Log rule conversions for use in pennsylvania stumpage price reporting

Unbiased log rule conversion factors are essential for accurate stumpage price reporting. This paper outlines the development of log rule conversion factors between Doyle, Scribner, and International 1/4" (Int. 1/4") from existing Pennsylvania inventory data. The inventory data are used to calculate the dbh and merchantable height for the average tree. These average tree dimensions are then used to scale the volume in the three log rules. The ratios of the volumes are compared and conversion factors calculated. The conversion factors from the Doyle to Scribner, Doyle to Int. 1/4", and Scribner to Int. 1/4" are 1.462, 1.695, and 1.159, respectively. The reciprocal conversion factors (e.g., Scribner to Doyle) are simply the reciprocal of the above values (e.g., 1/1.462-0.684). The conversion factors were then compared using Pennsylvania Bureau of Forestry sale information. The results showed close agreement with conversion factors developed in this study. Although geographic and temporal limitations exist to applying these conversion factors outside of Pennsylvania, the methods represent a standardized approach to developing log rule conversions.