2014 Volume 31 Issue 1 Pages 51-69
Natural beech (Fagus crenata) forests in Japan have been rapidly fragmented because of human activities since the end of the Second World War. In order to examine the effects of forest fragmentation on the species richness and composition of such forests, we surveyed the species of forest interior flora and the habitat conditions of 20 natural beech forest patches of various areas (450-856300 m^2) on Mt. Ouginosen, Japan, and analyzed the relationship between species richness or species composition and patch area on a whole-patch scale. A high positive correlation between the number of species and patch area was observed for all species, tree species, shrub species, terrestrial herb species, terrestrial pteridophyte species, endangered species (ES), rare species (RS), and species showing a preference for habitats with moist soil conditions (MS). Analysis of the relationship between the distribution of each species and patch area showed that many species, particularly ES, RS, and MS, tended to be absent in smaller patches. In addition, the first-axis score of a detrended correspondence analysis ordination for the patches was highly correlated with patch area. These results indicate that forest fragmentation has a considerable negative impact on species richness and can simplify species composition to a considerable extent. The absence of ES, RS, and MS in smaller patches may be attributable to certain factors associated with the decrease in patch area, such as a decreased likelihood of occurrence, an increased risk of extinction due to the decrease in population size, and the lack of landforms with moist soil conditions.
