TSI (Timber Stand Improvement) – The practice of removing undesirable trees, shrubs, vines, or other vegetation to achieve the desired stocking of the best quality trees.
Thinning – Cutting scattered trees or rows of trees to reduce the stocking and concentrate growth on fewer, higher quality remaining trees.
Threatened species – A plant or animal that may soon become endangered throughout all or part of its range.
Till – Unstratified glacial drift consisting of clay, sand, gravel, and boulders intermingled.
Timber – Standing trees, usually of commercial size.
Timber inventory – A collection of information about a stand made by measuring tree and stand characteristics such as tree volume and grade and stand density.
Tolerance – See shade tolerance.
Tract – A contiguous (connected) area of land (and water).
Transplant – A tree seedling that was transplanted at least once in the nursery.
Tree – A woody plant with a well-defined stem and a more or less definitely formed crown, which usually grows more than 10 feet tall.
Tree farm – A privately owned woodland dedicated to the production of timber crops and other environmental benefits. It may be formally recognized by the Tree Farm program of the American Forest Council.
Tree length skidding – When a tree is felled, the process of removing the top and limbs, then moving (skidding) the entire tree stem in one piece to the landing.
Trunk – The main stem or bole of a tree.