We examined the influence of small-scale gap disturbances on stand development and tree species coexistence in an old-growth Fagus sylvatica-Abies alba forest in the Dinaric Mountains of Bosnia-Herzegovina. The structure and composition of tree regeneration in gaps were compared to the forest as a whole, and the influence of gap size on the density and composition of regeneration was assessed. Transition probabilities were also calculated from gapfillers in different life stages to examine canopy replacement patterns. The structure and composition of tree regeneration were similar between gaps and the forest as a whole, and there was no relationship between overall regeneration density and gap size, indicating most individuals established prior to gap formation. Likewise, there was no strong evidence of gap-size partitioning for shade tolerant F. sylvatica and A. alba, although less tolerant Acer pseudoplatanus only recruited to taller life stages in larger gaps. Transition probabilities calculated from the seedling and sapling data suggest that most gaps will be captured by F. sylvatica, while probabilities based on pole-sized gapmakers indicate both A. alba and F. sylvatica will be maintained in the canopy. We suggest that gaps primarily play a role in reorganizing advance regeneration, and that coexistence of shade tolerant F. sylvatica and A. alba is more likely related to their differential ability to tolerate shaded understory conditions, particularly during larger life stages, rather than gap-size partitioning.

ContextDue to a long history of intensive forest exploitation, few European beech (Fagus sylvatica L.) old-growth forests have been preserved in Europe.Material and MethodsWe studied two beech forest reserves in southern Slovenia. We examined the structural characteristics of the two forest reserves based on data from sample plots and complete inventory obtained from four previous forest management plans. To gain a better understanding of disturbance dynamics, we used aerial imagery to study the characteristics of canopy gaps over an 11-year period in the Kopa forest reserve and a 20-year period in the Gorjanci forest reserve.ResultsThe results suggest that these forests are structurally heterogeneous over small spatial scales. Gap size analysis showed that gaps smaller than 500 m2 are the dominant driving force of stand development. The percentage of forest area in canopy gaps ranged from 3.2 to 4.5% in the Kopa forest reserve and from 9.1 to 10.6% in the Gorjanci forest reserve. These forests exhibit relatively high annual rates of coverage by newly established (0.15 and 0.25%) and closed (0.08 and 0.16%) canopy gaps. New gap formation is dependant on senescent trees located throughout the reserve.ConclusionWe conclude that these stands are not even-sized, but rather unevenly structured. This is due to the fact that the disturbance regime is characterized by low intensity, small-scale disturbances.

© iForest -Biogeosciences and Forestry IntroductionTraditional land use (agriculture and forestry) is being abandoned in the Alps due to socioeconomic changes, while an increasingly larger area is being used for tourism and infrastructure, which requires protection from natural hazards. Forests provide permanent protective functions, but only if they are properly and sustainably managed (Ott et al. 1997, O'Hara 2006, Mizunaga et al. 2010. There has been a general decline in forest management in Europe (Forest Europe 2010) and in the Alps in particular, where it is difficult to achieve positive economic returns (Schütz 1996). Climate change has increased the frequency of extraordinary weather phenomena, which causes higher risk from natural hazards and weakening of forest stability (Seidl et al. 2011). In many Alpine countries, state subsidies are used to facilitate the management of forests with direct protective functions (Mayer & Ott 1991, Brang et al. 2006. In order to maximize protective effects with minimal costs, a thorough understanding of natural hazards, their impact areas, and the potential role of forests is necessary (Lopez Saez et al. 2011). A detailed delineation of forest areas with direct protective functions is necessary to determine the areas where state subsidies should be directed. In addition, forest profile models must be developed to inform silvicultural measures and to verify their success (Mayer & Ott 1991, Berger & Rey 2004, Frehner et al. 2005.In Switzerland a method for the delineation of forests with direct protection functions was developed as part of the Silvaprotect-CH project: a standardized delineation of protection forests at the state level. The procedure involves multiple, stepwise modules that generate the actual forest areas with direct protection functions (Giamboni & Wehrli 2008). In France, the zoning classification of mountain forests with direct protection functions and the mapping of hazards and prohibition of the construction of infrastructure in risk areas were identified as the most effective preventive approach to ensure the maintenance of protective functions (Berger & Rey 2004). In Austria, a distinction is made between two types of protection forests: site-protection forests and infrastructure-protection forests, the latter also including forests that protect against noise and light pollution (Schima & Singer 2008). Delineation methods of forests in which slope processes (e.g., erosion, landslides, debris flow, etc.) are present differs among the federal states (Ziegner 2002).The negative effects of disturbances are best mitigated by uneven aged forests, where the presence and distribution of trees provide protection against natural hazards, and the ability to replace damaged trees with existing regeneration provides elasticity (O'Hara 2006). For such forests it is necessary to determine a (modified) selection forest target profile. In Switzerland the NaiS -Nachhaltigkeit und Erfolgskontrolle im Schutzwald is used for the management of protection forests (Fr...

Old-growth forest reserves in slovenia: the past, present, and future Slovenia has a small number of old-growth forest remnants, as well as many forest reserves approaching oldgrowth conditions. In this paper, we describe some of the basic characteristics of these old-growth remnants and the history of their protection in Slovenia. We then trace the long-term development of research in these old-growth remnants, with a focus on methodological changes. We also review some of the recent findings from old-growth research in Slovenia and discuss future research needs. The conceptual understanding of how these forests work has slowly evolved, from thinking of them in terms of stable systems to more dynamic and unpre