[Ecological Quality Assessment of the Wetlands in Beijing: Based on Plant Diversity]

Wetland plant diversity reveals key aspects of the environmental and ecological status of wetlands and plays an important role in the maintenance of ecosystem functions and services. The present study surveyed the plant species diversity of 22 wetlands in Beijing and, combining field data and remote sensing data, evaluated ecological qualities of the wetlands based on indicators of habitat status, plant species diversity, typical wetland plant community, and status of alien plant invasion. A total of 338 species (including varieties and subspecies) belonging to 220 genera of 74 families of wetland plants were recorded in Beijing. The wetlands could be divided into four types according to plant species composition, which showed a spatial gradient pattern from urban core to ecological conservation areas. Wetlands located in ecological conservation areas were of better ecological quality than those located in urban core and suburban plain areas. The value of ecological quality index (EQI) for Baihe River, Huaishahe-Huaijiuhe River, Jinniu Lake, Hanshiqiao Wetland, and Yongdinghe River (Mentougou Section) were in the top five, whereas the value of EQI for river-type wetlands located in suburban plain areas were relatively lower. The results of the canonical correspondence analysis indicated that the most critical factors affecting wetland plant species composition were the distance to the nearest road, water total nitrogen, and area percentage of ecological green land. Furthermore, the results of the canonical correlation analysis indicated that the most critical factors affecting wetland plant species diversity were the area percentage of construction land and water total organic carbon. Human activity intensity and water quality have a strong impact on the plant diversity and ecological quality of wetlands in Beijing. It is suggested that efforts should be made to strengthen the ecological protection and restoration of the river-type wetlands located in suburban plain areas.