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Dia Normal or diameter at breast height

The most common variable used in the most important measurement of trees (Dendrometry) and forests (Dasometry) is the tree diameter .

Source: Forest Mensuration : Measuring trees, stands and forests for ...

Although what we usually want to know, not the diameter, but the cross-sectional area to estimate the volume or basal area is the diameter or, failing that, the circumference of the parameters that are easier to measure.

To allow comparison of the measures taken on different trees or on the same tree at different times, must define a reference point on the trunk . It is important that this point is situated at a convenient height near the ground to allow easy location for measurement by different operators or in different times.

The universal convention is to measure the diameter, with bark unless otherwise specified, at a fixed height from ground level . This standard height breast height is . This location varies slightly between countries:

• In continental Europe, Australia, UK, Canada and others are considering breast height defined as 1.30 m in height from the ground .
• In New Zealand, India, Malaysia, South Africa and some other countries breast height is considered as 1.40 m from the ground.
• In the United States used 4.5 ft (1.3716 m)
• and Japan (1.25 m).

These heights are relatively comfortable and accessible for measurement caliper They are also, in most cases, sufficiently far from the influence of the broadening that occurs at the base of the tree. Although probably a greater height would be preferable for the latter reason and bother hinder the process of data collection.

in the literature can be represented by their initials DAP or called normal diameter (d n ) . In the literature written in English is usually called DBH Diameter at Breast Height.

Karri (Eucalyptus diversicolor ) in Pemberton, Australia.
81m in height and diameter of 1.98 m.
Author: Dennis Haugen, Bugwood.org

The "breast height" is a long tradition and convention used in forestry practice. However used in very specific cases other reference heights.

Researchers in silvopastoral and agroforestry systems use 0.3 or 0.7 m height above the ground as reference, because it has a strong correlation with estimates of powers between grass - crop - trees

Other researchers have found that for the purposes of calculating the volume of a tree is better to use relative heights rather than absolute height. That is, for example, calculate the diameters to 5% of the total height, giving a height measurement of different diameter for each tree.