Strength characteristics of Scots pine wood in forest stands of European North-East Russia

Currently, there is no consensus among researchers regarding the optimal growing conditions that contribute to the formation of pine wood of «optimal quality». The data published in the literature allow us to conclude that the variation of volume and strength characteristics of pine wood is within a narrow range, within low or medium levels of variability. The aim of the study was to identify the relationship between strength characteristics and macrostructure parameters of annual growth of pine wood, as well as to model the dependence of strength characteristics on pine wood structure parameters and density for the study region. The research of pine plantations covered the region of the northern part of the Russian Plain. All necessary measurements and calculations were carried out on the sample plots in accordance with the methods and standards in the field of forest taxation. Data processing was performed using standard or modified methods and software equipment. To determine whether there is a relationship between strength characteristics and individual linear parameters of tracheids of the early and late zone of the annual ring of pine wood, modelling was carried out using statistical methods. For a more detailed and complex analysis, multiple linear and non-linear regression was constructed with the assessment of the significance of the influence of the factors of microstructure of the annual ring by means of t- and F-tests using a specialised statistical analysis and forecasting package ALGLIB. The evaluation shows that the variability of the resistance of pine wood to compression along the fibres in the stands of the European North-East of the parameters of the structural elements of the annual ring is best explained by variations in the radial diameter of earlywood tracheids and the proportion of the early zone in the annual ring. The results of the study suggest that forest management measures aimed at «optimizing» the annual growth in diameter do not allow us to expect an improvement in the physical and mechanical properties of common pine wood in plantations of the European North-East of Russia. The confidence interval of changes in strength characteristics does not extend beyond the values of 35–50 MPa. The presence of a connection between the resistance of pine wood to compression along the fibres is explained by 50% of the sum of all influencing factors by structural components of radial growth. Modelling using statistical methods was carried out to determine whether there was a relationship between strength characteristics and individual linear parameters of the tracheids of the early and late zones of the annual ring of pine wood.

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