湖南桃源洞国家级自然保护区南方铁杉种群结构与生存分析

采用样方法对桃源洞国家级自然保护区的牛石坪南方铁杉(Tsuga chinensis)群落和梨树洲南方铁杉群落进行调查,分析群落种类组成和结构特征;采用Shannon-Weiner指数、Simpson指数和Pielou均匀度指数研究群落各层的物种多样性;依据径级频率分布分析2个南方铁杉群落中南方铁杉种群的年龄结构和更新状况。结果表明:(1)桃源洞的2个南方铁杉群落中常绿植物占优势,群落有一定的季相变化,夏季呈暗绿色,秋冬淡黄绿色。(2)牛石坪南方铁杉群落共有维管植物13科21属26种,梨树洲南方铁杉群落共有维管植物22科30属36种;地理成分分析表明温带成分明显高于热带成分,表现为亚热带山地性质。(3)群落垂直结构可分为乔木层(进一步分为乔木上层、乔木中层、乔木下层3个亚层)、灌木层和草本层。(4)2个群落的Shannon-Wiener指数和Simpson指数均为乔木下层乔木中层灌木层乔木上层,Pielou均匀度指数为乔木中层和乔木下层乔木上层和灌木层。(5)牛石坪南方铁杉群落的优势种群为马银花(Rhododendron ovatum)、南方铁杉、尖连蕊茶(Camellia cuspidata)和鹿角杜鹃(Rhododendron latoucheae),梨树洲南方铁杉群落的优势种群为银木荷(Schima argentea)、南方铁杉、鹿角杜鹃和背绒杜鹃(Rhododendron hypoblematosum)。(6)根据年龄结构和生存分析,牛石坪的南方铁杉种群为衰退型,低龄级个体和种群数量都严重不足,难以实现自然更新;梨树洲的南方铁杉种群为增长型,低龄级个体数较丰富,年龄结构分布基本连续,惟其群落郁闭度较高,自我更新还存在一定的挑战。根据以上结果建议对牛石坪的南方铁杉群落进行就地保护和适当人为干扰,对梨树洲群落加强后续监测工作。

Structure and Survival Analysis of Tsuga chinensis Populations in Taoyuandong National Nature Reserve, Hunan Province

Two T. chinensis communities, from Niushiping and Lishuzhou in Taoyuandong National Nature Reserve, are studied by using the methods of plots for the composition and structure of the communities, using Shannon Weiner index, Simpson index and Pielou index for species diversity of every layers and using diameter class frequency distribution of T. chinensis to analyze the age class frequency distribution and the regeneration of the target population. The results are as follows: (1) since the evergreen plants are dominant, the physiognomy of the two communities show some seasonal changes of dark green in summer and light yellow green in autumn and winter. (2) Twenty six species in 21 genera of 13 families compose the T. chinensis community of Niushiping and the T. chinensis community of Lishuzhou contains 22 families, 30 genera with 36 species. Their proportions of temperate genera of seed plants are higher than that of tropical genera, which shows the subtropical montane property of geographical elements. (3) The vertical structure of above two communities can be divided into three layers, i.e. tree layer, shrub layer and herb layer and the tree layer includes three sub layers, i.e. upper layer, middle layer and lower layer. (4) Shannon Wiener index and Simpson index arrange as lower layer of tree > middle layer of tree > shrub layer > upper layer of tree in both communities, and Pielou index of middle layer of tree and lower layer of tree is higher than that of upper layer of tree and shrub layer in both communities. (5) The dominant populations of the T. chinensis community in Niushiping are Rhododendron ovatum, T. chinensis, Camellia cuspidata and Rhododendron latoucheae while the dominant populations of the T. chinensis community in Lishuzhou are Schima argentea, T. chinensis, Rhododendron latoucheae and Rhododendron hypoblematosum. (6) According to the age frequency distribution and the survival analysis, the T. chinensis population from Niushiping is a declining population and unable to regenerate itself because of lacking of enough younger age individuals; the T. chinensis population from Lishuzhou is a increasing population with a certain number of younger age individuals and relatively reasonable age structure while the high canopy density could be a limiting factor that challenge its natural regeneration. In conclusion, we suggest that in situ conservation and proper human intervention are necessary for the T. chinensis community of Niushiping and further monitoring is essential for the T. chinensis community of Lishuzhou.