Comparison of Wood Properties of Hinoki (Chamaecyparis obtusa) Small Diameter Logs Collected from Different Tree Ages and Heights

Abstract

To effectively utilize small diameter logs as a civil engineering material, the wood properties of such logs of hinoki (Chamaecyparis obtusa Endl.) were investigated by determining density of air-dried logs, pilodyn penetration, annual ring width, basic density and compression strength parallel to the grain. Logs of small diameter were collected from two stands of different ages and at different sampling positions in the trees: 1) logs from 1.2 m height above ground of trees thinned in a 16-year-old stand, and 2) logs from treetops (about 18 m height above ground) derived from regeneration cutting in a 64-year-old stand. Logs from 16-year-old trees had only half the number of annual rings within logs compared with those from 64-year-old trees. Average values in basic density were 0.39 and 0.51 g/cm3, respectively. In both types of log, a significant negative correlation between pilodyn penetration value and basic density was found in the outermost part. Values of compression strength were greater for the 64-year-old trees than the 16-year-old ones. When small diameter logs are used as civil engineering materials for which high strength is required, it should be noted that strength properties of small diameter logs with almost the same diameter vary largely with age of trees and the position where the logs are collected. © 2006, The Japan Wood Research Society. All rights reserved.