2005 Volume 22 Issue 1 Pages 25-40
Distribution of woody species along environmental gradient in a subtropical oceanic island (Hahajima Island in the Bonin Islands) was studied. Vegetation data were analyzed by an ordination technique (CCA, canonical correspondence analysis), and distribution of species abundance on the ordination axes was calculated. Environmental gradients which related to moisture condition affected the species distribution. Maximum abundance and niche width were calculated from the species distribution on the ordination axes. Ardisia sieboldii, Rhaphiolepis indica var. umbellata, Bischofia javanica, Planchonera obovata had wide niche and relatively high abundance. On the other hand, the shrubs which appear on windy ridges tend to have narrow niche width and high abundance. Two alien species of B. javanica and Morus australis had different niches. Niche overlap by alien species with native species was calculated. Niche of B. javanica overlapped with 15 species out of a total of 31 major woody species, and with seven species by M. australis.
