Comparisons of some properties on wood quality among clones grafted with the elites of Abies sachalinensis, 2: Some properties of thinned clone trees from the Chikubetsu, Shiokari, and Gifu seed orchards

Some properties of wood quality of Abies sachalinensis were examined by using the clones thinned from the Chikubetsu, Shiokari, and Gifu seed orchards in central, northern, and eastern Hokkaido, respectively. The total numbers of specimens used were 139 clones and 440 individuals, and the tests were done concerning basic density (kg/m3), mean annual ring width, and moisture content for heartwood and sapwood. The results are as follows: The average basic densities of wood, including both heartwood and sapwood, were 294kg/m3, 302kg/m3, and 312kg/m3 in the Chikubetsu, Shiokari, and Gifu seed orchards, respectively, showing lower values and such low coefficients of variation as 6 to 7%. A statistically significant difference in basic density was shown among clones, but not among provenances in which elite trees were selected. The range of repeatability was from 0.39 to 0.48. The average mean annual ring widths of wood were 6.4mm, 5.0mm, and 5.2mm in the three seed orchards, respectively. These are relatively broad widths. A significant difference in mean annual ring width was also apparent among clones, excluding those from the Shiokari seed orchard, but not among provenances, and the range of repeatability was between 0.13 (the clones from the Shiokari seed orchard) and 0.38. Meanwhile, a significant negative correlation was shown between basic density and annual ring width of wood. In comparing the three seed orchards, the wood quality of clones from the Gifu seed orchard was superior in terms of moderate annual ring width (within the widest limit of 6mm for higher structural timber grades) and had a relatively high basic density, while that from the Shiokari seed orchard was inferior in that it had lower basic density in spite of narrower annual ring width. However, all the specific gravity of wood of clones, which was calculated with reference to basic density did not approach the lowest limit of 0.43 for the structural timber grades. The reasons are that, for the selection of the elite trees, emphasis was placed on their growth, the specimens were as young as about 20 years old after plantation, and the clones have been planted sparsely and grown while fertilization and thinning were practiced for rich seed production