EFFECTS OF A LARGE FLOOD ON SEED BANK AND SOIL PROPERTIES AT THE HAN RIVER FLOODPLAIN, SOUTH KOREA

초록

Flooding can have a major impact on riverside plant communities, which is likely to be especially important in monsoonal climates, where large floods occur after heavy rain. In urban areas, riparian vegetation remnants are the only remaining vegetation of conservation interest; understanding the impacts that floods have on such ecosystems is needed to inform their future conservation. Accordingly we assessed the impact of a flood caused by Typhoon “Ewiniar” on the soil seed bank of five plant communities in the only remaining fragment of high-quality riverine habitat within the Seoul city stretch of the Han River, South Korea. We surveyed the seed bank composition of the five dominant plant communities before and after the flood. We also measured selected soil physico-chemical properties in each community. We used uni- and multivariate methods to examine the effect of the flood on both seed bank and soil properties. Flooding resulted in variable deposition of sediment within and across plant communities; in four of them it ranged between 14.6 and 18.8 cm but the fifth (dominated by M. sacchariflorus) had much less (4.8 cm). The physico-chemical properties of the surface soil also changed after the flood, with the sediment particle size being most affected. The species richness and composition of the seed bank suffered significant changes after the flood. In soil properties and seed bank composition, there were a homogenization process, with was also reduced on seed number in different life forms (annuals and perennials). Our results suggest that an extreme flood can affect the riparian vegetation seed bank by removing wetland plant species and allowing common and ruderal species to establish. There may also be different interactions between the different plant communities in terms of sediment capture and this translates into altered soil conditions and seed banks. These results are of use to conservation policy-makers aiming to conserve a native flora within sever