Although semi-natural grassland has dramatically decreased in Japan, semi-natural grasslands containing rare species and high diversity are maintained by burning in Shiozuka plateau, Tokushima prefecture.

We investigated from 89 semi-natural and artificial grassland vegetation plots (each 1m square) in this area. Based on plant species composition, three vegetation types were categorized according to statistic analyses, TWINSPAN (Hill 1971) and INSPAN (Dufrene 1997). Gr1 had high species diversity and was plant community dominated by the native species. Gr2 had middle species diversity and was plant community including alien plants. Gr3 was invaded by alien plants. Gr1 could be resistant to the invasion by alien plants. The occurrence of the vegetation types corresponded well with the soil chemical properties, especially with soil acidity (soil pH) and plant-available soil P level. We clarified that the species composition, species richness (number of native plant species), species diversity (H’) had strong relation to the soil chemical properties.