D
debarker. Machinery that removes bark from a log.
d.b.h. (or dbh). The diameter of a tree outside of the bark at roughly breast height. Normally measured 4 V2 ft off the ground on the uphill side of the tree. It is easier to measure at this height, and many trees have large swells in the stem below this point that could increase errors in computing tree volumes.
deciduous. Term applied to trees (commonly broadleaf) that drop all their leaves sometime during the year.
deck. Sometimes applied to stacks of logs. Syn. log deck. See cold deck, hot deck.
defect. Any irregularity or imperfection in a tree, log, piece, product, or lumber that reduces the volume of sound wood or lowers its durability, strength, or utility value.
dendrology. The identification and systematic classification of trees and shrubs.
diameter. The longest distance at right angles, across any circle or cylinder. In standing trees, estimate diameter by dividing the circumference (length of a line taken completely around the outside of a tree) by 3.1416.
diameter breast high: See d.b.h.
diameter class. One of the intervals into which the range of diameters of trees in a forest is divided for purposes of classification and use. Generally this is done in 12in,even increments (12 in class would contain trees from 11 to 13 in).
diameter limit. The smallest (occasionally the largest), size to which trees or logs are to be measured, cut, or used. The points to which the limit usually refers are stump, breast height, or top.
diameter-limit cutting. A system of selection harvest based on cutting all trees in the stand over a specified diameter. This eliminates marking individual trees.
diameter tape. A graduated tape based on the relationship of circumference to diameter, which provides a direct measure of tree diameter when stretched around the outside of the tree.
d.i.b.. Abbreviation for "diameter inside bark."
dibble. A flat or round metal tool used to make a hole for planting containerized seedlings.
direct seeding. Sowing tree seed to regenerate a forest.
d.o.b. Abbreviation for "diameter outside bark."
dominant trees. Trees with crowns extending above the general level of the crown cover and receiving full light from above and partly from the side; larger than the averge trees in the stand, with crowns well developed, possibly somewhat crowded on the sides. See crown class.
D-plus (D +) rule. A rule of thumb in thinning; estimate desired spacing by adding a given number to the d. b. h. of the crop tree: a "D + 4" rule would mean that a 16in d.b.h. tree would need 16 + 4 or 20 ft of growing space.
dormancy. A biological process in which a plant ceases most growth activities and simply maintains existing tissue. Caused by periods of moisture and/or temperature stress.
Douglas-fir region. An area from northern California to southern British Columbia, west of the Cascades crest. The western portions of Oregon and Washington, where Douglas?fir grows in even?aged stands and is the predominant timber species.
dry rot. A decay of the "brown rot" type, caused by specialized fungi capable of conducting moisture from an available source and extending their attack to wood previously too dry to decay. Found chiefly in buildings. The term is open to the misinterpretation that wood will rot when dry, which is not true.
duff. Forest litter and other organic debris in various stages of decomposition on top of the mineral soil; typical of coniferous forests in cool climates, where rate of decomposition is slow and where litter accumulation exceeds decay.
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Forest Glossary