Conservation of Water Environment and Vegetation in Mire

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This study is to estimate the influences of human activities to ground water quality and vegetation of mire, such as changes of water cultivation system and to propose the conservation system of mire. We chose Sarobetsu Mire and Kiritappu Mire, typical. mire of Hokkaido as subjects of the study. We surveyed Sarobetsu 7 times and Kiritappu 6 tomes from 1997 to 1998. Vegetation of Sarobetsu Mire has been destroyed .by draining and building farmland after World War II, and the rest of mire is in peril of existence by invasion of Sasa. Kritappu Mire is changing in similar course of development as Sarobetsu Mire. We researched water quality of ground water, rivers and lakes of the mire and surrounding area, soil composition and growing state of Sphagnum and Sasa. According to the data, we found that human activities affects life of mire. We found that by draining water from mire, ground water level lowers and peat soil gets dry, concentration of nutrients arises by decomposition of peat soil, and mixing soil by exploitation increases amount of phosphorus and silicic acid. The change of composition seems to influence the growing state of plants. In Sarobetsu Mire, drainage leads Sasa to invade causing increase of inorganic nutrients as peat soil decomposes, and promote Sasa to grow. It is necessary to check matters to invade from outside of mire in order to restrain heterogeneous plants as Sasa as a typical one to get into mire.