A volume prediction system for Quercus robur L. in Galicia (Northwestern Spain) based on a volume ratio equation

M. Barrio Anta, J. G. Álvarez González, I. J. Díaz-Maroto Hidalgo

Abstract


Eight total-volume equations and four volume-ratio equations (for diameter limits) were fitted to a sample of 225 trees of Quercus robur of different ages. The trees were collected in stands growing in a great variety of site qualities and densities in Galicia (Northwest of Spain). The data employed to develop volume ratio equations have a longitudinal structure so a second order autoregressive model was used to correct the error dependence implicit in this kind of data. Several «goodness-of-fit» statistics were used in order to select the best equations within each group (total volume equations and volume ratio equations) and cross-validation was used to analyse the performance of the model. Finally, the models selected were combined to develop a volume equation with product classification.

Keywords


Quercus robur; equation; total volume; volume ratio; product classification



DOI: 10.5424/srf/2004133-00849

Webpage: www.inia.es/Forestsystems