| 概要 |
Morphology, age structure and growth of sprouts in Hamabiwa (Litsea japonica Juss.) growing in a coastal dwarf forest in northern Kyushu were investigated, and timing of sprouting was discussed in rel...ation to activities of terminal buds. Sprouts of Hamabiwa were collected and morphologyo f sprouts and their primordia were observed. On the stem surfaces of Hamabiwa, there were numerous suppressed buds with vascular traces connected to the pith. Similar vascular traces were observed at the base of sprouting positions. So, the primordia of sprouts in Hamabiwa were assumed to be suppressed buds. 67 sprouts from six clumps were randomly sampled for age structure analysis, Although there were large fluctuations in the frequency distribution of sprout age, sprouts existed in most age classes. The frequency distribution showed a gentle inverse-J shape indicating a high survival rate of sprouts. Disks of stems of one clump with 7 sprouts were sampled for stem growth and sprouting analysis. Sprouting was observed in years when the height growth rate declined or in the following years. This result suggested that sprouting was closely related to the activity of terminal buds. However, there was no significant relationship between sprouting and volume or radial growth rates. From these results, it was suggested that Hamabiwa growing in a coastal dwarf forest flushes sprouts constantly due to stress at terminal buds, and maintains their population at sites where seedlings are difficult to establish.
本研究では，海岸風衝低木林に生育するハマビワの萌芽幹の齢構成と成長を調査し，萌芽の発生を頂芽の活性に関連させて考察した．海岸風衝林群落内からハマビワの萌芽幹を採取し，萌芽の形態を観察した．また萌芽株6個体を任意に抽出し，成長錐で全萌芽幹（67本）のコアを採取して萌芽幹の樹齢を調査した．また，その中で7本の萌芽幹をもつ株を伐倒し，20cm間隔で円盤を採取して樹幹解析を行った．ハマビワの樹幹表面には髄まで連結する維管束状の組織を持つ抑制芽が存在した．萌芽発生部位にも抑制芽と同様な維管束状の組織が観察された．したがって，ハマビワの萌芽の原基は腋芽由来の抑制芽であると考えられた．萌芽の樹齢頻度分布は，樹齢による変動が大きいもののほぼ連続しており，萌芽が常時発生していることが示された．さらに，萌芽の樹齢頻度分布は緩やかな逆J型を呈し，萌芽の生残率が高いことを示した．萌芽の発生は伸長成長が低下した年あるいはその翌年にみられた．この結果は，常時塩風にさらされる海岸風衝林において，頂芽の活性と萌芽の発生が密接に関連する事を示唆していた．しかし，萌芽の発生と材積成長，肥大成長との関連は明瞭には認められなかった．これらの結果から，海岸風衝林に生育するハマビワは，頂芽にストレスを受けることによって抑制芽からほぼ連続的に萌芽を発生し，実生の定番が困難な立地で個体群を維持していると考えられた．続きを見る
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Mendeley出力
