Implementing linear mixed effects models to enhance estimation of the dimensional stability of wood of Laurus nobilis L.

Abstract

Aim of study: The properties of wood of laurel (Laurus nobilis L.) have not yet been adequately described. For example, information on variables related to dimensional stability during drying (shrinkage) is lacking, even though this is a key factor determining the suitability of the material for industrial uses with high added value. The aim of this study was to construct models for estimating shrinkage variables by using wood density as the predictor variable. Area of study: Seventeen laurel trees were felled in an inland area of Galicia (north-western Spain) in order to obtain the material for testing and modelling. Material and methods: The experimental tests were performed on 958 small standardised, defect-free wood specimens. Main results: The wood under study was moderately heavy and volumetrically unstable. Density varied only slightly, but volumetric shrinkage varied statistically significantly within and between trees. A linear mixed effects model was constructed to predict the variation in volumetric shrinkage from the oven-dry density, including the factors tree and height in the stem, with random slopes and intercepts. Research highlights: The model proved valid for all sampled individuals up to a height of two metres in the stem, thus enabling estimation of the volumetric shrinkage in commercial basal logs.