Differentiation of topo-communities along topographical gradients

本研究旨在阐明植被在沿着地形环境梯度上的分异格局及其控制因素。在当时的宏观气候条件下，由土壤水分状况、土壤养分、土壤深度、土壤表层物质稳定性等地形环境因素所划分的植物群落或斑块，对梯度上某一地点的植物群落性质具有决定性的影响，如在亚热带/暖温带，顶极森林主要是万年青的背叶乔木，如锥属的尖叶栎变种。sieboldii）、润楠（Machilus thunbertandum）和栎属（Quercus spp.）在中尺度的生境偏好中，坡顶为万年青阔叶树覆盖，岩脊为铁杉、赤松和小花松等针叶树覆盖，谷底附近的低坡为多药桉等落叶树覆盖，在特定的生境中，如山区的小山峰或小岛，狭窄的山脊顶部，迎风坡的顶部等，特别是被一个以Eurya spp.为主的小叶群落覆盖，山矾属和冬青属，它们的竞争力不如notophyllous社区。当对环境胁迫更敏感的阔叶树的生长或表现受到抑制时，小叶树成为优势树种。因此，地形栖息地本身具有一般的竞争等级，具有各种适应性状的不同生态群体相继选择这种等级。

The present study intended to clarify the differentiating pattern of vegetation and its controlling factors along topographical environmental gradients. The plant communities or patches which are differentiated through topographical environmental factors, such as soil moisture status, soil nutrients, soil depth, and stability of soil surface materials etc. have decisive effect on the nature of plant community on a certain site on the gradient, under the prevailing macro-climatic conditions.In the subtropical/warm-temperate zone, for example, the climax forests are dominated by evergreen notophyllous trees such as Castanopsis cuspidata var. sieboldii, Machilus thunbergii and Quercus spp. In a mesoscale topographical habitat preference, crest slope is covered by the evergreen notophyllous trees, rocky ridge is exclusively dominated by conifers such as Tsuga sieboldii, Pinus densiflora, and Pinus parviflora, and lower slope near the valley bottom is dominated by deciduous trees such as Euptelea polyandra, Morus etc. An interesting pattern of community differentiation can be observed on a specific habitats such as small peak within a mountainous area or in a small island, narrow ridge top, top of windward slope, etc., which are specifically covered by a microphyllous community dominated by Eurya spp., Symplocos spp, and Ilex spp., etc. They are competitively inferior to the notophyllous community. And the microphyllous trees become dominant when the growth or performance of the notophyllous trees, which are more sensitive against environmental stresses, are suppressed. Thus the topographical habitat itself has a general competitive hierarchy that is preferred successively by different ecological groups having various adaptational traits.