| Plant functional traits can reflect the response of vegetation to environmental changes,and can affect ecosystem functions.Seasonal floods of rivers entering the West Dongting Lake carry a large amount of sediment and could change the hydrological conditions of the floodplain,which directly affect the physical and chemical properties of the soil.It's significant to clarify the impact of plant functional traits on ecosystem functions by studying the changes of plant functional traits,community productivity and the relationship between them.In this study,nine sampling sites were selected along Yuan and Li flood channel into the West Dongting Lake.The vegetation of 9 sites were investigated and the soil bulk density and water content were measured to analyze the difference among sites.Species with a relative abundance of up to 80%in each site were collected,and 8 functional traits(the carbon,nitrogen,and phosphorus concentrations of plant roots and leaves,specific leaf area(SLA),and specific root length(SRL))were determined.The trait differences between species were analyzed.The plasticity of dominant traits on environmental gradients,the difference of interspecific and intraspecific differences(CV)of 8 functional traits were compared.The community biomass were collected and the differences in community biomass among sites were analyzed.The functional diversity indexes of community weighted means(CWM)and Rao's quadratic entropy(FD_Q)were calculated and their difference were compared among sites.The relationship between species diversity,and community functional diversity and the correlation between functional diversity indexes were analyzed.And the impact of species diversity and functional diversity on community productivity were analyzed.The main results are as follows:(1)Along the flood direction of Yuan and Li Rivers,there were significant differences in soil water content and bulk density between 9 sites.The soil water content of midstream of Li River(Li Md site)was significantly higher,and the soil water content decreases with the soil depth.The soil bulk density was opposite to water content.There were significant differences in species diversity among 9 sites,but no differences in species evenness index.The species richness and diversity index of Outlet site were lower.Species evenness and diversity index were positively correlated with soil factors.(2)There were significant differences of functional traits among the dominant species.The concentration of carbon,nitrogen and phosphorus in the leaves of Galium spurium were significantly higher,and SLA and SRL of Hydrocotyle sibthorpioides were higher.There was a certain correlation between functional traits,and there was a significant negative correlation between leaf carbon concentration and leaf nitrogen and phosphorus concentration,while there was a positive correlation between other functional traits.On the gradient of flood direction,there were some differences in the plasticity of SLA,the concentration of nitrogen and phosphorus in root and leaf,and the concentration of carbon in root among the main dominant species.(3)The differences of functional traits include interspecific and intraspecific variation.The intraspecific variation of root nitrogen and phosphorus concentration was similar to that of interspecific variation.The intraspecific variations of SLA,SRL and root and leaf carbon concentration were lower,and the interspecific variations were higher.On the whole,the difference of all functional traits comes from interspecific variation(65.6%),and intraspecific variation accounts for 24.9%.(4)There was significant difference in community productivity among sites,which in upstream of Li River(Li Up site)was the highest,and there was no significant difference among other sites.There were significant differences in the functional diversity among sites.The functional diversity of Li Md site was lower,and FD_Q and CWM value of root and leaf carbon,nitrogen and phosphorus concentration of Li Up site were higher.There was a significant positive correlation between community productivity and CWM of root and leaf nitrogen and phosphorus concentration,but not with species diversity and Rao's entropy.(5)Species richness was negatively correlated with SLA and root carbon concentration,while Shannon index was negatively correlated with leaf carbon concentration.There was a significant positive correlation between Rao's entropy index and CWM values of carbon and nitrogen concentration of root and nitrogen and phosphorus concentration of leaf,and there was also a significant positive correlation between CWM values of functional traits.Species responded to changes in environmental factors to varying degrees,and the functional traits of dominant species could better explain the changes in productivity of floodplain in West Dongting Lake.When conducting vegetation restoration and ecosystem function research,it is necessary to consider the impact of functional traits of dominant species on community construction and ecosystem function. |
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