This thesis presents visual grading of Slovenian beech, based on visual characteristics of beech samples and parameters, calculated by their visual characteristics. For the purpose of visual grading of Slovenian beech I used three different national standards (German, British and French), because of a non-existent Slovenian standard for visual grading of deciduous trees, including beech. In the final part of the thesis I made a rough draft of the standard, based on decision trees, which could be used for visual grading of Slovenian beech.
The conclusion of the thesis was based on the examination of existing standards for timber strenghth grading, with a focus on non-destructive methods of timber grading, including visual grading. I described standard methods of how mechanical and physical characteristics are defined, on which timber grading is based. Descriptions of non-destructive methods of timber grading are supported by reference of valid European standards with determination of methods and empirical equations for calculating mechanical and physical characteristics, required for a purpose of classification in strenghth classes. As part of non-destructive methods of timber grading I focused on a visual grading, which covers definition, identification and measuring of visual characteristics of wood or so-called wood defects. I checked the correlations between visual characteristics and characteristic value of tensile strenghth, mean modulus of elasticity and characteristic value of density, using basic statistical relations. As a result I specified the most affective visual parameters of visual grading, due to final strenghth classification of timber.
Due to visual grading by three different standards I checked their usability for the visual grading of beech from Slovenian forests. In the final step, I sorted beech samples from Slovenian forests in the different strenghth classes. Classification was done by considering the visual characteristics with the highest value of correlation between them and mechanical and physical characteristics, using decision trees, made in the Wolfram Mathematica programme. With the use of different methods of visual grading of timber I checked possible methods of visual grading of beech in Slovenia and evaluated the most suitable for Slovenian conditions.