ABSTRACT

Star magnolia, Magnolia stellata, is an endemic rare subcanopy tree species in the Pacific Ocean side of central Japan and an important component of Satoyama coppice forests in the area. This species is now faced with possible extinction due to the abandonment of Satoyama forests. To understand sprouting regeneration patterns of this species, to assist in its conservation, we defined four study plots whose area ranged from 156.25 to 500 m² and clearcut all vegetation in 2012–2019. We recorded survival, growth and formation of flower buds at the individual level for two years after clearcutting. The average survival rate was 95.8%. Average tree heights in the first and the second year were 0.85 m and 1.36 m, respectively. Tree height in the first year was significantly positively correlated with the total basal area of stumps (TBA), which is assumed to be proportional to the amount of carbohydrates stored in stumps. The average percentage of individuals forming flower buds in the second year after clearcutting was 32.0%. The probability for forming of flower buds in the second year was increased with increasing in TBA and the model predicted that individuals whose TBA was above 381 cm² had more than 50% probability of forming flower buds. Tree height in the second year for individuals with flower buds was significantly greater than those without. However, annual height growth of individuals with flower buds was significantly lower than those without. This indicates that a significant trade-off between height growth and reproduction exists.

摘要

明星玉兰，木兰，是日本中部太平洋一侧的地方性稀有冠层树种，也是该地区里山佐藤木林的重要组成部分。由于放弃了佐藤山的森林，该物种目前面临灭绝的可能。为了了解该物种的萌芽再生模式，以帮助其保护，我们定义了四个研究区，其面积从156.25到500 m ²并在2012-2019年间清除所有植被。清除后两年中，我们记录了个体水平上花蕾的存活，生长和形成。平均存活率为95.8％。第一年和第二年的平均树高分别为0.85 m和1.36 m。第一年的树高与树桩的总基础面积（TBA）呈显着正相关，TBA与树桩中储存的碳水化合物量成正比。清除后第二年形成花蕾的个体的平均百分比为32.0％。随着TBA的增加，第二年形成花芽的可能性也增加，该模型预测，TBA大于381 cm ^2的个体有超过50％的可能性会形成花蕾。有花蕾的人第二年的树高明显高于没有花蕾的人。但是，有花蕾的个体的年高度增长显着低于没有花蕾的个体。这表明身高增长与繁殖之间存在重大权衡。