Vacuum heat treatment was used to improve the dimensional stability of Toona sinensis wood in this study, the shrinking and swelling rates, the physical-mechanical properties, and the chemical compositions before and after the thermal treatment were evaluated. The results revealed that the volume shrinkage and swelling rate for the heat-treated wood samples were decreased by 45.60% and 49.95%, respectively at 220°C for 6 h indicating that thermal treatment could obviously improve the dimensional stability of Toona sinensis wood. Thermal treatment also decreased the mechanical strength. The surface color was changed by the treatment. The chemical composition results showed the decrease in density and mechanical strength was due to the partial degradation of hemicellulose during the treatment. The results of this study that vacuum heat treatment could improve the dimensional stability by sacrificing somewhat mechanical strength, the treatment conditions mainly the temperature should be properly controlled to archive an optimized improvement in dimensional stability with minimum reduction in mechanical strength.
Based on the principle of tree chronology, this paper measures tracheid morphological characteristics, ring width, and latewood rate of harvested wood from Cupressus funebris plantation in Deyang, Sichuan Province. Using meteorological data of average temperature, precipitation, relative humidity, sunshine percentage, and average ground temperature from 1983 to 2015, correlation analyses were conducted. The results of the analysis showed that the correlation between tracheid morphological characteristics, ring width, and latewood rate was not consistent with a single climatic factor. Moreover, the correlation between tracheid morphological characteristics and climatic factors, and the correlation between ring width, latewood rate, and climatic factors were significantly different. Temperature was the main limiting factor for ring width and latewood rate. In addition, relative humidity was positively correlated with ring width and negatively correlated with most indicators of tracheid morphological characteristics. Fewer indicators were affected by sunshine percentage. Meanwhile, precipitation was not significantly correlated with ring width and latewood rate. In conclusion, the correlation between various indicators and climate factors was from high to low in order of temperature, relative humidity, sunshine percentage, and precipitation.
The porosity and pore size distribution of recent and ancient buried Phoebe zhennan are studied in this paper by means of mercury intrusion porosimetry. The results show that the micropore and mesopore diameters of recent and buried wood are mainly distributed in range of 40.3 nm and 183.1 nm respectively, while the macropore in 45276.6 nm and 3503.9 nm separately. For both samples, the pores with diameters below 349.9 nm account for about 60% of the total intrusion volume, and contribute more than 98% of the surface area. The cumulative pore area of recent wood is slightly greater and the pore diameter ranges from 50.3 nm to 349.9 nm. While the cumulative pore area of buried wood is significantly larger than and the pore diameter ranges until 50.3 nm. These results can provide information for further investigations on the sorption behaviour and the liquid permeability of ancient buried wood.