Based on a sample of 2563 trees accumulated from a variety of sources in coastal British Columbia, the prediction bias of the existing total and merchantable volume equations (BCFS 1976; Demaerschalk & Kozak1977; Kovats 1977; Godfrey, unpubl. Memo 1983; pers. Comm., 1983) were evaluated for small coastal Douglas-fir. The equation of BCFS (1976) was generally unblased for total volume prediction, for trees with diameter 5 cm or more; however, the equations of Demaerschalk and Kozak (1977) and of Kovats (1977) consistently under-predicted total volume, and that of Godfrey (pers. comm. 1983) over-predicted total volume. All the equations were biased for trees with diameter below 5 cm. Demaerschalk and Kozak (1977) under-predicted the merchantable volume of smaller trees and over-predicted that of larger trees. Godfrey (unpub. memo, 1983) consistently over-predicted merchantable volume for all trees. New total and merchantable volume prediction equations were developed for trees less than 45 cm in diameter. It is recommended that existing volume equations be evaluated for trees larger than 45 cm in diameter for coastal Douglas-fir, as well as for the other significant species in the province.
FRDA Research Report 010 (1306 KB)
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Updated July 24, 2015