Effects of plant diversity, habitat and agricultural landscape structure on the functional diversity of carabid assemblages in the North China Plain

This study investigated the effects of plant diversity, habitat type and landscape structure on the functional diversity of the carabid assemblages in the agro-landscape of the North China Plain. We hypothesise (i) small, herbivorous and omnivorous carabids are more strongly affected by local plant diversity, while large and predatory carabids are strongly affected by landscape structure, and (ii) habitat type influences the diversity across functional groups. In 2010, carabid beetles were sampled by pitfall traps in six typical habitats of the agro-landscape: wheat/maize fields, peanut fields, orchards, field margins, windbreaks and woodland. Our results showed that (i) habitat type played a predominant role in driving the changes in the diversity of carabid assemblages, followed by local plant diversity while the landscape structure had little effect; (ii) small and omnivorous carabid were strongly affected by local plant diversity, while the composition of large and predatory carabid was strongly associated with the landscape structure; and (iii) habitats dominated by woody species harboured different assemblages to habitats dominated by herbaceous plants for overall carabids and three functional groups excluding omnivorous beetles. Informed by our results, we suggest the differentiated responses between functional groups should be appreciated in conservation management. In the intensively managed agro-landscape, maintenance of diverse habitats and creating a more complex vegetation structure would be the most efficient measures to enhance the diversity of carabid assemblages. Particularly, the maintenance of extensively managed habitats coupled with a targeted increase in the local plant diversity is crucial to optimise the biological pest control by carabid assemblages.