Development characteristics of aquatic plants in a constructed wetland for treating urban drinking water source at its initial operation stage

The development characteristics and improvement measures of aquatic plants were studied in Shijiuyang Constructed Wetland(SCW) at its initial operation stage.SCW was a large-scale wetland aiming to help relieve the source water pollution in Jiaxing City.A checklist of vascular plants in SCW was built,and species composition,life forms,biomass and association distributions were examined.Our objectives were to examine the diversity and community structure of aquatic plants in SCW at its initial operation stage,and to find out the possible hydrophyte improvement measures.The survey results showed that there were 49 vascular plant species belonging to 41 genera,25 families in SCW,which greatly exceeded the artificially transplanted 13 species.The life forms of present aquatic plants in SCW were dominated by hygrophilous plants(20 species) and emerged plants(17 species),which accounted for 75.5 % of the total number of aquatic plants.The aquatic plants transplanted artificially were dominated by emerged plants(accounted for 69.2 %),while those naturally developed were predominated by hygrophilous plants(accounted for 47.2 %).The horizontal distribution of aquatic plant community in SCW was mixed in the form of mosaics,which made up typical association complex.Except association Aeschynomene indica L.,the dominant species of other associations were all those transplanted artificially.The naturally grown species scattered throughout the SCW and only occupied a small percentage.A marked difference was detected on the species and species richness of aquatic plants in different regions of SCW.Biomass of aquatic plant associations in SCW was 167.7 t.SCW has shown a trend of succession heading for quick increase of plant diversity at the primary operation stage.This trend provides a good material base for the future stable community of aquatic plants in SCW.According to the current status of aquatic plants,some suggestions were put forward on the further optimization and utilization of aquatic plant systems in SCW.