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In the last century, a synchronous beech expansion has been observed for many mixed mountain forests in southeastern Europe. This change is associated with the interaction of various disturbances. We analyzed structural changes in the Pecka oldgrowth forest in Slovenia during the last century, using several inventories of the tree layer, regeneration, and site factors. Throughout the observation period, the density of silver fir in the regeneration layer and in the overstory steadily decreased. In 1893, silver fir accounted for about 60% of the growing stock, whereas in 2013 it accounted for less than 13%. This is likely because of silver fir’s decline in the canopy layer due to air pollution, successive windthrows, and overbrowsing. However, climate change may also have played an important role, as silver fir also declined in southeastern European old-growth forests where air pollution was less pronounced and ungulate densities were low. A gradual decline of silver fir in the overstory resulted in a decrease of overall tree density to 231 trees ha−1 , while growing stock remained relatively high at 712 m3 ha−1 . Median diffuse light at 1.3 m was 3.7% and regeneration density was 19,954 ha−1 . Beech was dominant (94%), followed by silver fir (4%), and sycamore maple (2%). No silver fir seedlings larger than 0.2 m were recorded. Silver fir, sycamore maple, and beech regeneration showed 87, 76, and 45% browsing damage, respectively. Regression models indicated some evidence of niche partitioning between silver fir and beech. However, many processes may be masked by the silver fir’s avoidance strategy. Given current red deer densities, climate change, and existing forest structure, the Pecka old-growth forest will likely reach an alternative stable state dominated by beech in a few decades. This calls for immediate reduction of ungulate populations. Despite the interaction of multiple disturbances, the Pecka old-growth forest has maintained a relatively high overall growing stock, a favorable microclimate, and succession pathway with shade-tolerant beech. This indicates the intrinsic resilience of natural forests. The mechanisms discussed here can be applied to the future governance of old-growth and managed montane mixed forests. Nasl. z nasl. zaslona. Opis vira z dne 4. 8. 2022. Bibliografija: str. 10-11. Abstract.

Silver fir (Abies alba Mill.) is a key species in the mixed mountain forests of the Dinaric Mountain range, where is typically co-occurs with European beech (Fagus sylvatica L.) and a number of other less dominant species, including Norway spruce (Picea abies). In these forests silver fir is an ecologically and economically important species providing high quality wood and a large range of ecosystem services. Silver fir is very sensitive to particular anthropogenic stressors. For example, many studies have reported several decades of silver fir decline as a result of air pollution, as well as recruitment failures in areas with high population densities of ungulates. After the reduction of industrial air pollution, the growth and health status of fir improved, showing its resilience and recovery potential. Recently, fir has become more important in European forests, especially as a conifer tree species that, according to some research, can be a source of quality technical wood under a warmer and more drought prone climate. Spruce, which has so far been the main source of technical timber in Europe, is dying out across much of its range due to a combination of adverse environmental factors and biotic disturbance. Whether silver fir will be able to partially take over the role of spruce, however, strongly depends on silvicultural measures. These must, among other, include solutions to promote the weakest part of the development of fir stands, namely regeneration and recruitment, as follows: i) using different selection sylvicultural systems (Dauerwald), ii) substantial and prolonged reduction of ungulate populations, iii) silvicultural treatments to improve the competitive power and growth of silver fir seedlings, iv) using sowing, planting, and silver fir wildlings, and v) testing southern (Submediterranean) provenances of silver fir and its performance under climate change.

V Evropi so razširjeni različni načini redčenj, ki so delno odgovor na različne cilje gospodarjenja delno so posledica tradicije in različnih kulturnih okolij. S spremembami v okolju in zaostrovanjem družbeno-ekonomskih razmer ter splošnim nazadovanjem nege gozdov postajajo odločitve o najprimernejšim načinu in intenzivnosti redčenj vse pomembnejše. V prispevku primerjamo situacijsko redčenje, redčenje šopov in skupin, redčenje spremenljive gostote in pri nas ustaljeno izbiralno redčenje. Navajamo usmeritve, kako redčenja kombinirati ter kako izbrati primeren način in program redčenj. Na temelju sinteze dosedanjih raziskav izpostavljamo, da so za utemeljeno izboljšanje načinov redčenj pomembni poskusi v naravi. Various methods of thinning forest stands are common in Europe. These are partly a response to diverse management objectives, partly due to tradition and cultural context. With environmental changes, rapidly transforming socio-economic conditions, and a general decline in forest management, decisions about the optimal method and intensity of thinnings are becoming increasingly important. In this paper, we compare situational thinning, thinning of clusters and groups, thinning of variable density and selective thinning, traditional in Slovenia. We propose guidelines for combining various thinnings and choosing a suitable model and program of thinning. Based on the synthesis of previous research, we point out that field experiments are important for the evidence-based improvement of thinning methods.

V prispevku smo analizirali in primerjali pomlajevanje po vetrolomih v letih 2008 in 2017. Ugotavljamo, da so gostote naravnega mladja med raziskovalnimi objekti in znotraj njih zelo različne in so posledica različnih ekoloških razmer v času ujme in po njej. Začetne gostote tri (vetrolom 2017) oz. štiri leta (vetrolom 2008) po ujmi so znašale približno 2100 do 23.000 osebkov na hektar. Zmes je bila bolj podobna, od klimaksnih vrst sta prevladovali smreka in bukev. Pomembno začetno gonilo sukcesije je precejšnja zastopanost pionirskih in svetloljubnih vrst, kot so iva, jerebika in breza. Avtorji izsledke raziskave dopolnjujemo z gozdnogojitvenimi smernicami za obnovo gozdov. Po ujmi smo pri tehnični sanaciji pozorni, da ne poškodujemo obstoječega pomladka, ki ima velik vlogo pri obnovi. Prevladuje naj naravna obnova gozdov, za umetno se odločamo v zaostrenih ekoloških razmerah, ko pričakujemo malo naravnega mladja ali to ni razvito. Pri umetni obnovi po zgledu iz tujine vnašamo jelko in hrast. Obžetev izvajamo točkovno in ne površinsko po celotni umetno obnovljeni površini, saj z njo odstranjujemo naravno mladje. V sistem obnove je treba vpeljati preverjanje uspešnosti saditve. In this paper, we analysed and compared regeneration after the 2008 and 2017 windthrow events. We found that the densities of natural regeneration between and within research sites were very diverse due to different ecological conditions during and after disturbance. Initial densities after three (windthrow 2017) or four years after the disturbance ranged from about 2,100 to 23,000 individuals per ha. Concerning species composition, spruce and beech were dominant among the late-successional species, while there was a considerable representation of pioneer and light-demanding species, such as willow, rowan, and birch, which made an important contribution to early successional forest recovery. The results of the research are supplemented with silvicultural guidelines for forest restoration. During post-disturbance salvage logging, attention is needed not to damage the existing advanced regeneration, which plays a major role in forest restoration. Natural regeneration should predominate, while artificial regeneration should be used on sites where we expect little or no natural regeneration. When using artificial restoration, following examples from abroad, silver fir and oak should be used more often. Weedings should be focused and not superficially employed over the entire artificially restored area, as it removes natural regeneration. Planting performance assessment must be introduced in the restoration system.

Regression of conifers in European mixed old-growth mountain forests has been observed for a long period and studied from different aspects. Old-growth (OG) forests in Bosnia and Herzegovina (BiH) have not experienced heavy air pollution and chronic overbrowsing that have affected many other European OG forests, while climatic and anthropogenic disturbances have been well documented. We analysed stand structure in the Janj OG forest, compared it with inventories of Lom and Perucica OG forests (BiH) and with earlier inventories of the same reserves. At present, OG forest Janj is characterized by a high growing stock (1215 m$^3$·ha$^{−1}$). This is due to good site quality, prevalence of conifers (84%) and dominant endogenous processes in recent decades. In all three OG forests, indicators of structural change exhibited progression of European beech over time. Historical evidence revealed the occurrence of warm summers and droughts followed by bark beetle outbreaks in the 1920s, 1940s and early 1950s, which in turn influenced a marked conifer decline. It seems likely that repeated canopy opening released waves of European beech regeneration. These stand structural changes have delayed the rejuvenation of conifers and can help explain the early observations of conifer decline.

In Europe the area of forested land is increasing, largely due to forest development on abandoned agricultural lands. We compared the structure and composition of woody species in young stands undergoing secondary succession and within gaps of late-successional (LS) forest in Haloze (Slovenia) to derive management options. In a subset of plots in succession, silvicultural measures were carried out in one half, while the other half was left untreated. The attributes of crop trees and their competitor trees were monitored over five years, and a study on the time investment of tending was conducted. We found lower tree density, a larger share of pioneer and shrub species, and a higher diversity of woody plants in succession compared to regeneration within LS forest gaps. Tending resulted in greater density of crop trees, their better social position, fewer competitor trees, and a larger diameter at breast height (d.b.h.) increment, while differences in crop tree stability and quality between tending and control were not confirmed. Our results indicated great structural complexity and species diversity in young successional forests. Their tending represents a cost efficient method of recovering the long-term commercial value and ecosystem services of forests, if applied less intensively than traditional tending of LS forest.

There is increasing interest across Europe in adopting forest management strategies, which promote species and structural diversity through the use of irregular silvicultural systems, an approach often described as continuous cover forestry (CCF). However, there is little information about the proportion of CCF practised across the continent or about the knowledge gaps and other obstacles that limit its use. A survey of respondents in 33 European countries sought to address these issues. The results indicated that the silvicultural systems associated with CCF were single stem, group selection and irregular shelterwood. Rotational forest management (RFM) was more frequent than CCF in about 66 per cent of countries, whereas in 25 per cent the reverse was true. We estimated that between 22 and 30 per cent of European forests are managed through CCF, although good data are lacking. The main knowledge gaps were: uncertainties arising from climate change (e.g. appropriate species choice, carbon storage in CCF), using CCF to increase forest resilience, deployment of mechanized harvesting systems, lack of knowledge about CCF amongst professional foresters and better information on economic implications of this approach. Major obstacles included: little awareness of CCF amongst forest owners, limited competence in CCF within the forestry profession and a scarcity of skilled forest workers to implement this approach, high ungulate populations damaging natural regeneration, a sawmilling sector geared to processing medium-sized logs, subsidy regimes favouring practices associated with RFM and a lack of experience in transforming plantation forests to more diverse structures. Better information on the use of different silvicultural systems is essential to allow policymakers and other stakeholders to monitor progress in diversifying forests. Establishment of a continental network of long-term operational trials (e.g. expanding the existing Association Futaie Irrégulière network) would improve professional understanding of CCF, would demonstrate this approach to forest owners and other stakeholders and could provide a valuable platform for supporting research.

Splošno sprejeto stališče je, da s sonaravnim gospodarjenjem zmanjšujemo tveganja pri gospodarjenju z gozdovi. Za potrditev tega stališča obstajajo dobri zgledi gospodarjenja in posredni dokazi, primanjkuje pa znanstvenih študij, ki bi na podlagi kvantitativnih analiz to potrjevale. V Sloveniji smo potrdili pozitivne povezave med ohranjeno drevesno sestavo, rednim gospodarjenjem in manj sanitarnimi sečnjami. V dobi izrazitih okoljskih sprememb je smiselno spodbujati redno gospodarjenje z gozdovi. V prihodnosti bo zaradi socialno-ekonomskih sprememb še bolj izraženo opuščanje gospodarjenja. V članku razpravljamo o številnih prednostih rednega gospodarjenja. V prihodnje bo treba poleg vloge rednega gospodarjenja za preskrbo lesnopredelovalne verige večji poudarek nameniti pomenu dejavnega gospodarjenja za prilagajanje gozda na okoljske spremembe in za zdravje gozda. The generally adopted standpoint is that we reduce the risks in forest management through close-to-nature management. There are good examples of management and indirect proofs confirming this standpoint, however, there is a lack of scientific studies confirming it based on quantitative analyses. In Slovenia, we confirmed positive links between the preserved tree structure, regular management, and fewer sanitary fellings. In a time of distinct environmental changes, it is reasonable to encourage regular forest management. Due to social and economic changes, abandoning the management will be even more distinct in the future. In addition to the role of the regular management for the wood processing chain supply, major stress will have to be given to the significance of the active management for adapting the forest to the environmental changes and forest health in the future.