Improved cubic volume prediction using a new measure of form factor

Abstract

For cubic volume estimation, commonly used measures of stem form, such as form quotient or crown measures, are difficult to obtain in the field and usually give only marginal improvement in mean square error of prediction. We develop prediction equations using stem height at a predetermined fraction of diameter at breast height outside bark, or the ratio of this height to total height, to predict cylindrical form factor and total stem volume for Douglas fir ( Pseudotsuga menziesii (Mirb.) Franco). Using an independent dataset, a comparison of the volume prediction for our model shows substantial improvement in mean square deviation for volume prediction compared to three commonly-used volume equations for Douglas fir in the Pacific Northwest.