Abstract:

The breast height form factor (f_1.3) is a subset on a series of the normal form factor (f_n), which has the specialities of f_n. Based on the mathematic derivation and calculation of a felled tree, the relationships between the specialities of f_n.and relative height (n), form index (r), and between the specialities of f_1.3 and total height (h), r are as follows: 1. To the same r, f_n, increases with increasing n, however f_1.3 decreases as h rises. 2. When 0.03≤n≤0.22 for f_n to the same n, 5.87≤h≤43.33m for f_1.3 to the same h, the larger the value of f_n and f_1.3, is the plumper the stem form is so that the stem form may be reflected. f_n and f_1.3 are used as conversion factors for volume; When 0.22 < n≤0.37 the same n for f_n, 3.51≤h < 5.87m, the same h for f_1.3 only apply to conversion factors for volume; When 0.37 < n < 1 for f_n, or 1.3 < h < 3.51m for f_1.3, a fraction of f_n or f_1.3 (it is various in different tree species) is used as a conversion factor for volume, but most of them are not ideal for applying to the reflection of stem form or conversion factors for volume.

Key words: Normal form factor, Breast height form factor, Stem form