Emulating natural disturbances in boreal Norway spruce forests: Effects on ground beetles (Coleoptera, Carabidae)

• Patch moisture impacted ground beetles more than burning, logging or dead wood.
• Species richness peaked on burned and logged sites due to open-habitat species.
• Closed-canopy species responded little to burning, logging or dead wood.
• Within-site variation largely determines the disturbance impact on ground beetles.

The disturbance regime of boreal forests has been substantially altered by human influence in northern Europe. In this context, emulations of natural disturbance have become increasingly common as management tools to minimize negative effects of forestry on biodiversity. In a large-scale habitat-restoration experiment conducted in Norway spruce stands in southern Finland, we tested the effects of controlled burning, partial harvesting, and increasing the amount of downed wood on ground beetles (carabids). We also evaluated the effects of moisture gradients within harvested sites. We collected beetles seven years after the treatments. The moisture gradient was the strongest determinant of carabid assemblages and even after the most intense disturbances, the moist patches within sites still supported fauna characteristic of mire habitats. The species richness of carabids and the number of open-habitat associated species peaked on burned and harvested sites but we did not observe a typical pattern in beetle assemblages whereby numbers of rare species and species unique to post-disturbance habitats were elevated. Our findings suggest that (a) the influx of disturbance-associated species was apparently ephemeral and difficult to observe seven years post disturbance, and (b) moist patches within disturbed sites can serve as refugia for many closed-forest associated carabids over the early phases of post-disturbance succession.