軟x線デンシトメトリによるスギ樹幹の年間重量成長量の推定 [in Japanese] Estimation of Annual Increase of Oven-dried Weight of Sugi (Cryptomeria japonica) Trunks [in Japanese]
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樹木の炭素吸収能力の経年変化を推定するために，年輪幅と年輪内平均密度から樹幹全乾重量の増加量の年変動を推定する方法を検討することを目的とした。スギ24個体について，地上0.2m部位から頂端までを 1 mごとに玉切った丸太の元口から約 5～10 cm厚さの円盤を採取した。このうち直径が約10 cm以上の円盤について髄を含むストリップを作製し，軟ｘ線デンシトメトリにより年輪幅及び年輪内平均密度を測定した。また，残りの部分を用いて円盤の全乾重量を測定し，試料採取時の丸太と円盤の重量比により 1 m丸太の全乾重量に換算した。年輪幅から求めた各年輪の面積に，その年輪の年輪内平均密度を乗じたものを合算し，それに丸太長を乗じて求めた丸太の推定重量は，実測の全乾重量と有意な直線関係にあり，年輪幅と年輪内平均密度から丸太の全乾重量の推定が可能であると考えられた。
In order to estimate changes of carbon absorption by trees, a method for calculating annual increases of oven-dried weight of individual trunks from width and mean density of annual rings was established. Discs at 1 m intervals above 0.2 m high from 24 sugi (<i>Cryptomeria japonica</i> D. Don) trees were collected after measuring green weight of 1 m long logs. Radial strips including the pith were cut from the discs for soft x-ray densitometry and the other parts of the discs were used for measuring oven-dried weight of the discs. Cross-sections 2 mm thick processed from the strips were exposed to soft x-rays followed by densitometry for measuring width and mean density of each annual ring. The weights calculated from the area and mean density of each annual ring and log length were significantly correlated with the oven-dried weights of the logs. Therefore, the densitometry was applicable for calculating the oven-dried weight of trees. It is believed that ring width and mean density can be used to estimate the annual increase of oven-dried weight of the tree trunks. The annual increase of the oven-dried weight calculated as accumulation of weight of each annual ring was influenced by the ring width, because it changed with variation of area of annual rings. Density variation seemed to affect the fluctuation of weight gain and its effects was considered to be smaller than the ring width.
- Mokuzai Gakkaishi
Mokuzai Gakkaishi 53(2), 99-103, 2007-03-25
The Japan Wood Research Society