Change in the composition of carabid beetle species associated with abandonment of paddy fields

We investigated changes in the diversity and species composition of carabid beetles associated with abandonment of rice paddies. In addition, we studied the environmental variables that affect carabid assemblages in these habitats. We collected 807 carabid beetles comprising 37 species from studied habitats. We found that the diversity and stability of the carabid beetles increased with increase in the time since abandonment of the habitat. Ordination analysis showed that the species assemblages for all habitats could be clearly separated from paddy fields, but early stages of abandonment showed no differences relative to paddy fields. Canonical correspondence analysis revealed that the most significant environmental variables influencing carabid assemblage were soil pH, organic matter, and the presence of tree cover. For early stages following abandonment, soil nutrients were the strongest factors influencing the species composition of carabid beetles. In contrast, the presence of tree, shrub, or herb cover were associated with increase in the diversity of carabid beetles in late stages following abandonment. The results of this study suggest that restoration and management of abandoned paddy fields provides an excellent opportunity to improve the diversity and habitat qualities of agricultural landscapes.