2011 Volume 28 Issue 1 Pages 39-47
Alien herb Coreopsis lanceolata often invades gravelly floodplain vegetation in Japan. The purposes of the present study were to clarify whether the soil texture types (i.e., gravelly, sandy, loamy and clayey types) affect the C. lanceolata invasions, and to detect the riparian endemic vegetation vulnerable to the invasions. On the gravel bars along the lower reaches of the Mibu River in Nagano Prefecture, central Japan, we surveyed the floodplain vegetation on each soil texture type using 164 quadrats consisting of 2m×2m plots. Coreopsis lanceolata cover on gravelly type was significantly lower than that on the other types. Coreopsis lanceolata cover tended to become higher from gravelly type to clayey type, indicating that gravelly type is less preferable for C. lanceolata than the other types. Negative correlations between the cover of C. lanceolata and total riparian endemic plants were observed on the finer-textured soil types, particularly loamy type, but not on gravelly type. Therefore, the endemic vegetation on loamy type mainly composed of Potentilla chinensis and Artemisia capillaris were considered to be vulnerable to the invasion impacts of C. lanceolata. The differences in influences of C. lanceolata on riparian endemics among soil texture types may be due to the differences in the dominance of this species among the soil texture types. Soil texture type is one of the factors affecting the invasion status of C. lanceolata on the gravelly floodplains, and endemic vegetation on finer-textured soil types such as loamy type will be endangered by the invasions.
