Vegetation communities in estuarine tidal flats in the different river and basin environments of the four major rivers of Ise Bay (Suzuka, Tanaka, Kushida), Mie Prefecture, Japan

摘要

In this study, we compared and analysed vegetation communities in the estuarine tidal flats of the four major rivers of Ise Bay (Suzuka River, Tanaka River, Kushida River and Miya River) in Mie Prefecture, Japan. Along the Suzuka River, Eragrostis curvula of the exotic plant accounted for 60.0% or more of the entire surface area, and the plant volume was high. Along the Tanaka River, Suaeda maritima community occupied the sand-mud zone in the vicinity of the shoreline on gravel bars, while Phragmites australis community was distributed along a shallow lake upstream. In the Kushida River, a salt marsh plant community (a community type found in areas flooded at high tide) of Suaeda maritima, Phragmites australis and Artemisia fukudo was distributed on the sand-mud surface along the main river. A salt marsh plant community (a community type found in areas that do not flood at high tide) of Phacelurus latifolius accounted for least 50.0% of the entire surface area. Along the Miya River, the area covered by the annual salt marsh plant community type was larger than the area occupied by this community type along the other rivers. The flow volume of the Miya River was high in April, June and August-October of 2006, July and September of 2007 and April-June of 2008. The flow volume was especially high in July 2007, when it reached levels above 1500.0 m3/s; change in flow volume was also large. We suggest that a large-scale disturbance occurred in the estuary, resulting in the formation of a gravelly sandy surface where an annual salt marsh plant community of Suaeda maritime and Artemisia fukudo has been established and grown as the annual precipitation and catchment volume of the basin have increased.