Abstract
Several small oligotrophic wetlands formed by seepage water (spring-fed wetlands) are found in hill lands in Japan. This paper discusses the relationships among the vegetation, topography, and sediments in these spring-fed wetlands based on investigation of eight study sites in the Owari Hills and Chita Hills, central Japan. The investigated wetlands were classified into two types (valley-floor type and hillside-slope type) on the basis of the topography off their locations. The study also examined the distribution of the sediment thickness and vegetation in belt transects set in each study site. The sediment was thick in the valley-floor type and thin in the hillside-slope type. Moliniopsis japonica dominated in the valley-floor type, while Rhynchospora species dominated in the hillside-slope type. However, there were some small, thick parts of sediment like round mounds found on hillside-slope type, and M. japonica dominated there. These results suggest that vegetation distribution is closely related to sediment thickness in spring-fed wetlands, and topography affects vegetation distribution indirectly through the control of the sediment thickness. Moreover, it was recognized that many types of sediment existed, forming layers in these spring-fed wetlands.
