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Basal area is the cross-sectional area of trees at breast height (1.3m or 4.5 ft above ground). It is a common way to describe stand density. In forest management, basal area usually refers to merchantable timber and is given on a per hectare or per acre basis. If one cut down all the merchantable trees on an acre at 4.5 feet (1.4 m) off the ...
When stocking, a tree's basal area is measured. The basal area is a cross-sectional area of the stump taken about 4.5 feet (1.4 m) above the ground. [7] The equation for calculating the basal area of trees in a stand is Basal Area = 0.005454 DBH 2, where DBH is the diameter of the tree at the aforementioned measuring height. [7]
Borderline trees occur only when the distance from the sampling point to the center of the tree is equal to the DBH times plot radius factor (PRF). The PRF is determined based on the type of prism or angle gauge being used. Basal Area Factor (BAF) 5, 10, and 20 angle gauges result in PRFs of 3.89, 2.75, and 1.94 (feet inch −1) respectively.
Basal area – defines the area of a given section of land that is occupied by the cross-section of tree trunks and stems at their base; Diameter at breast height (DBH) – measurement of a tree's girth standardized with different countries having different standards they are often at 1.3 meters (about 4.5 feet) above the ground
The above equation is an expression for computing the stand density index from the number of trees per acre and the diameter of the tree of average basal area. Assume that a stand with basal area of 150 square feet (14 m 2) and 400 trees per acre is measured. The dbh of the tree of average basal area D is:
An example of this would be Big Tree of Tule in Santa María del Tule, Oaxaca, Mexico [10] described above. The Tule tree has a diameter of 38 feet 1.4 inches (1,161.8 cm) as measured by tape wrap, but because of its irregularity a cross-sectional wood area expressed as a circle gave an effective diameter of only 30 feet 9 inches (937 cm).
For n trees, QMD is calculated using the quadratic mean formula: where is the diameter at breast height of the i th tree. Compared to the arithmetic mean, QMD assigns greater weight to larger trees – QMD is always greater than or equal to arithmetic mean for a given set of trees.
Each tree that is in the plot represents this number, the BAF, of square footage. It is multiplied by the number of trees on the plot to give basal area per acre. In the United States BAF is measured in units of square feet. For example, using a BAF 10 angle gauge a forester measures 12 trees that are in trees.