Pre-sawing detection of heart cracks in Norway spruce ( Picea abies (L.) H. Karst.) and silver fir ( Abies alba Mill.): variability and industrial implications

Optimising raw material use in the sawing process requires understanding variations in quality indicators. Cracks are defects that significantly reduce product value and can lead to the downgrading of the product. This study aimed to characterise heart crack variability in softwood stems before sawing and improve wood inspection. 1026 Norway spruce (Picea abies (L.) H. Karst.) and silver fir (Abies alba Mill.) stems were scanned using an industrial CT Log X-ray scanner. Among these, 250 stems exhibited heart cracks longer than 50 cm: 37% in silver fir and 18% in Norway spruce. Radial and longitudinal variability of crack metrics were analysed. Results confirm that internal cracks are present in approximately 25% of stems before sawing, with heart cracks length averaging 32% of total stem length. A significant positive linear relationship (R2 ≈ 0.28) was identified between heart crack length, stem diameter and taper. This suggests that factors associated with larger stem dimensions may contribute to increased crack length. These findings are crucial for the wood industry, enabling better crack management, minimising defects in end products and optimising yield and value. Further research on the relationship between silvicultural treatments and the formation of internal cracks is recommended.