Wood mechanical properties scale with distance to tree tip in the outermost growth ring of a Scots pine

Key message

Distance from the tree tip strongly influences axial variations in the elasticity (MOE) and strength (MOR) of fresh Scots pine wood, with both properties increasing towards the base of the stem.

Abstract

Scots pine (Pinus sylvestris L.), one of Europe's most used timber species, is valued in the construction, furniture, and paper industries. The anatomical structure of Scots pine wood follows the universal conduit widening model, where tracheid lumen size increases in each tree ring from the tip to the base of the stem, enhancing hydraulic efficiency. However, whether the physical and mechanical properties of the wood mirror its axial anatomical pattern remains unclear. For this study, we sampled an 8.6 m tall Scots pine and analysed its fresh wood mechanical, physical and anatomical properties of the outermost growth ring along the stem. In addition to the expected axial increase in tracheid size towards the base, we observed axial variations in latewood percentage and the density of rays and resin ducts. These anatomical differences correspond to axial trends in physical and mechanical properties, which show predictable patterns described by power law scaling. All three measured physical and mechanical traits, namely basic wood density, modulus of elasticity (MOE), and modulus of rupture (MOR), decrease from the stem base towards the tip. Mechanical properties correlate more strongly with distance from the tree tip than basic density or latewood proportion. These findings have practical implications for optimising timber selection in load-bearing applications and inspire new avenues for research and innovation in wood material science.