Effects Of Sediments And Flooding Duration On The Growth And Distribution Of Typical Wetland Plants In Poyang Lake

The growth and distribution of plants in wetlands are shaped by a variety of environmental factors.In spatial pattern,wetland plants are zonally distributed along the flooding gradient,and their growth is also heavily influenced by sediments,resulting in diversified plant distributions under the same flooding conditions.However,the underlying response mechanisms of wetland plants to sediments and flooding remain unclear.This study focuses on the Poyang Lake wetland and examines typical wetland plant species as the research objects.Through a combination of field surveys and controlled experiments,we conducted series of studies on sediments-flooding duration-plants.Our study aims to reveal the internal mechanisms driving plant growth and distribution in the Poyang Lake wetlands under the influence of environmental factors,and provide theoretical references and management strategies for the conservation and sustainable development of the Poyang Lake wetlands,particularly in the face of rapid changes in external environmental conditions.Our main findings are as follows:(1)Based on a field survey of plant communities across different surface soil sediment types(i.e.,lacustrine sediments,fluvio-lacustrine sediments,and fluvial sediments)along the continental beach of Poyang Lake,we found that the primary distribution of vegetation included Phalaris arundinacea community,Carex cinerascens community,Carex cinerascens-Polygonum criopolitanum community,and Polygonum criopolitanum community.Our field survey revealed a significant correlation between sediment type and the distribution of wetland plant communities(χ~2=76.557,p<0.0001).Specifically,the Phalaris arundinacea and Carex cinerascens communities shifted into the Polygonum criopolitanum community from the lacustrine sediments to the fluvial sediments,and the community diversity exhibited a gradual decreasing trend.The RDA ranking results indicate that clay content,silt content in sediments and flooding duration are the main environmental factors driving the differences in wetland vegetation distribution on different sediment types.(2)Our experiment on the soil seed banks of Poyang Lake under different sediment and flooding duration treatments revealed that prolonged flooding significantly inhibited seed bank germination and species diversity(p<0.001).Under unflooded conditions,the number of germinating wetland plant species was higher on sediments with high sand content.Overall,the flooding duration had a stronger effect on germination of wetland soil seed bank than sediment type.(3)Our experiment on the growth of three typical wetland plants(i.e.,C.cinerascens,P.arundinacea,and P.criopolitanum)under different sediment and flooding duration treatments revealed significant interaction effects between flooding duration and sediments on the growth of wetland plants(p<0.001).Under flooding stress,the responses of wetland plant functional traits,including chlorophyll content,plant height,and number of leaves and ramets,showed specific adaptive patterns to flooding stress;different substrate types can exacerbate or alleviate the stress of flooding on the plants,further affecting their survival and growth status.The total biomass of the three plant species almost decreased with increasing sand content of the sediments for shorter flooding durations(p<0.05),while their total biomass was higher on sediments mixed with moderate sand content for longer flooding durations.(4)Our experiment on the interspecific competition between wetland plants showed that sediment type influences interspecific competition among wetland plants and further drives vegetation differentiation in wetlands.On sediments with low sand content,C.cinerascens and P.arundinacea showed strong competitiveness and gained a competitive advantage,while on sediments with high sand content,C.cinerascens and P.arundinacea were less competitive,and P.criopolitanum was more likely to gain a competitive growth advantage.In summary,this study examines the response mechanisms of wetland plants in Poyang Lake to sediment types and flooding duration.Results indicate that sediment types in affecting the wetland plant growth process(i.e.,growth adaptation and interspecific competition)under flooding conditions,driving vegetation differentiation in wetlands.It further provides a theoretical reference and countermeasure basis for strengthening the scientific management and sustainable development of wetlands.