FOREST ROADS CAUSE EDGE EFFECTS ON PLANT SPECIES DIVERSITY IN ARTIFICIAL FORESTS

To evaluate the effects of narrow forest roads on plant species diversity in the forest understory, we analyzed the relationship between the distance from the forest road and vegetation structure in young and mature artificial forests of Japanese cedar (Cryptomeria japonica). Although exotic species appeared along the side of the forest road, their appearance frequencies and coverage were very small, suggesting that a decline in species diversity due to exotic species did not occur. Although an obvious decrease in vegetation coverage and species number with distance from the forest road was detected in the shrub layer of the young forest, a clear distance-dependency was not observed in the mature forest. However, even though the effects on local species number (α diversity) were unclear, replacement of species was detected with distance from the forest road (β diversity) in association with species’ shade tolerance. This replacement of species improved the overall diversity of forest (γ diversity). Thus, it was concluded that narrow forest roads can improve species diversity in artificial forests in association with a diversified environment and the replacement of plant species.