Abstract
Recent technological advances have made estimating outside bark, upper stem diameters on tree stems more commonplace. Inside bark diameters and bark thicknesses are also often needed at upper stem locations for volume determination applications, but those attributes are not easily measured, even with the newer technologies. Interest in bark and timber residue for bioenergy uses has also put increased focus on the ability to measure or estimate bark thickness at various heights aboveground. Bark factor (BF) equations allow one to estimate the ratio of inside bark diameter to outside bark diameter at a given height aboveground for a given tree. This ratio can then be multiplied by outside bark diameter measurements to yield estimates of inside bark diameters. Bark thickness can then be found via subtraction. This project developed BF equations for three hardwood species found in northwest Arkansas, nine hardwood species found in southeast Arkansas, and two hardwood species found in north central Wisconsin. Three distinct patterns in BF were observed, with the R2 of the fitted regression equations ranging from 0.76 to 0.97. Example applications are also described.