Abstract
In coastal dunes, the destruction of vegetation by vehicles is of great concern. The purpose of this study was to investigate the running impact of vehicles on vegetation and soil, by comparing disturbed and undisturbed areas. The study area was enclosed by a fence and vehicles were prohibited from entering from 1992. At that time the disturbed areas were bare ground. This study was carried out in 2001, in the Ishikari coastal dune in Hokkaido. In the zone dominated by Elymus mollis near the shoreline, vegetation in disturbed areas had almost recovered. The spread of the species, reproduced by rhizomes, was thought to be the reason for the fast recovery. However, in this zone, except for the areas nearest the shoreline, soil was hardened and running impact remained. The reason the impact on soil did not remain only nearest the shoreline is thought to be that the impacted soil had been buried by accumulated sand carried from the sea along with wind. In the zone dominated by Rosa rugosa farther from the shoreline, the species, which is a naturalized and not present in the undisturbed areas, invaded the disturbed areas. Thus, vehicle running destroyed the zonation of vegetation. The soil hardness was still observed from the surface to a depth of 50 cm. Since sand hardly accumulates in this zone, the impact on soil is considered to remain over the long term, and there is also thought to be the possibility of not recovering to original vegetation.
