Comparison between predicted volumes estimated by taper equations and true volumes obtained by the water displacement technique (xylometer)

The objective of this paper was to compare volumes estimated by taper equations to true volumes obtained by the water displacement technique (xylometer). Four previously published models and a fifth-degree polynomial were analyzed. Three sets of diameters measured on 52 fallen trees from Pinus elliottii Engelm. var. elliottii were used to fit the models. Clark et al.ʹs (1991; USDA For. Serv. Southeast. For. Exp. Stn. Res. Pap. No. SE-282) model was the best to predict diameters along the stem, merchantable volume, and total volumes. Max and Burkhartʹs (1976; For. Sci. 22(33): 283-289) model also had an excellent performance. The results still showed that the normal comparison between volumes estimated by integration of taper equations to those estimated by Smalian or Huberʹs formula (usual procedure) underestimates the true error which is achieved by comparison with true volumes (xylometer).