Polynomial models to represent profile and volume of Eucalyptus urophylla stem in north region of Goias State, Brazil

Abstract

Timber volume estimates of a certain forest due to its multiple products prediction may increase incomes from forest stands management. It is already clear that precise volume survey of a forest is essential to timber companies in order to increase commercial value to forests (native or planted ones), even by diversification of products, transforming residues into raw material. This research has as its main aim to evaluate accuracy of polynomial models proposed by Schöpfer (1966), Kozak et al. (1969) and Hradetzky (1976) to estimate diameter and volume along Eucalyptus urophylla stem, in the region of Niquelândia, Goiás State. The database was composed by 48 trees that had their absolute volume calculate by the Smalian method. The models precision was evaluated by analysis of residuals, the Standard error of estimate (S_yx) and the determination coefficient (R²). The model that produced the best statistics for diameter estimation along the stem was the model proposed by Hradetzky (1976), as well as the 5^th degree model proposed by Schöepfer (1966) proved to be superior to estimate total volume.