Gap recruitment and partitioning in an old-growth beech forest of the Dinaric Mountains: Inﬂuences of light regime, herb competition and browsing Jurij Diaci ⇑ , Tomaz Adamic, Andrej Rozman Department of Forestry, Biotechnical Faculty, University of Ljubljana, Vecna pot 83, 1001 Ljubljana, Slovenia article info Article history: Received 12 May 2012 Received in revised form 12 July 2012 Accepted 7 August 2012 Keywords: Old-growth forest Natural regeneration Fagus sylvatica Acer pseudoplatanus Allium ursinum Light climate abstract Canopy gap recruitment in beech (Fagus sylvatica L.) old-growth forests is inﬂuenced by the interplay of the canopy gap disturbance regime, site factors, and stand history. Persistent seedling and sapling banks of beech and other shade tolerant species often play a major role in canopy gap closure. To gain more insight into interactions between medium-sized gaps and pre-gap ground vegetation patterns, we studied beech regeneration over a 10-year period on a site rich in wild garlic (Allium ursinum L.) in a Dinaric beech old-growth forest. In 1999 we selected the ﬁve largest newly created gaps (200 m 2 ) and systematically established 13 permanent plots (1  2 m) in each gap. In 1999, 2004, and 2009, we sampled tree species regeneration (density, cover, and growth), ground vegetation (composition and cover), and light climate. Beech regeneration slowly increased in density and cover despite an overall decrease in light (11.0–5.7%). The same was not true for maple. While beech was present in all regeneration classes, dominant maple seedlings rarely reached 50 cm. Beech also had a signiﬁcantly greater height increment. Regeneration of both species was negatively affected by Allium cover, low light levels, and ungulate browsing. Gap parti- tioning was observed among shade tolerant Allium, which preferred microsites under closed canopy and low light levels, beech regeneration, which preferred gap periphery, and other less shade tolerant herbs, which favoured gap centres. The slow development of the regeneration indicated the importance of sev- eral gap releases. The high maple seedling density and less abundant beech advance regeneration in this study site compared to other beech sites suggests that Allium dominated managed forests might present an opportunity for growing less shade-tolerant species, if managed with a gap-oriented silvicultural sys- tem (e.g. irregular shelterwood). Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Natural regeneration in beech (Fagus sylvatica L.) is a result of the complex interactions of many biotic and abiotic factors (Wag- ner et al., 2010). Studies have shown that limited seed dispersal, seed predation, the formation of a seedling bank, shade tolerance, susceptibility to competition from herbs, susceptibility to drought, vulnerability to frost, and browsing are among the most important characteristics of beech regeneration ecology (e.g. Watt, 1923; Mosandl and el Kateb, 1988; Schmidt, 1997; Collet et al., 2001; Pages et al., 2003; Diaci, 1997; Mountford et al., 2006; Mihok et al., 2007; Hahn and Emborg, 2007; Petritan et al., 2007). A chal- lenge for studying beech regeneration ecology, however, is that because beech often forms a seedling bank due to its high shade tolerance and overall resource use efﬁciency during the regenera- tion phase, making it difﬁcult to accurately assess the effects of various ecological factors and their interplay (Madsen and Hahn, 2008). Thus, in old-growth forests, where stands were not inﬂuenced by silviculture, beech seedlings are subjected to extre- mely low light levels and therefore provide ideal test beds for studying the various ecological factors that inﬂuence beech regen- eration (Emborg, 1998). Although old-growth forests are rare in Europe, beech regenera- tion ecology has been intensively studied in old growth (Leibundgut, 1982; Korpel, 1995; Emborg, 1998; Zeibig et al., 2005; Commarmot et al., 2005; Nagel et al., 2006; Drössler and von Lüpke, 2007; Mihok et al., 2007). Such studies reveal important processes that could be used to improve silviculture in beech forests. Nevertheless, and de- spite beech’s growing importance for its role in mitigating climate change and for its role in close-to-nature silviculture, repetitive measurements of beech regeneration in old-growth forests are rare (sensu Runkle and Yetter, 1987; Hahn and Emborg, 2007). Because one-time observations can be strongly inﬂuenced by yearly climatic changes, they may yield only limited insight into the long-term regeneration process. Moreover, since research on stand regenera- tion patterns is specialised, gap dynamics research rarely includes measurements of ecological factors (sensu Drössler and von Lüpke, 2005). Likewise, specialised research on regeneration ecology rarely 0378-1127/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.foreco.2012.08.010 ⇑ Corresponding author. Tel.: +386 1 320 3533; fax: +386 1 257 11 69. E-mail address: jurij.diaci@bf.uni-lj.si (J. Diaci). Forest Ecology and Management 285 (2012) 20–28 Contents lists available at SciVerse ScienceDirect Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco