Methods for determining the volume of stems of small trees (Pinus sylvestris L.) in the southern taiga subzone of the Sverdlovsk region

The accuracy and efficiency of determining the volume of wood and bark content in the stems of Scots pine (Pinus sylvestris L.) determine the focus of the problem of predicting the dynamics of biomass and subsequent processing of small-sized wood. The biometric parameters of small trees (N = 400) aged 8–15 years were assessed, with 200 trunks selected in each growth variant – forest young growth and forest plantations. The volumes of stems and bark were calculated for three types of formulas: 1) sectional; 2) median section formula and 3) formula using the old species number and cross-sectional area at breast height. According to the nonparametric Sign test, the differences between the biometric parameters of stem volume and bark volume of P. sylvestris in each of the growth variants, calculated using the formulas of the first and second types, are statistically insignificant (Z = 0.205-1.430 at p = 0.153-0.758). The volumes of stems and bark calculated using the old species number, according to the Sign test (Z = 6.011-16.670 at p = 0.001), had a significant discrepancy with those determined using the sectional formula and the median section formula. In accordance with the calculated value of the true species number (λ0.1), the stems of pine trees in the forest young growth can be assessed as medium-full-boled - λ0.1 in the bark = 0.512-0.566 and λ0.1 without bark = 0.491-0.561, and the stems of trees in forest plantations as full-boled - λ0.1 in the bark = 0.816-0.919 and λ0.1 without bark = 0.707-0.778. The biometric parameters of tree stem volumes with and without bark, calculated using the second type formula with interpolation through D0.1H, are in good agreement with the parameters obtained using the first and second type formulas (Z = 0.104–1.812 at p = 0.100–0.916). It has been established that the bark content of trees in the forest young growth and forest plantations of P. sylvestris increases consistently with a decrease in the density of the forest stand - in very dense stands about 10%, in dense stands about 13%, in average density about 16% and in sparse stands - 19% or more. To conduct scientific research and practical forest inventory work both in the forest young growth and in forest plantations of P. sylvestris, which most closely correspond to the actual stock, it is necessary to recommend a formula of the second type, interpolated on a model tree taking into account the trunk diameter at one tenth of its height.