Effects of Forest Fragmentation on Carabid Assemblages in the Urban Setting: Implications for Planning and Management

Abstract

We compared carabid beetle assemblages (Coleoptera, Carabidae) between large (9.6–21.5 ha), medium-sized (4.2–8.2 ha), small forest fragments (0.5–3.0ha), their surrounding agro-urban habitats and a nearby continuous forest in southern Finland. Carabid species richness was lowest in the continuous forest and highest in the surroundings. In a multivariate analysis of vegetation and carabid samples, sites from each fragment size class formed groups of their own and the small fragments were found to be similar to the surroundings. The proportion of open-habitat species increased with decreasing fragment size indicating that open habitat species easily invade the small fragments from the surroundings. Some specialised forest carabids were exclusively caught in the continuous forest. To preserve forest arthropod faunas in urban areas it is essential to leave large, continuous forest tracts untouched. Since this may be difficult to achieve, sizeable forest fragments must be set aside and ecological networks of forested habitats must be created.