2018 Volume 35 Issue 1 Pages 1-19
Apocynum venetum var. bashikurumon （H. Hara） H. Hara is a rare plant, which is sporadically distributed, mainly in the coastal areas of Niigata, Aomori, and Hokkaido Prefectures, Japan. In order to record its habitat characteristics and vegetation types, we established 143 rectangular quadrats for conducting a vegetation survey in Niigata Prefecture. Vegetation type classification revealed that A. venetum var. bashikurumon was frequently found in plant communities under severe environmental stresses （e.g., sparse grasslands on the soft rocky cliffs of weathered tuff） or moderate levels of natural （e.g., semi-stabilized areas of sand dunes） and anthropogenic disturbances （e.g., wind-exposed grasslands on embankment slopes in the backshore zone）. The terrestrial parts of these communities generally occurred at low densities. These parts, together with extensive clonal growth of A. venetum var. bashikurumon using its long rhizomes, might facilitate the relatively high coverage of this species even in such habitats. These habitats are not rare in the coastal areas. Further studies on the characteristics of this species are essential for clarifying the reasons underlying the rarity of this species.
