IMPACT OF FLOOD DISTURBANCE EVALUATION ON THE STRUCTURES OF GROUND-BEETLE ASSEMBLAGE AT BIOTOPES

Abstract

In September 2011, the flood of the Shonai and Yada Rivers in the center of Japan brought lots of earth and sand into their biotopes and caused serious damage to their vegetation. Comparing our data of their ground-beetle assemblage in 2010, we could assess the impact of the flood disturbance. After the spring of 2012, when the damage to the assemblage and vegetation was found to be serious, the number of insects gradually increased as the vegetation recovered, and recovered to the original state by the end of the summer. However, the structure of the fauna was very different from the original. The recoverability of the ground beetle fauna was different in each river; the structures of ground-beetle fauna in the Shonai wetland and Yada grassland recovered soon, but those of floodplain forests in both rivers, which were controlled by people, remained the damage till the end of the autumn. Among these, the structure of fauna in the Shonai grassland was nearly at the level of urbanized areas. Since the number of insects increased along with the recovery of vegetation, we believe the recovery of river vegetation is important. Furthermore, in preparation for the possible disasters, we suggest to extend the non-mowing areas for the recovery of insect fauna.