The purpose of this study was to examine the patterns in vegetation diversity as they relate to changes in soil moisture, groundwater elevation, and other parameters along the Sunaji River located in Minamikomatsu, Otsu City, Shiga Prefecture.

To determine the facultative vegetation of the wetland representing different vegetation types along an elevation gradient, four 50-meter-long transects were set up in the study area. On each transect, vegetation surveys using the belt transect method were completed, with a 2x2 meter quadrat placed every two meters, within which species presence and absence data were recorded, including the measurement of groundwater and soil moisture.

Using this data, plants were separated into Types A, B and C, suited to “wet”, “variable”, or “dry” soil moisture conditions respectively. Furthermore, the distribution of Type B plants (including Microstegium vimineum and Euphorbia adenochlora) was found to be controlled by changes in groundwater level, while the distribution of Type A plants (including Phragmites australis) was found to be controlled by changes in soil moisture. This study will help to inform future wetland management in human-influenced environments.