Slow and fast drivers of the natural disturbance regime in Central European forest ecosystems Dominik Thom a , Rupert Seidl a,⇑ , Gottfried Steyrer b , Hannes Krehan b , Herbert Formayer c a Institute of Silviculture, Department of Forest- and Soil Sciences, University of Natural Resources and Life Sciences (BOKU) Vienna, Peter Jordan Straße 82, 1190 Vienna, Austria b Department of Forest Protection, Federal Research and Training Centre for Forests, Natural Hazards and Landscape (BFW), Seckendorff-Gudent-Weg 8, 1131 Vienna, Austria c Institute of Meteorology, Department of Water, Atmosphere and Environment, University of Natural Resources and Life Sciences (BOKU) Vienna, Peter-Jordan Straße 82, 1190 Vienna, Austria article info Article history: Received 17 May 2013 Received in revised form 11 July 2013 Accepted 11 July 2013 Available online 8 August 2013 Keywords: Forest disturbance regime Bark beetle damage Wind damage Disturbance predisposition Climate sensitivity Disturbance interactions abstract Forest disturbance regimes have intensified in many parts of the world in recent decades, and are an increasing problem for managers concerned with the sustainable and continuous provisioning of forest ecosystem services. In order to address these changes an improved understanding of disturbance regimes is needed, particularly with regard to their main drivers and climate sensitivity. Here, our objectives were to first quantitatively describe the recent disturbance regime of forest ecosystems in Austria (3.99 Â 10 6 ha). Second, our aim was to identify the main drivers of the disturbance regime, distinguish- ing slow, predisposing factors and fast, inciting factors. We utilized district-level disturbance observa- tions from 2002 to 2010, and focused on damage from wind and bark beetles, the most detrimental abiotic and biotic disturbance agents in Europe. In a two-stage approach, we first analyzed the influence of slow, predisposing variables on the spatial variation in mean disturbance damage, using principle com- ponent regression. Subsequently, the year-to-year residuals from these average damage levels were regressed against fast, inciting factors related to disturbance occurrence. Overall, this two-stage analysis explained 48.7% (wind) and 67.1% (bark beetles) of the spatio-temporal variation in disturbance damage. On average, wind and bark beetles damaged 0.26% and 0.19% of growing stock per year. The analysis of damaged forest areas suggest a mean disturbance rotation period of 746 and 365 years for wind and bark beetle disturbance. Variables related to species composition were the most influential factors on the predisposition to both disturbance agents. Societal factors were found to be of similar importance as climatic variables. Overall, these predisposing (slow) variables had a stron- ger influence than inciting (fast) drivers, of which weather-related variables and spatio-temporal inter- actions within the disturbance regime were the most prominent factors. Our results indicate that important drivers of the disturbance regime can be influenced by forest man- agement directly, but also underline that response times are likely to be slow. Furthermore, fast, inciting factors – although largely beyond the influence of management – have the potential to be used as early warning indicators of impending disturbance damage. Overall, disturbance regimes were found to be highly sensitive to both climate means and extremes, emphasizing the importance for improved risk management in forestry in the face of climate change. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Natural disturbances are key processes of forest ecosystem dynamics. They shape ecosystem structure at the stand to land- scape scale, initiate and reset species succession, and modulate the functioning of forest ecosystems (Franklin et al., 2002; Turner, 2010). Consequently, disturbances have considerable impacts on the provisioning of forest ecosystem services to society. Through a devaluation of wood, the need to harvest prematurely, and neg- ative market effects from large pulses of salvaged timber, distur- bances can have a strong disrupting effect on timber production and the timber-based economy (e.g., Nieuwenhuis and O’Connor, 2001; Gardiner et al., 2010). With respect to atmospheric CO 2 , dis- turbance events can turn forests acting as a carbon (C) sink into a C source (Kurz et al., 2008; Seidl et al., 2008; Laurance and Curran, 2008; Hayes et al., 2011; Coomes et al., 2012). They thus have the potential to strongly interfere with objectives to mitigate cli- mate change through forest management (Canadell and Raupach, 2008). Further examples of ecosystem services and functions dis- tinctly affected by disturbances include the protection against 0378-1127/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.foreco.2013.07.017 ⇑ Corresponding author. Tel.: +43 1 47654 4068; fax: +43 1 47654 4092. E-mail address: rupert.seidl@boku.ac.at (R. Seidl). Forest Ecology and Management 307 (2013) 293–302 Contents lists available at SciVerse ScienceDirect Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco