Notes on the ecological traits of smooth cordgrass (Spartina alterniflora) and encroachment into an estuarine salt marsh in Shimonoseki City, Yamaguchi Prefecture, western Japan

Spartina alterniflora Loisel., which is native to the Atlantic coast of North America and the Gulf Coast of Mexico, is a perennial grass that occurs on intertidal mudflats and in estuarine salt marshes. The distribution of this species is currently in- creasing worldwide owing to intentional introductions for conservation and management purposes (e.g. reclaiming tidal flats and protecting coastal areas) and/or via unintentional introduction pathways, including escape from managed sites. Spartina alterniflora affects native intertidal ecosystems and coastal industries by forming dense communities in areas where it has encroached. The species was first detected in Japan in 2008, in the vicinity of the Umeda River estuary in Toyohashi City, Aichi Prefecture. The species was also detected in Kumamoto Prefecture in 2010. Due to the threat that S. alterniflora may pose to intertidal eco- systems and coastal industries, all Spartina species, including S. alterniflora, were listed as invasive alien species by the Japanese government in 2014. Here, we summarise the morphological and ecological characteristics of S. alterniflora and report on a new population detected in an estuarine salt marsh in Shimonoseki City, Yamaguchi Prefecture, in 2020.