Glossary - T

Tap root
Main, downward-growing root.
The reduction of girth from the base to the tip of the stem. Greater in open grown trees than in close plantations.
Tariff system
A method of assessing the standing volume of thinning (or clear fell) by measuring the breast height diameter of a sample and the tree volume of a sub-sample. Suitable for fairly uniform stands and the standard method adopted by the Forestry Commission for standing sales.
Thicket stage
A plantation that has closed canopy, by which is meant that the branches are interlaced.
Periodic removal of trees in a stand which are competing with those better trees which are expected to form the final crop. The object is to benefit the final crop trees, and to get income from the thinnings before they die.
A proportion of stems removed in order to give the best stems space and light to grow into a more valuable crop. This is usually carried out some time after canopy closure and may be repeated at intervals. It is a necessary operation in the production of quality timber. A temporary reduction in standing volume will result.
Young tree that has been grown from seed and transplanted within the nursery in preparation for being planted out in the forest.