极小种群野生植物对开蕨种群结构特征和群落物种多样性

以国家Ⅱ级保护极小种群野生植物——对开蕨(Phyllitis scolopendrium)为研究对象,分析了在海拔729、1008m群落内,其种群大小、分布频度和密度,个体形态特征指标及其在种群内、种群间差异,苗高分布规律、相对苗高组替代年龄级结构,分布格局和群落各层次的物种多样性,群落的相似性。结果表明:对开蕨在自然分布区内为偶见种,呈斑块状分布。在400m~2内,海拔1008m处(01群落)种群密度为31株,样地分布频度为43.75%,最大密度15株/25m~2;海拔729m处(02群落)种群密度为91株,样地分布频度为93.75%,最大密度30株/25m~2。通过对其自然苗高,叶片数量,有孢子囊叶片数量,最大叶片长、宽值,最小叶片长、宽值,冠径,叶片厚度7个形态指标的分析显示,种群内变异较大,随着植株高度(年龄)的增加,其变异系数均随之减小而趋于稳定;种群间在自然苗高,最大叶片长度和宽度,成熟孢子叶片数量,冠径,叶片厚度上达到极显著差异(P0.01)。其苗高分布呈现双峰型,01种群波谷出现在15.1—20.0cm处;02种群波谷出现在10.1—15.0cm处,两群落均显示有一次较大的更新过程,同时01种群在40.1—45.0cm出现间断。年龄级分析得出,01种群划分为5个龄级,近于正态分布;02种群划分为4个龄级,为倒J型分布;两种群分别处于中龄期和幼龄期,没有出现衰退型年龄结构。格局分析得出,对开蕨种群均为聚集分布。两群落的乔木、灌木、草本层的Shannon-Wiener指数、Pielou均匀度指数、Marglef丰富度指数、生态优势度和种间相遇机率较低(与地带顶级植被相比)而且分布不均;对开蕨在两群落的草本层中重要值较低,仅为伴生种。两群落相似性分析显示,乔木、灌木、草本层的相似度指数分别为66.67%、69.23%和38.46%,草本层差异较大。

Characteristics of population structure and community species diversity of an extremely small population of protected Phyllitis scolopendrium

For Phyllitis scolopendrium, a second-class national protected wild plant with extremely small populations, which is distributed in a narrow region of the Changbai Mountains, we analyzed the population size, distribution frequency and density, individual features, and the variation of internal and external populations at 729 and 1008m above sea level (asl). The plant height, substitute age structure, distribution pattern, community biodiversity, and similarity of various layers were also described. Results showed that P. scolopendrium was a typical occasional species, which showed a patchy distribution pattern. At 729m asl, the population density was the highest (91 per 400m²), with a distribution frequency of 93.75% and highest density of 30/25m². At 1008m asl, the population density was only 31 per 400m², with a distribution frequency of 43.75% and highest density of 15/25m². Based on the analyses of morphological features, including plant height, leaf number, sporangium leaf number, maximum leaf length and width, minimum leaf length and width, canopy width, and leaf thickness, we found that the morphological features of the internal population showed the highest variation, indicating a decreasing trend with increasing height/age. Additionally, variations in plant height, mature sporangium leaf number, maximum leaf length and width, canopy width, and leaf thickness all showed significant differences (P < 0.01), indicating that the two populations were from different species types. Plant height showed a double peak pattern. Trough value of type 01 population occurred at 15.1-20.0cm, whereas the trough value of the type 02 population occurred at 10.1-15.0cm. There was a significant update process in both types, and a break of the type 01 population at 40.1-45.0cm. We analyzed the age structure of type 01 and 02 populations and found that there were five age classes of the type 01 population, which showed a normal distribution pattern, whereas the type 02 population had four age classes, which showed an inverted J distribution pattern. Type 01 and 02 populations were at juvenile and middle age stages, with no trend of senescence. Based on the spatial pattern analysis, we found that P. scolopendrium showed a negative binomial distribution pattern. The diversity indices, including Shannon-Wiener, Pielou, and Margalef, showed that the similarity index of tree, shrub, and herb layers in the two types was low, indicating a low biodiversity status compared with the local climax community. Phyllitis scolopendrium was considered a companion species because of lower importance value in type 01 and 02 communities. Similarity analyses showed that plants in tree and shrub layers were the most similar, followed by the herb layer with values of 66.67%, 69.23%, and 38.46% respectively, indicating that the herb layer had the most variation.