The Effect of Boundary Ridge Structures and Grass-cutting on Plant Communities Around Terraced Paddy Field

27 Mar The Effect of Boundary Ridge Structures and Grass-cutting on Plant Communities Around Terraced Paddy Field

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Abstract

棚田畦畔がもつ草地性植物の生育地としての機能を把握するため, 徳島県上勝町樫原地区において, 次のようなことを明らかにした。当地では, 全水田面積に対する畦畔面積の割合は29.4%であり, 水田に付随する草地の面積は大きい。植物群落は, 畦畔の物理的な構造に対応して異なっており, 土や石垣等の様々な物理環境の畦畔があることにより, 地域内の植物の多様性が高められている。畦畔における年間の草刈り回数の違いは植生高や遷移度に影響を与え, 刈取り回数が多いほど (最大3回), それらが低く保たれた。一方, 草刈り回数の違いは, 植物群落の種組成や多様度には大きな影響は及ぼさなかった。出現種数や多様度は草刈りが行われないまま2年間放置された畦畔でも変わらず維持されていたが, 5年間放置されると極端に減少していた。

English Abstract

The purpose of the study is to understand the ecological function of levees around terraced paddy fields, in terms of the habitat for grassland plants. Followings were clarified at Kashihara in Kamikatsu town, Shikoku, Japan. Wide levee has been kept incidental to paddy ma gement, and it provides the habitat to grassland species; the ratio of levee area against paddy field area is 29.4%. Several types of plant community occur in correspond with physical conditions of the levee surface, such as humidity, whether the surface is covered by soil or rock. The difference in the frequency of grass-cutting ma gement at the levee causes the differences in vegetation height and the degree of succession. While species richness and the diversity are not affected by ma gement frequency. When the grass-cutting ma gement is stopped, species richness and the diversity are kept during the following 2 years, but tend to decrease after 5 years. It seems that environmental heterogeneity of levees and continuous grass-cutting ma gement must be maintained to sustain plant species diversity