采用样方法对江西井冈山竹柏[Nageia nagi (Thunb.) Kuntze]种群的4 个样地进行了调查,并据此分析了种群的年龄结构、分布格局及其群落区系特征和物种多样性。结果表明:根据株高和胸径可将种群分为6 个径级,其中Ⅰ级幼苗和Ⅱ级幼树数量最多,比例分别达到33. 33%和30. 48%,种群的年龄结构为金字塔型。随径级增加种群生命期望值逐级递减、种群中的存活个体数逐渐减少;其中,Ⅰ级幼苗的死亡率最小、生命期望值最大,而Ⅵ级衰老株死亡率最大;种群存活曲线接近Deevey-Ⅱ型(直线型);种群的方差/ 均值比达到3. 41,表明其分布格局为集群分布。该竹柏群落包含维管植物34 科56 属62 种,其中,蕨类植物8 科8 属8 种、裸子植物1 科1 属1 种、被子植物25 科47 属53 种,以木本植物占绝对优势。群落维管植物科、属的区系地理成分较复杂,但均具有明显的热带性质。群落各样地间的多样性指数差异较大,但均为Pielou 指数较高,物种丰富度指数、Simpson 指数和Shannon-Wiener 指数均较低;群落不同层次的各项多样性指数差异明显,均为灌木层最高、乔木层最低,但乔木层的多样性变幅较大。研究结果显示:该竹柏种群为增长型种群,具有较强的自然更新能力,但物种多样性程度较低。

Four sampling plots of Nageia nagi (Thunb.) Kuntze population in Jinggangshan of Jiangxi Province were investigated by quadrat method. Hereby, population age structure, distribution pattern, and community floristic characteristics and species diversity were also analyzed. The results show that the diameter class of the population can be divided into six grades according to height and DBH, in which, numbers of seedling in Ⅰgrade and sapling in Ⅱgrade are the most with percentages of 33. 33% and 30. 48%, respectively, and the population age structure is the Pyrimid type. With increasing of diameter class, the life expectancy of the population decreases step by step and the survival number of individuals decreases gradually. In which, the death rate of seedling in Ⅰgrade is the smallest with the largest life expectancy, but the death rate of senescent plant in Ⅵgrade is the largest. And the population survival curve is approximately Deevey Type Ⅱ(linear type). The variance-mean ratio of population reaches 3. 41, meaning that the population distribution pattern is the clumped pattern. There are vascular plants of 62 species in 56 genera belonging to 34 families in N. nagi community, in which, there are pteridophyte of 8 species in 8 genera belonging to 8 families, gymnosperm of 1 species in 1 genus belonging to 1 family and angiosperm of 53 species in 47 genera belonging to 25 families with the absolute predominance in woody plants. The geographical elements at family and genus levels of vascular plants in the community are more complex, but both have obvious the tropic component. There are larger differences in every diversity indexes among four sampling plots, but Pielou index is higher while richness index, Simpson index and Shannon-Wiener index all are lower. There are obvious differences in all diversity indexes among different layers of the community with the highest in shrub layer and the lowest in arbor layer, but change range of species diversity in arbor layer is greater. It is suggested that the N. nagi population is a increasing type population with a strong natural reproductive capability, but its species diversity degree is lower.