Boreal carabid-beetle (Coleoptera, Carabidae) assemblages along the clear-cut originated succession gradient

We examined the occurrence of carabid beetles along a forest succession gradient in central Finland (forest age classes: 5, 10, 20, 30 and 60 years since clear-cutting). Species richness of carabids was higher in the two youngest age classes, while no clear differences were detected in carabid abundance. The high species richness in the young, open sites was due to invasion of open-habitat species. Many forest species were absent from or scarce in the young sites and became gradually more abundant towards the older forest age classes. The catches indicated a drastic decrease and assemblage-level change in concert with canopy closure, i.e. 20-30 years after clear-cutting. Some forest specialists with poor dispersal ability may face local extinction, if the proportion of mature forest decreases further and the remaining mature stands become more isolated. We recommend that, while harvesting timber, connectivity between mature stands is ensured, mature stands are maintained close (a few tens of metres) to each other and the matrix quality is improved for forest species by green tree retention.