采用经典样地法对湘西土家族苗族自治州细叶楠(Phoebe hui Cheng ex Yang)天然次生林群落的物种组成、属的分布区类型、生活型、垂直结构、物种多样性、径级结构以及乔木层优势种进行了调查和分析。结果表明:该群落物种丰富,共有维管植物90 科176 属243 种,以双子叶植物为主,且木本植物较多;该群落中含单种植物的科和属均较多,分别占总科数和总属数的44. 44%和74. 43%,说明该群落的植物分布比较随机。该群落属的分布区类型复杂,共有13 个分布型和10 个变型,其中泛热带分布型属最多,说明该群落具有明显的热带和亚热带性质。该群落植物以高位芽植物为主(占总种数的61. 73%),地面芽植物次之,说明该群落所处地区温热多湿、严冬期较长。该群落垂直结构分明,可划分成乔木层、灌木层和草本层3 个层次,其中乔木层可进一步划分为2 个亚层;该群落灌木层、草本层和乔木层的种类数分别为126、95 和37 种,其中灌木层种类最丰富、乔木层种类最少。在该群落乔木层中细叶楠具有明显优势,株数最多(509 株)、胸高断面积和重要值均最大(分别为30. 594 0 m2 ·hm-2 和51. 94%),平均胸径也较大(28. 19 cm)。群落的物种丰富度指数、Shannon-Wiener 指数、Simpson 指数和Pielou 均匀度指数(包括Jsw和Jsi )均为灌木层最大、乔木层最小。该群落中的木本植物以Ⅱ级幼树和Ⅰ级幼苗为主,说明该群落处于正常生长状态;该群落中细叶楠的径级结构以Ⅳ级中树和Ⅴ级大树为主,二者共占81. 82%,Ⅰ级幼苗和Ⅱ级幼树仅占6. 53%,说明此细叶楠种群处于成熟阶段,其种群更新存在一定困难。根据调查结果,对该群落的保护提出了一些建议。

Species composition, distribution type of genus, life-form, vertical structure, species diversity, diameter class structure and dominant species in arbor layer of community of Phoebe hui Cheng ex Yang natural secondary forest in Xiangxi Tujia and Miao Autonomous Prefecture were investigated and analyzed by classical plot method. The results show that species in the community is rich; there are 243 species vascular plants belonging to 176 genera in 90 families in the community, in which dicotyledon is main plant, and there are more woody plants. There are many families and genera with one species, which account for 44. 44% and 74. 43% of total family number and total genus number, respectively, meaning that plants in the community distribute randomly. The distribution type of genus in the community is complex, totally with 13 distribution types and 10 varieties, in which, pantropic genus is the most, meaning that the community possesses obviously tropical and subtropical property. Phanerophyte in the community is main plant ( accounting for 61. 73% of total species number), hemicryptophyte takes the second place, meaning that this area is warm and moist with long winter. Vertical structure of the community is obvious, it can be divided into three layers of arbor, shrub and herb, in which, arbor layer can be further divided into two sublayers. Number of species in shrub, herb and arbor layers of the community is 126, 95 and 37, respectively, in which, species in shrub layer is the richest, and that in arbor layer is the least. P. hui in arbor layer of the community has obvious advantage, its number is the most (509 individuals) with the largest section area at breast height and the highest important value (30. 594 0 m2 ·hm-2 and 51. 94%, respectively), and also higher average of DBH (28. 19 cm). Species richness index, Shannon-Wiener index, Simpson index and Pielou evenness index (including Jsw and Jsi ) of the community all are the highest in shrub layer and the lowest in arbor layer. Woody plants in the community are mainlyⅡclass of sapling and Ⅰclass of seedling, meaning that the community is in normal growth status. Diameter class structure of P. hui in the community is mainly Ⅳclass of middle tree and Ⅴclass of big tree, both of them totally account for 81. 82%,Ⅰclass of seedling and Ⅱclass of sapling only account for 6. 53%, meaning that this P. hui population is in mature status and there are some difficulties in its population regeneration. According to investigation results, some suggestions for community protection are proposed.