九州大学農学部木材理学講座
Laboratory of Wood Science, Faculty of Agriculture, Kyushu University | Laboratory of Industrial Chemistry of Wood, Faculty of Agriculture, Kyushu University
九州大学農学部木材理学講座
Laboratory of Wood Science, Faculty of Agriculture, Kyushu University | Laboratory of Industrial Chemistry of Wood, Faculty of Agriculture, Kyushu University
九州大学農学部木材理学講座
Laboratory of Wood Science, Faculty of Agriculture, Kyushu University | Laboratory of Industrial Chemistry of Wood, Faculty of Agriculture, Kyushu University | Laboratory of Industrial Chemistry of Wood, Faculty of Agriculture, Kyushu University
Variation in heartwood color of sugi (Cryptomeria Japonica D. Don.) is wide from pale red to black. In this study 21 trees of 29-45 years old were sampled to examine the effects of ash contents on black-heartwood formation. About 20 cm thick disk was taken from the breast height of each tree and pH of the heartwood was measured in green condition. After seasoning of the disks at room temperature, lightnesses in the radial sections of the heartwoods, ash contents in the heartwoods and in the sapwoods were determined. The results obtained are summarized as follows: 1) Ash contents were ca. 0.5% in the typical red-heartwoods having lightness values of 65 or more, and ca. 1.0% in the typical black -heartwoods having lightness values of 50 or less. As a result high correlations between ash contents and lightnesses in heartwoods were recognized. There were also significant correlations between ash contents in heartwoods and in sapwoods at the breast height of tree stems. 2) The pH values of typical black-heartwoods showed weak alkali, although the values of normal red-heartwoods indicated weak acid. On the other side, total contents of K, Ca, Mg and Na were more in black-heartwoods than in red-heartwoods. This suggested that heartwood of sugi was alkalized when the accumulation of these metals in the heartwood exceeded the permitted amount. 3) The mechanism of black-heartwood formation was discussed. From the relationship between diameter growth and heartwood lightness, it was presumed that the amount of transpiration took part in the formation of black-heartwood.