Polynomial taper model for Queensland plantation hoop pine

A stem taper model, involving a high order polynomial developed using plantation hoop pine (Araucaria cunninghamii Ait. ex D. Don) trees grown in Queensland, is presented. The stem profile for each tree was initially modelled using functions of diameter under bark and height, as the dependent and independent variables respectively. Parameter estimates from these individual tree regressions were subsequently modelled, using total height and diameter at breast height under bark (DBHub) as the independent variables. Finally, total height and DBHub were modelled in terms of predominant height' and diameter at breast height over bark (DBHob).

The largest mean error in the estimates of stem diameter predicted using the final model, with predominant height and DBHob as the independent variables, was 0.12 cm. The overall mean relative error in the estimate of volume, based on coefficients modelled using predominant height and DBHob, was 0.20 per cent. Apart from its accuracy, the main advantages of the model include its simplicity and its ability to model the whole tree using a single function.