Preferred term

tree diameter

Definition

any straight line segment that passes through the center of the circle and whose endpoints lie on the tree circumference. A standard method of expressing the diameter of the trunk or bole of a standing tree is Diameter at breast height, or DBH. Tree trunks are measured at the height of an adult's breast, which is defined differently in different countries and situations. In continental Europe, Australia, the UK, and Canada the diameter is measured at 1.3 metres above ground. In The US, New Zealand, Burma, India, Malaysia, and South Africa, breast height diameter is measured at a height of 1.4 metres. Previously 4.5 ft (1.37 m) was used. http://en.wikipedia.org/wiki/Diameter_at_breast_height#cite_note-1

http://vocabs.lter-europe.net/EnvThes/22303