Influence of wood defects in oak on grading

Oak wood is a valuable raw material, in particular the best quality of oak wood. The quality of round wood is determined by its defects. The aim of this paper was to analyse how particular defects influence the grading of oak wood. The research was carried out on 171 oak trees, on two areas – in two Forest Districts – Krotoszyn and Jarocin. Measurements were taken on veneer and saw logs. The length and diameter of each log was measured. The quality class of each log as well as the type and size of the wood defects were defined. Knots were the most common defect and influenced timber quality the most (75%). The influence of the other defects did not exceed 10%. It is therefore advisable for practitioners to prune young oaks at the early stage of stand development. Damage to residual trees after logging operations decreases the quality of the round wood from butt-end logs which are potentially the best part of the whole trunk. It is recommended that trees should be protected from damage during logging.