Definitions presented are from The Dictionary of Forestry (Helms 1998) and Forest Measurements (Avery and Burkhart 2002) where possible.  Remaining definitions are from other sources.

annual ringsee growth ring  

broken top  A tree whose uppermost whorls of branches and main stem have broken off the main trunk.  – note: a flattened top appears, and commonly rot is introduced to the main stem

butt swell   Flare of the main stem at the base of a tree providing mechanical support to keep the tree upright

caliper(s)   An instrument for determining tree and log diameters by measuring their rectangular projection on a straight, graduated rule via two arms at right angles to (and one of them sliding along) the rule itself

canopy   The foliar cover in a forest stand (may consist of one or several layers); generally refers to the top or overstory layer

clinometer  An instrument for measuring angles of elevation or depression

codominant – see crown 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

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

crown class  A category of tree based on it crown position relative to those of adjacent trees

codominant – a tree whose crown helps to form the general level of the main canopy in even-aged stands, or in uneven-aged stands, the main canopy of the tree’s immediate neighbors, receiving full light from above and comparatively little from the sides

dominant – a tree whose crown extends above the general level of the main canopy in even-aged stands, or in uneven-aged stands, above the crowns of a tree’s immediate neighbors and receiving full light from above and partial light from the sides

intermediate – a tree whose crown extends into the lower portion of the main canopy in 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, and receiving little direct light from above and none from the sides

suppressed or overtopped – a tree whose crown is completely overtopped by one or more neighboring trees

cruise intensity   The percentage of a population that is sampled

dendrochronology   The study and interpretation of annual growth rings of trees and their use in dating past variations in climate and in archaeological investigations

density   The size of a population in relation to some unit of space – note: density is usually expressed as the number of individuals or the population biomass per unit area or volume

determinate height growth (determinate growth)   Growth whose structures are initiated by a meristem in one year but do not complete development until the meristem resumes growth in the following year

diameter at breast height (DBH)  The diameter of the stem of a tree measured at breast height 4.5 ft or 1.37 m) from the ground – note: on sloping ground the measure is taken from the uphill side

diameter class  Any of the intervals into which a range of diameters of tree stems or logs may be divided for classification and use – e.g., the 6 inch diameter class includes diameters from 5.0 to 6.9 inches

diameter tape   A tape measure specially graduated so that the diameter can be read directly from the circumference of a tree stem or log

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

evenaged (stand)   A stand of trees composed of trees of the same, or approximately the same age

forked tree   A tree whose main stem splits into two or more main stems

global positioning system (GPS)  A satellite-based positioning system that gives a user’s position anywhere on earth

growth ring   The cumulative layers of cells produced during a single growing season, and characteristically containing earlywood and latewood cells of differing morphology

hypsometer   Any instrument based on geometric or trigonometric principles for measuring the heights of standing trees

increment borer  An auger-like instrument with a hollow bit and an extractor used to extract thin radial cylinders of wood (increment cores) from trees having annual growth rings, to determine increment or age

intermediate see crown class

live crown ratio  The ratio of the length of live crown to total tree height

merchantable (tree) height   The commercial height above ground or (in some countries) above stump height

multistoried stand   The cultivation of a large variety of mostly multipurpose plants in various vegetation layers to maximize the use of environmental factors such as water, nutrients, and sunlight

old-growth (forest)  The late successional stage of forest development – note 1: old-growth forests are defined in many ways; generally, structural characteristics used to describe old-growth forests include (a) live trees: number and minimum size, (b) canopy conditions: commonly including multilayering, (c) snags: minimum number of specific size, and (d) down logs and coarse woody debris: minimum tonnage and numbers of pieces of specific size – note 2: stand age, although a useful indicator of old growth, is often considered less important than structure because (a) the rate of stand development depends more on environment and stand history than age alone, and (b) dominants are often multiaged – note 3: due to large differences in forest types, climate, site quality, and natural disturbance history (e.g., fire, wind, and disease and insect epidemics), old-growth forests vary extensively in tree size, age classes, presence and abundance of structural elements, stability, and presence of understory

old-growth stage   A temporal stage of forest development typified by old-growth stand structure  – see old-growth

open shrub stage  A temporal stage of forest stand development immediately following disturbance characterized by low or no tree cover and dominated by understory plants

overstory   that portion of trees forming the uppermost canopy layer

overtopped see crown class

percent slope   A slope ratio with rise expressed as a % of the run. –see slope

pith   The central core of a stem, branches, and some roots representing the first year of growth, and consisting mainly of soft tissue

profiles   A side view of a hillslope, illustrating the changes in surface gradient

rise   The vertical distance between two points

run   The horizontal distance between two points

shade tolerance (tolerant)   Having the capacity to compete for survival under shaded conditions

site class   A classification of site quality, usually expressed in terms of ranges of dominant tree height at a given age

site index   A species-specific measure of actual or potential forest productivity (usually for even-aged stands), expressed as the average height of dominant, codominant trees at a specified index or base age

site quality  The productive capacity of a site, usually expressed as volume production of a given species –synonym site productivity

site tree   A tree used to determine site indexnote: site trees must meet defined criteria

slope   A measure of change in surface value over distance, expressed in degrees or as a percentage – e.g., a rise of 2 m over a distance of 100 m (or 2 ft over 100 ft) describes a 2 percent slope

slope distance  The extent of space between two points on a sloped surface

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

stand density   A quantitative measure of stem crowding within a stocked area

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

stand table   A tabulation of the total number of stems per acre by dbh and species

stem   1. The principal axis of a plant from which buds and shoots develop   2.  The trunk or main stem of a tree

stem exclusion stage   A temporal stage of forest stand development following crown closure

succession   The gradual supplanting of one community of plants by another. – note: the sequence of communities is called a sere, or seral stage

suppressed –see crown class, overtopped

suppression  The process whereby a tree or other vegetation loses vigor and may die when growing space is not sufficient to provide photosynthate or moisture to support adequate growth

topographic slope  A ratio of rise over run expressed as a one unit of change in elevation for every 66 units of change in horizontal distance – see slope

total (tree) height  Height of the main stem of a tree from a one-foot stump (generally) to the very tip of its leader

understory   All forest vegetation growing under an overstory

understory reinitiation stage   A temporal stage of forest development characterized by gaps in the forest overstory caused by suppression and introduction of new seedlings in the forest understory

uneven-aged (stand)   A stand with trees of three or more distinct age classes, either intimately mixed or in small groups

whorl   A circle of leaves, flowers, branches, or other organs developed from one node


Icon for the Creative Commons Attribution 4.0 International License

Glossary by Joan DeYoung is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.