樹幹横断面内の気体透過性への有縁壁孔閉鎖の関与 : 自然乾燥されたスギ材とカラマツ材についての考察

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木材の気体透過性と組織・構造との関係を明らかにするために，有縁壁孔の閉鎖が気体透過率に与える影響を検討した．すなわち，自然乾燥されたスギ（Cryptomeria japonica）とカラマツ（larix leptolepis）の心材部，移行部部，辺材部で，みかけの比透過率K_gが測定された．そのあと，試験片内の平均圧の逆数とK_gとの関係式から真の比透過率Kが求められ，これを供試試験片の気体透過率とした．他方，気体透過率が測定された試験片で，早材と晩材の有縁壁孔の閉鎖率が測定された．樹幹横断面内の気体透過率の推移を検討した結果，スギ材とカラマツ材の両者で，心材部の気体透過率が低かった．さらに，心材部から移行材部および辺材部に向かうに従って，気体透過率が上昇する傾向が認められた．しかし，スギの移行材部の一部には，気体透過性が著しく悪い部位の存在が認められた．他方，樹幹横断面内の有線縁壁孔の閉鎖率は，スギ材とカラマツ材の両者で，心材部から移行材部，さらに辺材部へと低下していく傾向が認められた．また，気体透過率と有縁壁孔の閉鎖率との関係を検討した結果，両者の間に有意な相関が認められることから，心材化に伴って生じる有縁壁孔の閉鎖が，気体透過性に大きく関与していることが明らかになった．しかし，スギの移行材部の一部で認められた低い透過性やカラマツ心材部内での気体透過率のバラツキは，有線壁孔の閉鎖に加えて他の要因が気体透過率に関与していることが明らかになった．The permeability of wood was measured as the magnitude of the air-flow through wood. The bulk flow which includes the air-flow takes place in the pressure treatments of wood with liquid preservatives and the impregnation of wood chips with pulping chemicals. The objectives were to establish the extent of any possible effect of pit aspiration and to determine the effect of aspirated pit to the permeability reduction. The effect of present investigation was therefore to determine the relationships between the air permeability and the fraction of unaspirated pits. Sugi (Clyptomeria japonica) wood and karamatsu (Larix leptofiis) wood were selected for this study. The permeability and the fraction of aspirated pits were assessed for heartwood, intermediate wood, and sapwood. The results were summarized as follows ; 1) In both wood species, sugi and karamatsu, longitudinal air permeability was quite low in heartwood and increased from intermediate wood towards sapwood (Fig.1 and 2). However some intermediate wood specimens from sugi showed remarkably less permeable than the others (Fig.1). 2) In both wood species, the percentage of aspirated pits declined with distance from heartwood towards intermediate wood and sapwood (Fig. 3 and Fig 4). 3) There was a significant correlation between the percentage of aspirated pits and longitudinal air permeability in air-dried sugi woods and karamatsu woods (Fig.8 and Fig.9). Therefore it was experimentally clarified that pit aspiration occurred during heartwood formation was related to longitudinal air permeability. As for less permeable specimens of sugi intermediate wood and the variation of K value in karamatsu heartwood, it may not be able to explain a reducing of longitudinal air permeability with only bordered pit aspiration.
九州大学の論文

樹幹横断面内の気体透過性への有縁壁孔閉鎖の関与 : 自然乾燥されたスギ材とカラマツ材についての考察

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