In a high, middle-aged stand of European hornbeam, on a site of mesophilous pedunculate oak, European hornbeam and narrow-leaved ash in the unflooded part of Ravni Srem (Carpino betuli-Quercetum roboris (Anić, 1959) Rauš 1971. subass. Fraxinetosum angustifoliae Tomić, 2007), the following tree species from the natural forest community were present: narrow-leaved ash, field maple and field elm. Pedunculate oak, a primary edificator of the community and economically the most important species was absent. The stand is 55 years old and originates from a failed regeneration of pedunculate oak. Thus, the silvicultural prescription is restoration. The number of trees in the unthinned part of the stand (EP 1) was 1217 trees per hectare and in the thinned part (EP 2) 530 trees per hectare. In the thinned part of the stand, 43.5% of the total number of trees and 40% of the total number of trees of European hornbeam were counted, compared to the unthinned part of the stand. The quadratic mean diameter (dg) and dominant trees diameter (Dg20) in the unthinned part of the stand were 17.4 and 23.6 cm and in the thinned part of the stand 19.0 and 27.6 cm. The Lorey's mean height and the dominant heights were between 22.2 and 23.9 m on EP 1 and 20.5 to 22.2 on EP 2. The amount of European hornbeam seed on the soil surface in different stands is similar. In the unthinned part of the stand, the mean number of European hornbeam seeds was 1195 pcs m-2 (100%) and in the thinned part 1177 pcs m-2 (98.5%). The mean number of healthy seeds on the soil surface in the thinned and unthinned stands was 1117-1142 pcs m-2. The seeds from previous years participate with 12.2-15.0% (136-171 pcs m-2) and the seeds from the 2018 mast year 85.0-87.8% (971-981 pcs m-2), with 95% of the seeds being healthy (971-981 pcs m-2). Due to the effect of thinnings, the stands that were dominated by European hornbeam become more mixed, which is a new element that defines the process of the restoration in the future. Seedbank in the middle-aged stand designated for restoration under different managing strategies is made up of 85-88% of healthy seeds from 2018, with 12-15% from previous years.

Istraživanja su obavljena u kulturi smreke (Picea abies /L./ Karst.), koja je osnovana sa 5.000 sadnica po hektaru na staništu planinske šume bukve na nadmorskoj visini 870 m. Na osnovi usporedbe elemenata rasta istraživane kulture s elementima rasta u drugim mladim do srednjedobnim kulturama smreke, istraživana kultura je u kategoriji visokoproizvodnih kultura u Srbiji i šire u Europi. Na trajnoj pokusnoj plohi, u dobro sklopljenom dijelu istraživane smrekove kulture u starosti 32 godine, izmjereno je 3.911 stabala po hektaru, s volumenom od 384,17 m3·ha-1, a ukupno evidentiran prirast drvne zalihe sastojine do 40. godine iznosio je 561,85 m3·ha-1, a do 50. godine 819,1 m3·ha-1. Na osnovi dvije prorjede, u 32. i 40. godini i naknadno posječenih tanjih stabala u razdoblju od 33. do 40. god., na pokusnoj plohi ukupno je posječeno 2.844 stabla po hektaru (72,7%) volumena 279,4 m3·ha-1 (tablica 1). Numerički pokazatelji strukture stabala na pokusnoj plohi u 32., 40. i 50. godini prikazani su u tablici 2, a debljinska struktura na grafikonima 2, 3 i 4. Za definiranje utjecaja prorjeda na prirast stabala uspoređen je tečajni debljinski (idt) i visinski (iht) prirast u razdoblju od 25. do 32. godine i 33.-40. godine kod detaljno analiziranih dominantnih stabala (D100 i D400), a na sastojinskoj razini uspoređen je tečajni debljinski (idt) i visinski (iht) prirast u razdoblju od 33. do 40. godine i 41.do 50. godine kod dominantnih stabala (D100 i D400). Testiranje razlika između tečajnih prirasta u različitim razdobljima obavljeno je uz pomoć t-testa. Na razini sastojine uspoređen je i tečajni prirast promjera, temeljnice i volumena svih stabala i stabala budućnosti (311 kom.∙ha-1) u razdoblju od 33.-40. godine i u razdoblju od 41.-50. godine. Neparametrijski Kolmogorov-Smirnov test korišten je za međusobnu usporedbu struktura stupnja vitkosti (odnos h/d1,3). Istraživanja su omogućila da se definira utjecaj prorjeda na prirast i stupanj vitkosti različitih kategorija stabla i sastojine u dva starosna razdoblja sastojine, 33.-40. i 41.-50. godine. Prva prorjeda u 32. godini, pri visini dominantnih stabala 15 m, imala je karakter selektivne prorjede, bila je niska (qd<0,85) i jaka (jačina prorjede je 36% volumena). Prorjeda je obavljena u starosti sastojine koja značajnije ne odstupa od razdoblja kada se izvode prve „komercijalne“ prorjede u Europi. Međutim, tokovi tečajnog debljinskog prirasta detaljno analiziranih dominantnih stabala (D100 i D400) pokazali su da je prekasno izvršiti prorjedu u 32. godini, a model rasta (prirasta) visina је pokazao kulminaciju u 25. godini (kada su dominantna stabla postigla visinu 11 m), pa bi se 25. godina mogla označiti i kao godina u kojoj je najkasnije trebalo izvršiti prvu komercijalnu prorjedu (grafikon 7). Zatečeni velik broj stabala, s velikom drvnom zalihom po hektaru, u 32. godini i jaka prorjeda uvjetovali su visoki iznos prorjednog etata, od 115,13 m3∙ha-1, što je u kategoriji najviših iznosa volumena koji se okvirno preporučuju u literaturi za sličnu starost smrekovih kultura. U razdoblju od 33.-40 godine debljinski prirast je iznosio kod preostalih stabala 0,31 cm∙god-1, a kod stabala budućnosti 0,54 cm∙god.-1 (tablica 7). Dominantna stabla, posebno 400 najdebljih stabala po hektaru, nalazila su se u fazi velikog visinskog prirasta u vrijeme i poslije prorjede u 32. godini (tablica 5 i 6), što je za posljedicu imalo povećanje stupnja vitkosti stabala, odnosno povećanje nestabilnosti sastojine (grafikon 8). Druga prorjeda u 40. godini, pri visini dominantnih stabala preko 20 m, imala je karakter selektivne prorjede, bila je niska (qd<0,85) i jaka (jačina prorjede je 34% volumena). Jaka prorjeda u 40. godini, s prorjednim etatom 142,28 m3∙ha-1, uvjetovala je veći debljinski prirast, odnosno bolju reakciju debljinskog prirasta na preostalim stablima, u odnosu na prorjedu u 32. godini. Stabla budućnosti imali su za 29%, a dominantna stabala (D100 i D400) za 36-42%, veći debljinski prirast u starosnom razdoblju od 41.-50. godine, u odnosu na starosno razdoblje 33.-40. godine, što je uz opadajući trend visinskog prirasta uvjetovalo i manji stupanj vitkosti, odnosno veću stabilnost stabala i sastojine (grafikon 8). Na osnovi navedenog, proizlazi da su provedene jake prorjede doprinijele uspostavljanju povoljnih odnosa u debljinskom i visinskom rastu stabala u istraživanoj kulturi i time poboljšale njihovu stabilnost.

The effect of plantation density on the stem volume development phases of mean trees of Populus x euramericana (Dode) Guinier, cl. I-214 were studied in the test plantation aged 25 years with two different planting densities 4.25x4.25 m (treatment A) and 6.00x6.00 m (treatment B). The modeling of stem volume growth of mean trees enabled the identification of development phases based on biological laws. Different growth dynamics of mean trees of the clone I-214, depending on plantation density, had a clear effect on the beginning and the end of individual phases, i.e. subphases of development, as well as on the diameters, heights and volumes of mean trees at the end of each phase of volume development.

Ash dieback is a major issue affecting European ash populations, including narrow-leaved ash (Fraxinus angustifolia Vahl). An important factor contributing to the decline of narrow-leaved ash is the fungal disease caused by Hymenoscyphus fraxineus. However, the mortality of trees also depends on stand structure that may influence the disease dynamics. In 2020, we analysed the stand structure of middle-aged, extensively managed, narrow-leaved ash stands growing on Humogley soil (Cariceto remotae-Fraxinetum angustifoliae, Jov., et Tom. 1979). This permanent sample plot is located in Posavina (Serbia), where we observed reduced tree vitality and mortality. The stand originates from natural regeneration after a succession of marsh habitats. At ages 20–25 years (1996) and 30–35 years (2006), selective thinning was carried out. Until the age of 45–50 years (2020), the stand was left unthinned, and the presence of ash dieback fungus was recorded in Serbia. In 2020, we measured the diameter at breast height (DBH) of each tree on the plot and assessed their crown class and degree of isolation. These parameters were evaluated in relation to the crown defoliation of the trees. The results indicate that reduced vitality and mortality of trees manifest in conditions of strongly expressed intraspecific competition in the stand, particularly during the stem exclusion stage. Healthy trees were observed primarily within the predominant/dominant crown class and exhibited the highest mean DBH. Trees classified as dead or dying (81%–100% defoliation) had a lower mean DBH compared to both healthy trees (<25% defoliation) and significantly defoliated trees (26%–80%). This was observed at both the stand level and in predominant/dominant trees, suggesting that tree mortality is primarily linked to their poor growth.

The application of silviculture measures on contemporary, rationalized basis in order to sustain and improve forests in the area of the National park ?Fruska Gora?, is the most im?portant segment of forest management, having in mind their anthropogenically deteriorated conditions and their purpose. For the improvement of stand conditions, intensive silvicultural tending measures are necessary in certain phases of development of the stands which is con?trary to the passive protection. The main reasons for the application of these measures are in the coppice origin of the stands on over 82% of the area of National park and the silver lime dominance compared to other edificators (oaks and beech). On the basis of the ecosystem approach in forest management, and especially in conditions of more pronounced climate change, the silvicultural measures need to be rationally synchronized with biological-ecological demands of the main species and dominant processes in forest ecosystems. In other words, there is a need to implement the elements of close-to-nature forest management. This paper points toward the most important determinations of silviculture in order to achieve the goals of special-purpose forests in the National park.

Quercus pubescens Willd. is a deciduous species that can retain leaves in the winter either as dead, standing leaves (marcescence), or as living, winter-green leaves. The retention of green leaves through winter is rare in continental areas. Winter-green leaves were observed on one-year-old seedlings of Q. pubescens in the winter of 2020 in the nursery of the Faculty of Forestry that lasted until the end of April 2021. The photosynthetic activity of photosystem II was measured using the rapid light curve method based on modulated pulse chlorophyll fluorescence. We assessed the potential photosynthetic activity of the leaves across the range of physiological stages: winter-green leaves retained from the previous growing season and on the leaves from the first, second, and third growth flush during the growing season. Photosystem II of winter-green leaves attained ~50-60% of the maximal photosynthetic activity obtained in spring and summer leaves, respectively. Climate data indicated that winter-green leaves exhibited frost resistance in the winter of 2020/2021, as their photosynthetic activity was preserved despite 33 days with sub-zero temperatures. The rapid light curve method also revealed the gradual acclimation of seedlings on a flush level, with leaves from the third flush best able to use available light under high temperatures and insolation efficiently. The results of rapid light use as an indicator of seedling acclimation are discussed. Some remarks on the possible practical significance of the winter-green leaves phenomenon (as in genetic selection) are highlighted.