Tree heights in the ring-formed years affect microfibril angles in the rings from juvenile to mature wood at breast height in hinoki trees (Chamaecyparis obtusa)

Abstract

In this study, we examined past growth traits of hinoki (Chamaecyparis obtusa) trees by stem analysis, as well as growth traits in the years when the rings at breast height were formed. We tried to clarify the effects of growth traits in the ring-formed years on the wood properties of the rings from juvenile to mature wood. Height to diameter ratio (H/D) had a larger correlation coefficient in relation to stem stiffness than tree height or diameter at breast height (DBH). The longitudinal variation in stiffness of logs, except for first and top logs, in each tree was assumed to be constant with the height position in the trunk. Tree height in the ring-formed year had a significant negative effect on microfibril angle (MFA) near the pith, in transition wood, and in mature wood. DBH in the ring-formed year had a significant negative effect on density in mature wood. We concluded that the effects of tree height on MFA and of DBH on density produced the effect of H/D on stem stiffness of the trunk. Greater tree height in younger age may contribute to the improvement of juvenile wood properties.