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

The objective of this paper was to compare volumes estimated by taper equat ions to true volumes obtained by the water displacement technique (xylomete r). Four previously published models and a fifth-degree polynomial were ana lyzed. Three sets of diameters measured on 52 fallen trees from Pinus ellio ttii Engelm. var, elliottii were used to fit the models. Clark et al.'s (19 91; USDA For. Serv. Southeast. For. Exp. Stn. Res. Pap. No. SE-282) model w as the best to predict diameters along the stem, merchantable volume, and t otal volumes. Max and Burkhart's (1976; For. Sci. 22(33): 283-289) model al so had an excellent performance. The results still showed that the normal c omparison between volumes estimated by integration of taper equations to th ose estimated by Smalian or Huber's formula (usual procedure) underestimate s the true error which is achieved by comparison with true volumes (xylomet er).