Base mineral inflow in a remnant cool-temperate mire ecosystem

Kiushitou (42°28N, 141°9E) is a lowland mire located in a residential area of northern Japan. We examined the 2-D distribution of hydrochemical variables and their seasonal changes in relation to plant communities in an attempt to conserve the Sphagnum fen (Sphagnum subfulvum). This mire is gently sloping and the upper area consists of alder and ash forests, while the lower area is covered with fen communities. The grassy fen, Moliniopsis japonica, occurs throughout the lower area, whereas the Sphagnum fen is restricted to the southwest part of the mire. anova and canonical correspondence analysis revealed that the occurrence of Sphagnum fen is negatively correlated with Mg, Ca and electrical conductivity (EC). These variables indicated that water in the upper forest area contained a high concentration of minerals from the neighboring residential area. Seasonal changes in EC values revealed that the watercourse from a spring point in an upper corner to the lowest drainage ditch was divided into two, southwest and northeast, courses. Because the northeast-course spring water joins mineral-rich water flowing from a point at the upper margin, the northeast part of the lower area contains considerable Ca and Mg. In contrast, the mineral-poor spring water flowing into the southwest part of the mire ensures the survival of the Sphagnum fen. Thus, when we stop the supply of mineral-rich water from the upper margin the area of the Sphagnum fen will expand into the northeast part of the mire. Two-dimensional details of the hydrochemical regime clarify the impact of mineral inflow and the expansion mechanisms of these minerals.