Glossary A - Z
Afforestation: The growing of trees in an area that has lacked forest cover for a very long time or has never been forested.Age: The number of growing seasons since planting.
Annual ring (annual growth ring): The layer of wood growth added each growing season to the diameter of the tree. In temperate regions, with distinct growing seasons, annual rings of most species are distinct, some very much so due to difference in cells formed early and late in the growing season. Many tropical timbers have no growth rings.
Anti-stain treatment: Fungicide solution applied to timber at some sawmills, to minimise staining during transit and storage.
Apical dominance: Growth concentrated on the leader, which tends to produce a straight stem and conical crown.
Autecology: The ecology of an individual organism.
Bark pocket: An opening between annual growth rings that contains bark - appearing as dark streaks on quarter sawn and rounded areas on flat sawn stock.
Bare root stock: Plants lifted from the nursery soil and despatched to the planting site with their roots bare of soil.
Bark: The outer protective tissue of a woody stem.
Basal area: The cross-sectional area of a tree measured at 1.3 m (breast height) from the ground, or the sum of the basal areas of trees in a specific area, expressed in mÂ².
Beam: A structural member loaded on its edge.
Bearing: The contact area over which one structural element, e.g. a joist, is supported on another, e.g. a wall plate.
Beating Up: The replacement of plants, which have died after planting, with new ones.
Biodiversity: The variety of all life forms at all levels including genetic diversity, species diversity and landscape diversity within an ecosystem.
Birdseye: Dimpling of the tangential surface of some hardwoods, notably sugar maple, which forms small circular features which are decorative.
Bleeding: Diffusion of resin, from such as a knot, through paint or varnish resulting in discoloration.
Blue stain: Blue-grey discoloration caused by mould-type fungi in damp timber (above 20%); also known as sapstain.
Board Mills: wood using industries which break wood down and reconstitute it into flat uniform sized boards, e.g. building boards like fibreboard (hardboard and insulation board); wood chipboard (particle board); medium density fibreboard (MDF); oriented strand board (OSB).
Bog Woodland: Woodland containing a scattered mix of stunted trees, often of considerable age, and open bog vegetation.
Bow: A curve along the face of a plank normally due to growth stress or poor stacking.
Box Beam: A built-up beam with solid wood flanges and wood panel product webs.
Boxed heart plank: A plank in which the pith (see pith) is enclosed; more liable to twist and fissure than other planks.
Brace, Lateral: A continuous member connected to a truss chord to maintain the vertical position of the truss and assembly of trusses.
Branch bark ridge: rough ridge separating the branch from the stem.
Branch collar: The area where a branch meets the stem, usually shown by a ring of rougher bark.
Brashing: The removal of lower branches up to a height of about 2 m to facilitate access for inspection, thinning or other purposes.
Broadleaved trees: A grouping of trees (botanically known as angiosperms) with lanceolate or other wide leaves (e.g. oak, ash, mahogany), often deciduous, which provide hardwood timber.
Broadleaves: Trees with broad, flat leaves, e.g. oak, ash, beech and sycamore. Growth is not in whorls but almost always diffusely branched.
Burr: A tumour-like swelling on a tree resulting from any number of causes, sometimes associated woth epicormic (lateral branching from trunk) growth.
Camber: An upward vertical displacement built into a truss or glued-laminated beam to offset deflection.
Calcareous soil: Soils which a pH >7 in the A or B horizon.
Canker: Dead area of a branch or stem caused by fungal or bacterial attack.
Canopy: The mass of foliage and branches formed collectively by the crowns of trees.
Cantilever: The part of a truss or structural member that extends beyond its support.
Case-hardening: Where the outer part of the wood has dried before the centre, and has become set in a stretched condition which causes stress between the outer and inner parts of the wood. The wood will likely distort if further sawn or machined.
CCA: Acronym for copper/chromium/arsenic wood preservative.
Cell: The minute structures of which wood is composed, including fibres, vessels and other elements.
Cellulose: The carbohydrate that is the principal constituent of wood. It has large, long-chain molecules which, when bonded together, provide a very strong framework to the wood cells.
Check: A separation of the fibres along the grain, forming a crack that does not extend through the timber.
Clear span: Horizontal distance between inner edges of supports.
Clearfelling: The cutting down of all trees on an area of more than 0.25ha.
Co-dominant trees: Trees in the upper canopy (which they help to complete) but which are below the crown level of the dominants.
Compatible species: Species that grow at about the same rate.
Compression failure: Localised buckling of wood fibres, due to compression along the grain, caused by direct compression or bending; in planed timber may appear as fine wrinkles across the surface.
Compression wood: Dense, short-fibred wood occurring on leeward side of wind-stressed conifer trees; usually darker in colour; causes unequal shrinkage, distortion and reduced strength.
Concealed surface: As intended by BS 1186, a surface in joinery or trim which, after installation, will be concealed, not only by decoration.
Conifer trees: A grouping of trees (botanically known as gymnosperms) with needle or scale-like leaves (e.g. pine, spruce, cypress), most of which are evergreen, which provide softwood timber.
Conifers: Trees and shrubs, which have needle like leaves and bear cones. They are usually, but not always, evergreen and grow in whorls.
Continous Cover: Use of a silvicultural system whereby the forest canopy is maintained at one or more levels without clear felling.
Coppice Stool: The part of a coppice which is left after cutting.
Coppice: Trees felled close to the ground so as to produce shoots from the resulting stools, giving rise to successive crops of poles and sticks cut over a rotation.
Coppicing: Cutting a coppice.
Cross-cut: A cut across the grain, to cut timber to length.
Crown length: The vertical measurement of the crown of a tree measured along the main axis of the stem, from a point halfway between the lowest live branch and lowest live whorl and the tip of the tree.
Crown thinning: The removal of selected trees in the upper canopy to allow growing space for the remaining trees.
Crown: Spreading branches and foliage of a tree.
Cultivar: A variant of a species that has been selected by gardeners or nurserymen. Cultivars are often loosely termed 'varieties.'
Cultivated: Considerable alteration to physical or chemical properties of the soil or vegetation by former agricultural use.
Cup: Curvature across the face of a plank.
Current Annual (volume) Increment: The volume increment produced during a short period (usually a few years) divided by the number of years in the period.
Current annual increment (CAI): The basal area or volume increments put on during the year in question.
Cut-off drain: A drain constructed to intercept surface water and lead it away to an outlet.
Dead load: A permanent load resulting from the weight of the building materials or installed equipment.
DBH: Diameter breast height - diameter of the stem measured at 1.3 m above ground level (mean diameter is the quadratic mean, the diameter corresponding to the mean basal area tree).
Debris dam: Accumulations of fallen deadwood of various sizes within streams which causes temporary but incomplete damming of a water flow.
Decay columns: Columns of dead and dying wood within trees caused by fungal or bacterial infection.
Decay: The decomposition of wood resulting from the action of wood-rotting fungi in damp/wet conditions; results in loss of strength and weight, generally with a change in texture and colour.
Deciduous: The shedding of leaves at the onset of winter, Most broadleaves are deciduous, whereas only some conifers are deciduous e.g. larch.
Density: The mass of wood substance per unit volume; expressed as kilograms per cubic metre, at a specified moisture content, generally 12%; there is a strong positive correlation between density and strength.
Destumping: Practice of removing stumps after felling to reduce risk of sprading butt rot fungus to newly planted trees.
Diameter, at breast height (DBH): The diameter of a tree in cm, measured at 1.3 m above ground level.
Diverse plantation: A mixed plantation with 80% or less of Sitka spruce or Lodgepole pine.
Dominant trees: These are the tallest and most vigorous trees in the crop, and usually have a large proportion of their crown free of competition.
Double mouldboard plough: A plough used for afforestation of bog, which throws out a ribbon of turf on both sides of the furrow
Durability: The level of resistance to decay or insect attack of heartwood. The durability of timbers is given in years of life before deterioration, described as: Very durable = > 25 yrs Durable = 15 - 25 yrs Moderately durable = 10 -15 yrs Slightly durable = 5 - 10 yrs Perishable = < 5 yrs
Earlywood: Also known as springwood; the portion of the annual ring formed at the beginning of the growing season; generally of lower density and weaker than the latewood (q.v.). The wood formed in the annual ring at the commencement of growth in spring; it consists of thin-walled cells with large spaces (lumina) within the cell walls.
Edge distance: The distance from the edge of the timber to the centre of the nearest fastening.
Edge: The narrow surface of a rectangular piece of timber.
Enclosed and Improved Land: land that was enclosed and improved for agricultural use by cultivation or manuring or both, and which is completely surrounded by man-made boundaries. Exotic species; species which are not native to Ireland.
End distance: The distance measured at right angles from the end of the timber along its length.
Epicormic branches: Small branchlets (shoots) originating from adventitious buds on the stem.
Equilibrium moisture content: The moisture contentÂ at which wood neither loses nor gains moisture when exposed to air at a constant relative humidity and temperature.
Exotic species: These are species that occur in a given place as a result of direct or indirect, deliberate or accidental actions by man.
Extraction: The operation of removing felled timber from the forest to a road accessible by lorry.
Face: The wide surface of a rectangular piece of timber; or any of the surfaces of a square piece of timber.
Fibre saturation point (fsp): The moisture content (m.c.) of wood at which all free water is lost from cell cavities, and only water bound within the cell walls remains; generally between 25 and 30% moisture content; shrinkage occurs only as wood m.c. drops below fsp.
Felling Coupe: An area proposed for felling in one operation.
Felling: the harvesting of trees
Figure: The pattern produced, on the surface of wood, by growth rings, rays and variations in grain structure.
Filling-in: The replacement of plant failures, also known as beating up. Usually carried out before the beginning of the second growing season.
Final crop: The trees, which remain after successive thinnings and are finally felled at maturity.
Fingerjoint: An end joint made by cutting wedges or fingers into the ends of boards, meshing them together and bonding with adhesive.
Fire break: fire line or fire belt. Strip of land where vegetation has been removed to assist in the prevention of fire entering a forest. Usually 6-7m. wide
Fire retardant: A chemical preparation which reduces flammability or retards the spread of flame over a surface.
Fire-resistance rating: The time, usually noted in minutes, that a material or structure will withstand the passage of flame when exposed to fire under specified conditions of test.
Fissure: A generic term to include checks, splits and shakes.
Flat-sawn timber: Timber sawn so that the growth rings are at an angle less than 45° to the face.
Flushed site: Considerable enrichment with nutrients from flush water, as indicated by the presence and vigour of tufted hair grass, purple moor grass, soft and bog- rush species.
Flushing: The commencement of growth of a plant above ground characterised by sap flow and swelling and bursting of buds.
Foliar sampling: The taking of samples of leaves or needles to determine nutrient levels and consequently determine fertiliser requirements
Forking: The occurrence of multiple leaders in a tree. It usually occurs when the leader or terminal bud is damaged. Double or multi leaders usually replace the leader.
Forwarder: usually an eight wheel drive or tracked vehicle capable of extracting timber over rough terrain
Frost damage: Damage to the soft tissues of trees by cold temperatures, which can occur in the nursery and in young plantations. Trees are most vulnerable when freshly flushed in late spring or early summer and again in autumn prior to "hardening off".
Frost hollows: Low- lying concave areas where cold air collects causing damage to new shoots of trees.
FSC: Forest Stewardship Council
Fungi: A mushroom, toadstool or one of the similar plants such as mould. They have no chlorophyll and obtain food from living and dead organic matter.
Glulam: Structural wood product made by bonding together laminations of dimension lumber.
Grain: Primarily, the direction of the main fibres of the wood; when qualified, may refer to their size, arrangement and/or appearance (see close, open, coarse grained).
Green timber: Freshly felled or undried timber with its moisture content above fibre saturation point.
Ground rock phosphate: common type of fertiliser used in forestry, usually at the establishment stage to encourage tree and more specifically root growth
Hardness: The capacity of the wood to resist indentation.
Habitat Action Plan: Plans within the UK Biodiversity Action Plan which identify actions needed to stabilise and improve the status of habitats with high conservation value.
Habitat Scale: Usually equated with stand scale (0.5 - 50 ha) but can also include smaller areas depending on context.
Habitat: Any place or type of place where an organism or community of organisms normally lives and thrives.
Hardwood: Timber of broad-leaved trees; the term relates to the botanical grouping of the trees and not to the hardness of the wood (some hardwoods, e.g. balsa, are softer than softwoods).
Heart Rot: Decay of inner wood (heartwood) of trees.
Heartwood: Wood of the inner growth rings, extending from the pith to the sapwood; no longer participating in the life processes of the tree. The starches are depleted and often replaced with resins and other substances which may make the wood darker and more decay resistant.
Heel: Point on a truss where the top and bottom chords intersect.
High Forest: Woodland which is not managed as coppice or pollards and which may or may not be managed for timber.
Honeycomb: Internal splitting in a plank as a result of casehardening (q.v.).
Hoppus Measure: Also known as 'quarter-girth measure'; a measurement method which defines the cross-sectional area of a bole or log as the square of one quarter of the circumference. One Hoppus foot equals 1.273 cubic ft true measure or 0.036 cubic metres.
Intumescence: The swelling of a fire-retardant coating when heated, resulting in a film providing a degree of resistance to surface spread of flame.
Increment: The rate of growth or the amount accreted (according to context) in the relevant parameter over a specified time period.
Indigenous species: These are species, which arrived and inhabited an area naturally, without deliberate assistance from man.
Indurated soil: Has strongly compacted material, which is low in organic matter. It normally occurs at depths of 30-75 cm and extends for 30-50 cm or more.
Ironpan: A hard impervious layer formed from iron compounds being washed down from the upper soil horizons; a soil in which iron compounds have been washed down from the upper layers and deposited as a hard layer lower down preventing free drainage and root penetration.
Joist: One of a series of parallel beams used to support floor or ceiling loads, which are themselves supported by bearing walls or other beams.
Juvenile Wood: Wood formed in the vicinity of the tree core under the live crown; (which gradually moves up the tree as trees grow and competition ensues) taken to be the first 12 years from the pith for Sitka spruce).
Knot: The portion of a branch that has been surrounded by wood in the subsequent growth of the stem. The shape of the knot on the surface of a plank will depend on the angle at which it is cut.
Knot area ratio (KAR): In a plank, the proportion of the cross-section at any point occupied by knots; used to calculate the visual stress grade of timber.
Latewood: Also known as summerwood; the portion of the annual ring formed in the later part of the growing season; generally of higher density and stronger than the early wood (q.v.).
Landscape Scale: Areas greater than 1 km2 - e.g. river catchments.
Latewood: Wood formed in the annual growth ring during the summer and early autumn; it consists of thick-walled cells with small spaces (lumina) within the cell walls.
Leader: The main or leading shoot of a tree.
Lichen: A combination of fungus and alga growing together.
Light demanders: Refers to trees which only thrive when allowed unimpeded access to light.
Lignin: The second most abundant constituent of wood; a cementing substance that bonds adjoining cells and the cellulose framework.
Live crown: The length, or depth of crown between the top of the tree and a point mid-way between the first live branch and the first full live branch whorl.
Live load: Loading of a temporary nature such as wind, snow and construction loads.
Load Cell Value: A measure of vertical deflection in the timber test pieces during stress grading.
Loamy: Used for surface-water gley soils and peaty gley soils where the texture throughout the profile is not finer than sandy clay loam.
Log: Fallen driftwood
Long Rotation Stands: Stands retained beyond the normal economic felling age (40 - 80 years), but which will be felled at some time.
Lop and top: Woody debris from thinning or felling operations. Also known as slash or brash.
Machine stress-rated timber: Timber that has been mechanically evaluated for stiffness from which its bending strength is automatically calculated resulting in the timber being assigned to a strength class.
Make good: A term usually applied to repairing wood by means of a plug, insert or filler.
Marl: soft calcium carbonate usually mixed with clay. If marl occurs within 70 cm of the soil surface, the site is classed as unplantable.
Mean Annual (volume) Increment: The average (volume) increment over the rotation, calculated as the total volume production divided by the rotation age.
Mean Height: The height of the tree of mean diameter.
Mensuration: Measurement of trees.
Mid-successional stands: Stands which have passed the establishment phase, but are not ready to be felled; a typical range of ages would be 20 - 50 years.
Minimal Intervention: Relating to stands where there is negligible management inputs, and practices such as felling, thinning and restocking do not take place.
Modulus of elasticity (MOE): A measure of the resistance to bending, i.e. directly related to the stiffness of a beam.
Modulus of rupture (MOR): The maximum load a beam will carry before breaking
Moisture content: The weight of water in a piece of wood expressed as a percentage of the weight of the wood when oven-dry.
Monocultures: An area of forest in which only one species is present or largely dominates.
Mounding: Formation of discrete heaps of soil, usually 20-30 cm in height, at the intended planting spacing.
Movement: The change in dimensions that accompanies normal fluctuations in relative humidity after wood is put in service; rated over a relative humidity (q.v.) change of 60 to 90% as follows: small = < 3% medium = 3 - 4.5% large = > 4.5%
Nominal size: A term whose definition may vary; normally refers to the size by which timber is known and sold, which is often different from the actual size of the timber; or to the size to which tolerances apply, but the tolerances may exceed those of EN 336.
Native Species: Species which are considered to be naturally occurring in Ireland
Native Woodland: Woodlands composed of site native and locally native tree and shrub species
Natural Disturbance: Disruption to forest stands, vegetation and wildlife by a natural event such as strong wind, fire or grazing.
Natural Heritage Areas (NHA): These areas are generally precluded from planting as they have been designated by the National Parks and Wildlife Service of the Office of Public Works as areas of nature conservation interest.
Natural regeneration: The regeneration of a crop through seeds from mother trees on the ground or in the vicinity.
Needle cast: Defoliation of conifers as a result of disease, or climate.
Notional charring rate: The rate at which a timber member of a particular species over a defined size chars when exposed to a standard fire test.
Nurse species: These are species, which enables more delicate or more site demanding species to grow satisfactorily on what would otherwise be considered unsuitable sites.
Oven dry weight: The weight obtained by drying wood in an oven at 102°C ± 3°C until no further loss in weight occurs.
Old Growth: A forest stand which has developed free from large-scale disturbance over a long period of time (80 - 500+ years) and contains large old trees, large fallen and standing deadwood in various states of decay, and a wide variation in tree size and spacing.
Open Growth: The form of trees grown in the absence of competition and shading.
Permeability: The capability of the wood to absorb preservative; often varies between sap and heartwood. The classification refers to heartwood only, as sapwood is generally permeable, and may vary with the preservative used and type of treatment.
Parkland: Area enclosed for keeping deer and/or amenity use.
pH: A value on a scale of 0-14 that gives a measure of the acidity or alkalinity of a soil. A neutral soil has a pH of 7. Acidic soils have pH values of less than 7 and alkaline soils have values greater than 7. The lower the pH the more acidic is the soil; the higher the pH the more alkaline.
Pioneer species: Species that colonise a physical environment sequentially until a final equilibrium state, the climax, is achieved.
Pitch pocket: An opening between growth rings which contains, or has contained, resin.
Pith: The core of a tree stem, consisting of dark-coloured very soft tissue; it can show on the surface of planks, taken from the centre of the tree, as a dark line of easily indented tissue.
Podsol: Soil type developed in light textured (sandy) material under acid conditions by downward leaching of organic matter, and iron and aluminium oxides, giving rise to a greyish (bleached) surface layer underlain by a darker layer. In extreme cases these layers may be separated by a root- and water-impenetrable hard-pan (e.g. Ballyhoura).
Pollard: A tree cut 2-4 m above ground level, producing a crop of branches which can be harvested in subsequent years.
Pollarding: Cutting a pollard.
Pores: Openings of vessels on the surface of cut timber, occurring only in hardwoods, seen as minute holes on end grain or scratches on side grain.
Post: A timber with the larger dimension not more than 50 mm greater than the smaller dimension and usually graded for use as a column.
Provenance: The location of trees from which seed or cuttings are collected.
Pruning: The removal of branches to produce knot-free timber.
Pulpwood: Logs suitable for processing into fibreboard, chipboard, etc. with small-end diameter between 7 and 14 cm.
Quarter-sawn timber (edge grain): Timber sawn so that the growth rings are at an angle greater than 45° to the face.
Rays: Bands of soft tissue vertically aligned and radiating from the centre of the tree; insignificant in softwoods and variable in hardwoods - if broad can produce distinctive figure - e.g. silver grain in oak.
Raptor: A bird of prey which kills with its feet.
Reforestation: Replanting of an area on which the previous crop of trees has been clearfelled.
Relative humidity (RH): The ratio of the amount of water vapour present in air to the amount which the air would hold if saturated at the same temperature.
Restocking: The practice of replanting after a stand of trees that has been felled.
Restoration: The re-establishment of native trees and natural processes on planted ancient woodland sites.
Retention: Stand retained beyond normal economic felling age (40 - 80 years) which will normally remain unfelled in perpetuity.
Ride: Unplanted strips between stands, used as firebreaks and access routes.
Ridelines: unplanted strips facilitating forest management.
Ring Barking: Complete removal of a section of bark encompassing the full circumference of a tree trunk, done to kill the tree.
Ripping: To cultivate deeply with a long heavy shank mounted on a tool bar to depths of 30-100 cm for the purpose of shattering compaction/induration: or disturbing deep-lying ironpan or cementation.
Root collar: The part of the stem around ground level where the shoot meets the root.
Rotation: The number of years required to establish and grow a crop to a specified condition of maturity, at which stage the crop is felled or regenerated.
Sapwood: Wood of the outer growth rings, extending from the heartwood to the bark; contains living cells, with carbohydrate food reserves, and conducts the sap up the tree; generally considerably wetter than heartwood when freshly felled, and is perishable.
SAC: Special Area for Conservation designated under the European Union Habitats and species Directive 1992 (EC directive 92/43).
Saproxylic: Organisms that depend on wood, usually but not always dead wood, for some part of their life cycle.
Sawlog: Logs, usually of at least 14 cm top diameter, which are intended for conversion in a sawmill.
Scrawing: The removal of the surface layer of organic matter from a soil. Such material being normally used as fuel.
Scrub: Non commercial unmanaged forest area.
Seasoning or drying: The process of removing moisture from green wood to improve its serviceability. Seasoning often refers to drying in the atmosphere; kiln drying to accelerated drying under controlled conditions in a drying chamber or kiln.
Semi-Natural woodland: Woodland containing native trees that were not originally planted.
Shade bearers: These are understorey species, (not always grown in the understorey) which are adapted to growing with limited access to light.
Shake: A separation of the fibres along the grain, usually between the annual rings. A defect in timber, consisting of cracks either radiating from the centre (star shake) or following the annual rings (ring shake).
Shaping: Removal of forks and large branches with the object of producing straight broadleaved stems.
Silt trap: helps to prevent silt entering rivers and streams and is constructed by deepening mound drains to 1 m x 1 m x 1 m. Water entering a silt trap will stagnate and the silt will be able to settle before the water flows out.
Silviculture: The science of forest establishment, maintenance and management.
Site Index: The mean height of the stand at a reference age (usually 50 years).
Skidder: a tractor which extracts timber by dragging it along the ground.
Snag: Standing dead tree.
Softwood: Timber of conifer trees; the term relates to the botanical grouping of the trees and not to the hardness of the wood ( some softwoods, e.g. yew, are harder than some hardwoods).
Soil reaction: Denotes soil acidity or alkalinity. Thus acid soils would be described as having an acid reaction.
Specific Gravity (nominal): The ratio of the oven dry weight of a given volume of green wood to the weight of an equal volume of water at 4°C.
Spiral grain: Growth of fibres in a spiral direction around the trunk of the tree; may cause twisting of timber during drying.
Spring: A curve along the edge of a plank; normally due to growth stress, e.g. compression wood (q.v.).
Stand: A group of trees of similar age.
Standard: a transplanted tree with 1.8 m or more clear stem.
Stress: The applied force per unit area or volume; the primary stresses are tensile, compression and shear; a combination of all three occurs in bending.
Structural Diversity: Variability in the structure of forest stands attributable to tree size, shape, density and distribution.
Structural timber: Timber which has a determined strength and thus may be used in calculated structural designs.
Stumping back: The cutting back of plants within a few years of planting to within 5-10 cm of ground level. This stimulates vigorous re-growth of multiple shoots, which can then be reduced to one shoot.
Sub-dominant trees: These trees are not in the upper crown but their leaders still have free access to light.
Suckers: These are new shoots produced from the base or under ground roots of an established plant.
Suppressed trees: These are trees whose leaders have no direct access to light and stand beneath the crowns of adjacent dominant, co-dominant and sub-dominant trees.
Surface-Water Gleys: Soils developed in heavy-textured (clayey) material where downward percolation of water is impeded leading to intermittent or prolonged water logging.
Tension wood: Comparable to compression wood (q.v.) in conifers, it occurs in broad-leaved trees, on the upper side of leaning trees. Shorter gelatinous fibres causes unequal shrinkage, distortion and reduced strength.
Tending: the removal of trees with defective stems in broadleaf crops.
Terminal height: The height by which it is predicted that 40% of a stand will be windblown and remaining trees will be clearfelled and replanted.
Texture: The appearance of the timber produced by variations in the size of vessels and other cells, from fine (narrow vessels and rays) to coarse (wide vessels and rays).
Thicket stage: stage after planting and before pole stage when young trees have grown up enough to form a dense thicket.
Thinning cycle: The interval in years between successive thinnings.
Thinning: The removal of a proportion of trees from an immature crop in order to improve the growth and form of the remainder.
Top height: The average height of the 100 trees of largest diameter per hectare.
Transplant: in a forest nursery seedlings are normally transplanted after one or two years in the seedbed so as to develop a better root system and a sturdier plant.
Tree Guard: a structure placed over small trees for protection against browsing animals.
Twist: Warping in which one corner of a plank twists out of the plane of the other three; associated with split and boxed-heart planks due to shrinkage of spiral-grained wood.
Understorey: Any plants or shrubs growing under a tree canopy.
Unenclosed Land: Land that shows no evidence of having been improved and enclosed by man- made boundaries for agricultural use other than extensive grazing.
Urea: Chemical used as a fungal retardent on stumps.
Visually stress-graded timber: Timber graded for strength based on visual assessment of limiting features (also see Knot area ratio (KAR).
Wane: The original rounded surface of a tree remaining (with or without bark) on timber after conversion.
Water repellent: A liquid that penetrates the wood and retards changes in moisture content while still allowing the wood to breathe; often incorporates a preservative, when it is known as a water-repellent preservative.
Windfirm: Descriptive of trees and plantations that, because of species, soil or relative exposure, are unlikely to suffer windthrow; Trees that are unlikely to blow over when exposed to strong winds.
Windthrow: Uprooting or breakage of trees caused by strong winds; Partial or complete overturning or breakage of trees.
Wolves: Dominant defective trees with large crowns and / or large side branches, which can damage better formed adjacent trees if not removed.
Wood Pasture: Grazed woodland characterised by open growth (often pollarded) veteran trees at various densities.
Workability: The degree of ease and smoothness with which wood can be sawn, planed and otherwise worked.
Working Circle: A forest area with a particular objective, under one silvicultural system and having one set of working plan prescriptions.
Yield class: A classification of rate of growth in terms of the potential maximum mean annual increment per hectare of volume to 7 cm top diameter (m³/ha/annum), irrespective of age of culmination, or of tree species.
Yield Table: A tabular statement of the development of a stand, at periodic intervals, from early youth up to a certain age usually a full rotation.