Cylindrical Form Factor Research Articles

Improved cubic volume prediction using a new measure of form factor

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.

Compatible variable-form volume and stem-profile equations for Douglas-fir

A simple measure of stem form derived from geometric principles provides a basis for compatible volume and stem profile equations. Height ratios corresponding to three diameter ratios provide this measure and are compared in simple linear regression equations that predict a cylindrical form factor using data from a Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stem analysis study. Further comparisons with existing volume and stem profile models from the literature show substantial gains in reducing above breast height volume prediction errors. Advantages and limitations of the models in both a theoretical and field application context are discussed.

Long-Term Effects of Fertilization on Stem Form, Growth Relations, and Yield Estimates of Slash Pine

Abstract The long-term effects of time-of-planting phosphorus (P) fertilization on stem form were evaluated in a 25-year-old slash pine plantation in north Florida. Cylindrical form factor (CFF), relative taper curves, the constant-stress principle of stem formation, and individual tree volume and biomass estimation equations were compared among treatments. Significant differences in CFF and taper existed between control and fertilized trees. Treatment-induced changes in crown size and accelerated tree and stand development may be responsible for these differences. Although statistically significant, alteration of stem form by fertilization was of minor importance relative to the accurate estimation of stand volume and weight. The cost and effort necessary to develop treatment-specific equations for quantifying fertilizer responses for slash pine on P-deficient sites appears unwarranted. For. Sci. 35(3):832-842.