Glossary

Basal area
The sum of areas of the stem cross sections taken at Breast Height (1.4m above ground level) of all the trees growing on one hectare.
Breast Height
The usual point of measurement of standing tree diameter, i.e. 1.4m above ground level on the uphill side of the tree.
Butt Log
The log directly above the stump. The biggest diameter log and usually having the greatest unit value of all the logs in the tree. If the tree has been pruned this log will contain most of the clearwood in the tree.
Clearwood
Wood showing no (or negligible) defects caused by knots, resin pockets or mechanical damage and usually displaying straight and even grain patterns. Clearwood is found in all trees. Pruning is designed to grow additional amounts, especially in long lengths.
Croptype
An aggregation of stands for the purpose of recording, analysis and forest management. Croptypes will generally be comprised of trees of identical species that have similar growth and yield patterns and will have experienced similar silvicultural treatment.
DBH
An acronym of “Diameter Breast Height”. A term used to describe a tree diameter measurement taken at the standard height of 1.4m above ground level. Usually measured and expressed overbark on the standing tree.
Defect core
The central core of a pruned tree outside of which clearwood is laid down and which contains the pith, branch stubs and any occlusion defects.
Diameter Over Stubs (DOS)
The diameter over the largest diameter whorl of branch stubs left on a tree stem immediately after pruning. Usually occurs at the first pruning operation and therefore in the butt log.
DOS height
The distance from ground level to the largest pruned whorl in a pruned log.
Epicormics
Shoots coming from the stem of a tree too small to be classed as branches and not within a whorl. Also used for needles growing directly from the stem.
Final crop tree
A tree expected to remain in the stand until clearfelling time.
Follower tree
A tree which, although not being removed in the current thinning operation may not remain in the stand until clearfelling or may not receive the full silvicultural treatment.
GF rating
A seed and plant classification system that provides comparative rank of genetic gain across seedlots. There are four breeds, each with its own improvement rating: GF (Growth and Form) LI (Long Internode) DR (Dothistroma Resistant) HD (High wood Density) The breed abbreviation is accompanied by an improvement rating, the higher the number the higher the rating. An example would be GF22. It is important to stress that improvement ratings are not a linear scale; they do not translate directly to gains of volume, value or anything else. They are merely a ranking.
Hectare
10,000 square metres (or approximately 2.471 acres).
Mean Top
DBH
The quadratic mean of the 100 largest (by DBH) trees per hectare, or if less than 100 trees per hectare, the quadratic mean of those remaining.
Mean crop height
The average height of the crop trees.
Mean Top Height (MTH)
The height predicted by the Peterson height/diameter curve for a tree with a DBH corresponding to the Mean Top DBH.
Net stocked area
The area of land currently occupied by the tree crop.
Occlusion
The process in a tree stem whereby new healthy tissue grows over and covers stem wounds, branch stubs, etc. This process may also enclose small bark or resin pockets associated with the wound and known as the occlusion defect.
Probable Limits of Error (PLE)
A term which refers to the confidence limits expressed as a percentage of the estimated mean. For example a PLE of 10% at the 95% probability level implies that there is a 95% chance that the true mean is within 10% of the estimated mean. For forest management it has become customary to adopt the 95% probability level for sampling.
Pruned height
The height above ground level of the lowest branch whorl remaining after the last pruning operation.
Pruned Log Index (PLI)
An index based on measurable log parameters that reflects the potential for producing clear grade timber from pruned sawlogs. PLI Pruned Log Quality0 – 1.9 Pruning ineffective 2 – 3.9 Poor4 – 5.9 Satisfactory6 – 7.9 Good8 – 9.9 Very good10+ Excellent
Pruning
The silvicultural practice of removing the lower branches of a tree while the tree is still growing to eliminate or prevent the formation of knots and deformation of the grain in the wood subsequently grown. A strategy to grow clearwood.
Recoverable yield
The amount of wood, usually expressed as a volume of round logs, produced from a stand during the harvesting operation.
Rotation
The span of years in which a tree or stand grows from first planting at the forest site through to felling. Usually has an economic connotation in that a rotation is optimised to some set of economic criteria.
SED
An acronym for “Small End Diameter”. Used in log measurement.
Site Index (SI)
A measure of the productivity of a forest site expressed in terms of the height growth attained by trees growing on it. In New Zealand the parameter usually is the Mean Top Height of Pinus radiata at age 20.
Skid site
An area of land in the forest, often specially prepared and surfaced, where logs or tree lengths extracted from the forest are accumulated, processed and loaded onto trucks for removal. ‘Skid’ refers to the (now discontinued) practice of pushing or rolling logs up an inclined plane for loading onto trucks. Also referred to as “landing” or “ dump”.
Stand
A block of trees of the same age, species and silvicultural regime. A unit of forest area record, usually a subdivision of a compartment.
Stocking
The number of live trees existing on one hectare, expressed as stems per hectare.
Stumpage
The value of the standing tree. Usually expressed as the value per cubic metre of the logs by quality in the tree. Also expressed as the value of all the standing trees on one hectare.
Sweep
A measure of the bend in a log calculated as the maximum distance of the centre of the log from a straight line joining the centre of the log at each end of the log. Sweep can be expressed as a proportion of the small end diameter of the log.
Tending
A collective term for silvicultural operations that are directly applied to the growing tree e.g. aerial fertilisation and fire protection are not usually referred to as “tending”, whereas pruning and thinning are referred to as “tending”.
Thinning
The silvicultural practice of removing selected trees to promote the more rapid growth of the crop trees. May be “to waste” where the thinned trees are left on the forest site or “production” where the thinned trees are removed for use.
Variable lift pruning
A pruning technique where each tree is considered individually. The height to which each tree in the stand is pruned is determined by a chosen factor. Factors commonly in use include: a percentage of the tree height, a proportion of the crown to be left or the diameter at the base of the remaining crown.
Veneer log
A log, usually of large diameter and high quality, used for making veneer. Also called a “Peeler” when used for rotary peeling.
Whorl
A group of branches growing radically around the tree. A typical branching habit of softwoods, but not of hardwoods.
Yield
The quantity of forest produce that is, or is expected to be, recovered from a unit area of land.