Ground beetle (Coleoptera: Carabidae) assemblages associated with a satoyama landscape in Japan: the effects of soil moisture, weed height, and distance from woodlands

Agricultural landscapes generally include not only crop fields but also semi-natural habitats. In Japan, such a mixed rural landscape is called satoyama. Although ground beetles are potential predators of pests, the environmental factors that determine their distribution in Japanese rural landscapes have not been fully elucidated. To understand the effects of distance from woodland edges, soil moisture, and weed height on assemblages of carabid beetles, we examined the number of adult beetles in pitfall traps placed in a satoyama landscape in the lowlands of western Honshu, Japan. Our results show that the carabid species could be largely differentiated into woodland, intermediate, and open-land species. The intermediate species group includes species that depend on woodland or woodland edges for at least part of their life cycles. Paddy fields must have long provided semi-natural habitats that complement those in natural grasslands and wetlands for open-land beetles that prefer wet conditions. Weeds can also increase the abundance of some intermediate and woodland species; thus, the arrangement of such landscape elements as woodlands and paddies can determine the species richness and abundance of ground beetles in agricultural fields.