Glossary of Forestry Terms - T - U

A-B    C    D-E    F    G-H    I-J-K    L-M    N-O    P-Q    R    S    T-U    V-W-Y

Target stocking standards the number of well-spaced acceptable trees per hectare that will, in normal circumstances, produce an optimum free-growing crop; the standards at which silviculture treatments are aimed.
Temporary access structure a structure that would be a permanent access structure except that it is not shown on a forest development plan, access management plan, logging plan, road permit or silviculture prescription as remaining operational after the completion of timber harvesting activities.
Temporary bridge a bridge having most of its major components constructed of untreated wood.
Temporary tenures non-alienated lands on which the timber is alienated to private interests, but where the Crown retains ownership of the lands. These lands include timber licences, timber leases and timber berths as well as pulp licences and pulp berths.
Tending any operation carried out for the benefit of a forest crop or an individual thereof, at any stage of its life. It includes operations both on the crop itself and on competing vegetation but not site preparation or regeneration cuttings.
Tenure the holding, particularly as to manner or term (i.e., period of time), of a property. Land tenure may be broadly categorized into private lands, federal lands, and provincial Crown lands. Most Provincial Forest Acts define a number of forestry tenures by which the cutting of timber and other user rights to provincial Crown land are assigned.
Tenure holder an individual, group, or company that holds a licence agreement as defined in a Provincial Forest Act
Tenure management plan a plan that relates to the management, development and use, by the holder of a licence or permit granted under a Provincial Forest Act, of the Crown range to which the licence or permit applies, including the management and use.
Return to Top of Page
Terrain the physical features of a tract of land.
Terrain hazard assessment an assessment or characterization of unstable or potentially unstable slopes on forested lands. A determination of the relative potential of landslide initiation and the type of landslide that may occur on different types of terrain, based on the data obtained from a review of available maps, photos, site data, and field observations.
Terrain stability risk a combined assessment of both the likelihood of landslide initiation and an order of magnitude estimate of the amount of landslide debris that might enter a stream or of the potential lengths of scour of a stream by a landslide.
Thinning a cutting made in an immature crop or stand primarily to accelerate diameter increment but also, by suitable selection, to improve the average form of the trees that remain.
Threatened or endangered habitats ecosystems that are:
  • restricted in their distribution over a natural landscape (e.g., freshwater wetlands within certain biogeoclimatic) or are restricted to a specific geographic area or a particular type of local environment; or
  • ecosystems that were previously widespread or common but now occur over a much smaller area due to extensive disturbance or complete destruction by such practices as intensive harvesting or grazing by introduced species, hydro projects, dyking, and agricultural conversion.
Threatened or endangered species species identified as red listed; these are indigenous species that are either threatened or endangered.


THE FISH AND WILDLIFE CONSERVATION ACT, 1997 Statutes of Ontario, 1997, Chapter 41

Timber trees, whether standing, fallen, living, dead, limbed, bucked or peeled.
Timber cruising the collection of field data on forests commonly by the measurement and recording of information in sample plots. Includes the measurement and estimation of volumes of standing trees.
Return to Top of Page
Timber harvesting land base the portion of the total area of a management unit considered to contribute to, and be available for, long-term timber supply. The harvesting land base is defined by reducing the total land base according to specified management assumptions.
Timber licence area-based tenures which revert to the government when merchantable timber on the area has been harvested and the land reforested. Many of these licences have been incorporated into tree farm licences.
Timber management prescriptions recommended forest management practices, usually pertaining to the sub-unit and operational levels of planning.
Timber mark a hammer indentation made on cut timber for identification purposes.
Timber operability (see also Operable timber) in a planning context, the term refers to the economic suitability of timber for harvesting. Parameters to consider in assessing operability include: terrain, timber quality, timber size, operating season, labour costs, development costs, and transportation costs. In the Environmental Protection Area program, operability refers to freedom from harvesting constraints which include environmental protection and other forest uses.
Timber sale licence usually defines a specific volume of timber to be harvested from a specific area. In special circumstances, an allowable annual cut (AAC) is specified. It allows the orderly harvest of relatively small volumes of timber by
  • operators with small cuts;
  • operators registered under small business enterprise programs, or others with temporary cutting rights; and
  • holders of pulpwood agreements.
Timber supply the available timber categorized by species, end-use, and relative value.
Timber supply analysis an assessment of future timber supplies over long planning horizons (more than 200 years) by using timber supply models for different scenarios identified in the planning process.
Timber Supply Area (TSA) an area defined by an established pattern of wood flow from management units to the primary timber-using industries.
Return to Top of Page
Timber Supply Block (TSB) a division of a timber supply area.
Timber supply model an analytical model (usually computer-based) that simulates the harvest and growth of collections of forest stands over several decades according to specific data and management assumptions.
Timber utilization the dimensions and quality of timber that is actually cut and removed from an area.
Tolerance the ability of an organism or biological process to subsist under a given set of environmental conditions. The range of these under which it can subsist, representing its limits of tolerance, is termed its ecological amplitude. For trees, the tolerance of most practical importance is their ability to grow satisfactorily in the shade of and in competition with other trees.
Top height the average height of the hundred trees of largest diameter per hectare.
Topographic break a distinct change in the slope of the land.
Topography the physical features of a geographic area, such as those represented on a map, taken collectively; especially, the relief and contours of the land.
Total chance planning early planning over an entire development area for the best overall realization of all objectives identified by broader planning.
Total resource plan a plan for long-term forest management over an entire area, such as a watershed. The plan identifies known resource values, capabilities and sensitivities; confirms or refines management objectives for those values; and establishes detailed management guidelines by which to achieve those objectives on the ground.
Trade-off a management decision whereby there is a reduction of one forest use in favour of another, such as a reduced timber yield in favour of improved wildlife habitat. In some cases, a management decision favouring one use in one location, is offset by a reverse decision favouring another use in another location.
Treatment prescription operational details required for carrying out individual silviculture activities such as site preparation and planting.
Return to Top of Page
Treatment season the season or year the planned treatment activity will be carried out.
Treatment unit the geographic unit of productive forest land area designated in a prescription for a specific silviculture activity or series of treatments.
Tree Farm Licence (TFL) TFLs are privately managed Sustained Yield Units. TFLs are designed to enable owners of Crown-granted forest lands and old temporary tenures or the timber licences which replace them, to combine these with enough unencumbered Crown land to form self-contained sustained yield management units. These licences commit the licensee to manage the entire area under the general supervision of a provincial Forest Service.
Tree-length harvesting system a method of harvesting that includes felling a tree, cutting of the top and delimbing it before transport to a mill.
TSA plan the overall forest management plan developed for a TSA. The TSA Plan establishes the overall direction for the management of the timber, range and recreation resources under a Forest Service jurisdiction in the TSA.
Turnout a widening in the roadway where a vehicle may pull or park to allow other vehicles to pass safely.
Return to Top of Page
Underplanting planting young trees under the canopy of an existing stand.
Understorey any plants growing under the canopy formed by other plants, particularly herbaceous and shrub vegetation under a tree canopy.
Uneven-aged silvicultural system: a silvicultural system designed to create or maintain and regenerate an uneven-aged stand structure. Single-tree and group selection are uneven-aged silvicultural systems.
Uneven-aged stand a stand of trees containing three or more age classes. In a balanced uneven-aged stand, each age class is represented by approximately equal areas, providing a balanced distribution of diameter classes.
Unmanaged forest land forest land that is not subject to management under a forest management plan.
Unmerchantable of a tree or stand that has not attained sufficient size, quality and/or volume to make it suitable for harvesting.
Unrecovered timber timber as described in the Provincial Logging Residue and Waste Management Procedures Manual.
Unrecovered volume timber that is within the cutting specifications of the minimum utilization standards of the cutting authority and not removed from the area.
Unsalvaged losses the volume of timber destroyed by natural causes such as fire, insect, disease or blowdown and not harvested, including the timber actually killed plus any residual volume rendered non-merchantable.
Unstable or potentially unstable terrain an area where there is a moderate to high likelihood of landslides.
Uplands terrain not affected by water table or surface water or else affected only for short periods so that riparian (hydrophilic) vegetation or aquatic processes do not persist.
Urban forestry the cultivation and management of trees and forests for their present and potential contributions to the physiological, sociological and economic well-being of urban society.
Utilization (of forage and browse) the level of forage and browse use on a site. For herbaceous species, it is measured as a percentage of the current year's growth removed; for browse species, it is measured as a percentage of stem ends removed.
Utilization standards the dimensions (stump height, top diameter, base diameter, and length) and quality of trees that must be cut and removed from Crown land during harvesting operations.
Return to Top of Page

Home | Forest Capital of Canada | About Our Website |
Ontario's North (West) Forest | Boreal Forests of the World | North (West) Forest Industry |
World Links and Resources | "Forest Finder" Search Engine | Educational Resources |
What's Happening | Contacts | Site Map |