Phytosociological studies on grassland vegetation in western Japan
The grassland vegetation in Kyushu and western Honshu, Japan, was studied phytosociologically. The major types are the tall-grass type dominated by Miscanthus sinensis and the short-grass type dominated by Zoysia japonica. These were recognized as alliances. Mowing, grazing and burning, either as a single factor, influences effectively preventing forest development and maintaining the grasslands. About 330 stand-samples of grassland communities collected at 54 localities were used in the present study to develop a comprehensive phytosociological system. The vegetation units were abstracted primarily on the basis of the distribution of plant species along the geographic gradient. The units were ranked at the association or equivalent level. A subdivisioning into units of lower rank was done also. The associations and the equivalents recognized, which belong to the two alliances, and their distributions can be summarized as follows. I. Miscanthion sinensis, the mowed grassland communities. 1. Themedo-Miscanthetum sinensis, low-elevation mowed community in northwestern Kyushu. 2. Arundinario-Miscanthetum sinensis, mid- and high-elevation mowed or lightly grazed community in central Kyushu. 3. (Arundinello-) Saussureo-Miscanthetum sinensis, mid- and high-elevation mowed or lightly grazed community in western Honshu. 4. Rhododendron kiusianum-Miscanthus sinensis community, a shrub-rich community in Unzen area, western Kyushu. II. Zoysion japonicae, the grazed grassland communities. 5. Centello-Zoysietum japonicae, coastal and low-elevation grazed community in Kyushu and in westernmost parts of Honshu. 6. Geranio-Zoysietum japonicae, mid- and high-elevation grazed community of Kyushu and western Honshu, and further north. 7. Angelica longiradiata-Zoysia japonica community, a grazed community on specialized habitats influenced by constant volcanic ash fall out from the active cone of the Aso volcano, central Kyushu. It occurs mostly on the central cones and partly on the caldera slopes. The present results were compared with results of a previous ecological gradient analysis of the grasslands in western Honshu. The two different approaches gave very similar results.