チガヤ-ヒメジョオン群集の特性

抄録

Imperata cylindrica type grassland on embankment slopes, levee slopes and reclaimed land etc. was studied phytosociologically. The results show that this grassland was recognized as a new association (Erigeronto-Imperatetum cylindricae) characterized by the presence of Erigeron annuus, Rumex acetosa, Solidago altissima etc. and the absence of many character and differential species of Miscanthetea sinensis, Haloragis micrantha, Gentiana scabra var. buergeri, Potentilla freyniana etc. Its geographical distribution in Japan was from Tohoku to Kyushu district. Semi-natural grasslands in Japan are represented by two typical grasslands ; one is mowing grassland dominated by Miscanthus sinensis, the other is grazing grassland dominated by Zoysia japonica. This association is a new type of grassland (weeding grassland dominated by Imperata cylindrica) maintained by two or three weedings per year. The distinguishing factors which differentiate this association from Miscanthus-Zoysia type associations occur in the life-form spectrum, the phytosociological spectrum and naturalized plants ratio, as well as the floristic composition. The association was divided into two seasonal lower units, spring aspect and autumn aspect, and belongs to Miscanthetea sinensis, Caricetalia nervatae and Zoysion japonicae. Furthermore, Erigeronto-Imperaterum cylindricae on levee slopes in Sanda, Hyogo Pref. was divided into two lower units : one is Adenophora triphylla var. japonica lower unit characterized by the presence of Adenophora triphylla var. japonica, Cirsium japonicum, Sanguisorba officinalis etc. ; the other is typical lower unit characterized by the absence of these species. The former unit is distributed on levee slopes with no consolidation and the latter unit is on levee slopes with consolidation.