Abstract
Investigation was conducted on relationship between vegetation of floodplain mire and fluctuation of water level, in order to clarify specific water level fluctuation and appropriate indices relating to their distribution. Water level was recorded every one hour from May to October in 2002 at an alder forest of back swamp, a fen of back swamp and a riparian herbaceous stands on natural levee at Kushiro mire in Hokkaido. Frequency and amplitude of water level fluctuations and seasonal water level were analysed for each vegetation site. Results showed that the water level of the riparian herbaceous stands changed frequently with high amplitude, and that of the fen was high from spring to summer compared to the alder forest. The water level of the fen and that of the alder forest showed similar fluctuation pattern in frequency and amplitude. Standard deviation of water level had high correlation with frequency, amplitude and seasonal water level, indicating that it was not appropriate index to characterize the water regime among vegetations. There were significant correlation between frequency and amplitude of water level, but seasonal water level was independent to them. In conclusion, we suggest that the indices independently representing amplitude and seasonal difference were effective even though measurement of water table was once a week or a month.
