Plant Diversity And Water Environment Status Of Constructed Wetland In The West Lake Of Hangzhou

In the last few years, a series of constructed wetlands as the Maojiabu Scenic area have been built in Hangzhou city, which played an important role in the reconstruction of wetland ecosystem and the abundance with wetland plants, as well as the improvement and protection of its water quality around the West Lake. As an example of modern constructed wetland park, the Eco-park of Long Bridge Stream in Hangzhou confirmed the possibility of the combination of ecological recovery and water landscape design.As the typical constructed wetlands in Hangzhou city, the Maojiabu scenic area and the Eco-park of Long Bridge Stream were selected as the investigated cases. The paper made a systematic survey and discussion about the plant diversity, water quality and the combination of ecological recovery and water landscape design, which was based on a field investigation for more than two years. Furthermore, this paper put forward several suggestions with the protection of the plant diversity and plant preformance. The results were summarized as follows:1. Based on the filed survey of plant status in the Maojiabu scenic area during March to July in 2006, the results showed that total plants were 292 species which concerned to 222 genera and 105 families. There were 116 species of trees and shrubs, belonging to 84 genera and 52 families. Total herbaceous plants were 176 species which concerned to 138 genera and 61 families, involving 72 species of aquatic plants refer to 53 genera and 30 families. Regarding the percentage of wild species with the cultural or native species, the composition of herbaceous plants was analyzed.2. Wild wetland plants accounted for high proportion of flora in the Maojiabu scenic area, and showed good ornamental characteristics. Based on the plant diversity investigation in Maojiabu scenic area, several species of wild wetland plants such as Oenanthe javanica and Hydrocotyle sibthorpioides were introduced. The configuration, living environment, ornamental characteristics, as well as the potential use in the wetland landscape were discussed. 6 species perennials such as Sagittaria sagittifolia and Colocasia antiquorum showed rampantly growth and potential invasion. 6 species plants such as Ludwigia peploides and Alternanthera philoxeroides showed non-acclimation for plant growth and landscaping.3. Water quality of Maojiabu scenic area was evaluated by the results of monthly water quality monitoring in three months of eight cross sections by single factor index and synthetic pollution index. The conclusions were as following:(a) Water quality of the scenic area reached IV which completely meet the request of V in the general landscape area according to the standard of ((The earth's surface water environment quality standard)) (GB3838-2002); (b) Form November in 2006 to January in 2007, the water temperature degree descended gradually while DO, TN and NO₃^--N totally enlarged ; (c) The temperature and DO of the river and lake water were higher than that of the pond water. The pond water had the biggest degree of EC, COD_Mn and BOD₅ while the lake water had the lowest muddy degree ; (d) It didn't express an obvious relativity with the function of aquatic plants and the water quality.4.With the case study of planning and constructing of Eco-park of Long Bridge Stream in Hangzhou, the paper analyzed the natural design of recover ecological system of water environment, as well as the planting design with aquatic plants. Concerned the valuable ecosystem and performance, the combination of ecological recovery and water landscape design was discussed. Further more, the exist problems and suggestions for the eco-park were also indicated.5. Through long-term investigation, this paper put forward that the establishment and protection of the plant diversity should be continually paid attention to during the constructing and management of the constructed wetland park in the furture, as well as the monitor and forecast to the variation tendency and the constructing of indigenous plant landscape in wetland. The protection of the water environment should be concerned about, as well as combination of the ecological recovery and water landscape design.