Variability in Wood Quality and Moisture Content Measured by an Industrial X-Ray Scanner Across 700,000 Sawlogs of Picea abies, Abies alba, and Pinus sylvestris

Evaluating sawlog quality is vital for both forest managers and wood processors. While external traits, such as tree form, branch architecture and visible growth features can be evaluated through visual inspection, many key wood quality indicators remain hidden, such as knot type and distribution, or the heartwood-to-sapwood ratio. This highlights the need for technologies capable of “seeing through” logs. Today, X-ray scanners in sawmills enable comprehensive, continuous, non-destructive assessment of internal stem structure at large scale. This study leveraged a newly compiled database of approximately 726,000 scanned logs to characterize variability in knot distribution and sapwood proportion across three major European softwood species and estimate the moisture content. The analysis highlights inter-and intra-species differences. Sapwood proportion decreased with sawlog diameter in spruce and silver fir but remained high in pine. Pine also presented significantly larger and more variable knots. Between March and August, we observed a seasonal trend in sapwood moisture content, affecting fresh density, while heartwood moisture content remained stable. These findings provide valuable information to support decision-making processes, linking tree characteristics to wood qualities and guiding forest management.