Comparison of Allometric Relationships among Sugi (Cryptomeria japonica) Cultivars

The allometric relationships between tree height and diameter of the following six native cultivars of sugi (Cryptomeria japonica) in Kyushu region are analyzed: Kumotooshi, Yaichi, Obiaka, Yabukuguri, Measa and Ayasugi, using the stem analysis data obtained from 21-year-old sugi cultivars in the experimental plots established in the Kyushu University Forest in Kasuya. The different allometric relationships are observed in the two-gradient before and after crown closure each cultivar, and then the relative growth coefficients are estimated each gradient. Both in the analysis of variance by one-way layout with the factor of the cultivar and the test by the multiple comparison method, there are significant differences among the cultivars each gradient. In consideration of the above results, the estimated relative growth coefficients each gradient and their changes in the gradient, the six cultivars are classified into the following three groups: 1) Kumotooshi, 2) Yabukuguri and Measa and 3) Yaichi, Ayasugi and Obiaka. From the results obtained, it is indicated that the models with different structures for the cultivar or the classified cultivar group are necessary for the construction of the system yield table of the sugi plantations.九州大学粕屋地方演習林内の九州産挿しスギ6品種(クモトオシ･ヤイチ･オビアカ･ヤブクグリ･メアサ･アヤスギ)の21年生林分の樹幹解析木の資料を用いて,品種間の樹高と胸高直径の相対成長の差異について検討した.いずれの品種においても,林分閉鎖前後で異なる相対成長関係が認められた.そこで,相対成長係数を閉鎖前後の2階梯に分けて推定し,その相対成長係数を品種を要因とする1元配置の分散分析,及び多重比較を行った結果,両階梯とも品種間に有意差が認められた.これらの結果と,第1,第2成長階梯の相対成長係数及びその変化を考慮し,各品種の類型化を行ったところ,①クモ卜オシ,②ヤブクグリ,メアサ,③ヤイチ,アヤスギ,オビアカの3グループに分類された.このことから,システム収穫表作成時には品種,あるいは類型化された品種ごとに異なる構造のモデルを作成する必要があることが明らかとなった