PS 2-20
Early-successional changes of riparian vegetation after low-head dam constructions in large rivers, South Korea
In the last years the four large rivers of South Korea have been modified by low-head dams, as a consequence riparian ecosystems had been greatly altered. Low-head dams can modify the structure of riparian vegetation through governing the timing and magnitude of flows and obstruct dispersal of seeds from seed sources upstream due to reduced flow. Moreover, improper low-head dam construction can be a major disturbance in the riparian ecosystem. Following low-head dam construction, monitoring of the changes in downstream and floodplain vegetation is important for river management. The aim of this study was to monitor early-successional changes of riparian vegetation after low-head dam construction. In summer of 2013, we surveyed flora and plant community structure from the bank slope to channel margin at Han River, Geum River, Nakdong River and Yeongsan River. In each low-head dam, we selected five different areas; a downstream 500 m, a downstream 1500 m, an upstream 500 m, an upstream 1500 m from the low-head dam and a tributary to the main river and examined various environmental factors such as floodplain slope degrees, floodplain width, height above water level, soil texture and stream width.
Results/Conclusions
The total numbers of plant species were 69 at Gangcheon low-head dam of Han River, 54 at Gongju low-head dam of Geum River, 84 at Gumi low-head dam of Nakdong River and 65 at Seungchon low-head dam of Yeongsan River. A result of DCA indicated that Gangcheon low-head dam was related with soil texture and Gongju low-head dam was related with slope degrees. Gumi low-head dam was the largest among four low-head dams and floodplain was so long that it was affected by floodplain width. At Seungchon low-head dam less disturbed, various hydrophytes and hygrophytes were established and maintained. Herbaceous flowers for landscape of the park were planted on the bank slopes and Salix spp. were established in the relatively low-gradient floodplain flooded frequently. Most of floodplains were often dominated by pioneer species, especially annual herbs, and bare sites were dominated by alien species. Submerged macrophytes such as Potamogeton crispus, Myriophyllum spicatum were established at low current velocities. This study provides baseline data on early-successional changes of riparian vegetation after low-head dam constructions and stream works. It is necessary to survey and monitor the succession of riparian vegetation near the riparian ecosystem of the constructed low-head dams.