Variation in wood density between mature sessile oak and English oak trees growing in different vegetation zones

Abstract

Wood density is a fundamental functional trait influencing ecological adaptation, hydraulic safety, and timber utilisation in temperate hardwoods. This study investigated variation in wood density (12% moisture) across mature stands of two economically and ecologically vital European oak species, sessile oak [Quercus petraea (Matt.) Liebl.] and English oak (Quercus robur L.), growing in their characteristic vegetation zones in the Czech Republic. We assessed wood density at two heights (at 1.3 m and at the crown base) across six trees per plot and examined its relationship with tree-ring width and height. Results demonstrated statistically significant interspecific differences, with Q. petraea consistently exhibiting higher wood density (721 kg.mMINUS SIGN 3) than Q. robur (662 kg.mMINUS SIGN 3) at 1.3 m. Q. petraea showed a statistically nonsignificant higher density of 710 kg.mMINUS SIGN 3 at the crown base and an overall average of 717 kg.mMINUS SIGN 3, while Q. robur had densities of 701 kg.mMINUS SIGN 3 and 669 kg.mMINUS SIGN 3, respectively. Radial density profiles revealed species-specific patterns, with Q. robur showing a more uniform density distribution than the pronounced pith-to-bark gradients observed in Q. petraea. Regression analysis indicated that tree-ring width explained only 12-13% of the variance in density, so other anatomical factors, such as latewood proportion and tree-ring structure (number and cell size), should be examined as anatomical drivers of wood-density variation.