Properties of Japanese cedar (Cryptomeria japonica) plantation from different growing sites and thinning treatments
| Autor: | Jin-Hau Chen, 陳勁豪 |
|---|---|
| Rok vydání: | 2009 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 97 The study used nondestructive testing (ultrasonic instrument and Pilodyn) and destructive testing (longitudinal compressive strengths, LCS) to research the effect of different thinning treatments and grown condition (dominant, intermediate and suppressed trees) on the mechanical properties, wood anatomy and carbon storage of Japanese cedar (Cryptomeria japonica) located at Chilanshan area and Dweigaoyuei area. Additionally, the study also established the relation between nondestructive and destructive testing. The mechanical properties of Japanese cedar located at Chilanshan area with different strip thinning intensities showed that the longitudinal ultrasonic velocities, longitudinal dynamic moduli of elasticity (DMOE), radial ultrasonic velocities, radial DMOE, longitudinal compressive strengths and penetration depths subjected to stripe thinning of various intensities 16 years prior to the study were analyzed using the ANOVA method. No significant difference among the variables was detected. Positive correlations existed between the wood ring densities (RD) and earlywood densities (ED), latewood densities (LD), minmum densities (Dmin), maximum densities (Dmax), and latewood proportions (LWP), however. Samples from 2 plots at the same region but with different growth conditions tended to significantly differ in densities, longitudinal ultrasonic velocities, surface hardness penetration depths, DMOE and longitudinal compressive strengths. Also, sapwood and heartwood from the different plots exhibited different results as well. Wood density correlated positively with the DMOE and compressive strengths. Whereas, DBH of the trees showed negative correlations with the ultrasonic velocities, wood surface hardness penetration depths correlated negatively the compressive strengths of the sapwood. So was that between the wood surface hardness penetration depth and their DMOE. Japanese cedar trees from the untreated plots of the Dweigaoyuei experimental forest had the least DBHs and the greatest standard deviations. The harvested logs exhibited 4 types of ultrasonic velocity patterns each both along the steams and across the stems. Among the logs from different planting densities, there were marked difference between the Type A and Type B planting densities. All Type B logs had greater compressive strengths and micro destructive test strengths than those of Type A. There was no apparent distinction between mature wood and juvenile wood, however. The compressive strengths of the wood had a significant linear correlation with the wood densities. The influences of tending practices on the lengths of tracheids could be separated into the planting densities and thinning effects. The average tracheid lengths of planting density Type B were all greater than those of the Type A density. The tracheids of mature wood tended to maintain the trend. In juvenile wood, the pattern was indistinct. Juvenile tracheids from the 6 plots and those from the post-first thinning having different planting densities all were not significantly different. Yet, the tracheid lengths of trees from the planting density Type B were greater than those of the trees from planting density Type A. Tracheid lengths increased from pith outward to the bark, the lengths showed a highly linear correlation with the tree ages, which started to moderate between 15 to 22 years of age. Afterward, there were only minor fluctuations without notable increases. There were distinct differences between the tracheid lengths of the mature and juvenile woods. Boundary of mature and juvenile wood as determined by 3 different methods indicated that the transition occurred at ca. 19th year. There was no significant difference among the results of the methods. The timber volume stocked at the Dweigaoyuei forest averaged 354.4 m3/ha. Based on the stand age of 36 years, it translated to an annual incremental tree stem carbon sequestration rate of 2.45 ton/ha. The sampled logs had an overall lumber output of 39%, and electricity consumption equal to 8.93 kg carbon emission. There was a net carbon sequestration of 457.77 kg from the logs. On the other hand, Japanese cedar forest of Chilanshan averaged 2.38 ton/ha per year from increments of stem volumes. There were no differences between the forest carbon sequestration capacities of these 2 regional forests. When the moisture content (MC) of the logs was below the fiber saturation point, there was a negative linear correlation between the MC and the longitudinal compressive strength. If MC of 12% was taken as the basis, every percentage increase in MC caused an increase of 3.6% in the average longitudinal compressive strength. If over-dry MC was taken as the basis, then every percentage change in MC entailed a modification of average longitudinal compressive strength of 2.52%. At MC above the fiber saturation point, however, there was no apparent correlation between the variables. As for the patterns of test failures the crushing failure occurred at the highest frequency. When this occurred, a higher compressive strength was observed. Whereas shear failures often accompanied by lower compressive strengths. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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