Diversity of carabids (Coleoptera, Carabidae) in the desalinized agricultural landscape of Quzhou county, China

Diversity and species composition of carabid beetles were investigated at Quzhou county in the North China Plain. The study area was originally affected by high salinity and desalinized in three stages in 1973, 1978 and 1982. At sites desalinized in 1982, carabids were sampled at field margins as well as inside fields to investigate the role of field margins as refuge habitats. Furthermore, samples were taken from field margins desalinized in 1973 and 1978, respectively, to explore long-term developments of carabid assemblages following desalinization. At margins, soil salinity, N contents and the number of plant species as well as the height of dominant plants were recorded and their correlation with the species composition of carabids explored. Overall carabid diversity at Quzhou was low compared to areas not affected by high salinity. Field margins yielded significantly higher numbers of both species and individuals, whereas assemblages within the field had a low diversity and a homogeneous species composition. Carabid diversity slightly increased in relation to decreased soil salt contents and time elapsed since desalinization. These results may be explained by field margins serving as refuge to many carabid species and by an overall low species pool of carabids in Quzhou due to former high salinity, current high levels of fertilizer and pesticide applications, and by a comparatively low colonization rate of carabids to the area. As different carabid species varied strongly in their reaction to environmental parameters, the preservation of a diverse set of habitats will best protect the current diversity of these beetles in the agricultural landscape of Quzhou.