Distribution of plant communities in relation to hydrological condition of Furen mire, northern Japan.

通过研究植物群落的分布与水文和化学变量的关系，研究了混合沼泽的形成机理，该沼泽是一个微营养沼泽，具有许多泥炭泥的营养沼泽。我们研究的区域是1400米宽的湿地，分布在一个非常缓缓的斜坡上，从山边向下一直延伸到辅仁河。混合沼泽与200 m宽的山体边缘相邻，微营养沼泽分布较低，水量平衡分析表明，混合沼泽内地表水在每次降雨后即开始流出，而地表水在短时间内停止流出，维持在一个稳定的水位。当水位上升到湿地表面以上2 cm以上时，浅水池和孤立水池中的水变成一个整体，沿着缓坡向下流动。在1998-1999年水位最高的时候，洪水河水指示着水的化学成分、高EC和大量的矿物质和营养物质，流入了下游的沼泽区。然而，混合沼泽地区没有洪水中的矿物质和营养物质供应。然而，混合沼泽中的水也显示出很高的EC值，因为富含矿物质的水是通过上述径流机制从山上的牧场提供给混合沼泽的。由于混合沼泽中的沼泽比湿地表面高出50 cm或以上，地下稳定的地下水位不会将矿物质和营养物质带到沼泽的中上部。因此，生长在微营养水体上的沼泽可以保持恒定水位下的营养状态。

We studied the mechanism of the establishment of the mixed mire, which is a minerotrophic fen with many ombrotrophic hummocks of Sphagnum fuscum by examining the distribution of plant communities in relation of hydrological and chemical variables. The area we studied was 1400 m wide wetland distributed on a extremely gentle slope going downward from a hill margin to Furen river. The mixed mire was adjacent to a margin of the hill with 200 m wide, and the minetrophic fen was distributed in a lower part.Analysis of water budget showed that surface water in the mixed mire began to flow out just after each rainfall whereas surface water flowing stopped within a short period, maintaining in a stable water level. When the water level increases to more than 2 cm above a wetland surface, waters in shallow and isolated pools become to connect into one and flow downward along a gentle slope.At the time of the highest water level within 1998 to 1999, the flooding river-water indicating water chemistries, high EC and much minerals and nutrients, flowed into the fen area of the lower part. The area of the mixed mire, however, was free from the supply of minerals and nutrients in flooding water. Water in the mixed mire, however, also showed high EC value because mineral-rich water was supplied from pasturage lands on the hill into the mixed mire through the run-off mechanism before mentioned. As a result, both ends of the wetland area keep higher EC values than middle part.Since hummocks in the mixed mire are 50 cm or more higher than the wetland surface, an underlying stable water table does not carry minerals and nutrients into middle to upper part of hummocks. Accordingly, hummocks growing on the minerotrophic water can keep the ombrotrophic condition as it is under the constant water level.