Semi-empirical estimation of log taper using stem profile equations

Abstract

In January 2019 the forest industry in Ukraine adopted European standards for measuring and grading of round wood based on mid-point diameters, which caused major discrepancies from traditionally used estimates of timber volume using top diameters. To compare methods of merchantable wood volume estimation, we investigated the stem form inside bark for two dominant tree species in Ukraine, i.e. Scots pine (Pinus sylvestris L.) and common oak (Quercus robur L.). We used tree stem measurements to fit stem profile equations, whereas simulation was applied to derive log taper. We found that Newnham's (1992) variable-exponent taper equation performed well for predicting stem taper for both tree species. Then, we simulated the structure of harvested wood, so that it replicated annual distribution of logs by their length and diameters. As a result, the average log taper was estimated at 0.836 ÷ 0.855 cm·m<sup>–1</sup> and 1.180 ÷ 0.121 cm·m<sup>–1</sup> for pine and oak, respectively. The study also indicated that log taper varied along stems. The higher rates of diameter decrease were found for butt logs, for which the taper was 2.5–3.5 times higher than its average for the whole stem. The results of our study ensure the stacked round wood volume conversion between estimates obtained using top and mid-point diameters.

Plant strategies for greatest height: tapering or hollowing

“…In contrast to trees, bamboos, which have a shorter lifespan than trees and are connected by underground stems 42 , adopt a strategy of reducing self-weight at the expense of resistance to external forces to increase the number of shoots reaching the ground and ensure rapid growth. Bamboos, a representative example of hollow plants among woody species, simultaneously adopt both a tapered form and hollowing 19 , thus enabling them to reach the same height as trees at an astonishing speed. Furthermore, the tapered form achieves higher self-weight buckling characteristics at a smaller fixed-end radius than hollowing.…”

Stem volume by height classes of immature, mature and overmature stands of the main forest-forming species of Ukraine

“…Stem profile equations are used when in addition to the total stem volume, it is necessary to characterise its taper or estimate the volume of stem zones with certain qualitative characteristics (e.g., commercial timber) [16]. In Ukraine, this approach has been used relatively recently [18]. Much more often, the stem volume is considered as the product of three factors: the basal area (g), height, and form factor (f), where f is a conversion coefficient between the volume of cylinder (gh) and stem volume.…”

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“…Modern methods of data collection and analysis and modelling can substantially improve tax standards in the context of systematic accumulation and addition of the research database (Robinson & Hamann, 2011). Modelling of the tree stem taper of the main forest-forming species of Ukraine provides initial conditions for taxing the volume of tree stem and round timber obtained from them (Bilous et al, 2021b). Accurate accounting of the volume of business wood contributes to the development of a transparent wood market and fair relations between sellers and consumers of wood.…”

“…But still, the model of A. Kozak (2004) is more widely used in a number of modern studies (Bilous et al, 2021b;Myroniuk et al, 2023). The study by Z.…”