三峡水库消落带出露期植物群落动态特征

Plant Community Dynamic Characteristics During Exposed Period in Hydro-fluctuation Belt of Three Gorges Reservoir

【目的】调查研究三峡水库低水位运行期间消落带植物群落物种构成、优势种的消长和物种多样性在1个生长季的动态特征。【方法】以三峡水库小江和汝溪河为研究区域,在152~170m高程范围设置7条固定样带,于2016年5—9月进行植物学群落调查。【结果】调查共记录维管植物22科55属60种,以禾本科(Gramineae)和菊科(Compositae)物种最多。不同高程的优势物种组成变化不大,但重要值所占比例不同。随着高程升高及出露期延长,一年生植物重要值升高。多年生植物狗牙根(Cynodon dactylon)和香附子(Cyperus rotundus),一年生植物苍耳(Xanthium sibiricum)、狼杷草(Bidens tripartita)、稗(Echinochloa crusgalli)、马唐(Digitaria sanguinalis)等是消落区优势物种;随着高程升高和出露期延长,狗牙根和香附子重要值降低,苍耳和狼杷草重要值升高,稗和马唐重要值先升高后降低。消落带植物群落的丰富度、多样性、均匀度指数在高程梯度上的差异在p<0.05水平具有统计学意义,物种多样性沿高程升高和出露期延长整体呈增加趋势。【结论】三峡水库消落带的物种组成趋于简单化,尤其在低高程区,耐淹种和具有强竞争力的植物是消落区的优势物种组成。不同植物的生长生态特性及对生境适应能力的差别是消落带植物群落形成和变化的主要因素。

[Purposes]The temporal-spatial dynamic characteristics of plant species composition,growth and decline of the dominant species and species diversity of plant communities were investigated during the low water level of Three Gorges reservoir operation within a growing season.[Methods]Plants growing in 7 permanent belt transects from 152~170 m elevation gradients were periodically investigated in hydro-fluctuation zone（HFZ）of the Xiaojiang river and Ruxi river of the Three Gorges Reservoir from May to September in 2016.[Findings]There were 60 vascular plant species belonging to 55 genera and 22 families recorded in HFZ,and the dominant plant families were Gramineae and Compositae.The main plant species composition almost remained unchanged in various elevations of the research area,but the proportion of their important values was different.Annual plants covered higher proportion as elevation rose or exposed period extended.Perennials Cynodon dactylon and Cyperus rotundus,and annual plants Xanthium sibiricum,Bidens tripartita,Echinochloa crusgalli,Digitaria sanguinalis were dominant species in the research area.With the increased elevation and prolonged outcropped period,important values of C.dactylon and C.rotundus were reduced,which of X.sibiricumand B.tripartita were increased,and the values of E.crusgalli and D.sanguinalis were firstly increased but then reduced.The richness,diversity and evenness indexes of plant communities were significantly different along with elevation gradients（p0.05）,and showed a trend of increase with elevation on the whole.[Conclusions]The species composition in HFZ of the Three Gorges reservoir tended to be simplified,especially in the low elevation area,and dominant species composition were those which could tolerance submergence or become stronger competitors.The adaptabilities of different ecological plants to changing habitats were the main driving factors of plant community formation and change.