Effects of nutrient loadings from catchments on Asajino mire, a small coastal ombrotrophic mire in northernmost Japan

The relationship between water chemistry and vegetation was studied in a co astal ombrotrophic mire in northern Hokkaido, Japan. The distributions of S phagnum and Phragmites communities were separated clearly by the pH and ion concentration of the peat surface-pore water. The drainage ditches along t he road across the center of the mire had a high pH and ion concentration, as did the peat water in the western part of the mire. It was found that fi elds used for livestock farming on a hill to the west of the mire leached m aterials into the mire through drainage ditches, surface runoff, and probab ly also through ground water, and thus influenced the water chemistry of th e mire. Management of the water, including that in the catchment of the mir e, should be introduced before biological buffering capacity against excess nutrient loading caused by human activity is exceeded and the mire loses i ts ombrotrophic status.