Tree taper is the degree to which a tree's stem or bole decreases in diameter as a function of height above ground. Within Forestry and for the purposes of timber production, trees with a high degree of taper are said to have poor form, while those with low taper have good form. The opposite is the case for open-grown amenity trees. The form of a tree is sometimes quantified by the

Girard form class Girard form class is a form quotient calculated as the ratio of diameter inside bark at the top of the first 16 foot log to the diameter outside bark at breast height ( DBH). Its purpose is to estimate board-foot volume of whole trees from measur ...

, which is the ratio, expressed as a percentage, of the butt-log scaling diameter to

diameter at breast height Diameter at breast height, or DBH, is a standard method of expressing the diameter of the trunk or bole of a standing tree. DBH is one of the most common dendrometric measurements. Tree trunks are measured at the height of an adult's breast, ...

. Taper is often represented by mathematical functions fitted to empirical data, called taper equations. One such function, attributed to Ormerod,Ormerod, D.W., 1973. A simple bole model. '' Forestry Chronicle''. 49:136-138. is

d(h)^2 =    \left(\right)^

where:

d(h)

= stem diameter at height h,

D

= tree diameter at breast height,

H

= tree total height,

h

height of interest (h ≤ H), and

h_b

= breast height. Once developed, taper equations can be used to predict the diameter at a given height, or the height for a given diameter.

Footnotes

{{Forestry Forest modelling

See also

Footnotes