Responses of Riparian Vegetation to Flooding Disturbance in the Stream Cheongmi, Korea

초록

This study compared soil seed bank, vegetation map, transect, vegetation structure and plant morphology before and after flooding in Cheongmi Stream, a sand stream, in order to investigate responses of riparian vegetation against flooding disturbance. We conducted seedling emergence trials for five months after collecting soils in 0 to 5 cm depth from dominant vegetations of the study site in March 2003. In this experiment, annual or biannual ruderal plants were mainly germinated. Sorensen coefficients of soil seed bank and existing vegetation for each community were as low as 50%. In particular, existing dominant perennial plants of vegetations, including Artemisia selengensis, Miscanthus sacchariflorus, Phragmites japonica and Phalaris arundinacea, were not found in soil seed bank. The number of seedlings germinated from the clear-cutting site of Phragmites japonica, where more incident light was supplied, increased compared with the vegetated control site. It was believed that removal of aboveground shoots of plants due to various disturbances could trigger germinations of some ruderal plants from soil seed bank. Landform around channel was remarkably changed due to flooding disturbance in the sand stream, Cheongmi Stream. Erosion and deposit particularly provided new habitats to riparian vegetation such as Phragmites japonica and Rorippa islandica. As water supply increased due to flooding, Persicaria thunbergii community also increased in low landform adjacent to stream water. Miscanthus sacchariflorus with strong stem survived flooding disturbance, and had wider distribution area. Humulus japonicus invaded above Phragmites japonica community fallen by flooding disturbance. Major riparian vegetations in Cheongmi Stream were quickly restored and sustained after flooding disturbance, giving little changes to community structure.