A. Kozak, EFFECTS OF UPPER STEM MEASUREMENTS ON THE PREDICTIVE ABILITY OF A VARIABLE-EXPONENT TAPER EQUATION, Canadian journal of forest research (Print), 28(7), 1998, pp. 1078-1083
Like several other taper equations, the predictive ability of Kozak's
(1988. Can. J. For. Res. 18: 1363-1368) variable-exponent taper equati
ons can also be improved by an additional upper stem outside bark diam
eter measurement. This study indicated that improvements were small an
d were mainly restricted to increasing the precision of the estimates.
Also, it was demonstrated that if additional diameter measurements ar
e justified, they should be taken between 40 and 50% of the height abo
ve breast height for greatest improvement. Measurement errors in upper
stem diameters and in their heights above breast height affected both
the precision and bias of predictions.