Radial variations of ray spacing and intra-annual variation of biseriate ray frequency in Pinus koraiensis and Larix kaempferi woods grown in Korea.

Radial variations of ray spacing and frequency of biseriate ray were examined in the woods of most commercially important Korean softwood species of Pinus koraiensis and Larix kaempferi. Ray spacing, or ray number per mm in cross section, averaged 4.6 and 9.0 in Pinus koraiensis and Larix kaempferi, respectively. Thus, rays of Larix kaempferi appeared to be more closely arranged than those of Pinus koraiensis. Ray spacing was the densest around pith, and then slowly decreased toward bark. In tangential section, biseriate ray frequency of Larix kaempferi was higher than that of Pinus koraiensis. Biseriate ray was designated, based on the number of cells of biseriate portion in vertical extent, as the type of B+1 (one cell high), B+2 (two cells high), and so on. The dominated type was B+1 in Pinus koraiensis but B+2 in Larix kaempferi. The biseriate ray types of B+3, B+4, and B+5 were occasionally found in earlywood. Interestingly, even B+6 and B+7 types were observed in Larix kaempferi. In conclusion, it was considered that ray spacing could be used for separating juvenile wood from adult wood. Also, characteristics of ray spacing and biseriate ray might be used for identifying these two species.