Identification and characterisation of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) juvenile and adult wood grown in Southern Germany

Abstract

More than one-third of Germany s Douglas-fir resources, stock in age-classes from twenty-one to fifty-nine years. As such timber increasingly enters markets, detailed knowledge of the anatomy and properties of its wood is of importance to forest managers and wood processors. Anatomical and mechanical wood analyses in this study were carried out on twenty trees from four scientifically managed plantations in Southern Germany. The age of the trees selected was forty-two years whereby varying growth conditions were considered. Juvenile and adult woods were identified by segmented linear regression of radial profiles of anatomical characteristics, such as latewood percentage, tracheid wall thickness microfibril angle and density. Additionally, the width of earlywood, latewood and growth rings as well as bending modulus of elasticity were determined. Variance was dependent on the trait used for differentiation, j uvenile wood comprised of an eleven to thirty-one growth rings resp. radial amounts of fifteen to sixty-five percent. When compared to adult wood, juvenile wood showed corresponding features of approximately thirty percent wider growth rings, th irty four percent lower latewood percentage, fourteen percent thinner tracheid walls, and eighty percent larger microfibril angles, eleven percent lighter wood and fifty -seven percent lower bending modulus of elasticity. As the assortment features fast grown trees, adult heartwood characteristics were slightly inferior to the characteristics of European Douglas-fir.