We examined the occurrence of carabid beetles (Coleoptera, Carabidae) at the edges of oak (Quercus pyrenaica) and beech (Fagus sylvatica) forests in León, NW Spain. Pitfall traps were used to collect beetles from April to October 2002, and leaf litter cover and depth were measured. Traps were placed at three distances (0, 50 and 100 m) from the edges of eight forest patches. A total of 5436 carabids belonging to 43 species were collected. We found no statistically significant edge effect at the carabid assemblage level, i.e. the number of species and individuals was not higher at the edge compared to the forest interior. However, individual species were affected by distance from the edge. Five of the 14 species analysed responded predictably to the edge, three of them statistically significantly so. Four species did not respond in the predicted direction, two of them statistically significantly so. We found a considerable difference between forest types in terms of carabid assemblage composition and response to the edge. Oak forests were species richer and beech forests had a higher number of individuals. These differences were probably due to small-scale habitat heterogeneity in the oak forest patches, caused by man, and the homogeneous structure of beech forests. Leaf litter appeared to be one possible factor influencing the distribution of some species from the interior to the edge of forests.
Carabid abundance, species richness and diversity were compared along an urban-rural gradient in Helsinki, Finland. Increased urbanization was found to result in significant reductions in species richness, though the reductions in abundance and diversity were not statistically significant. Forest habitat-specialist species were scarce in rural sites and virtually absent from urban and suburban sites. There was no evidence of higher diversity at intermediate disturbance levels (suburban sites), as predicted by the intermediate disturbance hypothesis. Species with flight ability and the ability to utilize open habitat were more predominant in urban and suburban sites. Flightless species were more predominant in rural and suburban sites. Carabid abundance data were sufficient to reveal the negative impact of urbanization, so similar studies could be conducted in regions where carabid taxonomy is poorly known. Species composition patterns do, however, provide invaluable information. To conclude, if biodiversity is to be maintained in urban areas, priority must be given to the provision of those habitat features which are essential for sensitive species, such as decaying wood and wet microhabitats. These must be incorporated into urban green networks in particular, if biodiversity and species other than common generalists are to benefit from them.