ALTERATION OF VEGETATION AND LANDSCAPE UNITS AFTER THE GREAT EAST JAPAN EARTHQUAKE

Abstract

The Great East Japan Earthquake brought serious damage from the earthquake, tsunami, and radioactive contamination along Japan’s east coast of the Pacific Ocean. The catastrophe resulted in not only direct physical disruption but also in land abandoned over the long term caused by radioactive contamination. Since the earthquake occurred on March 11, 2011, five years and eight months have passed. To assess the change in vegetation before and after the earthquake, a vegetation survey was carried out in Minami-Souma and surrounding regions from the coast to inland for about 16 km. The abundant rice fields were occupied with perennial weed plant communities, but after the decontamination, working annual plant communities took their place over five years. The rice field has two successive series in different wet and dry habitats, and the landscape of the rice field is classified into three sigma-associations. Absolute abundant wet rice fields under the radioactive contamination belong to Scirpo‒Typhaeto orientalis‒Sigmetum. The survey used rice fields characterized by Sagittario‒Monochorieto‒Sigmetum and divided into two sub-sigma-associations, Phragumito australis‒subsigmetum in wet rice fields and Solidago altissima‒subsigmetum in dry rice fields. The forest landscape did not change at the point of physiognomy, but the characteristic plant communities of those landscapes are early successional plant communities such as pioneer shrubs and sub-trees which belong to Rosetea multiflorae and Clerodendro-Mallotion.