Water, Capillary. Water that is retained around the soil particles and in the capillary pores in the soil at forces approximately between values of pF 2.7 and 4.5; capable of movement under the influence of surface tension, and the main source of supply to forest trees.
Water, Gravitational. Water in the soil body in excess of the capillary capacity. Held by forces somewhat less than pF 2.7 and incapable of being retained under conditions of free drainage.
Water, Ground. The body of water in the ground, accumulated above impermeable layers that completely fills the pore space to a level whose depth below the surface varies from place to place and, generally from time to time. (BCFT). See Water table; Zone of saturation.
Water, Hygroscopic. That portion of the soil water which is retained as a thin film by the soil particles at forces greater than pF 4.5 i.e., after capillary water has been removed. It is incapable of movement by gravitational or surface tension forces, and is associated mostly with the colloidal part of the soil. Sometimes referred to as water of imbibition.
Water Logging. (Ped.) A condition in which the soil pores get filled with water to the exclusion of air. A consequence of inadequate soil drainage.
Watershed. Strictly a water parting, the dividing line between Catchment areas. The use of this terms as a synonym for Catchment or drainage area is deprecated. (BCFT).
Weathering (Ped.). All physical and chemical changes produced in rocks, at or near the earth's surface, by atmospheric agents, and which result in more or less complete disintegration and decomposition. (SSSA).
Weed. Any unwanted plant that interferes or tends to interfere with the growth of individuals of favoured species.
Wilt Disease. (a) A plant diseases in which the drooping of foliage is the most conspicuous symptom. (b) (Entom.). A fatal virus disease of insect larvae which causes their bodies to become flaccid after death. (BCFT).
Wilting Coefficient. The soil moisture content at which a specified standard plant permanently wilts.
Wind, Anabatic. An upward motion of (heated) air due to convection, e.g. the morning upward wing in valleys. Syn. Valley breeze, (BCFTmodif.).
Wind, Katabatic. A downward motion of (cooled) air due to convection, e.g. the evening downward wind in valleys. (BCFTmodif.).
Winter Drying. The desiccation of foliage or twigs by dry winds at times when water conduction is restricted by freezing of the stem or of the ground. It may also occur on unfrozen but cold soil. Syn. Parch blight. (BCFT).
Witches Broom. An abnormal bushy growth of parts of the branch system on trees or shrubs, markedly different from that of the normal plant and characterized by the shortening of the internodes and excessive proliferation, generally pathogenic origin. (BCFT).
Wood. (a) See (Xylem). (b) Sometimes used to indicate firewood and small timber for domestic purposes as distinct from "timber". (c) Any area of land more or less covered with trees. (d) See Stand. (BCFT).
Woodland. Land bearing vegetation composed essentially of woody plants. There is a modern tendency to restrict the term to plant communities, in which trees, often small, are present, but form only an open canopy the intervening area being occupied by lower vegetation typically grass, in contrast to (close) high forest. (BCFT).
Woodland, Farm. The wooded portion of a farm or the wooded land in connection with a farm. Syn. Farm woodlot. (BCFT).
Working, Circle. A forest area (forming the whole or part of a working plan area) organized with a particular object, and under one silvicultural system and one set of working plan prescriptions. In certain circumstances working circles may overlap. (BCFTmodif.).
Working Scheme. A term used in some countries to denote a plan of management not so detailed or so nicely calculated as a Working Plan (BCFT).
Wrench. To break the finer roots of nursery plants, without removing them from the soil by heaving the soil with a fork or similar implement, or by partly lifting the plant and refirming. Cf. Pruning root. (BCFT).