Changes of flora and vegetation distribution in the artificial wetlands for 15 years after their construction
Artificial wetlands are planted with new wetland vegetation in order to perform the water purifying function of the hydrologic cycle. Succession in wetlands allows terrestrial plants to replace aquatic plants. The terrestrial plants settle and proliferate in wetlands due to the sediment, the soil organic matter, and the ground water reduction. This study was conducted to explore changes of the flora and vegetation distribution at different kinds of artificial wetlands for 15 years after their construction. The artificial wetland systems of total area of about 3,000 m2 were composed of kidney-shaped wetland, ecological water lane, ecological lake, and water purification wetlands. Flora surveys were conducted in October 1999 and May 2013.
The number of plants has increased from 68 species in 1999 to 93 species in 2013. The rate of obligate wetland plants and facultative wetland plants was 50% in 1999, whereas it has decreased by 10% in 2013. Annual and biennial herbs that are pioneer vegetation in successional stage have decreased; however, perennial herbs have increased as a result of long-term stabilization of vegetation. Dominant species in each wetland type were Typha angustifolia and Phragmites australis in the kidney-shaped wetland, Calamagrostis epigeios and Carex dimorpholepis in the ecological water lane, T. angustifolia and Nymphaea tetragona in the ecological lake, and Zizania latifolia and C. dispalata in the water purification wetlands. It is possible that water depth in the different wetland system affects vegetation distribution. In conclusion, this result suggests that the artificial wetland has experienced the terrestrialization of vegetation for 15 years.