Impact of Natural Climate Factors on Mechanical Stability and Failure Rate in Silver Birch Trees in the City of Donetsk

摘要

A survey has revealed a relationship between the temperature factor and the biomechanical parameters (the modulus of elasticity) for wood tissues in the silver birch tree (Betula pendula Roth). At thawing temperatures, the elastic modulus decreases, on average, 2-2.5 times. A decrease of this kind is uneven, gradual. The rate of elastic-modulus change relative to the rate of woody-plant specimen/trunk thawing has the greatest effect on the mechanical stability of a tree. During thawing, the mechanical stability parameters tend to fall by 45%, on average. These changes affect the angles of divergence from the vertical axis of the trunk portions, the angles of its skeletal branch attachment, bending strength, and tree resistance to wind and gravity loads. Under a low anthropogenic impact, the bending stiffness value for plants at the age of 40-45 years is 22 +/- 2% higher than that under the higher anthropogenic load in a city. Under the impact of anthropogenic load affected by the impact of wind loads, temperatures, and the other factors affecting weather, the transformation of architectonics of the silver birch crown occurs, which can cause irreversible deformations or trunk breakage under a blizzard and freezing rain. Therefore, 63 trees were uprooted and 168 woody plants underwent irreversible deformation, causing a high failure rate on the experimental plots in Donetsk from 2014 to 2020. Splits were recorded in plants at heights of 2-4 m (35%), 5-6 m (17%), 7-8 m (52%), and 9 m (6%). Correlation analysis revealed a strong positive relationship between the L : D morphometric coefficient (trunk length-to-diameter ratio) and the mechanical stability (R = 0.87), along with the failure rate (R = 0.79) of silver birch trees. In this regard, it seems possible to use the L : D coefficient as a morphometric marker for mechanical stability in silver birch trees in the south of the East European Plain (Donetsk Hill Ridge).