TITLE:
Vegetation Formation in Estuarine Tidal Flats: Influences of Basin Scale and River-Crossing Structures of the Eight Rivers of Ise Bay in Mie and Aichi Prefectures, Japan
AUTHORS:
Korehisa Kaneko, Seiich Nohara
KEYWORDS:
Annual Salt Marsh Plant, Perennial Salt Marsh Plant, River-Crossing Structure, Water Level, River Basin
JOURNAL NAME:
Open Journal of Ecology,
Vol.4 No.15,
November
28,
2014
ABSTRACT: In this study, we examined the influences of the differences in basin
scale and river-crossing structures of 8 rivers of Ise Bay in Mie and Aichi Prefectures,
Japan on the vegetation in the estuarine tidal flats of these rivers. The
dominant plant communities of the estuarine tidal flats formed from rivers of large-scale
river basins (exceeding 300 km2) were determined. In the Miya River,
the dominant plant community was the Suaeda
maritima and Artemisia fukudo community. In the Kushida River, the dominant plant community was composed of Phacelurus latifolius, Artemisia fukudo, Phragmites australis, and bamboo. In the Kumozu River, the dominant
community was composed of the coastal plants Calystegia soldanella, Lathyrus
japonicus, and Carex pumila and the exotic plant of Lolium multiflorum. The plant community
of Suzuka River was dominated by the exotic plant of Eragrostis curvula. Among the estuarine tidal flats influenced by a
small-scale river basin (50 km2 or less), the plant community of Shinbori
River (Fukue tidal flat) was dominated by Suaeda
maritima, and the plant communities of the Shio and Harai Rivers were
dominated by Phragmites australis. The
plant community of Tanaka River was dominated by Phragmites australis and coastal plants. Regarding the relationship
between the vegetation and the river environment for each study site, we
hypothesised that in a large basin area with few structures crossing the river,
the river water catchment in the estuary after heavy rains caused large areas
of disturbance and formed bare land, providing suitable habitat for an annual
salt marsh plant community. In contrast, in cases with many structures crossing
the river, a stable channel, an excavated riverbed and the suppression of
runoff and the resulting disturbance of the estuary, flooding did not occur
during high tide. Moreover, we hypothesised that in a small basin with many
structures crossing the river, disturbance to the estuary was not likely, and
the perennial salt marsh plant community of Phragmites
australis would be widely distributed, except for a river type such as the Shinbori
River, in which tide and river flow were managed by a final closure.