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九州で選抜されたスギ精英樹クローンについて，幹の形状の変異を明らかにするために，6地方の演習林において同一条件で設定されたスギ品種試験地から，精英樹25クローンについて，各試験地，各クローン毎にその平均胸高直径に相当する標準木を選定し，計150本の標準木の樹幹解析をおこない樹幹形について解析した。樹幹形の解析には相対幹形曲線をもちい，完満度の指標として，相対材積ならびに相対直径列をとりあげ検討した...結果，前者は完満度をはぼ代表しうることが認められた．クローンと試験地との二元配置の分散分析を行った結果，相対材積は，クローン間ならびに試験地間に有意な差が認められた．一方，相対材積に影響する樹木内部の形態的要因として樹高および相対枝高（力枝高／樹高）においても，クローン間に有意な差があり，前者では試験地間にも有意差が認められた．そこで，樹高や相対枝高の影響を除外してもなお相対材積は，クローンや試験地間に違いがあるかを調べるため共分散分析をおこなった結果，相対財積の修正平均値は，依然としてクローンや試験地の影響があると判断された．九州産のこれらの25クローンの中の15クローンは，それぞれ外部形態やアイソザイム分析によって7種の在来品様に同定されている．そこで，在来品種と対応させると，同一品種に同定されるクローンの相対材稽の大きさは，当然ながら類似した値を示し，その順序において大きな矛盾はないことも明らかとなった．この事実から，樹幹形は，遺伝的に大きく決定されることがさらに確認され，オビアカやトサアカなどの品種に同定されるクローンは，ヤブクグリ，アヤスギなどの系統のクローンに比べて樹幹は完満であることが明らかとなった．また，樹高との共分散分析による相対材積の修正平均値を試験地間で比較すると，鹿児島大高隈演習林の場合は，九州大宮崎演習林の場合より大きく，これらの試験地間の差異をもたらす原因は，気温などとの関係の深い標高との間で有意な負の相関がみられたことから，これらの環境要因が影響していると推量された．さらに，樹幹の容積密度（年輪幅との共分散分析による修正平均値）と相対材積の修正平均値との間には，高い負の相関が得られた．以上のことから，スギの樹幹形は幼齢時から，環境要因と同様に遺伝的要約に強く影響を受けていることが明らかにされた．
In order to clarify the stem form variations of clones of Clyptomeria japonica plus trees which had been selected in Kyushu, one sample tree from 25 clones was collected, respectively, from the experimental forests which had been settled 13 years before as the progeny tests (clonal test) in 6 different experimental forests in the islands of Kyushu and Shikoku (Fig. 1, Table 1). The total of 150 sample trees with the diameter equal to the average of each clone in each plot were used for the stem curve investigation. The relative stem curve was obtained by plotting the relative radius based on the diameter at nine-tenths of the total height from tip over the relative height. By using the relative stem curve, the relative volume and the relative radius at the relative height of 0.1, 0.3. 0.5, and 0.7 of tree (0.1, 1)0.3, 1)0.5, 1)0.7) were used as a measure for the relative stem form. The results obtained were as follows. The relative volume could be used alone to represent the stem form tapering of a ramet (Fig, 2). As a result of the analysis of variance on the relative volume, there were significant differences both among the clones and the forests (Table 2). On the other hand, there were also significant differences in tree height both among the clones and the plots, and in the relative branch height (branch height/ tree height) among the plots (Table 3, Table 4). Therefore, the significant differences of the relative volume might result from the difference of the height and/or the relative branch height. Hence, in order to ascertain whether there are still differences of relative volume among clones and plots even when the effect of tree height and the relative branch height are eliminated, the analysis of covariance between tree height and relative volume was made, and showed the significant difference in corrected mean of relative volume among clones and plots (Table 5, Table 7, Fig. 3, Fig. 4). According to the report on the morphological aspect and the isozyme analysis, 15 out of 25 clones were identified as 7 native cultivars, respectively, which are already widely planted in Kyushu, The relative volumes of the clones, possibly same clone of a cultivar, were similar as a matter of course (Table 6). This facts certified furthermore the genetic variation of stem form of Clyptomeria japonica is great. The clones identified as Obiaka and Tosaka have a greater relative volume than the ones identified as Yabukuguri and Ayasugi. The corrected mean of the relative volume obtained by the covariance analysis based on the tree height also differ significantly among plots which has a different environment (Table 8, Table 9, Fig. 7, Fig. 8). The corrected mean of relative volume of Kagoshima University forest was greater than the one of Kyushu University forest in Miyazaki. As a result of a brief examination, a highly negative correlation was found between the corrected mean of relative volume and the altitude which might be related with air temperature or some other environmental factors related to the altitude (Fig. 5, 6). There was negatively high and significant correlation between the corrected mean of relative volume and the corrected mean of bulk density with annual ring width which were reported in the other paper for the same clones (YAHATA et al., 1986) (Fig. 9). This result indicates that trees with a greater bulk density could not have a full bole as if the total mass seemed constant. Although the age of sample trees was very young, the relative stem volume was significantly influenced by the hereditary elements as well as the environmental factors (Fig. 10).続きを見る
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