![]() Size more than 120cm in length is rarely used. ![]() One is fixed at right angles to one end of the rule and the other movable parallel to the fixed rule. It is generally made of wood and consists of a graduated rule and two arms. Instruments such as diameter callipers, tapes and wooden scales are most commonly used and the details of their descriptions are presented below: GUB = GOB – 2πt where, t is the bark thickness GBH = Perimeter of Stem at Breast Height = 2πr should be removed before measurement so that they do not distort the result. Obstacles such as branches, climbers, loose bark etc. Tapes should maintain a loop, at right angles to the stem, around the tree. Callipers should be held in such a way that the arm of the calipers is at right angles to the stem. BH of the tree with aerial root/ buttress formation is measured by shifting BH mark a little above the buttress formed. If forking renders the BH point abnormal, foregoing rule should be applied and the tree is counted as one or two depending on the place of measurement. If tree is forked below the BH, each fork should be treated as separate tree. If tree is forked above BH, it should be considered as a single tree. In abnormal trees, BH mark should be shifted little up or down as little as possible to a more normal position of stem and diameter is measured. Convenient height for taking measurement. In New Zealand, DBH is measured at 1.4 m. In Europe, Australia and UK, DBH is taken as 1.3 m which is recommended by FAO as standard. Universally adopted standard height for measuring girth, diameters and basal area of standing trees is 1.37 m and being practiced in India, Burma, America, Union of South Africa and other British Colonies. Generally DBH is not measured on dead trees or on those of less than 7 cm DBH. Diameter at Breast Height (DBH) is the most common parameter used in the measurement of standing timber. When measuring live trees most information is presented as over bark dimensions. Because trees are measured with the bark on, this is also called the Diameter at Breast Height Over Bark (DBHOB). By convention, the diameter of forest trees is measured in centimeters at 1.37 m above the ground and is termed the “Diameter at Breast Height” or DBH. In many countries, especially India, this will be at 1.37 m above the base of the tree where the tree meets the ground. In the past, girth has been used but this is no longer recommended.Ī carefully defined point should be used for measuring the diameter of the tree. In forestry, diameter should always be used for the description of the tree. It is not only necessary for calculation of volume of logs, but also necessary for making inventory of growing stock as well as to correlate height, volume, age, increment of trees.
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