Gap regeneration in two old-growth forest reserves in Slovenia (Rajhenavski Rog) and Croatia (Čorkova Uvala) was analysed in relation to within gap light heterogeneity. Both reserves were located in ...the Dinaric mountain range in south-central Europe and were dominated by beech (Fagus sylvatica L.) – silver fir (Abies alba Mill.) forest communities with similar growing conditions. In total, the two largest gaps (700–2000 m2) in each reserve were included in the study (n = 4), plus a further four gaps in Rajhenavski Rog and three in Čorkova Uvala (200–500 m2). All the gaps were ∼10 years old and originated from one or two successive events, mostly due to a combination of fungi attack and windthrow. Consequently, all gaps had complex geometry and were covered by a well-developed regeneration layer. Each gap was mapped, followed by establishment of a N–S oriented 5 × 5 m grid within and around the area of the canopy opening. At the grid intersections 773, 1.5 × 1.5 m plots were established. On each plot, the coverage of tree regeneration and ground vegetation, seedling density in different height classes and browsing damage were recorded. In addition, the total stretched length and last growing season increment of the leading stem was measured on selected seedlings in each plot. Relative diffuse and direct radiation were estimated using digital hemispherical photographs. All plots were classified into four microsites according to direct and diffuse radiation levels, and microsites were tested for differences in regeneration height and density. While there was more woody regeneration and an almost fivefold higher (6.2 vs 1.3 m−2) average total regeneration density in Rajhenavski Rog, mainly due to a high (5.5 vs 0.6 m−2) density of beech, there was more ground vegetation and a higher density of silver fir seedlings in Čorkova Uvala. The within-gap regeneration patterns proved to be similar in both forest reserves and showed that 1-year-old seedlings of beech and silver fir and small beech seedlings preferably recruit on microsites under closed canopy or close to gap edges with lower levels of direct and diffuse radiation. There was no significant difference in density of large-beech seedlings among the microsites, yet height and height increment were higher on microsites receiving the highest levels of direct and diffuse radiation. Within-gap heterogeneity in light conditions appears to significantly influence general patterns of beech and silver fir regeneration, while the differences in total average density, regeneration and ground vegetation abundance and spatial distribution cannot solely be explained by light. Since climate, parent material, soil, exposition, relief and stand conditions were very similar between both reserves, it appears that these differences are a result of different densities of large herbivores, which are reported to be much higher in Rajhenavski Rog. This was also confirmed in our research, as much more browsing damage was found in Rajhenavski Rog compared with Čorkova Uvala. Implications for silvicultural practice are outlined.
Područje poplavnih šuma crne johe (Alnus glutinosa (L.) Gaertn.) u Sloveniji čini samo 0,4 % (približno 4708 ha) ukupne površine šumskog zemljišta (Čater i sur., 2001.). Veći kompleks takvih ...sastojina u Sloveniji su Črni i Polanski Log, a istraživanje je provedeno na području potonjeg (slika 1). Kako čiste sastojine johe odlikuju brojne specifičnosti, potrebno im je prilagoditi šumskouzgojne postupke. Da bi se utvrdio odgovarajući intenzitet prorjede takvih sastojina, 1967. godine u Polanskom Logu postavljene su pokusne plohe. Od tada do 2018. godine na plohama je izvršeno pet do sedam mjerenja. Sva stabla na plohama su bila obrojčana. Izvršeno je mjerenje prsnih promjera i procjena sljedećih elemenata na stablima: pripadnost etaži, vitalnost, uzgojna perspektiva, uzgojna uloga, duljina krošnje i kvaliteta (tablica 3). Svaka ploha bila je podijeljena u tri polja (40 x 50 m) s različitim metodama rada: bez intervencije, umjereno i intenzivno prorjeđivanje. Uzgojni postupci koji su poduzeti tijekom praćenja pokusa prikazani su u tablici 2. Danas su te sastojine u zreloj fazi razvoja, stoga smo u ovom radu analizirali reakcije crne johe na različite intenzitete prorjeđivanja i dobivene rezultate usporedili s preporukama autora tradicionalnih uzgojnih modela i modela koji se temelje na situacijskoj njezi šuma.Ustanovili smo da se na plohama s intenzivnim prorjeđivanjem gustoća sastojine koja je u dobi između 50 i 70 godina i na kraju je ophodnje kreće od 295 do 690 kom/ha (slika 3), dok se na plohama bez intervencije ova vrijednost kreće u rasponu od 370 do 790 kom/ha. Drvne zalihe u istom su se razdoblju kretale u rasponu od 277 do 458 m3/ha na plohama s intenzivnim prorjeđivanjem, dok su na plohama bez intervencije bile veće, u rasponu od 309 do 516 m3/ha (slika 4). U to su se doba temeljnice nalazile u rasponu između 23 i 41 m2/ha na plohama s intenzivnim prorjeđivanjem, a na plohama bez intervencije u rasponu od 26 do čak 51 m2/ha (slika 5). Tijekom cijelog razdoblja praćenja ploha, stabla su, bez obzira na metodu rada, narasla za tri do četiri debljinska stupnja (slika 2). Na plohama s umjerenim prorjeđivanjem i onima bez intervencije, debljinski prirast stabala bio je skoro jednak (0,33 cm godišnje) (slika 6). Statistički je značajan veći debljinski prirast stabala na plohama s jako intenzivnim prorjeđivanjem (0,37 cm godišnje). Debljinski prirast dominantnih stabala bio je nešto veći, od 0,46 cm godišnje na plohama bez intervencije do 0,50 cm godišnje na plohama s jako intenzivnim prorjeđivanjem, ali statistički značajne razlike između metoda rada nisu utvrđene (slika 6). Međutim, otkrili smo da kod dominantnih stabala ne postoje statistički značajne razlike s obzirom na njihovu slojevitost, vitalnost, tendenciju, dužinu krošnje i kvalitete s obzirom na korištenu metodu rada.U usporedbi s uzgojnim modelima koji su se koristili za manji broj odabranih stabla, gustoća i temeljnica ispitivanih sastojina je znatno veća, a debljinski prirast manji. Autori tradicionalnih i modela s manjim brojem odabranih stabala zagovaraju rano prorjeđivanje takvih sastojina (tablica 1). Veće razlike nastaju u konačnom broju stabala po hektaru i u intenzitetu intervencije. Razlog malog debljinskog prirasta i razlike između metoda rada na našim plohama pripisali smo nedovoljnom intenzitetu i djelomično nedosljednoj provedbi postupka prorjeđivanja. Ipak, ukazala se potreba za intenzivnim prorjeđivanjem i pospješivanjem rasta stabala najvećeg prsnog promjera, vitalnosti i tendencije, lijepo oblikovane i duge krošnje (slika 7, slika 8).
•We examined the crown architecture of dominant beech trees in the regeneration.•Crown irregularities are significantly related to light, regeneration age and density.•The occurrence of plagiotropic ...beech saplings decreases with increasing light.•The occurrence of forked and broom-shaped saplings increases with increasing light.•The number of saplings with unwanted architecture dropped dramatically over a 5-year period.
Basic dimensions and morphological characteristics of European beech (Fagus sylvatica L.) saplings were measured in an old-growth forest and in a selectively managed mixed Dinaric silver fir–beech forest in 2000 and 2005. Over the 5-year period, average relative diffuse radiation above saplings (DIF), sapling length, and root collar diameter significantly increased. Light proved to be an important factor influencing beech sapling crown architecture. There was a strong negative relation between plagiotropic sapling occurrence and DIF, while the relation between DIF and forked and broom-shaped crown forms was positive. Occurrence of all three crown irregularities was negatively related to the regeneration density. Crown plasticity was less expressed after the 5-year period of growth, as the number of plagiotropic, broom-shaped, and forked saplings decreased dramatically. The results of this study indicate that broom-shaped, forked, and plagiotropic trees did not recruit successfully, or that these types of morphological adaptations were no longer an advantage in the late sapling stage of development. The hypothesis that small-scale uneven-aged silvicultural systems, such as the selective system, result in poor beech regeneration architecture to the extent that the future quality of beech logs is affected was not confirmed by the results of this study.
Integrative forest management attempts to simultaneously fulfill both wood production and biodiversity conservation in a given forest region, and presumably supplants the need for unmanaged forest ...reserves. This is the dominant management paradigm in the temperate zone of Europe, yet few studies have examined the validity of this approach. We used Slovenia as a test bed to examine how the long-term practice of integrative forest management has influenced two structural components of mature forest conditions, namely coarse woody debris (CWD) and large living trees, as well as the distribution of the White-backed Woodpecker, a species dependent on such conditions. Data were compiled from national inventory plots, coupled with separate surveys in 51 forest reserves. The mean volume of CWD and density of large beech trees across managed forests in Slovenia was 15m3ha−1 and 6ha−1, respectively; these mean values were significantly higher (165m3ha−1 and 55ha−1) in old-growth reserves. CWD was primarily comprised of small diameter pieces in managed forest, whereas large diameter pieces in multiple stages of decay represented most of the volume in reserves. These results, coupled with the limited distribution of the woodpecker across the country, suggest that integrative management practiced over a large scale may be insufficient for maintaining biodiversity dependent on mature forest conditions at current levels of wood extraction.
•We examined successional trajectories in fenced and unfenced salvaged stands.•Spruce’s share in regeneration density decreased over time.•Fencing accelerated successional development and favoured ...broadleaves.•Regeneration niche partitioning was affected by meso-relief and forest edge.•Shorter distances to seed trees favoured spruce and anemochorous broadleaves.
Management of Norway spruce monocultures in Europe is becoming increasingly difficult due to frequent natural disturbances. Their transformation could be especially challenging if several disturbances interact. In 2003 a spruce bark beetle outbreak damaged large tracts of spruce bottomland successional forest in southeast Slovenia where overabundant ungulate populations are present. In openings (5.4–7.5ha in size) in four salvaged forest compartments, we studied the effects of meso-relief, forest edge, seed trees and fencing on vegetation succession and tree regeneration. In 2005 and 2013 we sampled seedling density on 240 plots according to height class and species. In the second inventory we also assessed distance to seed trees and on a subsample of the plots the coverage of vascular plants. The results indicated sufficient natural regeneration and niche partitioning among species groups, with Norway spruce seedlings being more successful at stand edges, pioneers and anemochorous broadleaves in gap centres, and zoochorous broadleaves on plateaus as opposed to sinkholes. Seedling density of all anemochorous broadleaves was higher closer to seed trees. Spruce seedling abundance was negatively associated with the cover of herbaceous vegetation and that of pioneer trees with shrubs. Fencing resulted in significantly greater density, height and coverage of seedlings as well as a higher share of broadleaves. While bark beetle outbreak triggered regeneration of broadleaves, overbrowsing acted in the opposite direction by facilitating spruce. Thus, to accelerate successional development and to prevent a spruce dominated alternative ecosystem state, a significant reduction in deer abundance is needed. To safeguard seed sources, promote seed dispersal by encouraging perches and shelters, and preserve potential habitats, some damaged trees should be retained during salvaging operations.
Data were analysed on the volume of dead wood in 86 beech forest reserves, covering most of the range of European beech forests. The mean volume was 130
m
3/ha and the variation among reserves was ...high, ranging from almost nil to 550
m
3/ha. The volume depended significantly on forest type, age since reserve establishment and volume of living wood. More dead wood was found in montane (rather than lowland/submontane) reserves, longer-established reserves (time since designation) and reserves with higher volumes of living wood.
On average, fallen dead wood contributed more to the total dead wood volume than standing dead wood. The percentage of dead wood that was standing was almost twice as high in montane than in lowland/submontane forest reserves (45% versus 25%). The volume of dead wood at selected sites changed considerably over time. The fluctuations were significantly higher in lowland/submontane than montane reserves, possibly connected with differences in the disturbance regimes and especially damage caused by windstorms. In NW Europe, the blow down of formerly managed, even-aged stands led to extraordinary high volumes of dead wood shortly after reserve establishment.
The implications for forest management and biodiversity conservation are discussed. An increase in dead wood volumes must be carried out in accordance with the local/regional forest type and disturbance regime. Thus, in order to fulfil the requirements of as many wood-depending organisms as possible, it is important to preserve not only larger amounts of dead wood, but also dead wood of different types and dimensions as well as securing a long-term continuity of dead wood.
Understanding how forests respond to multiple disturbances is becoming increasingly important under global change. We examined the simultaneous influence of canopy decline and deer browsing on ...regeneration in an old-growth reserve and surrounding managed forest dominated by Fagus sylvatica L. and Abies alba Mill. in Slovenia. We quantified both disturbance processes by measuring characteristics of canopy gaps and reconstructing historical deer densities. Forest response was assessed with repeated measurements of tree regeneration and regeneration patterns within deer exclosures. Most gaps were formed by mortality of A.alba (71%), and gapmaker characteristics suggest that gaps formed slowly and often expanded, resulting in a mosaic of openings covering 17% of the old-growth reserve. Fagus sylvatica dominated the regeneration layer throughout the reserve and recruited to taller height classes over the past 26 years. The recruitment failure of preferred browse species (A.alba and Acer pseudoplatanus L.) in the reserve and the successful recruitment of these species within exclosures indicate that selective browsing by deer has altered the successional response to A. alba decline, facilitating the dominance of F.sylvatica. Given that global change may increase forest decline worldwide and the ubiquitous nature of deer browsing in many temperate forests, understanding their combined effects on forests will become increasingly important.
Slovenia has a small number of old-growth forest remnants, as well as many forest reserves approaching old-growth 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 unpredictable ones due to the influence of natural disturbances and indirect human influences. In accordance with this thinking, the methods used to study old-growth forests have changed from descriptions of stand structure to studies that address natural processes and ecosystem functions.
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