| 造園樹木の樹形形成に関する形態学的研究 : ユリノキの剪定木について. Morphological Studies on the Developing Process of Tree Form of Landscape Plants : A Pruned Tree of Liriodendron tulipifera L.. | |||||||||||||
Abstract | |||||||||||||
| ユリノキ(Liriodendron tulipifera L.)の4年生段階で加えた剪定を第1回として, その後毎年1回計4回の冬期剪定を加え, その間の成長を測定, 解析した.剪定後の樹高成長は, 1984年, 85, 86年の3回の剪定後でほぼ同じであった.その樹高成長量は2mに及び, 7年生までの無剪定木の年間最大伸長量に匹敵するものである.根元径成長は剪定によって緩慢なものとなる.以上の傾向は, 4本の剪定木でほぼ共通したものであったが, 剪定枝の総乾重については, 第1回剪定後に乾重が大きく増加するのは4個体とも同じであるが, 第2回剪定以降の推移では個体差が大きかった.剪定木1の各枝の伸長量を剪定前後で比較すると, 3回の剪定のいずれにおいても, 長い枝を剪定すると長い枝が伸び, 短い枝からは剪定後も短い枝しか伸びないことがわかった.また, 各枝の伸長率は剪定回数を重ねるにつれて減少した.さらに, 枝数も剪定を重ねるにつれて減少した.剪定の繰返しによって減少した枝は短い枝であり, 従って剪定を重ねるにつれて長い枝の割合が相対的に高まる形となる.剪定木1の枝ごとの葉材比を第1回及び第3回の冬期剪定後, 新たに伸びた枝が伸長を停止した時点で求めた結果, それぞれの年の葉材比は枝ごとに差異がなくほぼ一定であり, 第1回と第3回剪定後の葉材比はそれぞれ0.89, 0.58であった.無剪定木の場合, 若い枝ほど葉材比が高い傾向があるから, 第1回剪定後に伸長した枝の方が第3回剪定後に伸長した枝より若い状態にあるものと言えよう.第1回剪定後に伸長した枝の長さとその枝の葉面積合計の関係を無剪定木と比較すると, 剪定木の長い枝(ほぼ50cm以上)の葉面積合計は無剪定木のそれに比べてより高く, 逆に短い枝(ほぼ50cm以下)では剪. Shoot elongation of a tulip tree (Liriodendron tulipifera L.) was investigated after the winter pruning. Tree height recoveries of four individuals were mostly the same after the first, the second, and the third pruning. Their annual increment of tree height was nearly two meters, which corresponded to the maximum annual elongation of non-pruned individual until the seven-year-old stage. The trunk enlarging rate was decreased by the pruning. The shoot length elongated after the pruning depended on the shoot length before the pruning, and it decreased with the repetition of pruning. Moreover, the number of shoots especially short ones decreased with the repetition of pruning. Consequently, the proportion of long shoot increased with the repetition of pruning. The leaf/branch ratio in dry matter weight was mostly the same among the shoot elongated after the pruning, and the average ratios were 0.89 and 0.58 after the first and the third prunings, respectively. The shoots elongated after the first pruning were more vigorous than those after the third pruning, because the younger branches had the higher leaf/branch ratio than older ones in the non-pruned individuals. The total leaf area of a shoot longer than about 50cm elongated after the first pruning was greater than that of the same size of a shoot in the non-pruned individuals. On the contrary, the total leaf area of a shoot shorter than about 50cm elongated after the first pruning was smaller than that of the non-pruned one. The short and inferior shoots did not appear with the repetition of pruning. These differences in the total leaf area between the pruned and the non-pruned individuals resulted from the differences in the average area of a single leaf, but not from the number of leaf, i. e. the leaf area does not change with the shoot length in the non-pruned individual, and on the contrary the shoots longer than about 50cm of the pruned individual had lerger leaves than the non-pruned one, and the shoots shorter than about 50cm of the pruned individual had | |||||||||||||
Publication details | |||||||||||||
| |||||||||||||