Emulating natural disturbances in boreal Norway spruce forests: Effects on ground beetles (Coleoptera, Carabidae) Tero Toivanen a,c , Tanja Heikkilä a , Matti J. Koivula b,⇑ a Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, FI-40014 Jyväskylä, Finland b School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland c BirdLife Finland, Annankatu 29 A 16, FI-00100 Helsinki, Finland article info Article history: Received 20 August 2013 Received in revised form 20 November 2013 Accepted 21 November 2013 Keywords: Carabid Dead wood Fire Harvesting Restoration Soil moisture abstract 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 manage- ment 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 character- istic 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 dif- ficult 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. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Disturbances are the driving force of forest ecosystems. They create and maintain the spatio-temporal variability of habitats and species assemblages (Sousa, 1984; Kuuluvainen, 2009) by dis- rupting the community structure and modifying the physical envi- ronment or the availability of resources or substrates (Pickett and White, 1985). The post-disturbance succession of species assem- blages is affected by, for example, the intensity of disturbance, the structure of the post-disturbance habitat, and the connectivity of the new habitat patch to similar patches that host source popu- lations of potential colonizers (e.g., Spies and Turner, 2001). The disturbance regime of boreal forests ranges from stand- replacing disturbances, such as intense fires, to minor events repre- sented by deaths of individual trees (Angelstam and Kuuluvainen, 2004). Of the major natural disturbance factors, fire is generally re- garded most important at least in terms of affected area, but espe- cially in Europe human actions have substantially altered the disturbance regime during the last centuries. While large-scale fires are still common in North America (Bergeron et al., 2002), they have become extremely rare events in northern Europe (Niklasson and Granström, 2000), and have been largely replaced by anthropogenic disturbances, particularly forest harvesting. These changes in dis- turbance dynamics have substantially affected the structural diver- sity of boreal forests, and led to a decline of legacy elements important for biodiversity, such as dead wood (Siitonen, 2001). These alterations have often led to major losses of species: in Fin- land, for example, forest management is considered one reason for one-third of all red-listed species being threatened (Rassi et al., 2010). To diminish the negative impacts of forest man- agement on biodiversity, natural disturbance regimes as general guidelines for management are increasingly adopted (Bergeron et al., 2002; Long, 2009; Päivinen et al., 2011). Within protected areas of northern Europe, restorative measures such as prescribed burning that aim at re-introducing the effects of natural fire into managed forests are today a common practice (Kuuluvainen, 2002). While initial post-harvest evaluations of prescribed burning have been done, longer-term studies – that would be needed to characterize ecosystem recovery – have been rare as most experi- ments have only been established within the previous decade (e.g., Koivula, 2013). Ground beetles (Coleoptera, Carabidae; hereafter carabids) have been extensively used as model organisms to explore the effects of habitat variation and alteration on biodiversity (e.g., Niemelä et al., 2007; Koivula, 2011). Soil moisture and forest-floor vegetation, for 0378-1127/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.foreco.2013.11.028 ⇑ Corresponding author. Tel.: +358 45 11 44 929. E-mail address: matti.koivula@uef.fi (M.J. Koivula). Forest Ecology and Management 314 (2014) 64–74 Contents lists available at ScienceDirect Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco