Estimation of Over- and Under-Bark Volume of Scots Pine Timber Produced by Harvesters

Monika Sedmíková,Jiří Dvořák,Radim Löwe,Rostislav Linda,Martin Jankovský,Pavel Natov

doi:10.3390/f11060626

Abstract

Harvesters produce one third of timber in Czechia. The aim of this study was to analyze the over- and under-bark volume estimates of Scots pine (Pinus sylvestris L.) timber produced by a mid-performance harvester. The data were collected between March 2017 and June 2018. In total, 4661 stems cut into 29,834 logs were analyzed. For volume estimation, StanForD offers several price categories using various algorithms. Three of these price categories are relevant for Czech forestry—M3s, M3toDE, and M3miDE. The M3s price category is based on the estimation of partial volumes of 10 cm long sections, which are summed. Therefore, this price category represents the volume estimation closest to the true volume. By comparison, the M3toDE and M3miDE price categories use the same algorithm for volume estimation, which is based on the Huber formula using a midspan diameter rounded down to the nearest whole centimeter. The M3toDE price category underestimated the over-bark volume by 6.48% compared to the reference price category M3s. The mean log volume estimated through the M3s price category was significantly higher than the M3toDE volume both in individual grades and without grading. We found significant differences between under-bark volume estimates by the diameter band bark deduction method (DBM) and the parametric linear bark deduction method (PLM) used in harvester’s systems according to the Guidelines for Electronic Scaling of Timber for Harvesters in Czechia (GEH) for Scots pine butt logs with rough bark, and also for other logs with normal bark thickness. To obtain under-bark volume estimates of Scots pine timber that are comparable with the Guidelines for Timber Scaling in Czechia (GTS) using the parametric nonlinear bark deduction method (PNM), we recommend using the algorithm of the M3toDE price category, with double bark thickness determined by the diameter band bark deduction method.

Highlights

The use of harvester technology is closely linked to the cut-to-length (CTL) logging method [1].This method represents a series of operations, during which standing trees are converted into timber assortments directly at the stump location [2]
To obtain under-bark volume estimates of Scots pine timber that are comparable with the Guidelines for Timber Scaling in Czechia (GTS) using the parametric nonlinear bark deduction method (PNM), we recommend using the algorithm of the M3toDE price category, with double bark thickness determined by the diameter band bark deduction method
The logs were measured by the machine and two different algorithms of the M3s and M3toDE price categories were used for over-bark volume estimation (Table 3)

Summary

Introduction

The use of harvester technology is closely linked to the cut-to-length (CTL) logging method [1]. This method represents a series of operations, during which standing trees are converted into timber assortments directly at the stump location [2]. Mechanized harvesting increases productivity and reduces production costs compared to motor-manual logging [3,4,5,6]. The CTL method is currently almost exclusively used for harvesting in some European countries, such as Finland, Sweden, and Norway [7,8]. There are barriers to increasing the share of mechanized CTL harvesting. Ferrari et al [9]

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Conclusion