Can tree hollow diameter be predicted? A study of native commercial trees in the eastern brazilian Amazon

The objective of this research was to test selected and validated generic and species-specific equations to estimate three different hollow diameter measurements in native commercial trees from a managed forest in the state of Pará, Brazil. A sample of 4,912 hollow trees, involving 29 species, was used to model the mean hollow diameter at tree level, and another composed of 3,867 hollow trees, belonging to 28 species, was used to model the mean hollow diameter of the first log of the commercial stem and the hollow diameter at the base of the tree. 30% of the two samples were previously randomly separated to validate the equations. The variables diameter at breast height (DBH), commercial height (hc), diameter of the log at the base of the tree (Db) and stem quality (SQ) were used in the modeling. In general, the models showed low adjusted coefficients of determination and the relevant standard errors of estimation. Despite this, validation indicated that the equations could generate accurate estimates. It has been found that it is more efficient, in terms of accuracy, to estimate the mean hollow diameter of the first log of the commercial stem, although it is more practical to estimate the hollow diameter at the base of the tree. Compared to generic equations, specific equations can generate more accurate estimates. Therefore, the hollow diameter in commercial trees can be estimated as a function of variables obtained from the forest inventory, and the best strategy is the use of species-specific equations to estimate the average hollow diameter in the initial portion of the commercial stem.