Studies On The Status Quo Of Aquatic Plant Biodiversity In The Riverways And Littoral Zones Of The Taihu Lake Rim And The Growing Response Of Invasive Plant Eichhornia Crassipes To Water Level

The Taihu Lake rim has a robust economy and a dense population.In the meantime,this area is facing serious environmental issues such as eutrophication,habitat degradation and invasion of introduced aquatic species.Surveys on aquatic plant diversity were carried out to make clear the status quo of native and introduced aquatic plants and to evaluate the decrease of aquatic habitat and invasion of introduced aquatic plants in this area in the year of 2018.Based on the survey results,an introduced plant Eichhornia crassipes(Mart.)Solms was found to be the most dangerous invasive species in this area.For example,in some river sections,the plant have overwintered and rooted in some water levels.In order to explore the reasons for these two survival phenomenon in the natural state phenomena,two controlled experiments were set up,and an native plant Hydrocharis dubia,a similar ecological niche plant with E.crassipes,to explore the effect of water level on E.crassipes growth and reproduction.Research indicates:1.(1)38 aquatic plants species in 22 families and 29 genera were recorded in the Taihu Lake rim in the year of 2018;(2)the relative importance value(RIV)occured the highest in an invasive submerged plant Cabomba caroliniana Gray among 31 riverway quadrats,followed by another invasive free-floating plant E.crassipes,and the latter one has the highest RIV among 34 littoral zone quadrats.(3)the aquatic plant biodiversity indices decrease with the increase of coverage of C.caroliniana and E.crassipes in riverway and littoral zone quadrats,respectively,indicating that invasive plants had reduced the biodiversity of aquatic plants.(4)Although there be no invasive plants found in the littoral zones of the Taihu Lake,it is recommended to focus on the expanded distribution of the free-floating plant E.crassipes,and the submerged plant,C.caroliniana,may invade the Taihu Lake alongside river channels.Facing the issues of reducing of aquatic plants and invasion of introduced plants,the spread of invasive aquatic species should be monitored and aquatic vegetation restoration can be made in this area.2.(1)Under the same experimental conditions except the water level,Eichhornia crassipes undergoing overwintering at the same water level,but after processing with SPSS 19 the morphological indices and physiological indices difference is not significant.(2)Under different water levels,there are significant differences in the morphological indicators of the E.crassipes(the same as the physiological indicators described in Conclusion 1),It roughly shows that it decreases as the water level rises.Comparing the wintering and non-wintering groups,the performance is similar.(3)In some groups,it was found that the root system of E.crassipes touched the bottom material,and it was found that the plants that touched the bottom material grew more vigorously than the plants that did not touch the bottom material.This phenomenon has been proved in the experimental data analysis.The root system of E.crassipes will take root in the sediment under the condition of lower water level,absorb the nutrients in the sediment and accelerate its growth.3.(1)Different water levels have a significant effect on the growth of E.crassipes and H.dubia.Generally,the plant grows more vigorously as the water level decreases.(2)The E.crassipes and H.dubia are floating plants,however,under certain conditions,the root systems of the two can contact and be rooted in the sediment.(3)The water level affects whether the root system of the E.crassipes and H.dubia rooted in the mud and affects both growth and reproduction.Whether it is Eichhornia crassipes or Hydrocharis dubia,the rooted plant can absorb more nutrients through the root system to intensify its growth and reproduction.Due to the limitation of the experimental barrel,the two plants will continue to grow vertically when they are grown to the full surface of the water surface,and the E.crassipes will stand up above the water surface,and the stems and leaves of the H.dubia will not be like the Eichhornia crassipes The firmness will make the newly grown leaves layer-by-layer covered,and the leaves above will block the leaves below,thus affecting the growth of the leaves at the lower layers.