The radial variation of rays within the stems of Dahurian larch and Japanese larch growing in Korea was studied to obtain valuable information to identify the two species and determine wood quality. Uniseriate ray height, fusiform ray height, ray number, ray spacing, and epithelial cell number were investigated by optical microscopy. The heights of uniseriate and fusiform rays and epithelial cell numbers in Dahurian larch were lower than those in Japanese larch. Dahurian larch wood had greater ray number and ray spacing than Japanese larch wood. In both species, the heights of uniseriate and fusiform rays and epithelial cell number increased with increasing growth ring number but then stabilized from a certain growth ring number. However, ray number and ray spacing decreased with age but were stable toward the bark. There were significant differences in all ray properties between the two species. Furthermore, in both species, the number and spacing of rays showed a significant negative correlation with uniseriate ray height. The relationships between uniseriate and fusiform ray height, and between ray spacing and ray number were significantly positive. In conclusion, the results from this study provide basic information that can be used to identify these species, and the quality indices from ray properties will improve the effective utilization of the two woody species.

To compare the wood quality of Dahurian larch and Japanese larch growing in Korea, the physical and mechanical properties were examined using the Korean standards. The proportion of heartwood was 82% and 72% in Dahurian and Japanese larch, respectively. The percentage of latewood was 42% in Dahurian larch and 35% in Japanese larch. The growth ring width of Dahurian larch was narrower than that of Japanese larch. Dahurian larch showed about 20% higher green moisture content compare to Japanese larch wood. Density and shrinkage of Dahurian larch were higher than Japanese larch. Axial compression strength, young`s modulus in compression, and shearing strength in heartwood of Dahurian larch were 11 MPa, 686 MPa, and 2.3 MPa, respectively, showing higher value than Japanese larch. The hardness was in the range of 13.8–38.7 MPa in Dahurian larch and 17.7–48.4 MPa in Japanese larch. The compression strength parallel to the grain and shearing strength in both species were significantly correlated with oven-dried density. Besides, the hardness in Dahurian larch was significantly correlated with latewood percentage and oven-dried density. In conclusion, the differences in the properties of both species were revealed and the results can be used for quality indices of both wood species.