- A National Forest's annual goals for accomplishment for natural resource programs. Targets represent the commitment the Forest Service has with Congress to accomplish the work Congress has funded, and are often used as a measure of the agency's performance.
- Thermal cover
- Cover used by animals against weather. For elk, thermal cover can be found in a stand of coniferous trees at least 40 feet tall with a crown closure of at least 70%.
- A cutting made in an immature stand of trees to accelerate growth of the remaining trees or to improve the form of the remaining trees. Thinning is often used to enhance old growth characteristics.
- Threatened species
- Those plant or animal species likely to become endangered throughout all or a specific portion of their range within the foreseeable future, sometimes designated by the U.S. Fish and Wildlife Service under the Endangered Species Act of 1973.
- Tractor logging
- A logging method that uses tractors to carry or drag logs from the stump to a collection point. This method produces the highest and longest ranging negative environmental impacts.
- TSI (Timber Stand Improvement)
- Actions to improve growing conditions for trees in a stand, such as thinning, pruning, prescribed fire, or release cutting.
- Type conversion
- The conversion of the dominant vegetation in an area from forested to non-forested or from one species to another.