Present status and changes over the past 38 years in marsh vegetation in Yonaguni Island

Abstract

This study performs to survey present marsh vegetation in Yonaguni island, Okinawa, Japan.　Over 38 years, the change of the vegetation has been reported.　In this study, twelve types of plant communities are identified, however, five of them were not reported in previous studies.　Also, most of survey plots, which are classified as newly found five communities, appears in abandoned paddy fields or reclaimed meadows from paddy fields.　Regarding exotic species, nine species are reported.　Out of nine, two species, Urochloa mutica and Symphyotrichum subulatum var. subulatum, are the first to appear in this study, and other two, Paspalum distichum and Alternanthera sessilis, shows the increase number of appearance compared to the previous studies.　Additionally, the land use maps reveal that the total area of the paddy fields have decreased by 68% from 1976 to 2014.　Some of the former paddy fields have marsh vegetation.　Large part of marshes in this island are composed of these secondary marshes.　This indicated that the former paddy fields could be important habitats for both native and exotic marsh species.