Soft X-ray photography has been widely used in wood science and related fields, notably for constructing wood density profile. However, this useful method has not yet been popularly applied for examinations of bark structure. Therefore, we attempted to characterize the soft X-ray photographic images of barks for a total of 12 angiospermous tree species from Hokkaido, Japan. High contrast images were obtained, and the contrast reflected not only anatomical features but also maldistribution of calcium crystals. This means that soft X-ray photography is effective to visualize the accumulation of calcium crystals, which are ubiquitous across plant kingdom, in bark tissues. Optical microscopic observations further revealed that the sclerenchyma was exclusively associated by prismatic crystals even when other morphological types of calcium crystals were present. There is a possibility that the prismatic crystals serve some mechanical functions to supplement sclerenchyma in bark tissues.
Morphological features were examined for a total of 166 charred wood specimens of which estimation of use and wood identification had already been reported after unearthing from four pit houses in Satsumon culture located at Oshima 2 site (Kitami city, Hokkaido, Japan). It was possible to estimate the diameter classes of tree stems from which the wood specimens were taken, and trimming mode of timbers from the stems for 97 of the 166 specimens. They were divided into round woods from stems of small diameter and split timbers from stems of large diameter. The round woods were mainly used for flooring/bench seats and approximately two-thirds of them were Populus. The split timbers were mainly used for rafters, and approximately two-thirds of them were Quercus. These results suggest that size and trimming mode of wood are closely related to construction components and the choice of species. Average annual ring width of Quercus specimens was 0.58 mm; much narrower than that of other species/taxa examined. It is likely that Quercus woods were collected in natural forests around the site and widely used because the woods were easy enough to trim and strong enough.
For the purpose of developing a simple strength grade prediction method for lumber products at the log stage, the effectiveness of strength grade prediction for lumber products (lamina) by determining the strength grade of logs using estimated density for logs produced in Kyoto Prefecture was verified. The cost of determining the strength grade of logs at the mountain site was also verified. As a result, when the estimated density was used to determine the strength grade of logs, the appearance rate of lamina for each strength grade was not much different from that when the measured density was used. In addition, by selecting logs with a dynamic Young's modulus of 9 GPa or more, the appearance rate of L100 lamina increased 1.6 times, confirming the effectiveness of strength grade classification at the log stage in lamina production. Although the purchase unit price of logs increases due to the strength measurement cost, the logs whose strength grade are determined can be selectively purchased. As a result, the total purchase cost of the logs can be reduced by about 30% compared to the case where the strength grade is not determined. From the above, it can be judged that the strength grading of logs using the estimated density is a practical and effective method.
In this study, NaOH-Na2SO3-thiourea-urea aqueous solution was used to treat refiner mechanical pulp (RMP) prepared from poplar (Populus simonii var.) branch at temperature in the range of 120 to 140 °C for the modification of the enzyme saccharification, and the single factor tests were applied to determine the optimal conditions. As the results, a combination of the NaOH dosage of 4%, the Na2SO3 dosage of 12%, the CS(NH2)2 dosage of 13%, the CO(NH2)2 dosage of 16%, the treating temperature of 130 °C, the keeping time of 60 min, the soaking time of 15 min, and the pulp consistency of 20% was chosen as the optimal condition for the enzymatic saccharification. The glucose conversion of RMP cellulose obtained by the NaOH-Na2SO3-thiourea-urea treatment was 70.2%, which was higher than that (63.7%) by the NaOH-thiourea-urea treatment.