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Sycamore is a valuable tree not only economically but also ecological and culturally. Even though it has a vigorous regeneration system from its stump, its coppice management has triggered limited formal investigations. Therefore, the present study focused on finding the most suitable coppice strategy for achieving ground coverage and biomass, as well as developing growth and yield models for sycamore maples. Using a series of eight measurements spanning twenty-one years, starting from age six, we found that single-shoot coppices provided superior yields for height than seed-managed trees up to age twelve and up to age twenty for DBH. The coppice trees outperformed the seed trees up to age 10. The yield of DBH and the height for single-shoots and seed-managed trees were described by parsimonious formulations, namely the Schumacher model for DBH and the square root for height. The relationship of DBH–height exhibited a clear linear form, pointing toward the main limitation of the study, namely the confinement to ages less than 20 years. Nevertheless, all the models exhibited a bias

Articolul prezintă rezultatele unui exercițiu de inventariere pe scară mică, realizat într-un arboret (u.a. 34B, U.P. I Săliște, Ocolul silvic Obștea Săliște) care include duglas verde (DF) și molid de Sitka (MOS, specie exotică utilizată foarte rar în România), instalat prin plantare (1,5 x 1,5 m) în anul 1962 în completarea regenerării naturale a fagului. La 60 de ani, duglasul se comportă mai bine decât molidul de Sitka în sens biometric, iar cele mai relevante caracteristici ale celor două specii sunt după cum urmează: - diametrul de bază maxim: 67,1 cm (DU) și 37,7 cm (MOS); - diametrul mediu al suprafeței de bază dg: 41,81 cm (DU) și 27,43 cm (MOS); - înălțimea maximă: 39,5 m (DU) și 30,5 m (MOS); - înălțimea corespunzătoare lui dg: 32,00 m (DU) și 24,95 m (MOS); - indicele de zveltețe mediu: 84 (DU) și 90 (MOS); - diametrul mediu al coroanei: 462 cm (DU) și 361 cm (MOS); - ambele specii prezintă un elagaj natural imperfect, ca și în alte culturi instalate în întreaga Europă. Duglasul verde s-a adaptat la condițiile locale ca și în alte părți din România, unde se întâlnește pe cca 12.700 ha, și prezintă un potențial ridicat de producție de lemn. Molidul de Sitka a fost capabil să supraviețuiască în condiții locale dificile (spre exemplu, altitudine mare, climat temperat-continental, foarte diferit de cel oceanic din arealul natural și de pe coastele nordice și vestice ale Europei), fără a produce la fel de mult lemn ca în alte țări europene gen Marea Britanie și Irlanda.

Articolul prezintă rezultatele unui proiect la scară redusă de cercetare-demonstrativ privind silvotehnica molidișurilor tinere, realizat într-o plantație pură de 0,4 ha, cu schema de 2 x 1 m (5000 puieți ha-1), instalată în anul 2001. În anul 2009, după aplicarea unui elagaj de acces la toți arborii din plantație, 60 „potențiali” arbori de viitor au fost aleși pe întreaga suprafață a arboretului, pe baza criteriilor vigoare-calitate- distribuție (spațiere), fiind ulterior elagați până la 4-4,5 m înălțime. În același an au fost instalate două suprafețe de probă (SP) de câte 300 m2 și s-a aplicat o curățire combinată și puternică în mod clasic (specifică pentru silvicultura de arboret, în SP1), respectiv dinamic (ca la silvicultura pe arbori de viitor, în SP2). O curățire clasică (consistența medie după intervenție 0,8) s-a aplicat, de asemenea, la nivel de arboret, cu arborii „potențial” de viitor lăsați în stare de creștere liberă (fără competiție) la nivelul coroanei. O răritură combinată, similară intervenției din 2009, s-a aplicat în cele două SP și pe întregul arboret în anul 2013, cu desimea rămasă de 1167 arbori ha-1 (SP2) și 1567 arbori ha-1 (SP1), respectiv cu suprafața de bază rămasă de 20,67 m2 ha-1 (SP2) și 23,47 m2 ha-1 (SP1). În anul 2020, diametrul mediu aritmetic și diametrul mediu al suprafeței de bază în SP2 și la „potențialii” arbori de viitor au atins 20 cm. Dintre acești arbori, peste 50% au cel puțin 20 cm în diametru. Suprafața de bază în SP1 și SP2 este de peste 35 m2 ha-1, astfel încât o nouă răritură se va aplica în anul 2020, pentru a reduce suprafața de bază sub nivelul critic de 30 m2 ha-1. Înălțimea medie a atins 15 m în anul 2020, iar indicele de zveltețe a crescut în mod semnificativ doar în SP1, atingând valoarea de 85. Proiectul de cercetare-demonstrativ a arătat clar posibilitatea de a produce arbori de molid cu diametrul de bază de 20 cm în 20 de ani, utilizând o silvicultură pe arbori de viitor începută devreme, de-a lungul fazei de prăjiniș.

Europe has a history rich in examples of successful and less successful introductions of non-native trees (NNT) - trees with an evolutionary origin outside of Europe. NNT have been introduced for various reasons such as ornamental purposes, food production, land reclamation/amelioration and timber production. The use of NNT also causes controversies due to potential negative impacts on natural ecosystems of NNT that become invasive. Many international legal frameworks responded to the presence and use of NNT, such as international treaties and conventions ; and also the European Union deals with the issue of invasive alien species in Regulation (EU) No. 1143/2014. However, especially the national and regional responses to NNT affect current and future management decisions in the forest sector and furthermore shape forest landscapes of Europe. In this comprehensive study of the legal landscape concerning NNT we identified all relevant legislations, the different legal approaches and the regulatory intensity in every European country (except microstates). Hard and relevant soft law items at the national and sub-national (regional) level for 40 European countries were collected and proofed using a targeted questionnaire sent to country experts across Europe mainly coming from the forestry and nature conservation sector. In addition, international and national legislation information systems and databases were consulted to complete the information. Legislations included updates until June/July 2019. In total, 320 national and regional law items were identified to be relevant for the regulation of NNT in the investigated 116 legislative units (countries, and regions with own legislation) in Europe. Countries and regions were empirically categorised according to ad hoc created legislation indicators dealing with the general ban of introduction of non-native species, the generally allowed and prohibited NNT, approval mechanisms, e.g. mandatory forest management plans, and areas and cases where NNT are restricted or completely prohibited. Our study revealed a very diverse legal landscape in Europe, with a large variety of approaches being pursued to regulate NNT, and the intensity of regulation ranging from very little restrictions on the species choice and plantation surface area to a complete ban of NNT in forests.

Black walnut (Juglans nigra L.) is a light-demanding, competition-intolerant, and tall forest tree species, introduced in Europe from North America at the beginning of the seventeenth century. It has an important economic role in Europe for producing wood and fruits, in agroforestry systems, as an ornamental tree for parks and avenues, for rehabilitation/restoration of degraded lands. The best sites for black walnut growth have warm and mild climates, with frequent and well-spread precipitation, and rich, deep, near neutral, well-drained and moist soils. Black walnut is a fast grower in youth and its height and diameter growth reach their peaks before age 30–35 years. It is globally the best known allelopathic species due to the juglone substance present in all parts of black walnut trees. The species is storm-resistant and not affected by any major pest or disease in Europe. It is regenerated by planting or direct seeding on bare land, in monocultures and mixed stands. The management of stands with black walnut, with a rotation period generally up to 80 years, include weeding (mandatory), cleaning-respacing (in dense stands), thinning (mostly from above), high and formative pruning (mandatory), with the aim of producing valuable wood for sliced veneer, solid furniture, flooring/parquet, cabinetry, panelling, sculpture, musical instruments, gunstocks.

O plantație pură de stejar roșu, 2 x 1 m (5000 puieți ha-1), a fost instalată în parcul castelului Mikes (Zăbala, județul Covasna) în primăvara anului 2012. Condițiile ecologice locale (temperatura medie anuală 7,6 oC, precipitațiile medii anuale 616 mm, Districambosol tipic) sunt de bonitate mijlocie pentru stejarul roșu, ca și pentru vegetația naturală (goruneto-făgete). O lucrare de curățiri a fost aplicată în cele două suprafețe de probă (SP) de cercetare / demonstrative instalate în aprilie-mai 2019, care a prezentat câteva caracteristici interesante înainte de intervenția la vârsta de 7 ani: (i) desime 4692 arb ha-1 (SP1) și 3692 arb ha-1 (SP2); (ii) diametrul mediu aritmetic 4,84 cm (SP1) și 5,01 cm (SP2); peste 40% din arbori, în ambele SP, au avut diametre peste 5 cm (creșterea medie în diametru peste 7 mm an-1); (iii) diametrul mediu al suprafeței de bază: 5,05 cm (SP1) și 5,12 cm (SP2); (iv) înălțimea medie aritmetică: 6,48 m (SP1) și 6,77 m (SP2); peste 40% din arbori, în ambele SP, au avut peste 7 m înălțime (creșterea medie în înălțime peste 1 m an-1); (v) înălțimea corespunzătoare diametrului mediu al suprafeței de bază: 6,75 m (SP1) și 6,88 m (SP2). Lucrarea de curățiri a fost predominant de jos și de intensitate puternică (SP1), respectiv moderată (SP2), pe număr de arbori, și moderată (ambele SP) pe suprafață de bază. Arboretul rămas, în ambele SP, este încă des (desimea peste 3200 arb ha-1; suprafața de bază peste 7 m2 ha-1), cu diametre medii și înălțimi medii mai mari decât cele inițiale, respectiv indici de zveltețe mai mici. Numărul de „potențiali” arbori de viitor, aleși și însemnați cu vopsea înainte de curățire pe baza criteriilor vigoare-calitate-spațiere, a fost mai mare (538 arb ha-1 în SP1, 461 arb ha-1 în SP2) decât în alte țări europene (maximum 400 arb ha-1). Deoarece o parte din acești arbori prezintă înfurciri la înălțimi sub 4 m, doar 150-200 arb ha-1 din aceste exemplare vor fi selectate de-a lungul fazei de păriș, când se dorește aplicarea unei silviculturi pe arbore, care urmărește creșterea liberă (fără competiție la nivelul coroanei) a acestora.

Black locust (Robinia pseudoacacia L.), a species native to the eastern North America, was introduced to Europe probably in 1601 and currently extends over 2.3 × 106 ha. It has become naturalized in all sub-Mediterranean and temperate regions rivaling Populus spp. as the second most planted broadleaved tree species worldwide after Eucalyptus spp. This wide-spreading planting is because black locust is an important multipurpose species, producing wood, fodder, and a source of honey as well as bio-oil and biomass. It is also important for carbon sequestration, soil stabilization and re-vegetation of landfills, mining areas and wastelands, in biotherapy and landscaping. In Europe, black locust is drought tolerant so grows in areas with annual precipitation as low as 500–550 mm. It tolerates dry, nutrient poor soils but grows best on deep, nutrient-rich, well-drained soils. It is a fast-growing tree and the height, diameter and volume growth peak before the age of 20. It mostly regenerates vegetatively by root suckers under a simple coppice system, which is considered the most cost-effective management system. It also regenerates, but less frequently, by stool sprouts. Its early silviculture in production forests includes release cutting to promote root suckers rather than stool shoots, and cleaning-respacing to remove low-quality stems, reduce the number of shoots per stool, and adjust spacing between root suckers. In addition, early, moderate and frequent thinning as well as limited pruning are carried out focusing on crop trees. The species is regarded as invasive in several European countries and its range here is expected to expand under predicted climate changes.

The paper focuses on the use of alley cropping, an arable agroforestry system comprising rows of trees planted with a companion crop grown in the alleyways between the rows, in two sub-compartments (81B%: 0.75 ha, elevation 715 m asl; 81E: 3.4 ha, elevation 735 m asl) artificially regenerated at 1.80 m x 1.60 m spacing in the south-east of Transylvania (Romania) in 1997 (81B%) and 2003 (81E). The climate (Dfbx, specific to low and middle mountains) and soil (luvisol, of moderate fertility for pure or mixed Quercus petraea stands) are only moderately favourable to strawberry culture. The rows of tree species consists of Quercus rubra, Acer pseudoplatanus, Prunus avium (81B%), and Quercus petraea, Fagus sylvatica, Acer pseudoplatanus, and Larix decidua (81E). Strawberries (variety Elsanta,) were planted at 60 x 60 cm spacing in two pure rows in-between the tree rows as well as within the rows of planted trees. Both plantations were fenced, with manual topsoil hoeing up to four times a year, lighly fertilized (N, P, K complex) and chemically protected against browsing and pests. Strawberry rotation (six years, of which five years - two to six - with fruit production) was longer than the one (maximum three years) recommended in pure crops. Strawberry production reached the maximum level in years 3 or 4. Under the local conditions, the alley cropping with strawberries had demonstrated to be a viable alternative to the 'classical' monocropping system in terms of (a) survival rate of plants (over 95 per cent), (b) initial height growth of plants (very quick, resulting from reduced competition with grasses and naturally regenerated forest trees such as pioneer species), (c) establishment of a new forest culture, the full forest cover being achieved immediately after the end of strawberry production, as well as (d) economics (early and relevant revenue from the crop).

Black locust (Robinia pseudoacacia L.) was the first North-American tree species imported to Europe at the beginning of the seventeenth century. It is commonly planted worldwide because of its adaptability to environmental stresses, its valuable wood, easy propagation, frequent and abundant seed production, excellent coppicing, high seedling survival, and relatively high wood yield. In Europe, Romania and Hungary have the most highly-developed black locust growing techniques and experiences. As a result of increasing interest in black locust in many countries, this review aims to provide a comprehensive overview of state-of-the-art site requirements, propagation, improvement and management (including growth and yield as well as use in energy plantations).

This paper discusses the early silviculture of silver fir (Abies alba Mill.), a major softwood in Romania covering more than 294,000 ha. Three research plots (DRP1, DRP2 and DRP3) were established in a 25-year-old silver fir-dominated stand in May 2012. In DRP1 and DRP2, heavy cleaning-respacing were carried out while DRP3 was kept as a control. After the treatments in 2012, the plots had stocking between 1470 trees ha−1 (DRP2) and 10,030 trees ha−1 (DRP3), basal areas between 11.8 m2 ha−1 (DRP2) and 31.6 m2 ha−1 (DRP3). The average diameters were between 5.7 cm (DRP3) and 9.6 cm (DRP2). Measurements in September 2016 confirmed the rapid response of silver fir to cleaning-respacing. The best results in average diameter increments and basal area between 2012 and 2016 were in DRP2: 3.7 cm (36.4%) and 7.7 m2 ha−1 (85.0%) respectively. The largest diameter trees in 2012 were the best growers, and a strong linear correlation between the initial diameter of the remaining trees and their increment was established. Natural dieback of trees occurred only in DRP3 (8.6%). The selection of crop trees based on the vigour, quality, and spacing criteria during cleaning-respacing was possible as individuals stood out in terms of vigour and early diameter growth. An issue encountered in DRP1 and DRP2 was the occurrence of epicormic shoots, especially on less vigorous individuals with small crowns. However, four years after cleaning-respacing, these branches are small and do not significantly affect the wood quality.

Background and Purpose: The aim of this study is to highlight the importance of black locust (Robinia pseudoacacia L.), a North American-originating tree species of major importance in Romania, in extreme site conditions such as sand dunes. In this respect, a Research and Development (R&D) project has been carried out in Carei-Valea lui Mihai Plain (north-west of Romania) since 2016. Materials and Methods: Three sub-compartments were selected in IV Valea lui Mihai Working Circle, Săcueni Forest District: two pure natural regenerations by root suckers of black locust at different ages (sub-compartments 3B and 52A%) and a mixed black locust - black cherry stand (sub-compartment 23D). Biometrical measurements and analyses as well as biomass estimations were performed. A thorough statistical analysis using the data on initial, extracted and residual trees/stands was also performed. Results: The main outputs of the project are as follows: (1) Black locust was established naturally by root suckers and the stocking of newly established stands can be as high as 50,000 suckers·ha-1; (2) The initial growth of black locust regeneration is quick and the young regeneration can close the canopy in 1-2 years, resulting in an appropriate dune fixation and wind erosion control; (3) The young pure or mixed black locust-dominated stands are left untended until the first cleaning-respacing (mean diameter 5-6 cm), when the stand shows high stocking/density and a wide variation in tree size. This intervention is from below, heavy (intensity over 25% by number of trees or basal area) and of negative selection type, removing mostly low Kraft’s class, dead or dying, and defective trees. Conclusions: This R&D project has shown the high potential of black locust to establish naturally by root suckers after a low coppice cut and stump removal, as well as the fast initial growth of regenerated black locust. The quick canopy closure of young regeneration results in an appropriate dune fixation and wind erosion control.

Summary We assessed wood quality in common walnut using a combination of physical properties and structural features. Five common walnut trees were selected and processed in order to produce wood samples for further analyses. The results showed a wide spread of values of structural features and of wood water content. The color indices were strongly grouped around the averages. All experimental distributions were stratified following at least one of the analyzed factors (tree and its structural directions i.e. longitudinal, radial, and tangential). The radial anisotropy was the most pronounced. The longitudinal stability of density and water content, the inter-tree stability of color saturation as well as the homogeneity of all color indices on the girth were noticed. The heartwood covered up to 12.5% of transverse section and included 1–10 growth rings. The annual rate of bio-accumulation allowed the separation of stages of radial development of the structure using the width of growth rings: juvenile wood, composed of the first 8–9 rings from the pith; a transition zone to the mature wood (10 rings); and mature wood under way to be formed. Wood density was not a reliable criterion for differentiating the sapwood from heartwood but brightness, redness and hue’s color could be used for this purpose.

Northern red oak (Quercus rubra L. syn. Q. borealis F. Michx.) is a valuable broadleaved tree species originating from the eastern half of the USA and Canada. It was introduced to Europe in 1691 and currently covers over 350 000 ha, being found all over the continent, except the coldest part of Scandinavia. It is a fast-growing and valuable broadleaved tree due to its ecological characteristics, good wood properties and high economic value. Northern red oak prefers deep, loose, moderately humid and acid soils, without compact horizons and of at least moderate fertility. It does not grow well on dry, calcareous soils as well as waterlogged or poorly drained soils. It is either naturally regenerated using a group shelterwood system or planted using seedlings of European provenance, collected in certified seed stands. As northern red oak is light-demanding, its management should be ‘dynamic’ and includes heavy interventions (cleaning–respacing and thinning from above), in order to minimize crown competition between the final crop trees. These should produce large diameter trees for valuable end uses (e.g. veneer, solid furniture, lumber, etc.) within a rotation period generally of 80–100 years. The necessity for pruning (both formative and high) depends on the stand stocking at establishment, the subsequent silvicultural interventions as well as the occurrence of forking. The adaptation potential of northern red oak to predicted climate change, especially drought, seems to be higher than for European native oaks, the importance of the species is expected to increase in the future.

The management of tree species non-native to Republic of Croatia has a certain tradition within Croatian forest management practice; nowadays, their potential should be regarded and re-evaluated in the new frame of climate changes and growing society demands for forest products and services. This paper is a contribution to non-native tree species (NNTS) introduction and use in Croatia, aiming at providing state of the art of NNTS as well as overview of studies and examples of possible management opportunities. Because of the complexity of the matter and growing need to further investigate risks and challenges of NNTS in Croatia, authors have continued their research and will publish the results in a separate paper. Amount of the area occupied by NNTS forest cultures point to the conclusion that the use of these tree species in forest practice is not reached by far and the nursery production does not back up the need for NNTS use. Paper also provides a comprehensive overwiev of different aspects and benefits of the use of NNTS in Croatia. For example, increased wood production and non-wood forest products; production of high quality timber in short–time periods; use of fast-growing tree species for bioenergy production in higher proportion and enhancement of ecosystem services. Increase of stability and adaptive capacity of forest stands by the use of NNTS is highlighted as new silvicultural option for facing climate change. Their use in reforestation or conversion of degraded forest to more valuabe and more resistant/resilient stands offers new possibilities. Integrated and site-specific management is a strategy, which seems to be an appropriate approach for guidelines for the introduction and management of NNTS in Croatia. The use of high productive, resistant NNTS presents new silvicultural solution especially important in terms of site amelioration and enhancement of resistance and resilience of forest stands, which is the most important component of adaptive forest management strategies., Gospodarenje alohtonim vrstama ima tradiciju u hrvatskome šumarstvu, ali njihov potencijal se treba ponovno razmotriti i ocijeniti u novonastalim okvirima klimatskih promjena te rastućim potrebama društva za šumskim proizvodima i uslugama. Unatoč činjenici da svaka država ima svoj popis introduciranih vrsta, uključujući i Hrvatsku, autori prihvaćaju definiciju COST Akcije FP1403 NNEXT te rad baziraju na šumskim vrstama drveća kojima se prirodni areal nalazi izvan granica Europe. Ovaj pregledni rad doprinos je saznanjima o introdukciji i aktivnoj uporabi alohtonih vrsta u zemlji, a obuhvaća dostupne znanstvene i stručne studije te primjere uspješne uporabe u gospodarenju šumama. Zbog složenosti ove problematike autori će objaviti pregled rizika i izazova uporabe alohtonih vrsta u zasebnome radu. Dostupni podaci o prisutnosti alohtonih vrsta na pokusnim objektima te u šumarskoj praksi ukazuju kako se u praksi koristi tek manji broj vrsta (Tablica 1), dok su stvarni potencijal i njihove koristi daleko veće. Analiza podataka ukazuje kako su najzastupljenije alohtone vrste u šumarskoj praksi: Robinia pseudoacacia L. (12003.88 ha), Pinus strobus L. (3218.69 ha), Juglans nigra L. (2376.66 ha), F. pennsylvanica Marshall. i Fraxinus americana L.(1099.77 ha), Pseudotsuga menziesii (Mirb.) Franco. (393,05 ha) i L Quercus rubra. (51,99 ha). Podaci o proizvodnji šumskoga reprodukcijskog materijala navedenih vrsta ukazuje da rasadnička proizvodnja nije usklađena s potencijalom njihove uporabe u praksi. U radu se daje i iscrpan pregled različitih gledišta i koristi uzgoja alohtonih vrsta u Hrvatskoj. Samo neke od njih su (Slika 1, Tablica 2): nove mogućnosti proizvodnje visoko kvalitetnog drveta u kraćim ophodnjama, kao i drveta za bioenergiju, novih drvnih proizvoda i tehnologija; socijane koristi (mali i srednji poduzetnici, privatni šumoposjednici); povećanje stabilnosti i adaptabilnosti šumskih sastojina, ali samo u slučajevima velikih šteta i male plastičnosti i otpornosti domaćih vrsta; smanjenje intenziteta šumskouzgojnih radova, kao i uloženih sredstava na pripremi staništa prilikom pošumljavanja; ostvarivanje većih mogućnosti uporabe zapuštenoga poljoprivrednog zemljišta i ostalih prikladnih površina; sanacija progala ili većih površina nakon šteta u sastojinama domaćih vrsta (npr. obične smreke); supstitucija osjetljivih vrsta otpornijim i plastičnijim vrstama (mogućnosti mješovitih ili obogaćenih sastojina otpornijim alohtonim vrstama) te umanjenje negativnog djelovanja biotskih i abiotskih čimbenika. Njihova uporaba u sanaciji površina te konverziji degradiranih i devastiranih šuma pruža nove mogućnosti posebice na područjima s nepovoljnim ekološkim uvjetima, za koja se predviđa da će biti najpogođenija područja Hrvatske u budućnosti. Alohtone vrste mogu osigurati i niz opće korisnih funkcija šuma (npr. povećanje vezanja ugljika, fitoremedijacija zagađenih tala). Zbog složenosti problematike preporučujemo da se odluke o uporabi alohtonih vrsta donose na osnovi usporedbe s domaćim vrstama za svako stanište te na osnovi pregleda potencijalnih koristi, ali i rizika i izazova. Ističemo kako pojedine alohtone vrste treba poticati, dok neke zbog svoga invanzivnog potencijala trebaju biti strogo ograničene. Uporaba visokoproduktivnih, otpornijih i plastičnijih alohtonih vrsta predstavlja nova šumskouzgojna rješenja, koja su posebice važna u smislu pripreme staništa za prihvat autohtonih vrsta te povećanja otpornosti i plastičnosti šumskih sastojina, što je neizostavna komponenta adaptacijskih strategija gospodarenja šumama. Ipak, daljnja znanstvena istraživanja potrebna su kako bi se kvantificirala uporabljivost svake alohtone vrste, ali i olakšalo donošenje odluka u praksi.

This study focuses on the occlusion of pruning wounds on northern red oak (Quercus rubra L.) trees grown in two plantations established in the south-east of Transylvania, Romania in 1997 and 2004. In total, 184 green branches of elliptical cross section (i.e. with the horizontal axis Ha shorter than vertical axis Va and ranging between 0.6 cm and 4.5 cm) were pruned in April 2007 and May 2009. Of these branches, 161 (88%) were fully occluded after five growing seasons and, the majority of these, 148 wounds (80%), had occluded in three seasons. The main factors affecting the wound occlusion on trees subject to artificial pruning are diameter at breast height increment and branch size: the occlusion is more rapid in trees with faster diameter growth rates and on small branches of maximum 3 cm Ha. Consequently, artificial pruning should be concentrated on small branches on well formed, vigorous and evenly spaced final crop trees which can subsequently be favoured by heavy and targeted thinning from ...

Sessile oak (Quercus petraea (Matt.) Liebl.) is the most important Quercus species in Romania, covering over 700000 ha. It is located in the hill and low mountain ranges, and forms either pure or mixed stands with other broadleaved tree species such as European beech (Fagus sylvatica L.), common ash (Fraxinus excelsior L.), sycamore (Acer pseudoplatanus L.), linden (Tilia sp.), hornbeam (Carpinus betulus L.), etc. Sessile oak in Romania is established by natural seeding following a mixed uniformgroup shelterwood system as well as by manual seeding or planting (1.5 x 1.0 m or 2.0 x 1.0 m). After the regeneration phase, lasting usually for 15-20 years, pure or mixed sessile oak stands are successively tended through a series of release cutting, cleaningrespacing, and thinning, that halt at the age of 70-80 years (sawtimber as target wood assortment) or 100-120 years (stands for veneer wood production). The rotation age of sessile oak-dominated stands depends on the two wood assortments and varies between 120-140 years (sawtimber production) and 160-200 years (veneer production).