Taper functions allow determining size classes and volumes of trees with direct application in the planning
of technical and economic forest activities. For this purpose, the aim of this study was to describe the taper
of the trunk of Araucaria angustifolia
(Bertol.) Kuntze in the portion between the ground level and the
insertion of the crown of individuals in remnant of native forest. Also tried to fit the regression model to
represent relations height/DBH, diameter at the insertion of the crown in function DBH and the development
of assortment timber table. Eighty-five trees were measured their diameters and heights relatives using
Hohenadl cubed method and the diameter of the insertion crown with Criterion RD 1000 instrument.
The taper models were adjusted by regression analysis using polynomial of the 5th
degree, Kozak (1988),
Lee et al. (2003) and Sharma and Zhang (2004). The adjusted coefficient of determination (R²aj), the standard error of estimate in percentage (Syx%) and graphical analysis between estimated values in function
of observed were used statistics to evaluate the quality of fit and models precision. The model height/DBH
and diameter at the insertion point of the crown evidence good fit statistical and precision, allowing its
application in activities intended at planning and forest inventories. The flexibility and efficiency of Kozak
(1988) model in predicting diameters and volumes until the crown insertion point favors the use and obtain
timber assortments of araucaria.