Mathematical analysis and modification possibilities of Ozolinš’ taper curve on the example of Hiiumaa pines

This paper discloses algorithms for calculating the volume and lateral area of a stem or part of the stem (assortment) using the integral of the Ozolinš’ stem taper curve. An algorithm was also developed to change the taper curve constants in case another diameter was measured higher than the breast height. The experiment was performed with 580 Scots pines (Pinus Sylvestris L.) measured in Hiiumaa, which included height, diameter at breast height and diameter from the root collar at a height of 5 m. The volumes of tree stem and assortments were estimated with both – the original and corrected (with the measured additional diameter) Ozolinš’ taper curve. Using the original Ozolinš’ taper curve, the stem volume of pines in Hiiumaa is estimated at 4% higher according to the analysis results of 580 measured trees. In the case of Hiiumaa Scots pines (Pinus Sylvestris L.), it is recommended to use 119.717, −289.805 and 1152.016 as the values of the coefficients a₀, a₁ and a₂, respectively, of the Ozolinš’ taper curve equation. In conclusion, for a more accurate assessment of the forest reserve, it is recommended to measure one additional diameter at 5 to 8 m above the root collar on some or all trees.