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静岡県産スギ精英樹交配家系が植栽された林分で高ヤング率が推定された立木から挿し木苗をクローン増殖後，苗畑内の試験区に植栽し，若齢期における立木の応力波伝播速度（立木Vp）と生長形質の年次変動を計測した。また，それらを6～10年時に伐採した丸太ヤング率を計測し，若齢期における材質評価手法の適用について検証した。各系統の立木Vpは，苗植栽後の2～10年時にかけての年次変動に伴う系統間差が認められ，各計測年次間における回帰式が高い決定係数となり系統間差が継続していることが窺えた。また，苗植栽後6～10年時に伐採した丸太の動的ヤング率（丸太Efr）でも系統間差が認められ，各系統の立木Vpと丸太Efrとの回帰式の決定係数も高い値であったことから，若齢期におけるヤング率を非破壊で評価する手法として立木Vpは有効と考えられた。更に，丸太から採材した髄から5年輪までと6年輪から外周部のEfrの回帰式が高い決定係数であったことから，若齢期の段階で高ヤング率のスギ精英樹交配家系の系統はその後も同様の材質を形成する可能性の高いことが示唆された。

Cuttings from Japanese cedar (Cryptomeria japonica D. Don) mating families, which were presumed to have high Young's modulus, were clonally propagated and planted. The stress wave propagation ... velocity (standing tree Vp) and annual fluctuations in growth characteristics were measured from 2 to 10 years after planting. In addition, the applicability of the evaluation method with Vp in early age was verified by comparing them with the Young's modulus of logs cut in the 6th to 10th years. The Vp of standing trees showed a difference among the lines due to the annual fluctuation from 2 to 10 years after planting the seedlings. The coefficient of determination was high even in the regression equation for each measurement year, and the difference among the lines continued to appear. Differences among the lines were also observed in the dynamic modulus of elasticity (Efr) of logs cut down 6 to 10 years after planting the seedlings, and the coefficient of determination of linear regression between the standing tree Vp and the log Efr of each line was also high. Therefore, Vp measurement was considered to be an effective method for non-destructively estimating Young's modulus. Furthermore, the regression equations of Efr from the pith to the 5-year ring and from the 6-year ring to the outermost ring showed a high coefficient of determination. This suggested that clones with a high Young's modulus in the early stages would continue to form materials of similar qualities. more