Diameter Breast Height (DBH) – Diameter at Breast Height (measured at 4 1/2 feet above soil grade). DBH is required for determining tree value. Multi stemmed trees require diameters for each stem. In addition, the stem diameter must be factored by the relative crown ratio of the stem.
Decay – The process of degradation of woody tissues by fungi and bacteria through decomposition of cellulose and lignin.
Deciduous – A Perennial plant that loses all its leaves at one time during the year.
Decurrent – Round-headed or spreading plant with no main leader to the top of the plant.
Defect – A fault or weakness in a tree support system.
Dominant Leader/Trunk/Stem – The stem that grows much larger than all other stems and branches.
Dripline – The width of the crown, as measured by the lateral extent of the foliage.
Drop-Crotch Pruning Cut – A thinning cut, which removes the terminal portion of a large branch or leader back to a lateral large enough to assume the terminal role.