Abstract
In Hokkaido, we still have many mire fields where specific plants grow. They aregradually disappearing by human activities. We researched the quality of ground water in the mire and studied the water cultivation system that maintains the mire under the natural condition at Sarobetsu Mire. The results are summerized as follows;
(1) The ground water quality of rised bog (located at center of Sarobetsu Mire) is in a unique circumstance, with high concentration of organic matters composed of humic-acid and with low pH, 4.8 on the average.
(2) In the ground water of the upper layer of the raised bog, the concentration of the common inorganic components is low and the composition is similar to rain water. It is absolutely necessary to recharge the ground water by rain water to maintain the natural mire.
(3) In the region of raised bog (Sphgnum moss area), the decomposition activity is extremely low as the concentration of nutrients is low and the organic nutrients are dominant.
(4) While nutrient state of the high water level region of the Sarobetsu Mire is oligotrophic, that of the low ground water level region is eutrophic where inorganic form of nitrogen is dominant.
(5) In the region where bamboo grass invades, the concentration of organic matters and that of dissolved nitrogen (especially inorganic nitrogen) have a positive relationship. Nutrients are in a state liable to dissolve by the bacterial decompositon under the low level of ground water.
(6) Where bamboo grass invades, the concentration of Silicate increases. Influences of geological features should not be disregarded.
