Seedling populations from sea-borne seeds on drift debris in northern and western Kyushu, Japan

Abstract

Seedling populations from sea-borne seeds found on the coastal drift lines were studied in the context of sea current dispersal. The studies were done in northern and western Kyushu, Japan, where drift debris carried by the Tsushima Warm-current frequently washes ashore. Two thousand twelve seedlings comprising 47 species were found at 126 sites on 35 beaches in 10 regions. Not only maritime species, but also several inland species were commonly found. The most frequent seedlings was Tetragonia tetragonoides followed by Salsola komarovii. These two species comprised the drift plant communities. Most maritime species have sea-current dispersal seeds. Some inland herbaceous species such as Rumex japonicus and Polygonum senticosum of which seedlings were frequently found, also commonly grow on shingle beaches. Some inland woody species such as Cinnamomum camphora and Melia azedarach of which seedlings were also frequently observed, can not usually establish on beaches, but have a potential of sea-dispersal ability. Seedlings of tropical and subtropical plants such as Ipomoea pes-caprae and I. fimbrisepala were found far away from their propagation areas.