Abstract
The primary interest of forest owners is the amount of income that will be derived from forest operations. Before cutting operations are carried out, the quality and quantity of the wood yield need to be estimated as accurately as possible. To calculate the pro?t from a future cutting operation, the upper diameters (example of 4-m above the ground) of the stems of trees in the stand need to be estimated. The aim of this study was to estimate these diameters by applying a relative stem taper curve. The equation was developed based on diameter at breast height (DBH) data in order to eliminate the effect of root spread. The curve equation is a third-order polynomial based on data from 571 sugi (Cryptomeria japonica D. Don) trees measured between 1996 and 2004; the equation ?t the data well (R2>0.99). There are more than 60 local varieties of sugi, and relative stem taper curve equations were developed for 8 of these varieties. By applying the relative stem taper curves, forest managers can estimate the upper stem diameter and log yield before cutting trees.
