Diameter at breast height (DBH) and stress-wave velocity (Vs) of stem were investigated in “Aoyajiro”, a mutant of natural Japanese cedar (Cryptomeria japonica D. Don), and compared with data from plus trees (PLT) and snow-resistant trees (SRT). Vs of “Aoyajiro” trees was similar to that of SRT but significantly faster than that of PLT. A negative correlation was observed between Vs and DBH in “Aoyajiro”. These results suggested “Aoyajiro” trees have sufficient snow-resistance based on high dynamic Young's modulus and its elasticity value decreasing with aging. Moisture content, crude ash and volatile components of heartwood obtained by the use of increment borer in “Aoyajiro” were analyzed and compared with those of PLT. There were no significant differences among these components, although “Aoyajiro” tended to contain higher crude ash content than PLT. Cubebol or δ-cadinene were detected by GC (Gas Chromatography) analysis as the major volatile components in “Aoyajiro”. Cubebol has the potential to change antimicrobial substances, such as cubenol, epicubenol and δ-cadinene, affecting specific lactobacilli that rot Sake. We propose that cubebol and δ-cadinene contents be used as indices to evaluate the superiority of “Aoyajiro”.

We investigated the relationship between quality of veneers of Japanese larch (Larix kaempferi) and their radial locations in logs. In addition, we investigated the effect of pruning on veneer quality. There was a positive correlation between the moduli of elasticity of logs determined by the longitudinal vibration method and those of veneers determined by the ultrasonic velocity method. The moduli of elasticity of veneers increased with the distance from the center of the veneer lathe spindle. This tendency was marked for pruned logs. When we separated juvenile from mature veneers at 15 annual rings from the pith, the average modulus of elasticity of mature veneers was 60% higher than that of juvenile veneers. The ratio of mature veneers rapidly increased when the veneers were cut outside of 10 cm from the center of the spindle, which indicated that high-strength veneers could be obtained by separating the veneers at this distance. In pruned logs, there were almost no knots in veneers cut from more than 12 cm from the center of the spindle indicating that veneer quality was improved by pruning.

A life cycle assessment of greenhouse gas (GHG: CO₂, CH₄, N₂O) emissions for a district heating and cooling (DHC) system using woody biomass was conducted, and reductions in emissions from substitution of fossil fuels with woody biomass were analyzed in Shiwa, Iwate Prefecture. From the process of log production to heating, the life cycle GHG emissions of the DHC system were 70.8 kg-CO_2-eq/GJ-heat. Of these emissions, the majority (92%) originated from the heating process. Substitution of liquefied petroleum gas (LPG) with wood chips resulted in a reduction of GHG emissions of 92.4 kg-CO_2-eq/GJ-heat. With this substitution taken into account, the net GHG emissions of the DHC system were -21.6 kg-CO_2-eq/GJ-heat, which indicated that the DHC system had the potential to reduce GHG emissions. The GHG emission reductions generated by the DHC system would not be obtained if the heat usage efficiency were reduced from the current 29% to less than 23%. Conversely, if the heat usage efficiency were improved to 75%, reductions in GHG emissions corresponding three times the current levels could be obtained. The GHG emission reductions could also increase if kerosene or heavy oil were used as a substitute for the currently used LPG. However, compared to the significant impact of heat usage efficiency, the substitution of fossil fuels had a relatively minor effect on the reduction of GHG emissions.

The equilibrium moisture content of wood in Japan is considered to be 15% and is based on weather and experimental data of past years. With the increase of uninhabited weather observation points, weather data has increased over recent years. The objective of this paper was to investigate the recent values of equilibrium moisture content of wood using weather data from 1981 to 1995 for the entire area of Japan. Therefore, contour line maps were used to denote the equilibrium moisture content for the entire year in Japan. The average value of the equilibrium moisture content of Japan was 15%, and the numerical value range was 12-19%. This value did not change when compared with that reported previously. However, the average value of the equilibrium moisture content of wood changed to 13.5% when compared for the past year the same meteorological stations that had reported previously.

A practical method was proposed for determining optimum cross sections of green Japanese larch timber with pith to improve the yield of products taking account of twist, crook, and bow caused by the drying process. Green Japanese larch square-sawn timber was dried to target moisture contests of 10% and 20%. The required cross-sectional dimensions of this timber were 105 mm×105 mm after drying and reshaping. Resultant twist, crook, and bow were measured. The optimum cross-sectional size of green square-sawn timber was calculated based on the data above. The calculated optimum size of green timber was affected by twist clearly more than by crook and bow for both target moisture contents. The theoretical cross-sectional size of green timber that maximized volume yield was 123.9 mm for specimens with target moisture content of 10% and 118.8 mm for specimens with target moisture content of 20%. When the cross-sectional sizes of green timber were these values, 98% of the total products met the required sizes.