绿汁江下段天然灌草丛群落分布格局及环境关系分析

  目的  研究绿汁江下游区域天然灌草丛群落在同一地理单元中的分布格局与环境变化规律，探索群落分布形成机制，找到干热河谷地区生态系统整体性修复的重要挟点，提出系统修复和综合治理办法。  方法  运用双向指示种分析法(TWINSPAN)和主成分分析(PCA)，以峨山县绿汁江下段灌草丛群落森林资源调查数据为依据，研究植被分类并分析环境关系。  结果  TWINSPAN数量分类方法显示:854个图斑可划分为19个群丛组65个群丛。PCA排序结果显示:第1轴呈现了土层厚度、雨水截留量、保水能力的变化，第2轴呈现了干热方向的变化。垂直气候梯度灌草丛的丰富度从大到小依次为高原面亚热带、干热河谷带、中山南温带。各垂直气候带中都具有典型指示类型。干扰强度大的地区形成了以华西小石积Osteomeles schwerinae、山矾Symplocos sumuntia、萌生栎Quercus spp.、杜鹃Rhododendron simsii灌草丛为主的分布格局。  结论  生境过滤和人为干扰是灌草丛群落分布格局的主要形成机制。通过分析同一地理单元的天然灌草丛群落分布，可了解种群生态幅度和最适生存区。参照群丛组与环境关联关系可判断生态系统中物种所受到的主要生态胁迫。图3表5参34

Analysis on the distribution pattern and the environmental relationship of natural shrub-grassland communities in the lower section of Lüzhi River

  Objective  With an investigation of the distribution patterns of shrub-grassland communities as well as their relationships with the environment in the same geographical unit in the lower section of Lüzhi basin, this study is aimed to explore the formation mechanism of community distribution and then to find out the important pinch point of ecosystem restoration in dry-hot valley area so as to propose methods of systematical restoration and comprehensive management.  Method  Two-way indicator species analysis (TWINSPAN) and Principle component analysis (PCA) were employed to classify shrub-grassland communities before a proper analysis was conducted of the relationship between the shrub-grassland communities and the environment on the basis of the forest resources investigation data of the shrub-grassland community in the lower section of Lüzhi River in Eshan County.  Result  The 854 patches were divided into 19 association groups and 65 associations using the TWINSPAN method. In terms of the PCA ordination, the first axis demonstrated the changes in soil depth, rainfall interception and water holding capacity, while the second axis demonstrated the changes in dry, and heat ranges. Under the vertical climate gradient, the richness of shrub-grassland communities was presented in the following pattern: subtropical plateau zone＞dry-hot valley zone＞south temperate middle mountain zone. Each vertical climate zone was featured with respective typical indicator types of shrub-grassland community and. In the areas with high disturbance intensity, the main distribution patterns were Osteomeles schwerinae, Symplocos sumuntia, Quercus spp., and Rhododendron simsii.   Conclusion  Habitat filtering and human disturbance are the main formation mechanisms of shrub-grassland community distribution and with an analysis of the distribution of natural shrub-grassland communities in the same geographical unit, the ecological amplitude and the optimal living areas of species populations can be found, which can provide the selections of native tree species for ecological restoration in the dry-hot valley area. Also, the main ecological stresses on the species in the ecosystem can be confirmed in accordance with the relationship between association groups and the environment, thus providing basis and support for systematical restoration and comprehensive management. Ch, 3 fig. 5 tab. 34 ref.]