Scots Pine (pinus Sylvestris) and Silver Birch (betula Pendula) Bark Thickness Comparison To Bark Algorithms Used In Stanford 2010 Forest Machine Standard.

The diameter of round timber, starting from the forest inventory and ending with the measurement of the timber before processing is usually measured with bark, but the calculation of the volume of wood is usually based on the diameter without bark, which has a greater economic value. For such cases, local or regional algorithms for estimating bark double thickness and volume have been developed and adapted for many tree species. The volume of the bark is on average 8% of the volume of round timber. Timber accounting using harvester data is used, firstly, to settle with service providers, and secondly, to prepare round timber in exactly the required sizes for further processing companies. Certain countries also use the volume measured by the harvester in transactions between timber buyers and sellers. There are several conditions for the accurate measurement of timber, and one of the most important is the appropriate algorithms for calculating the double thickness of the bark. The volume of the bark in different parts of the trunk can vary from 3-15%, as well as the thickness of the bark at the end of the trunk can reach 4 cm. To ensure the accuracy of diameter and length measurements, the harvester is regularly calibrated, while to accurately calculate the volume of round timber without bark, the appropriate bark reduction algorithms for each region must be used. In Latvia, from 2019-2021, a large-scale study was conducted to find out the accuracy of existing bark algorithms included in StanforD2010 for the most economically important tree species in Latvia - Scots pine, Norway spruce, Silver birch, aspen, oak, ash, and black alder. A total of 215 sample plots were created by measuring the assortments of the selected sample trees with the 1-meter step measurement method, which is adopted as the most accurate measurement method in Latvia. In the study, the variation of the double thickness of the bark was evaluated for each tree species depending on the growth region, the type of cut, the quality (tree height at certain age) and the place in the trunk. In Latvian conditions, the double thickness of the bark of Scots pine varies on average from 21 mm in the root part (first log) to 4 - 5 mm in the top part of the trunk. In comparison with linear algorithms (Zacco, 1974), a difference of 11 mm is found in the root part (first log). The double thickness of Silver birch bark varies on average from 22 mm in the root part (first log) to 10 - 12 mm in the top part of the trunk. Compared to the linear algorithms (Zacco, 1974), a difference of 4 - 5 mm is found in the root part (first log). Compared to the algorithm developed by "Skogforsk" in 2004 for pine, this difference is insignificant. Before starting work with the harvester, it is important to make sure of the double thickness algorithms set in the software, because they significantly affect the results of the calculated volume.