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香果树根萌苗生长特性及影响因子分析

Growth Characteristics and Influencing Factors of Emmenopterys henryi Root Sprouts

  • 摘要: 香果树(Emmenopterys henryi)为我国Ⅱ级野生保护植物,由于生境遭到破坏、过度开发利用以及种群自然更新能力差等原因,导致自然环境下香果树种群数量迅速衰减。运用方差分析、多重比较、主成分分析等方法,对自然环境下香果树种群的根萌苗生长状况及其主要影响因子进行了研究。结果表明:香果树根萌苗的数量随着苗龄的增长逐渐减少,1a根萌苗的死亡率最高;苗高和基径均随苗龄的增大呈指数增长;香果树根萌苗主要生长在母树东南方120°~150°(以正北方为0°按顺时针方向旋转,下同)位置、距母树树干2 m以内及直径2 cm、长度30 cm的露根上;根萌苗苗高受母树方位影响较小,受露根直径、露根长度以及与母树间距离的影响稍大;母树南向(168.75°)根萌苗的基径显著大于其它方向的根萌苗基径;与北向和南向相比,母树东向和西向根萌苗的冠幅较大;根萌苗苗高、基径和冠幅等形态指标均随着与母树树干间距离的增加而降低,但随着露根直径的增加各形态指标均呈先升高后降低的趋势(露根直径6.5 cm时苗高和基径达到最大值),随着露根长度的增加各形态指标呈先降低后升高的趋势;与树冠内根萌苗相比,香果树母树树冠外根萌苗的死亡率较高。主成分分析结果表明,随着林内光照条件的改善、土壤中有机质含量的增加、砾石覆盖率的增加以及适度的人为干扰均有利于香果树根萌苗的生长。因此,减小林冠郁闭度、增加人工抚育措施对维持香果树的种群发展、实现其种群自然更新具有重要作用。

     

    Abstract: Emmenopterys henryi Oliv., belonging to the genus Emmenopterys in the family Rubiaceae, is a rare and endangered second class state-protected plant in China. The population size of wild E. henryi has declined rapidly due to habitat destruction, overex-ploitation, and poor natural regeneration. Using variance analysis, multiple comparisons and principal component analysis, the growth characteristics and main influencing factors of E. henryi root sprouts were investigated and analyzed. The results showed that the number of E. henryi root sprouts decreased with increasing age, and one-year-old root sprouts showed the highest mortality. Height and stem base diameter both showed exponential equations with monthly increases in the age of root sprouts. Most root sprouts generated southeast of (120°-150°) and within 2 m of their mother tree, and growth occurred mainly from exposed roots with a diameter of 2 cm and a length of 30 cm. The height of the root sprouts was influenced less by orientation around the mother tree, but more by the diameter and length of the exposed roots from where the sprouts generated. Compared with other sides, root sprouts growing south of the mother tree showed significantly larger stem base diameters and reached a maximum at 168.75°. The crown breadths of the root sprouts from the east and west were larger than those from the north and south. Morphological indices, including height, stem base diameter, and crown breadth of the root sprouts, declined with increasing distance from the trunk of the mother trees. The morphological indices firstly increased and then decreased with increasing diameters of the exposed roots, with the height and stem base diameter of the root sprouts reaching a maximum when the diameter of the exposed roots was 6.5 cm. The indices showed a reverse trend with increasing length of the exposed roots. The mortality of the root sprouts beyond the crown of the mother tree was larger than that under the crown. Principal component analysis indicated that light conditions, soil organic matter content, gravel coverage, and moderate artificial interferences were the main factors promoting E.henryi root sprout growth. To maintain development and realize natural regeneration of the E.henryi population, the canopy density of E. henryi should be reduced and artificial cultivations increased.

     

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