Intraannual and vertical variations in rays of Pinus koraiensis and Larix kaempferi woods grown in Korea.

Variation of wood rays within a growth ring and along axial direction in Pinus koraiensis and Larix kaempferi, which are important Korean commercial softwoods, was examined to get some useful information for their effective utilization. Ray height in cell number and ray number per 0.25 in tangential section were investigated by optical microscopy. The average heights of uniseriate rays in Pinus koraiensis and Larix kaempferi were 6.3 and 9.1 cells, respectively. The average numbers of uniseriate rays per 0.25 in Pinus koraiensis and Larix kaempferi were 6.5 and 7.5, respectively. The average heights of fusiform rays were about 20 cells but were not significantly different in both species. From earlywood to latewood within a growth ring, the heights of uniseriate and fusiform rays decreased but their numbers remained almost constant. Along axial direction, the heights of uniseriate rays in both species increased with the increase of stem height, and the numbers of uniseriate rays per 0.25 in Pinus koraiensis were nearly constant from 0.2 m to 5.2 m but increased up to 19.2 m beyond 5.2 m. However, a constant pattern in the numbers of uniseriate rays was not observed in Larix kaempferi. The heights of fusiform rays in both species were the highest in middle part of stems but were the lowest in base and top of trees. In conclusion, the ray variation pattern was comparatively clear within a growth ring but not clear along axial direction.