Height–diameter allometric models for commercial species in the south-western region of the Brazilian Amazon

Accurate total height estimates in Brazilian Amazon forests are still scarce. This study aimed to (1) evaluate a method for stratifying data by potential height (quasi-asymptotic heights) to group the species; (2) fit a regression model using potential heights (quasi-asymptotic heights); and (3) apply the traditional method of non-linear regression analysis for fitting an equation. The Näslund model was used to estimate the total height and fitted to a sample of 213 trees from 33 species from the Brazilian Amazon. The deterministic fitting method, which assumes the mean potential height (quasi-asymptotic heights) of each group, proved to be more consistent when compared with the estimates obtained by nonlinear least-squares (traditional method). The increased precision was also achieved by applying the potential height (quasi-asymptotic heights) grouping method. The equations fitted according to both strategies, when applied to the tree groups, yielded good fits and were supported by validation statistics. The estimate from the deterministic method is the most suitable and recommended.