摘要
The annual ring width, density and shrinkage variation from pith to bark in Chinese fir (Cunninghamia lanceolata) and Boka sugi (Cryptomeria japonicd) were studied and compared. The results show that the ring width decreased sharply from pith to bark for Chinese fir. However, the ring width variation pattern for Boka sugi followed a different way, i.e., the ring width decreased to the fifth ring, increased to the tenth ring, decreased again to the fifteenth, and then increased to the twentieth, where it...
The annual ring width, density and shrinkage variation from pith to bark in Chinese fir (Cunninghamia lanceolata) and Boka sugi (Cryptomeria japonicd) were studied and compared. The results show that the ring width decreased sharply from pith to bark for Chinese fir. However, the ring width variation pattern for Boka sugi followed a different way, i.e., the ring width decreased to the fifth ring, increased to the tenth ring, decreased again to the fifteenth, and then increased to the twentieth, where it became constant. The large variations of Boka sugi appeared to show the maintenance of fast growth for many years. The annual ring mean density of Chinese fir increased gradually from pith to bark. However, the density changes for Boka sugi indicated the opposite trend, i.e., the mean density decreased gradually from pith to bark. The former showed a pattern as the same as a pine and a larch, and the latter was often found in a cedar and a cypress. The longitudinal shrinkage in juvenile wood was much higher than mature wood regardless of the species and density variation. It seemed to be related to large microfibril angles of tracheid S2 layer in juvenile wood. The wood shrinkage in transverse direction decreased gradually from pith to bark for Boka sugi but increased gradually for Chinese fir. The difference of shrinkage variation patterns between the two was correlated with the density variations. The shrinkage in longitudinal, radial and tangential direction was about 0.279%, 3.826% and 7.785% for Chinese fir, and 0.207%, 2.831% and 5.606% for Boka sugi, respectively, in mature wood. For both species the ratio of tangential to radial shrinkage was approximately 2.0.
