Xixi National Wetland Park Wetland Aquatic Vegetation Characteristics And Its Relationship With The Water Environment

Urban wetland park is a rising model which is effective to protect and utilize wetland in China in recent years. Wetland vegetation is an important part of wetland parks, it not only has important ornamental function and aesthetic value, but also has important implication to maintain the water quality. Xixi National Wetland Park in this paper as an example, comprehensive utilization of field investigation, laboratory analysis, remote sensing, GIS techniques and statistical analysis, systemic revealed that the aquatic vegetation features and the relationship between it and the water environment, to guide future urban wetland park planning and construction and management to provide a scientific basis. The results showed that:(1) The aquatic plants in Xixi Wetland Park were variety, diversity obvious. The survey results showed that there were 22 species of aquatic plants in Xixi Wetland Park belonging to 16 families and 21 genera. The dominant species of aquatic vegetation in Xixi Wetland Park, which were Zizania latifolia, Phragmites australis, Arundo donax, Nelumbo nucifera, Alternanthera philoxeroides, Typha orientalis, Pontederia cordata, Thalia dealbata etc. Alternanthera philoxeroides because of its strong growth and reproduction and resistance, it was the main aquatic weed.(2) The aquatic vegetation in Xixi Wetland Park was various. The Two-way Indicator Species Analysis results showed that, the aquatic plant communities could be divided into 10 types in Xixi Wetland Park. They were Ass. Pontederia cordata, Ass. Arundo donax+ Eichhornia crassipes+Alternanthera philoxeroides, Ass. Alternanthera philoxeroides+ Salvinia natans, Ass. Alternanthera philoxeroides, Ass. Thalia dealbata+Alternanthera philoxeroides, Ass. Thalia dealbata+Zizania latifolia+Alternanthera philoxeroides, Ass. Phragmites australis+Typha orientalis+Alternanthera philoxeroides, Ass. Phragmites australis+Typha orientalis+Nelumbo nucifera, Ass. Zizania latifolia+Typha orientalis +Lemna minor, Ass. Thalia dealbata+Nelumbo nucifera. Among them, the first 8 types were the common types of aqutic plant communities in Xixi Wetland Park.(3) In different aquatic vegetation conditions, the water quality seasonally fluctuated. SD was volatile in the ponds with vegetation, usually came to maximum in winter or spring; DO did not change significantly in the ponds without vegetation, but significantly in ponds with vegetation, it was higher in winter or spring on most vegetation types; CODMn, TN, TP, NH3-N, Chla had no significant seasonal fluctuations in law in the different aquatic vegetation conditions. Judging from the whole year, the ponds which had aquatic vegetation could maintain a better state with water environment compared with those without. In the different aquatic vegetation types, Ass. Phragmites australis+Typha orientalis+Nelumbo nucifera, Ass. Thalia dealbata+Zizania latifolia+Alternanthera philoxeroides, Ass. Alternanthera philoxeroides could maintain relative good state with water environment compared to the other types. The Principal Component Analysis results showed that Nutrient Salts Factor (NS), Dissolved Material Factor (DM) and General Indicator Factor (GI) were the 3 principal components which affected the water environment.(4) The different aquatic plant communities had different responses to different water environment factors. The Canonical Correspondence Analysis results showed that, CODMn, TN, TP, Cond, SD and DO were the 6 main water environment factors which affected the water environment. Ass. Pontederia cordata, Ass. Arundo donax+Eichhornia crassipes+Alternanthera philoxeroides and Ass. Alternanthera philoxeroides+Salvinia natans were weak to reduce N and P nutrients, meanwhile in the environment where they growed the DO was lower than others, so they were not conducive to improve water quality; Ass. Phragmites australis+Typha orientalis+Nelumbo nucifera, Ass. Thalia dealbata+Zizania latifolia+Alternanthera philoxeroides and Ass. Thalia dealbata+ Alternanthera philoxeroides were beneficial to reduce N and P nutrients, meanwhile in the environment where they growed the DO, SD were heigher than others, this showed that they could maintain relatively good condition with the water environment.Considering the aesthetic and view function of wetland plants and its interaction with water environment and other factors, when planning and management aquatic vegetation in the future, local species should be selected first to increase species richness, select the appropriate type of combinations, such as Ass. Phragmites australis+Typha orientalis+ Nelumbo nucifera, Ass. Thalia dealbata+Zizania latifolia+Alternanthera philoxeroides and so on.