Abstract:
Six 40-year-old red alders (Alnus rubra Bong.) were harvested from a mixed stand of A. rubra and big-leaf maple (Acer macrophyllum Pursh) in the Oregon Coast Range to evaluate variation in their wood characteristics at two heights. Because the trees had a slight lean (4 to 14°), we sampled along a diametric strip from the lower to upper side of the lean. For a disk from breast height and one from an upper height (5.8 to 6.1 m), we sampled 12-14 designated growth rings on both sides of the pith. For each sample we determined fiber length, vessel diameter, tissue proportion (proportion of a cross section occupied by fibers, vessels, rays, or axial parenchyma), and specific gravity. The variation of these properties between the two heights, between the lower and upper sides of the lean, and along the radius was analyzed among the within trees.
Variations between the two heights and between the lower and upper sides of the lean were minor or not significant for all measured characteristics. In the radial direction, fiber length and vessel diameter increased rapidly during the first 8 to 12 years (from 0.8 to 1.2 mm and 47 to 60 um, respectively) and then leveled off. From pith to bark, there was no significant change in ray proportion, a small increase in the vessel proportion (from 23 to 28%), and a small decrease in the fiber proportion (from 63 to57%). Specific gravity was constant radially and with height but varied significantly among trees (from 0.45 to 0.51 for tree means). These results suggest that the wood characteristics of A. rubra are quite uniform within individual trees with the exception of fiber length and vessel diameter, which increase radially in the first several growth rings.
