Abstract
We investigated managed and abandoned vegetation on the levee slopes between paddy fields in order to clarify the relationship between the time since the last management and the species richness or species composition of semi-natural grasslands. The mean species richness per square meter in the managed grasslands was 25.3 and significantly higher than that in the abandoned grasslands. Species richness was significantly negatively correlated with the time since the last management. The negative correlation between cumulative cover and species richness was significant in layers below 0.6m. The composition of managed grasslands was similar to that of grasslands abandoned within the past 3 years but was different from that of grasslands abandoned for 4 years or more. The managed grasslands had 28 indicator species, while the abandoned grasslands had 1 indicator species. Competitive species such as Solidago altissima and Pleioblastus spp. gained height and cover in the abandoned grasslands within a few years. This increase is considered to be the reason for the decrease in the species richness and the change in the species composition.
