Evaluation On Wetland Characteristics In Nanjishan And Environment Factors On The Growth Of Vallisneria Natans

Poyang Lake,an important lake with the function of regulation and storage in theYangtze River basin,Submerged macrophytes are an important components in wetlandecosystems,the disappearance of submerged macrophytes would lead to deterioration ofwetland ecosystems. The nutrient levels substrate is the one of the most factors of in anumber of abiotic of submerged vegetation to the growth and reproduction. This study wasbased on Nanjishan wetlands nature reserve to evaluate their characteristics from theNutrient pollution and the pollution of heavy metal;choosing Vallisneria natans L.Hara,base on different N concentration、P concentration、depth by a serial of laboratorialexperiment to illuminate the characteristics of substrate and respond of morphologicalindex and physiological index. Major conclusions were described as follow:(1)Based on comprehensive pollution index and organic index, the pollution of threelakes spatial distribution trend were:Nansheng Lake>East Lake>Chang Lake.The threelakes all have on organic pollution environmental qualities of sediments in the wholelakeside zones still belonged to clean category.(2)The accumulated degree and the potential ecological risk of heavy metals of thesediment quality in Nanjishan situation was at medium-concentration level and lowpotential ecological risk level and Cd is the primary ecological risk factors．The resultsshowed that the heavy metals in the surface sediment of Nanjishan had homogeneity，andthe pollution degree of the heavy metals followed the order ofCd>As>Pb>Cr>Cu>Zn>Ni.(3)Basing on the respond of morphological index under different total nitrogenconcentration（4、8、16mg/L）,the conclusions are:Vallisneria natans can grow well in4mg/L-8mg/L nitrogen concentration,that nitrogen concentrations indicating nitrogenconcentration oxidative stress to the plant without oxidative damage，the morphologicalindexes were in high growth;under16mg/L or0mg/L nitrogen concentration enzymedefensing system collapsed,and made Vallisneria natans dead,and non nitrogenconcentration is more damage to it.(4)Under different total phosphorus concentration（0.05、0.1、0.5mg/L）aboratorialexperiment,we know the stress of Vallisneria natans is not obvious under0.05-0.1mg/Lphosphorus concentration, the morphological indexes were in high growth with nosignificant difference.Under0.5mg/L phosphorus concentration Vallisneria natans endurebig stress but cell system not compromised; but Vallisneria natans degeneration in thecondition of non phosphorus concentration.(5)Under different water depth condition(35cm、75cm、105cm)， Vallisneria natansneed a suitable depth environment and they grow best in the depth of105cm.(6)Under the experimental conditions,Vallisneria natans grow well under the conditions of4-8mg/L total nitrogen concentration,0.1mg/L total phosphorus concentrationand75cm-105cm depth，the biomass and height and he tiller numbers of plant were thebest.