an area where it might otherwise be felled

Lethal Dose (LD)

The amount of a pesticide necessary to kill a specified proportion of a population

Liberation

A release treatment made in a stand not past the sapling stage in order to free the favored trees from competition of older, overtopping trees.

Live Crown Ratio

The ratio of crown length to total tree height

Long-term Sustained Yield

The highest uniform wood yield that may be sustained under a specific management intensity consistent with multiple-use objectives on lands being managed for timber production

Lop

To cut limbs from trees, whether standing, felled, or fallen (syn prune, delimb)

Lop-and-scatter

A hand method of removing the upward-extending branches from tops of felled trees to keep slash low to the ground, to increase rate of decomposition, lower fire hazard, or as a pretreatment prior to burning

Low Forest

A forest produced from vegetative regeneration, i.e., coppice or coppice with reserves (see Regeneration Method, High Forest)

Managed-Yield Table

A yield table, usually developed from remeasured plot data, that accounts for the effects of differences in stand origin, stand density, and effects of management treatments such as thinning and fertilization in addition to the variables site index and age

Management Objective

A concise, time-specific statement of measurable planned results that correspond to preestablished goals in achieving a desired outcome

Management Plan

A predetermined course of action and direction to achieve a set of results, usually specified as goals, objectives, and policies

Mature

Of trees or stands pertaining to a tree or even-aged stand that is capable of sexual reproduction, has attained most of it potential height growth, or has reached merchantability standards

Mean Annual Increment (MAI)

The total increment of a tree or stand (standing crop plus thinnings) up to a given age divided by that age (see Culmination of Mean Annual Increment, Current Annual Increment (CAI), Periodic Annual Increment (PAI), periodic increment)

Mean Diameter

Of a group of trees, crop, or stand Quadratic mean diameter, the diameter corresponding to their mean basal area.

Monoculture

A stand of a single species, generally even-aged.

Multiaged (Multicohort) Stand

A stand with two or more age classes or cohorts (see age class, cohort, uneven-aged stand)

Natural Pruning

The process of branch death and shedding caused by physical and biotic agents (syn self-pruning)

Natural Regeneration

The establishment of a plant or a plant age class from natural seeding, sprouting, suckering, or layering

Net Annual Growth

The average annual net increase in the volume of trees during the period between inventories --note components of net annual growth include the increment in net volume of trees at the beginning of the period surviving to the end of the period, plus the net volume of trees reaching the minimum size class during the year, minus the volume of trees that died and the net volume of trees that became cull during the period

Net Primary Production

The gross primary production minus biomass used in respiration by primary producers

Nonindustrial Private Forest (NIPF)

Forest land that privately owned by individuals or corporations other than forest industry and where management may include objectives other than timber production

Normal-Yield Table

A yield table showing the average development of well-stocked stands over time, usually by site index classes --note in North America usage, normal-yield tables were usually developed from one-time measurements in unmanaged stands of natural origin and are historically important but of limited usefulness under modern conditions; in Europe usage, normal-yield tables do not necessarily represent stands of natural origin only and are often based on remeasured plots, sometimes with low thinning

Nurse Tree (Nurse Crop)

A tree, group or crop of trees, shrubs or other plants, either naturally occurring or introduced, used to nurture, improve survival or improve the form of a more desirable tree or crop when young by protecting it from frost, isolation, wind, or insect attack

Objective

See Management Objective

Old-growth Forest

Late successional stage of forest development

Overmature

Of trees or stands 1. A tree or even-aged stand that has reached that stage of development when it is declining in vigor and health and reaching the end of its natural life span. 2. A tree or even-aged stand that has begun to lessen in commercial value because of size, age, decay, or other factors

Overstory

That portion of the trees, in a forest of more than one story, forming the upper or uppermost canopy layer

Overstory Removal

The cutting of trees constituting an upper canopy layer in order to release trees to other vegetation in an understory (see Clearcutting).

Overtopped

(see Crown Class)

Partial Cutting

Removal of only part of a stand for purposes other than regenerating a new age class -- note partial cutting is not considered a regeneration method (syn selective cutting)

Periodic Annual Increment

The growth of a tree or stand observed over a specific time period divided by the length of the period (see Mean Annual Increment (MAI), Current Annual Increment (CAI), Periodic Increment)

Periodic Increment

The growth of a tree or stand during any specified period, commonly 10 or 20 years

Pest

An organism that is undesirable or detrimental to the interests of humans

Phenotype

1. The observed state, description, or degree of expression of a character or trait. 2. The product of the interaction of the genes of an organism (genotype) with the environment

Pioneer

A plant capable of invading bare sites, e.g., newly exposed soil, and persisting there or colonizing them until supplanted by successional species

Plantation

A stand composed primarily of trees established by planting or artificial seeding

Plus Tree

A tree selected on the basis of its outstanding phenotype but not yet clonally or progeny tested

Pole

A tree between the size of a sapling and a mature tree -- note the size of a pole varies by region

Precommercial Thinning (PCT)

The removal of trees not for immediate financial return by to reduce stocking to concentrate growth on the more desirable trees

Prescribed Burn

To deliberately burn wildland fuels in either their natural or their modified state and under specified environmental conditions, which allows the fire to be confined to a predetermined area and produces the fireline intensity and rate of spread required to attain planned resource management objectives

Prescription

A planned series of treatments designed to change current stand structure to one that meets management goals

Principal Species

The species to which the silviculture of a mixed forest is primarily directed, for either economic or protective value

Production

The amount of goods or services produced over a given time

Productivity

The relative capacity of an area to sustain a supply of goods or services in the long run (see Site Quality)

Productivity Class

A classification of forest land in terms of potential annual cubic volume growth per unit area at culmination of mean annual increment in fully stocked natural stands

Progeny

The offspring of a particular tree or mating

Progeny Test

A planting generally designed to evaluate parents by comparing the performance of their offspring or to provide selection of future parents from with the planting itself

Protection Forest

An area, wholly or partly covered with trees, managed primarily to regulate stream flow, maintain water quality, minimize erosion, stabilize drifting sand, conserve ecosystems, or provide other benefits via protection

Provenance

The original geographic source of seed

Provenance Test

A planting in which population samples from stands of known geographic origins are grown together in one or more locations

Pruning

The removal, close to the branch collar or flush with the stem, of side branches (live or dead) and multiple leaders from a standing tree

Pruning Lift

Pruning to a specified height or stem diameter in one operation or stage

Quadratic Mean Diameter

See Mean Diameter

Radiational Cooling

The cooling of the earth's surface and adjacent air accomplished (mainly at night) whenever the earth's surface suffers a net loss of heat due to terrestrial radiation

Recruitment

1. Regeneration 2. The additional trees moving from one size class to another

Reforestation

The reestablishment of forest cover either naturally or artificially

Regeneration

1. Seedlings or saplings existing in a stand 2. The act of renewing tree cover by establishing young trees naturally or artificially (syn. Reforestation).

Regeneration Cut(ting)

Any removal of trees intended to assist regeneration already present or to make regeneration possible

Regeneration (Reproduction) Method

A cutting method by which a new age class is created. The major methods are Clearcutting, Seed Tree, Shelterwood, Selection, and Coppice (see Harvesting Method).

Coppice Methods

Methods of regenerating a stand in which the majority of regeneration is from stump sprouts or root suckers.

Coppice

All trees in the previous stand are cut and the majority of regeneration is from sprouts or root suckers.

Coppice Selection

Only selected stems of merchantable size are cut at each felling, giving uneven-aged stands

Coppice with Reserves (Coppice with Standards)

Reserve trees are retained to attain goals other than regeneration. The method normally creates a two-aged stand.

Even-Aged Methods

Methods to regenerate a stand with a single age class.

Clearcutting

The cutting of essentially all trees, producing a fully exposed microclimate for the development of a new age class. Regeneration is from natural seeding, direct seeding, planted seedlings, or advance reproduction. Cutting may be done in groups or patches (Group or Patch Clearcutting), or in strips (Strip Clearcutting). In the Clearcutting System, the management unit or stand in which regeneration, growth, and yield are regulated consists of the individual clearcut stand (see Group Selection). When the primary source of regeneration is advance reproduction, the preferred term is Overstory Removal.

Clearcutting with Reserves (see Two-Aged Methods)

Seed Tree

The cutting of all trees except for a small number of widely dispersed trees retained for seed production and to produce a new age class in fully-exposed micro-environments. Seed trees are removed after regeneration is established.

Seed Tree with Reserves (see Two-Aged Methods)

Shelterwood

The cutting of most trees, leaving those needed to produce sufficient shade to produce a new age class in a moderated microenvironment. The sequence of treatments can include three distinct types of cuttings: 1) an optional preparatory cut to enhance conditions for seed production; 2) an establishment cut to prepare the seed bed and to create a new age class; and 3) a removal cut to release established regeneration from competition with the overwood. Cutting may be done uniformly throughout the stand (Uniform Shelterwood), in groups or patches (Group Shelterwood), or in are in strips (Strip Shelterwood). In a strip shelterwood, regeneration cutting may progress against the prevailing wind.

Shelterwood with Reserves (see Two-Aged Methods)

Two-Aged Methods

Methods designed to maintain and regenerate a stand with two age classes. In each case the resulting stand may be two-aged or tend towards an uneven-aged condition as a consequence of both an extended period of regeneration establishment and the retention of reserve trees that may represent one or more age classes.

Clearcutting with Reserves

A clearcutting method in which varying numbers of reserve trees are not harvested to attain goals other than regeneration.

Seed Tree with Reserves

A seed tree method in which some or all of the seed trees are retained after regeneration has become established to attain goals other than regeneration.

Shelterwood with Reserves

A variant of the Shelterwood Method in which some or all of the shelter trees are retained, well beyond the normal period of retention, to attain goals other than retention.

Uneven-Aged (Selection) Methods

Methods of regenerating a forest stand, and maintaining an uneven-aged structure, by removing some trees in all size classes either singly, in small groups, or in strips. (syn All-aged Stand)

Group Selection

Trees are removed, and new age classes are established, in small groups. The maximum width of groups in approximately twice the height of the mature trees, with small openings providing microenvironments suitable for tolerant regeneration and the larger openings providing conditions suitable for more intolerant regeneration. In the Group Selection System, the management unit or stand in which regeneration, growth, and yield are regulated consists of a landscape containing an aggregation of groups (see Clearcutting).

Group Selection with Reserves

Some trees within the group are not cut to attain goals other than regeneration within the group.

Single Tree Selection

Individual trees of all size classes are removed more-or-less uniformly throughout the stand to promote growth of remaining trees and to provide space for regeneration

Regeneration (Reproduction) Period

The time between the initial regeneration cutting and the successful reestablishment of a new age class by natural means, planting, or direct seeding.

Regular Uneven-Aged (Balanced) Stand

A group of trees in which three or more distinct age classes occupy approximately equal areas and provide a balanced distribution of diameter classes.

Relative Stand Density

The ratio, proportion, or percent of absolute stand density to a reference level defined by some standard level of competition (see Stand Density)

Relative Thinning Intensity

The periodic (annual) yield of a stand from thinnings, expressed as a percentage of its periodic annual increment

Release (Release Operation)

A treatment designed to free young trees from undesirable, usually overtopping, competing vegetation. Treatments include cleaning, liberating, and weeding (see Stand Improvement).

Removal Cut

See Regeneration Method

Reserve Trees (Standards, Green Tree Retention)

Trees, pole-sized or larger, retained in either a dispersed or aggregated manner after the regeneration period under the Clearcutting, Seed Tree, Shelterwood, Group Selection, or Coppice Methods (syn Standard, Green Tree Retention)

Resilience

The capacity of a (plant) community or ecosystem to maintain or regain normal function and development following disturbance (see Forest Health)

Rhizome

A modified stem that grows below ground, commonly stores food materials, and produces roots, scale leaves, and suckers irregularly along its length and not just at nodes -- rhizomatous plants include bamboo, horsetail, and bracken fern (see Stolon)

Root Pruning (Undercutting)

The cutting of seedling roots, with minimum disturbance, in a nursery bed to limit their vertical and lateral growth (see wrenching)

Rotation

In even-aged systems, the period between regeneration establishment and final cutting.

Salvage Cutting (Salvage)

The removal of dead trees being damaged or dying due to injurious agents other than competition, to recover value that would otherwise be lost.

Sanitation Cutting

The removal of trees to improve stand health by stopping or reducing actual or anticipated spread of insects and disease (see Stand Improvement)

Sapling

A tree, usually young, that is larger than a seedling but smaller than a pole. Size varies by region.

Scalp

To remove vegetation and other organic or inorganic material to expose underlying mineral soil and prepare an area for planting or seeding

Scarification

1. Mechanical removal of competing vegetation or interfering debris, or disturbance of the soil surface, designed to enhance reforestation 2. Chemical, mechanical, heat, or moisture treatment of seeds to make the seed coat permeable and improve germination

Seed Bed

The soil or forest floor on which seed falls

Seed Certification

The process of guaranteeing by an accredited agency of the origin (geographic, genetic), purity, quality, clean condition, etc., of a given lot of seed

Seeding (Direct Seeding, Sowing)

1. The production or shedding of seed by a plant 2. The distribution of seed by hand or machine in regeneration

Seedlot

A collection of seeds, usually of known origin

Seed Orchard

A plantation consisting of clones or seedlings from selected trees for early and abundant production of seed and to promote balanced, random mating

Seed Production Area

An existing stand that is usually upgraded and opened by removal of phenotypically undesirable trees and then cultured for early, abundant seed production

Seed Tree

(see Regeneration Method)

Seed Year

A year in which trees or other plants produce abundant seed as individuals or as a stand

Seed Zone

A designated area, usually with definite topographic bounds, climate, and growing conditions, containing trees with relatively uniform genetic (racial) composition as determined by progeny testing various seed sources

Self-thinning

Mortality attributable to overcrowding within a stand

Seral Stage

A temporal and intermediate stage in the process of succession

Sere

The individual sequential stages of forest succession

Serotinous

Pertaining to fruit or cones that remain on a tree without opening for one or more years --note in some species cones open and seeds are shed when heat is provided by fires or hot and dry conditions

Shade Intolerant

Having the capacity to compete for survival under direct sunlight conditions (see Shade Tolerant, Tolerance)

Shade Tolerant

Having the capacity to compete for survival under shaded conditions

Shelterwood

(see Regeneration Method)

Shrub

A woody, perennial plant differing from a perennial herb in its persistent and woody stem, and less definitely from a tree in its lower stature and the general absence of a well-defined main stem

Sib (Sibling)

An offspring that has one or both parents in common with another individual --note full sibs have both parents in common, half sibs only one

Silvics

The study of the life history and general characteristics of forest trees and stands, with particular reference to environmental factors, as a basis for the practice of silviculture

Silvicultural Prescription

See Prescription

Silvicultural System

A planned series of treatments for tending, harvesting, and reestablishing a stand --note the system name is based on the number of age classes or the regeneration method used

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.

Single Tree Selection

(see Regeneration Method)

Site

The area in which a plant or stand grows, considered in terms of its environment, particularly as this determines the type and quality of the vegetation the area can carry

Site Class

A classification of site quality, usually expressed in terms of ranges of dominant tree height at a given age or potential mean annual increment at culmination.

Site Height

The average height of trees used to estimate site index in an even-aged stand

Site Index

A species-specific measure of actual or potential forest productivity expressed in terms of the average height of tree included in a specified stand component at a specified index or base age.

Site Preparation

A hand or mechanized manipulation of a site designed to enhance the success of regeneration. Treatments may include bedding, burning, chemical spraying, chopping, disking, drainage, raking and scarifying. All treatments are designed to modify the soil, litter, and vegetation and to create microclimate conditions conducive to the establishment and growth of desired species (see chopper, disk, grub, scalp, windrow)

Site Productivity Class

A species-specific classification of forest land in terms of inherent capacity to grow crops of industrial, commercial wood -- note usually derived from Site Index)

Site Quality (Productivity)

The productive capacity of a site, usually expressed as volume production of a given species.

Snag

A standing, generally unmerchantable dead tree from which the leaves and most of the branches have fallen.

Sprout

Generally, a shoot arising from the base of a (woody) plant, whether from the stool (a stool sprout) or as a sucker

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 (see Mixed, Pure, Even-Aged, and Uneven-Aged).

Mixed Stand

A stand in which there is a mixture of species.

Pure Stand

A stand composed of essentially a single species

Stratified Mixture

A stand in which different species occupy different strata of the total crown canopy.

Standard

See Reserve Tree

Stand Density

1. A quantitative measure of stocking expressed either absolutely in terms of number of trees, basal area, or volume per unit area or relative to some stand condition 2. A measure of the degree of crowding of trees within stocked areas commonly expressed by various growing space ratios, e.g., height/spacing (see Relative Stand Density, Stand Density Index)

Stand Density Index

1. A widely used measure developed by Reineke (1933) that expresses relative stand density in terms of the relationship of a number of trees to stand quadratic mean diameter 2. Any index that expresses relative stand density based on a comparison of measured stand values with some standard condition

Stand Improvement

A term comprising all intermediate cuttings made to improve the composition, structure, condition, health, and growth of even - or uneven- aged stands (see Release)

Stand Structure

The horizontal and vertical distribution of components of a forest stand including the height, diameter, crown layers and stems of trees, shrubs, herbaceous understory, snags, and down woody debris.

Stewardship

The administration of land and associated resources in a manner that enables their passing on to future generations in a healthy condition

Stocking

An indication of growing-space occupancy relative to a preestablished standard. Common indices of stocking are based on percent occupancy, basal area, relative density, stand density index, and crown competition factor.

Stolon

A stem or branch that grows along the ground surface and takes root at its nodes (see Rhizome)

Stool

A living stump (capable of) producing sprouts (see Coppice)

Stratification

The exposure of seed to a cold, moist treatment to overcome dormancy and promote germination

Stratum (Canopy Layer, Story)

A distinct layer of vegetation within a forest community.

Stumpage (Stumpage Value)

1. Standing timber as viewed by a commercial cutter 2. The value of timber as it stands uncut in terms of an amount per unit area

Stump Sprout

Regeneration of shoot growth from either adventitous or dormant buds form a cut tree stump

Subclimax

The (seral) stage in plant succession, immediately preceding the climax (see Seral Stage)

Succession

A series of dynamic changes by which organisms succeed one another through a series of plant community (seral) stages leading to potential natural community or climax

Sucker

A shoot arising from below ground level either from a rhizome or from a root (see Coppice)

Suppressed

(See Crown Class)

Surfactant

An ingredient in a pesticide formulation that modifies the relationship between the surfaces of a liquid and another liquid or surface

Sustainability

The capacity of forests, ranging from stands to ecoregions, to maintain their health, productivity, diversity, and overall integrity, in the long run, in the context of human activity and use

Sustainable Forest Management (Sustainable Forestry) (SFM)

The practice of meeting the forest resource needs and values of the present without compromising the similar capability of future generations --note criteria for sustainable forestry include (a) conservation of biological diversity, (b) maintenance of productive capacity of forest ecosystems, (c) maintenance of forest ecosystem health and vitality, (d) conservation and maintenance of soil and water resources, (e) maintenance of forest contributions to global carbon cycles, (f) maintenance and enhancement of long-term multiple socioeconomic benefits to meet the needs of societies, and (g) a legal, institutional, and economic framework for forest conservation and sustainable management (Montreal Process, 1993)

Sustained Yield

The yield that a forest can produce continuously at a given intensity of management --note sustained-yield management implies continuos production so planned as to achieve, a t the earliest practical time, a balance between increment and cutting

Tending

See Intermediate Treatments

Thinning

A cultural treatment made to reduce stand density of trees primarily to improve growth, enhance forest health, or to recover potential mortality.

Chemical Thinning

The killing of unwanted trees by using a herbicide, e.g., including band or frill girdling

Crown Thinning (Thinning from Above, High Thinning)

The removal of trees from the dominant and codominant crown classes in order to favor the best trees of those same crown classes.

Free Thinning

The removal of trees to control stand spacing and favor desired trees using a combination of thinning criteria without regard to crown position.

Low Thinning (Thinning from Below)

The removal of trees from the lower crown classes to favor those in the upper crown classes.

Mechanical Thinning (Geometric Thinning)

The thinning of trees in either even - or uneven-aged stands involving removal of trees in rows, strips, or by using fixed spacing intervals.

Selection Thinning (Dominant Thinning)

The removal of trees in the dominant crown class in order to favor the lower crown classes.

Thinning Grade

One of several traditional degrees of thinning, based essentially on dominance, crown and stem classes, and the extent to which these classes are removed (and the canopy therefore opened) at any one thinning (see Crown Class)

Thinning Intensity

A measure of the combined effect of thinning weight or severity and thinning frequency, usually in terms of the volume removed divided by the number of years between successive thinnings (see Relative Thinning Intensity)

Thinning Interval

The period of time between successive thinning entries, usually used in connection with even-aged stands (see Cutting Cycle).

Thinning Regime

A term comprising the type, grade, and frequency of thinning for a given area, generally along with their year of commencement and sometimes termination

Tillage

The mechanical manipulation of the soil profile for any purpose

Tilth

The physical condition of the soil as related to its ease of tillage, fitness as a seedbed, and impedance to seedling emergence and root penetration

Timber Stand Improvement

Obsolete (see Stand Improvement)

Tolerance

The capacity of trees to grow satisfactorily in the shade of , and in competition with, other trees

Tolerant

A plant capable of becoming established and growing beneath overtopping vegetation

Total Yield

The sum of intermediate and final products

Trait

A characteristic of an organism which may be quantitative (continuous) or qualitative (discontinuous) (see Character, Genotype, Phenotype)

Tree

A wood perennial plant, typically large and with a well-defined stem or stems carrying a more less definite crown --note sometimes defined as attaining a minimum diameter of 5 in (127 mm) and a minimum height of 15 ft (4.6 m) at maturity, with no branches within 3 ft (1 m) of the ground

Tree Injection

The deliberate introduction, by pressure or simple absorption, of a chemical (generally a water-soluble salt in solution) into the sapstrem of a living tree -note the object of tree injection is to kill the tree or to prevent or control insects or diseases

Two-Aged System

A planned sequence of treatments designed to maintain and regenerate a stand with two age classes.

Undercutting

The root pruning of seedlings in a nursery bed to limit root depth extension (see Root Pruning, Wrenching).

Underplanting

The setting out of young trees, or sowing of tree seed under an existing stand --note the tree themselves are termed underplants

Understory

All forest vegetation growing under an overstory

Uneven-Aged Stand

A stand of trees of three or more distinct age classes, either intimately mixed or in small groups.

Uneven-Aged System

A planned sequence of treatments designed to maintain and regenerate a stand with three or more age classes (see Single Tree Selection, Group Selection)

Vegetative Propagation

The propagation of a plant by asexual means, as in budding, grafting, rooting, air layering, and tissue cell culture

Viability

The capacity of a seed, spore, or pollen grain to germinate and develop under given conditions --note potential viability is commonly estimated by germination tests or by cutting

Weed

A plant growing where it is not wanted

Weeding

A release treatment in stands not past the sapling stage that eliminates or suppresses undesirable vegetation regardless of crown position

Wettable Powder

A pesticide formulation in which the pesticide is absorbed, generally on an inert carrier, together with an added surfactant and the whole finely ground so that it will form a short-term suspension when agitated with water

Wetting Agent (Penetrant, Surfactant)

A surfactant compound that reduces the surface tension of water (producing "wet water") or other liquid, causing spray solutions to spread, contact plant surfaces more thoroughly, or penetrate more effectively

Wildland

Land other than that dedicated for other uses such as agricultural, urban, mining, or parks

Windrow

Brushwood, slash, etc., concentrated (usually by machine) along a line, to clear the intervening ground for regeneration (see Site Preparation

Wolf Tree

A generally predominant or dominant tree with a broad, spreading crown, that occupies more growing space that its more desirable neighbors (see Crown Class)

Woodland

A plant community in which, in contrast to a typical forest, the trees are often small, characteristically short-boled relative to their crown depth, and forming only an open canopy with the intervening area being occupied by lower vegetation, commonly grass

Wrenching

The disturbance of seedling roots in a nursery bed (e.g., with a tractor-drawn blade) with the objective of stimulating the development of a fibrous root system.

Yield

The amount of wood that may be harvested from a particular type of forest stand by species, site, stocking, and management regime at various ages

Yield Table

A table showing the expected timber yields by age of an even-aged stand, usually by site index classes, and typically including quadratic mean diameter (DBH), height, number of stems, basal area, and standing volume per unit area