三峡库区移民区和淹没区植物群落物种多样性的空间分布格局

Spatial pattern of plant species diversity in the inundation and resettlement region of the Three Gorges Reservoir

为研究三峡库区移民安置区和淹没区植物群落物种多样性的空间分布格局,在从坝区到重庆的长江南北两岸各设置了7条样带,从海拔70m到610m每上升50m设置一个样方,共调查了129个样方。采用物种数和基于盖度的Shannon-Wiener指数作为物种多样性指标,分析了不同海拔、样带、坡向与南北岸位置的植物群落物种多样性的空间分布特点;采用DCCA排序阐明物种多样性与环境因子的相互关系,并进一步分析了造成上述空间分布格局的环境因子。结果表明:南岸的物种多样性高于北岸;物种多样性随海拔升高而增加,但趋势不显著;从坝区到重庆物种多样性变化没有明显的规律性,在坝区和万州最高,重庆和巫山最低。DCCA排序结果表明,影响物种多样性变化的外在环境因子最主要的是南北岸位置,其次为海拔;而增加物种多样性的主导生境因子是群落乔木层的盖度,灌木层的盖度则对物种多样性具有抑制作用,说明群落自身的结构特点决定着物种多样性。总之,研究区域由水热条件组合影响的物种多样性空间分布格局的规律性由于人为活动的异质性干扰发生了改变,而干扰后群落自身的结构特点,特别是群落冠层的盖度,决定着群落自身的物种多样性。

To reveal the spatial pattern of plant species diversity in the inundation and resettlement region of the Three Gorges Reservoir,129 plots were investigated along 14 sample belts. The sample belts were located at different aspects on both sides of Yangtze River,within the counties of Xietan,Wushan,Fengjie,Wanzhou,Fuling and Chongqing as well as the dam area. The investigated plots in each sample belt were taken at altitude intervals of approximately 50 m within an altitude range of 70-610 m above sea level. The spatial pattern along the altitude gradient was firstly examined by adopting the number of species and the Shannon-Wiener index based on coverage as species diversity indices. Secondly,DCCA （Detrended Canonical Correspondence Analysis） was used to illustrate the relationship among environmental variables and species diversity indices to explore factors involved with spatial patterns of species diversity. The results indicated that the species diversity was higher on the southern side of Yangtze River than on the northern side. Species diversity increased but not so evidently with an increase of altitude. There was no evident correlation found between stream position （upstream or downstream） and species diversity,however it was found that the belts with the highest species diversity were located in the dam area and Wanzhou,while the lowest were in Chongqing and Wushan. DCCA revealed that the environmental variables most affecting species diversity was firstly the southern or northern location on the Yangtze River and secondly altitude. DCCA also revealed that the coverage of the canopy layer positively affected the species diversity,but the coverage of shrub layer affected it negatively. This suggests that the species diversity was determined by the characteristics of community structure,especially the coverage of the arbor layer. It was concluded that the relationships between the spatial pattern of species diversity and environmental factors were altered by human disturbances,which are long-term and heterogeneous in space and intensity. The species diversity of the disturbed community was determined by characteristics of community structure,especially the coverage of the canopy layer.