海南濒危植物蕉木种群结构与动态特征

【目的】分析海南濒危植物蕉木的年龄结构和数量动态特征,探讨两种干扰程度下蕉木种群生存现状和动态变化趋势,揭示蕉木种群与环境之间的关系,探索蕉木种群濒临灭绝的原因,为维护和恢复蕉木种群提供依据。【方法】利用典型群落样方法对海南蕉木分布的9个典型样地进行群落学调查,详细记录各样地的海拔、坡度、坡向、林分郁闭度、植被群落等生境指标。同时,调查每个样地内和其他非典型群落分布点蕉木个体的树高、胸径等指标;在对蕉木典型群落组成和结构调查的基础上,将所有蕉木种群个体所在群落分为受人为干扰较强和较弱两种生境进行比较和分析;将蕉木胸径大小划分为7个径级,并以胸径代替龄级来反映种群结构;将龄级与胸径大小级对应,绘制蕉木种群的径级结构图;使用种群动态量化方法编制种群的静态生命表,分析其存活曲线、死亡率曲线等重要参数;运用时间序列模型模拟并推测蕉木种群的数量动态和发展趋势。【结果】①典型蕉木群落中乔木层和灌木层的物种多样性均较高;②两种干扰生境中的蕉木种群年龄结构有所差异,但幼龄和中龄植株总数量均占有一定优势,种群具有一定的恢复潜力;③两种干扰生境的蕉木幼苗数量均较少,Ⅱ龄级呈现衰退趋势,种群自我更新能力较差,对外界的干扰具有较高的敏感性;④种群生存呈Deevey-Ⅱ型存活曲线,曲线呈对角型,各龄级阶段具基本相同的死亡率;⑤人为干扰程度强的生境中蕉木种群存活能力比人为干扰程度弱的生境中低。【结论】人为活动导致的适宜生境地减少和种子自然萌发率低是蕉木种群濒危的主要原因。因此,应加强对蕉木种群及栖息地的保护,保护蕉木现有的成年个体;而对于蕉木植株分布较密集区域,在果实成熟季节应定期采收蕉木种子并加以一定的人工抚育促进种子萌发和幼苗的更新;可通过适当修剪老龄的蕉木个体促进其萌芽,提高开花结实率;对于干扰程度较强生境的蕉木种群应加强植物的保护宣教工作,降低人为干扰;而在干扰程度较弱生境,也应加强对中小径级蕉木个体的人工抚育,促进蕉木种群的自然更新和恢复。

Population structure and dynamics of the endangered plant Chieniodendron hainanense in Hainan

【Objective】Understanding the survival status of endangered plants and their population dynamics is of great significance for their conservation in Hainan Province, China. The present study analyzed the age structure and population dynamics of the endangered plant Chieniodendron hainanense in two habitats with different disturbance intensities, explored the relationship between the C. hainanense population and the environment, and discussed the main factors threatening C. hainanense. It aimed to provide evidence for the maintenance and restoration of C. hainanense. 【Method】 In 2018-2019, a community investigation was carried out in nine typical plots of C. hainanense in Hainan using the quadrat method. The elevation, slope, aspect, canopy density and vegetation of each plot were recorded. The height and diameter at breast height (DBH) of each C. hainanense individual were recorded both in typical and atypical communities. Based on the composition and structure of the typical communities, all the surveyed communities were assigned to habitats with either high or low levels of human disturbance. The DBH of the C. hainanense population was divided into seven diameter classes, which were used as a surrogate of its age class to examine the population structure. The size structure of the C. hainanense population was analyzed. We used the quantitative analysis to establish a static life table of the C. hainanense population, analyzing survival and mortality curves, and other important parameters. A time series model was applied to model and predict the quantitative dynamics and development trend of the C. hainanense population. 【Result】①Species diversity in the tree and shrub layers were both higher in the typical communities. ②The age structure of the C. hainanense population differed between the two habitats. The young and middle-aged individuals were somewhat prominent, suggesting the potential for restoration of the population. ③The number of seedlings in the two habitats was low, with the age class II population showing a decreasing trend. The population showed a low self-renewal capacity and was vulnerable to external disturbances. ④The population survival curve belonged to the Deevey-Ⅱtype, and was diagonally shaped, with each age class stage showing the same overall mortality. ⑤The survival ability of the C. hainanense population was lower in the high disturbance habitats than in the low disturbance habitats. 【Conclusion】 The loss of suitable habitats caused by human activities and the low natural germination rate of seeds are the two most influential factors that endanger the C. hainanense population. Therefore, the protection of existing C. hainanense adults and their suitable habitats should be strengthened. For the C. hainanense aggregated areas, it is proposed to harvest the seeds regularly during the fruit maturation period and apply artificial care to promote seed germination and seedling regeneration. It is also proposed to prune the old C. hainanense individuals appropriately to increase seed germination and flowering and fruiting rates. Finally, around the high disturbance areas, it is necessary to improve the public awareness of plant protection to minimize human disturbance. Similarly, in the low disturbance areas, artificial care should be strengthened for the medium and small-sized C. hainanense individuals to promote the natural regeneration and restoration of the C. hainanense population.