Monitoring of environmental properties associated with maintenance of small irrigation ponds for conservation of endangered submerged plants: A case of ponds in Nakatado region, Kagawa prefecture [Japan]
2006
Mineta, T.(National Inst. for Rural Engineering, Tsukuba, Ibaraki (Japan)) | Ishida, K. | Hirose, Y.
Irrigation ponds have contributed to preserve bio-diversity in rural environment as habitat for many organism including endangered aquatic plants. Although existence of aquatic plants is particularly important to conserve biodiversity of irrigation ponds, recently these species have tendency to decrease. Furthermore, especially disuse of small irrigation ponds by increase of cultivation abandonment or change of irrigation system has accelerated disappearance of habitat of aquatic plants. It is important to analyze population dynamics and environmental properties of submerged plants for conservation bio-diversity of irrigation ponds. It is considered that the submerged plant responds for slightly environmental changes sensitively. Therefore we attempted to explain environmental properties of some endangered submerged plants associated with maintenance of several irrigation ponds in Nakatado region, Kagawa Prefecture. The frequency of appearance of the endangered submerged plant was high in a small irrigation pond less than 2,000 m3 storage capacity. Therefore we monitored population of Blxa aubertii and Ottelia japonica, which are belong Hydrocharitaceae of endangered submerged plants, and observation of water quality, lights condition and change of fluctuation pattern in water level associated with management of some irrigation ponds. As a result, it was shown that moderate degree of aquatic plant cutting, dry maintenance and regular water use provide for suitable lights condition and water quality for growths of submerged plants. In addition, it was considered that excessive disturbance against endangered submerged plants and abandonment of management applied instability or negative impacts on growth environment of these species.
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