Anatomical properties in Thuja occidentalis:Variation and relationship to biological processes

Abstract

The variability in wood properties of eastern white cedar (Thuja occidentalis L.) is relatively poorly known. Here we report the axial and the radial variation in selected anatomical properties, namely, ring width, wood density, and tracheid length and width. Forty-five trees were randomly sampled and felled from three selected sites in the Abitibi-Témiscamingue region, Quebec, Canada. Disks were systematically sampled at 0.5, 1.3, and 3 m stem height and at every 2 meters thereafter up to the tree top. Average ring density at breast height was 355 kg/m3 with a small difference between earlywood and latewood. The latewood proportion was uniform and constant within the tree at about 32%. The tracheids were fine and long, averaging 25.3 μm in width and 2.07 mm in length. The variation in wood density components between trees was highly significant. The cambial age effect on all measured properties was highly significant. Ring density decreased from a maximum near the pith to a minimum in the juvenile–mature wood transition zone and remained constant or decreased slightly thereafter. Annual ring width decreased from a maximum near the pith to a minimum at the 10th ring and increased thereafter. Tracheid length and width showed typical radial variation characterized by a steady increase from pith to bark. Within-tree axial variation was highly significant, but ring width showed more substantial changes. Changes in wood properties with height depend on cambial age and thus are implied since the proportion of juvenile wood in the stem increases from the base to the top.