<紀要論文>
ヒノキおよびカラマツ人工造林木の木材性質のバラツキ : 一林分内のバラツキ

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概要 この研究は,ヒノキとカラマツの木材基本性質(Intrinsic Wood Porperties)について,同一林分内におけるバラツキを明らかにすることが目的である.すなわち,両樹種の樹幹胸高部において,髄から5年輪間隔で,5年輪にまたがる容積密度数を求めた.ヒノキでほ髄から5年輪目と15年輸目 カラマツでは髄から5年輪目ほ25年輪目で晩材仮道管長の測定を行い,それらの樹種内でのバラツキを検討した....さらに,ヒノキについては縦圧縮試験を行い,縦圧縮に関する力学的性質のパラツキについての検討も行った.ヒノキとカラマツともに,容積密度数は樹幹半径方向の部位によって異なるが,その変動係数には横断面内の部位による著しい違いが認められず,樹幹横断面内の変動係数値に,両樹種ともに約7%の値を得た.胸高部位同一年輪で得られた個件間の晩材仮道管長の変動係数には,ヒノキとカラマツの両樹種で年輪間に大きな違いは認められなかった.ヒノキでは6~8%の値が得られ,カラマツでは7%の値が得られた.基本性質間の相互関係では,容積密度数と晩材率との間に相関関係が認められるが,容積密度数を管理する指標に晩材率を使うには,さらに詳細な検討が必要である.また,成熟材年輪幅は,容積密度数や仮道管長を推定する指標としては不適当かもしれない.ヒノキの圧縮に関する性質のバラツキ(変動係数)は,未成熟材部と成熟材部で大差なく,縦圧縮強さで9%,縦圧縮ヤング率で約26%の値を得た.なお,縦圧縮強さのバラツキには,比重(容積密度数)のバラツキが強く関与しており,その縦圧縮強さの管理指標に比重(容積密度数)が有効であることを認めた.
The purpose of this study is to clarify the variation of the instrinsic wood properties and mechanical properties among hinoki (Chamaecyparis obtusa) trees and karamatsu (Larix leptolepis) trees within a stand. Fifty hinoki trees from 25- and 20-year-old stands, and twenty karamatsu trees front a 41-year-old stand were obtained as test trees. The breast height diameter and the tree height of sample trees were measured and then two disks of 1Ocm and 50cm thick were taken from the breast height of sample trees. The lOcm thick disks were used for measureing basic density, tracheid length, growth ring width and latewood percentage. The 50cm thick disks from hinoki trees were used for compressive test parallel to the grain. The results of this study were summarized as follows ; l) The basic density properties of hinoki- and karamatsu-wood were not uniform from the pith outward at a given stem. The basic density decreased outward from the pith for hinoki-wood and increased outward from the pith for karamatsu-wood. The differences in the coefficients of variation in the basic density for juveile and mature wood were not so large in hinoki and karamatsu. Their values were about 7% at a given stem level for hinoki- and karamatsu-wood, 2) In hinoki- and karamatsu-wood, no remarkable differences in the latewood-tracheid length variation were found between annual rings from the pith. The coefficients of variation in tracheid length among hinoki trees within a stand were 6% at the 5th annual ring and were 6 to 8% at the 15th annual ring from the pith. Among karamatsu trees, they were 7% at 5th and 25th annual rings from the pith. 3) There were statistically significant relationships between the basic density and the latewood percentage of hinoki- and karamatsu-wood. The growth ring width of mature wood were not valid as a wood quality index. 4) The coefficients of variation in the compressive strength and the Young's modulus parallel to the grain among hinoki trees were 9% and 26%, respectively. The Young's modulus variation was greater than the compressive strength variation. 5) The compressive strength variation was mainly affected by the differences in specific gravity among trees. The sepcific gravity (basic density) was useful as a quality index to estimate the compressive strength. The compressive strengths were highly correlated with Young's modulus in juvenile and mature wood, respectively.
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登録日 2009.04.22
更新日 2021.03.03

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