Wood defects in Silver fir (Abies alba Mill.) from mixed uneven-aged forest stands

Knowledge of the quantity and quality of forest wood assortments obtainable from trees is crucial for their economical utilization. In Bosnia and Herzegovina, the quality assessment and classification of forest wood assortments are carried out according to Yugoslav standards (JUS), which base the grading process on the dimensional characteristics of assortments (diameter and length), as well as the presence, size, and frequency of wood defects. Considering the previously emphasized importance of wood defects in the roundwood classification system, the main aim of this study was to identify wood defects in silver fir (Abies alba Mill.) and to analyze the influence of assortment characteristics (diameter and position along the stem), and tree attributes (diameter at breast height and position within the stand based on Kraft’s classification) on the size of specific defects. The study was conducted in uneven-aged, mixed silver fir and spruce stands with beech. The length and diameter of all processed wood assortments, as well as the presence and size of wood defects, were determined immediately after felling. Analysis of the produced assortments revealed the following wood defects: knots, wet heart, rot, damage caused by physical and mechanical influences, pith eccentricity, compression wood, curvature, scars, ingrown bark, split tree stem, ring shake, heart shake, double heart, brown stain, insect damage, ellipticity, and taper. Smaller wood defects that significantly affect the quality of wood assortments, primarily knots and taper, were generally observed in the lower sections of the stem. The only notable exception is the wet heart defect, whose size tends to decrease from the base of the stem toward the crown. These findings confirm that the lower part of the stem is the most valuable, not only due to its larger diameter but also because of its superior wood quality. Continued research is essential to expand the database of wood defects and to develop reliable models that can be integrated into modern harvesting technologies.