长江重庆段消落区植物群落分布格局与多样性

Distribution patterns and diversity of plant communities in fluctuating areas of Chongqing section of Yangtze River

以长江重庆段消落区为研究区域,通过样方调查,使用Ward最小方差法对植物群落类型进行划分,结合典范对应分析(CCA)探讨了9种环境因子对群落分布格局的影响,并对群落的物种多样性进行了分析。结果表明:调查共记录维管植物103科286属419种,其中菊科、禾本科等为优势科;消落区共分为18种群落类型,其中灌草丛2个,草丛16个,狗牙根+雀稗+鳢肠群落出现频率最高;海拔与土壤含水量、土壤有机质及有效磷含量呈极显著负相关,与底质类型呈显著负相关,与多样性指数呈极显著正相关;CCA排序第一轴对植物群落空间分布的解释量为8.91%,占总解释量的41.21%,较好解释了群落与生境的关系;植物群落分布受到多种环境因子的综合影响,海拔与土壤含水量在环境因子中起主导作用;消落区中Shannon多样性指数、Pielou均匀度、Gleason物种丰富度随高程上升呈增加趋势;Simpson优势度则相反;相异性指数和Cody指数随高程上升呈增大趋势。消落区群落总体上尚处演替的初级阶段,生态系统不稳定,其中不同高程区段植物群落分布及多样性具有差异,水淹是造成差异的主要原因。研究结果可为长江重庆段消落区的监测、保护以及生态修复奠定理论基础和实践依据。

The Ward’s minimum variance method was used to classify plant community types through plot survey in the fluctuation area of Chongqing section of Yangtze River.We analyzed plant species diversity in the communities and the effects of nine environmental factors on community distribution patterns using Canonical Correspondence Analysis(CCA).The survey recorded a total of 419 vascular plant species from 286 genera and 103 families.Compositae and Gramineae were dominant families.The fluctuation area was divided into 18 community types,including two shrub communities and 16 grass communities.The occurrence frequency of Form.Cynodon dactylon+Paspalum thunbergii+Eclipta prostrata was the highest.Altitude was significantly negatively correlated with soil water content,soil organic matter content,available phosphorus content and substrate type,and positively correlated with diversity index.The interpretation of the spatial distribution of plant communities by the first axis of CCA was 8.91%,accounting for 41.21%of total interpretation,which better explained the relationship between community and habitat.The distribution of plant communities was affected by the combination of various environmental factors.Among all the environmental factors,altitude and soil water content played a leading role.Shannon diversity index,Pielou evenness and Gleason species richness in the falling zone increased with elevation,while Simpson dominance showed opposite trend.The dissimilarity index and Cody index increased with elevation.Those results suggested that plant community of the fluctua-tion area was at the primary stage of succession,and that the ecosystem was unstable.The distribution and diversity of plant communities in different elevations were different.Flooding was the main factor accounting for such difference.Our results can lay a theoretical foundation and practical basis for the monitoring,protection and ecological restoration of the fluctuation area of Chongqing section of Yangtze River.