Ecological characteristics of Imperata cylindrica var. koenigii in Kuju-Aso area, Kyushu [Japan]

In order to know the factors and condition which make Imperata cylindrica var. koenigii dominant in vegetation, the ecological characteristics of Imperata in Kuju-Aso area, Kyushu Island were investigated in relation to typical types of seminatural grassland, Miscanthus sinensis and Pleioblastus chino var. viridis. Eleven sites with rather high coverage of Imperata were selected and examined the floristic composition and Imperata growth. From the floristic composition, the studied stands bacically belonged to Miscanthus = Pleioblastus type of vegetation grouped by Suzuki and Abe (1959) in Kuju-Aso area. Similarity of stands and ordination of the stands revealed that Imperata dominant vegetation located in transient phase from Miscanthus grassland in mowed habitats to Pleioblastus grassland in continuously grazed habitat and vice versa. This suggests that Imperata dominant vegetation might be formed and maintained under more than once a year of cutting and lighter grazing condition