Juvenile wood effect in red alder: Analysis of physical and mechanical data to delineate juvenile and mature wood zones

The objective of this study was to investigate the influence of juvenile wo od on the mechanical and physical properties of red alder. Tree growth in t he first 10 to 20 years, usually referred to as juvenile wood, often influe nces wood quality by adversely affecting mechanical strength properties. St rength can be reduced up to 50 percent by the presence of juvenile wood. Mo re knowledge of juvenile/mature wood properties will provide practical info rmation for silviculturists and processors of red alder, leading to a more appropriate usage of this species. Six red alder trees were used in this in vestigation and a collaborative anatomical study by Oregon State University (OSU). The three-point-bending test mini-specimens were taken from a pith- centered, radially oriented slab in the green condition. Sample material wa s taken at breast height and below the first major branch for height compar ison. Measured variables for the Purdue study were modulus of elasticity (M OE), modulus of rupture (MOR), specific gravity (SG), and work-to-failure ( Work). MOE in red alder was found to have a mean join point(end of juvenili ty) of approximately 16 years and 10 years for the bottom and the top secti ons, respectively. The variability of MOR, SG, and apparent Work property v alues over time rendered them unsuitable for indicating a juvenile-mature w ood join point.