Effect of growth rate on the anatomy, specific gravity, and bending properties of wood from 7-year-old red alder (Alnus rubra)

Abstract

Understanding the association between growth rate and wood properties is of practical importance to maximizing and sustaining wood and fiber production. Anatomical characteristics, specific gravity, and bending properties were determined at breast height for thirty 7-year-old trees with varying growth rates, from a red alder (Alnus rubra Bong.) plantation. Wood was sampled from the growth ring with a cambial age of 5 years. Growth varied from 2.0 to 9.3 mm/year (ring width), or 264 to 3350 mm 2 /year (ring area). We analyzed the relationship between growth rate, in terms of both annual ring width and area, and each wood property. Because both measures of growth rate yielded the same qualitative results, we only used ring width in our analyses. Regression analysis showed that growth rate had no effect on specific gravity, the modulus of elasticity in bending, the modulus of rupture in bending, fiber diameter, or the proportion of growth ring that was fiber or vessel. Fiber length, vessel diameter, and ray proportion, however, were positively correlated with growth rate. Fiber-wall thickness and axial parenchyma proportion decreased slightly with growth rate. The results indicate that the growth rate of A. rubra trees can be increased through silvicultural practices with few negative effects on wood and fiber quality, at least in the juvenile wood zone of the stem.