RELATIONSHIP OF MANAGEMENT PRACTISES TO THE SPECIES DIVERSITY OF PLANTS AND BUTTERFLIES IN A SEMI-NATURAL GRASSLAND, CENTRAL JAPAN, pp. 241-265
Authors: (Masako Kubo, Takato Kobayashi, Masahiko Kitahara and Atsuko Hayashi, National Institute for Land and Infrastructure Management, Ministry of Land, Infrastructure and Transport and Tourism, Tsukuba, Ibaraki, Japan, and others)
Abstract: In the past, semi-natural grasslands in Japan were maintained using traditional management practices such as mowing, burning, and grazing. However, grassland areas have been decreasing drastically recently due to land development or the abandonment of management. Thus, conservation measures are urgently required for organisms specific to semi-natural grassland habitats. To examine management schemes for conserving such organisms, we investigated plant species and seasonal fluctuation patterns in species and individuals of flowering plants and adult butterflies in a semi-natural grassland in central Japan. Our study sites were firebreaks where the grass was mowed and removed, plantation areas that were mowed, unpaved roads with mowed banks, abandoned grassland, and scattered scrub forest. Areas that had been abandoned for less than five years were dominated mostly by Arundinella hirta, while areas that had been abandoned for more than ten years were dominated by large tussocks of Miscanthus sinensis or scrub forests of Rhamnus davurica var. nipponica. The plant species composition differed between grassland sites and scrub sites, and that of firebreaks was different from other grassland sites. The sites under management sustained a larger number of flowers and butterflies than the sites without management. Furthermore, the firebreak sites sustained flowers in June and July, while the plantation and banks of unpaved road sites sustained flowers primarily in August and September. The number of butterflies increased in the firebreak in June and at the other sites in August and September, in relation to the occurrence of flowers at each site. These results suggest that management is essential to sustain this grassland and that different management regimes, such as mowing alone and mowing with grass removal, induce different plant species compositions and different numbers of flowers, and lead to different numbers of adult butterflies during a season. On the other hand, R. davurica var. nipponica, which composed the scrub forest, is a host plant for a threatened butterfly species. In conclusion, heterogeneous environments with different vegetation structures by season and seral stage under different management regimes support plant and butterfly diversity in semi-natural grassland habitats, and continuation of traditional management practices in the future may be important.