- A burn by a surface fire that can consume ground vegetation and "ladder" fuels.
- The trees and woody shrubs growing beneath the overstory in a stand of trees.
- Uneven-aged management
- Actions that maintain a forest or stand of trees composed of intermingling trees that differ markedly in age. Cutting methods that develop and maintain uneven-aged stands are single-tree selection and group selection. (See even-aged management.)
- Unregulated harvest
- Tree harvest that is not part of the allowable sale quantity (ASQ), such as road hazard trees.