兵庫県新産のウンヌケ(イネ科)の分布とその生育環境  [in Japanese] Distribution and habitat of Eulalia speciosa (Poaceae) newly recorded from Hyogo Prefecture, western Japan  [in Japanese]

兵庫県東播磨地方において, これまで近畿地方から記録のなかったウンヌケ(Eulalia speciosa)の新産地を見いだした。東播磨のウンヌケは, 流紋岩類からなる丘陵地の溜池の土手や禿山の草地に群生しており, これまで約30ヵ所の自生地が確認されている。新産地を含む日本列島におけるウンヌケの分布図を各地の標本庫に収蔵されている標本に基づき提示した。東播磨地方においてウンヌケの生育を維持してきた主な要因は, 古くからの人為作用と乾燥した気候, それに伴う山火事の多発による禿山の形成にあると考えられる。さらに, その周囲に多数存在する溜池の土手草地が, 近年における禿山の緑化や遷移の進行によるウンヌケの生育通地の減少に対して, レフュジアとしての機能を果たしてきたものと推測される。

Eulalia speciosa, a rare plant in the Poaceae of the warm-temperate zone, has been considered to be one of the 'Tokai floral elements' by various authors. In 1994, however, E. speciosa was found in the eastern Harima region, Hyogo Prefecture, Kinki district, western Japan. An intensive survey followed revealed that about 30 localities of E. speciosa populations exist in this region. A distribution map of E. speciosa in the Japanese archipelago was presented on the basis of herbarium specimens, including those from the new localities. In the eastern Harima region, E. speciosa grows in the Miscanthus-type dry grasslands formed on bald hills and on irrigation pond embankments. Nearly all localities are geologically restricted to areas with rhyolite pyroclastic rocks and lavas. The establishment of bald hills caused by fires and cutting, together with a dry climate and unique geology, may be the main factors supporting the E. speciosa populations in this region. Additionally, the establishment of a large number of small grasslands on irrigation pond embankments seems to have provided suitable refugia for E. speciosa through recent loss of grassland habitats caused by reforestation and progressive succession.