SUCCESSION ON A SANDY COAST FOLLOWING THE CONSTRUCTION OF BANKS PLANTED WITH ELYMUS MOLLIS

Abstract

Elymus mollis, an introduced species, was planted on the seaward slope of sand banks constructed along the coast of Kuju-Kuri Hama (sand beach), central Japan, some 15 years ago. Since that time, the zone of Elymus has advanced seaward at a speed of about 5 m/yr, which was 2.5 times as fast as that of land accretion. Since E. mollis produced few seeds at Kuju-Kuri, the advancement was solely caused by the elongation of new rhizomes, whose mean length amounted to 4.8 m. Certain native species such as Carex kobomugi established themselves behind the Elymus zone and was replacing E. mollis. Saccharum spontaneum var. arenicola, which was planted on the opposite (landward) slope of the banks, remained on the slope without further spreading, being gradually replaced by Imperata cylindrica var. koenigii. The mechanism of these changes and local differences in the semi-natural vegetation of the coast were discussed.