宝华玉兰生存群落的自组织特征映射网络排序与分类

为了解国家Ⅱ级保护植物宝华玉兰Magnolia zenii的种群分布规律及其濒危原因，进一步揭示宝华玉兰野生种群与群落及环境之间的生态关系，应用自组织特征映射网络（SOM）对宝华玉兰生存群落进行了排序和分类，以期为保护和管理宝华玉兰种群野生种质资源提供理论依据和新的方法。结果如下:①群落结构分析表明，宝华玉兰天然更新缺乏，且紫楠Phoebe sheareri，建始槭Acer henryi等优势种占据了主要生存空间与资源，影响了宝华玉兰种群增长和发展，使其在群落中处于不稳定地位；②SOM将40个样方进行聚类分析，得到7个群落类型。不同群落类型之间的物种组成存在差异，界限清晰，排序结果与优势种实际分布情况吻合，说明SOM的分类结果具有合理性；③环境因子可视化分析揭示了宝华玉兰分布于坡度较缓的半阳坡，种群分布主要受到坡向和坡度2个环境因子的影响，由于宝华玉兰自身生长过程中对环境要求的特殊性和不适应性，造成了其濒危现状；④SOM具有高度非线性拟合的特点，且能够同时进行排序和分类，并将分类结果可视化，呈现样方之间的相似性，说明SOM应用于群落分类和排序，反映种群与群落及环境之间的生态关系是合适的。

Classification and ordination of a Magnolia zenii community based on a self-organizing feature map

To understand the population distribution of the National Grade Ⅱ protected plant, Magnolia zenii, and reasons for its endangered status; to reveal the ecological relationship between the M. zenii community and the environment; and to provide a theoretical basis and new methods for protecting and managing the wild germplasm resources of M. zenii, a self-organizing feature map (SOM) network was used to sort and classify the living communities of M. zenii. 40 samples (quadrats) of 10 m×10 m for forest, 5 m×5 m for shrub land and 1 m×1 m for grass land were set up and species data was recorded in each sample. The classification and ordination was carried out by use of the NNTool box in MATLAB(6.1). Results of the community structure analysis showed that (1) natural regeneration of M. zenii was lacking with the dominant species, Phoebe sheareri and Acer henryi, occupying the main living space and resources. (2) The SOM clustered 40 quadrats of plant communities to obtain seven community types. Species composition of the different community types varied, the boundaries were clear, and the ranking results were consistent with actual distribution of the dominant species. (3) Visual analysis of the environmental factors showed that M. zenii was distributed on the semi-sunny and gentle slopes. Population distribution was mainly affected by two environmental factors:slope and slope direction. (4) The SOM had a highly nonlinear fitting, could sort and classify at the same time, and could visualize the classification results to show similarity between quadrats. The study suggests that the dominant species occupy the main environmental resources of the community, which affects the growth of M. zenii population, furthermore, the special requirements of its growth process and being unable to adapt caused its endangered status. Additionally, SOM is an effective quantitative technique in plant ecology, and it is applicable to reflect the ecological relationship of population, community, and the environment.