Differentiation And Maintenance Of Vegetation Patterns Along The Topographical Gradients In Mid-subtropical Hilly And Lower Mountainous Area In East China

The spatial differences in vegetation structure are related to particular configuration of landforms nearly. The landforms could influence vegetation directly though geomorphic process, such as slope failure, transportation sedimentation and erosion etc., on the other hand, they could create a gradient of light, water and nutrient available etc. though their relief and then influence vegetation indirectly. So landforms are assumed to be one of the most principle and decisive factors affecting the vegetation pattern within a climatic region. The humid hilly regions are the habitat complex containing various disturbance frequency eroded by water and they are a reasonable research unit for the study on the relationship between vegetation and topography.The mid-subtropical area is one of the key areas of biodiversity in China. In its eastern part, hills and lower mountains are the main geomorphic type. It's the area nearly related to human life, so it's also the area most affected by human activities. The vegetation developed there often show high diversity and complexity under the combined gradients of human disturbances and habitats. So we selected Tiantong National Park, a representative hilly and lower mountainous land area with well-protected vegetation in East Zhejiang, to study the form and maintenance of rich community types and species from the viewpoint of relations between vegetation and landforms.The multi-leveled classification of landform units established in temperate region in Japan was introduced and used as the survey of vegetation and the corresponding environmental factors, such as the physical and chemical characters of soil, the light and temperature within the stand etc. Then differentiation and maintenance of community patterns along the topographical gradients were analyzed based on the field survey data from different scales. Main results include:1) Seven micro-landform units were recognized in Tiantong National Park, namely CS(Crest slope), US(Upper sideslope), HH(Head hollow), LS(Lower sideslope), FS(Foot slope), FT(Flood terrace) and RB(River bed). There was a clear border line(Erosion line) dividing the seven micro-landform units into two parts, UHA(Upper hillslope area, CS, US, HH) and LHA(Lower hillslope area, LS, FS, FT, RB). These two detailed landform units then formed an intermediate-scale section,hilly and lower mountainous land area.2) The water content of soil increased from CS to HH in the UHA, and decreased to FT in the LHA, and the soil nutrient conditions in UHA, especially CS and US, were better than those in LHA. The light quantum within the stands in LHA is lower than that in UHA except for RB, and the temperature hadn't obvious difference among four plots along a transect with a relative elevational difference of 140m.3) The seven micro-landform units were divided into two parts based on the similarity of species composition, namely UHA and LHA, and that was coincident with the result divided by erosion line. And three species group were obtained based on the distribution patterns among the UHA and LHA. Group A mostly or strictly confined to UHA, group B confined to LHA and group C associated statistically with neither part. Evergreen species of Fagaceae, Theaceae, Symplocaceae and Aquifoliaceae were the main components of the vegetation developed in UHA, however, deciduous species of Juglandaceae, Ulmaceae, Anacardiaceae and evergreen species of Lauraceae were the main components of vegetation developed in LHA. The diversity among the micro-landform units in UHA was higher than that in LHA, especially species richness and Shannon-Wiener index. And these two indexes of ground vegetation were higher than that of woody layer among the seven micro-landform units.4) Though the densities were higher, the vertical structure of the forest stands on the micro-landform units in UHA was more complex than that in LHA. The existence of emergent layer and individuals composed by species of Juglandaceae, Ulmaceae and Anacardiaceae was the remarkable feature of the forest stands in LHA.5) F...