Intra-species variation in maximum moisture content, cell-wall density and porosity of hardwoods

Abstract

Some properties of wood, such as maximum moisture content, cell-wall density and porosity, are not well known, even though they affect the performance of chemical preservatives, glues and coatings on wood. This knowledge gap was addressed in the present study by analysing these physical properties in laurel (Laurus nobilis L.) wood. Laurel is a common hardwood tree in southern Europe. Seventeen laurel trees were felled for the study, and 300 defect-free specimens were obtained from the trees for analysis. The following mean values were obtained: wood maximum moisture content, 114 %; cell-wall oven-dry density, 1198 kg m-3; and oven-dry wood porosity, 45 %. Significant inter- and intra-tree variations in the three properties were observed. The inter-tree variation was mainly attributed to the tree age, and the trend suggests that wood maximum moisture content and porosity are expected to be lower in older trees than those under study. The values of the three properties were slightly, but statistically significantly, lower at the highest positions in the tree. Harvesting of the basal logs of young trees is therefore advisable only if more porous wood is required, and commercial exploitation of the whole trunk of mature trees is recommended if more compact wood is required. The variation in cell-wall density was not negligible, although this variable is often assumed to be approximately constant for all wood species. Maximum moisture content and wood porosity can be estimated using bulk or apparent density as a predictor variable.