Abstract:

In the stem-form curve formula of Pinus tabulaeformis y=[a₀x^a₁-a₂+a₃/(a₄-x)]^0.5, three conditions must be satisfied: (1)a₄ is given value beyond the range 0~H, H stands for the tree height; (2) -a₂=-a₃/a₄; (3) The value of expression within radical sign must be positive on any point of the tree stem. Fitting curve based on 129 P.tabulaeformis trees leads to the results: Sharing 89.9% at the condition of R²>0.98, the absolute value of systematic error < 3% coves 79.1%, and the absolute value of systematic error is less than 7% at the most. Comparing the tree stem valume derived form formula of stem-form curve of the one derived from sectional measurement by means of Smalin's formula, the absolute values of error are not more than 4%, where below 1% shares 76.7% of sample trees. The systematic error of 129 trees is 0.53%. The proposed formula of stem-form curve in this paper can reflect the stem-form profile of P.tabulaeformis very suitablely.

Key words: Formula of stem-form curve, Pinus tabuleformis Carr, Stem form