Thickness and Weight Variability of Birch Bark along the Trunk Length

Abstract

Due to the special properties birch bark finds wide application in construction, pharmacology, medicine, cosmetology and other branches of economy. The study object is downy birch (Betula pubescens Ehrh.). The stand composition consist of 5 birches, 3 aspens, 2 alders and 1 spruce; the average trunk diameter is 21.5 cm; the average stand height is 22.5 m; the relative density is 0.7; the bonitet is II; the stem wood stock is 220 m³/ha. The research purpose is to determine the variability of birch bark parameters along the trunk length depending on trunk diameter and tree age. Nine model birch trees from the different diameter classes were sawn for the detailed analysis. At the height of 0.3, 1.3, 2.0 m and then every 2.0 m the disk shaped samples with thickness of 2–3 cm were sawn out the tree trunk. The freshsawn disks were weighed; after that the bitch bark upper layer was separated and weighted, then the same was done with phloem. All fractions were dried up to the air dry condition and weighed again. According to the results of the second weighing, the humidity of the samples and the content of bark, birch bark upper layer, and phloem were determined in the total weight of a sample. It has been established that thickness, weight, and humidity of phloem and birch bark upper layer vary in trunk height with certain regularity. The maximum content of phloem and birch bark upper layer for all model trees is found in the upper third of a trunk, in the crown; 16–21 and 4–7 %, respectively; little less than in butt. The minimum content of these fractions is typical for the branchless part of a trunk; the share of phloem is 7–9 %, the share of birch bark upper layer is 2–3 %. The mass and thickness of bark expectedly decrease from the butt to the top; however, there are some exceptions for the samples taken at branch points, especially at the points of thick branches attachment. In these areas thickness and mass of butt are always greater in comparison with the areas below or above the trunk. On average, the share of phloem is 3.45 % from the tree mass; the share of birch bark upper layer is 12.41 %. The humidity of phloem and bitch bark varies in height of the trunk. Herewith, the obtained patterns are similar to the change of mass and thickness of these fractions. The highest humidity of phloem and birch bark upper layer is found in the crown area; the lowest humidity is found in the clear stem of a trunk. In all cases, the phloem humidity is higher than that of wood and birch bark upper layer; 147.0; 131.2 and 105.8 %, respectively. It was also shown that the lower the age of model trees, the higher the humidity of birch bark upper layer and phloem. The obtained data allow us to determine more accurately the volume of bark and birch bark upper layer stock. It is possible to estimate more accurately the share of birch bark upper layer and bark from the total weight of the trunk, in view of their humidity in general.
For citation: Gryazkin A.V., Belyaeva N.V., Danilov D.A., Vandzhurak G.V., Hung Vu Van. Thickness and Weight Variability of Birch Bark along the Trunk Length. Lesnoy Zhurnal [Forestry Journal], 2019, no. 2, pp. 32–39. DOI: 10.17238/issn0536-1036.2019.2.32