This paper investigates the juvenility limit and structure–property relationship in secondary quality beech (Fagus sylvatica L.) and oak (Quercus petraea (Matt.) Liebl.). The juvenile wood occupies a very small area near the pith. The stabilization of the different parameters varies over time. Adding the microfibril angle (MFA) and the grain angle to the MOE prediction model significantly improves the quality of the model, despite little variation in both parameters.
Context Using secondary qualities and small logs of hardwoods such as beech and oak for engineered wood products is an increasingly important issue due to the technological challenges of processing smaller logs and denser woods. Secondary quality hardwoods are expected to have less variation in mechanical properties compared to softwoods with high juvenile wood content.
Aims The first objective of this study was to investigate the radial variation in wood properties of suppressed growth beech and oak trees obtained from thinning operations. The second objective was to develop a model to predict the mechanical properties of these hardwood species based on their structural parameters.
Methods The microfibril angle, ring wood density, and ring width from the pith to the bark were determined using an X-ray densitometer. The modulus of elasticity and modulus of rupture were evaluated on the small clear specimen using a three-point bending test. The wood density, grain angle, and microfibril angle of this small clear specimen were also measured.
Results The results show that the juvenile wood in oak has a wider ring and higher microfibril angle, whereas it has wider latewood and higher microfibril angle in beech. For both species, the juvenile wood occupies a very small area, less than 5 cm from the pith. The mechanical properties of oak and beech wood from suppressed growth trees are comparable to properties reported in the literature for dominant trees. The modulus of elasticity of oak was best predicted using wood density, grain angle, and microfibril angle. The modulus of rupture of oak is better predicted with wood density and grain angle, whereas it is best predicted with wood density alone for beech.
Conclusion Juvenile wood found in the suppressed growth trees of both hardwoods can be used in place of mature wood. It is important to take structural parameters into account when predicting the mechanical properties of hardwood species.
Oak; Beech; Thinning; Radial variation; Mechanical properties; Ring properties
Purba, C.Y.C., Dlouha, J., Ruelle, J. et al. Mechanical properties of secondary quality beech (Fagus sylvatica L.) and oak (Quercus petraea (Matt.) Liebl.) obtained from thinning, and their relationship to structural parameters. Annals of Forest Science 78, 81 (2021). https://doi.org/10.1007/s13595-021-01103-x
For the read-only version of the full text:
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.