Forest fragmentation and its effect on species diversity in sub-urban coppice forests in Japan

Abstract

Forest fragmentation and its influence on plant species diversity was studied in 38 sub-urban coppice forest stands of the Kanto Plain, central Japan. Analyses of historical aerial photographs showed that rapid forest fragmentation has occurred on these sites, especially on sites near big cities. The forests tended to remain in hilly areas with high topographic variations, which are not suitable for other type of landuse. Species diversity of both the trees and forest floor plants were affected by forest fragmentation. For trees, both the number of species per unit area and Shannon's diversity index had significant positive correlations with the mean size of forest patch and the proportion of forested area. Those diversity indices for forest floor plants also had significant positive correlations with the mean size of forest patches and the topographic complexity of the site. Frequencies of forest interior species and rare species increased with the increase of forest patch size, while that of forest edge species decreased. Forest management regimes also had some effects on species diversity. Tree diversity increased with stand development, suggesting longer management cycles would increase the tree diversity. The diversity of forest floor plants was low where the amount of dwarf bamboo was high. Traditional methods of shrub cutting and litter collection had the effect of decreasing the amount of dwarf bamboo, and thus increasing the diversity of forest floor plants.