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.

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

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Europe has a history rich in examples of successful and problematic introductions of trees with a native origin outside of Europe (non-native trees, NNT). Many international legal frameworks such as treaties and conventions and also the European Union have responded to the global concern about potential negative impacts of NNT that may become invasive in natural ecosystems. It is, however, national and regional legislation in particular that affects current and future management decisions in the forest sector and shapes the landscapes of Europe. We identified all relevant legal instruments regulating NNT, the different legal approaches and the regulatory intensity in 40 European countries (no microstates). Information on hard and effective soft law instruments were collected by means of a targeted questionnaire and consultation of international and national legislation information systems and databases. In total, 335 relevant legal instruments were in place in June/July 2019 to regulate the use of NNT in the investigated 116 geopolitical legal units (countries as well as sub-national regions with their own legislation). Countries and regions were empirically categorized according to ad hoc-defined legislation indicators. These indicators pay respect to the general bans on the introduction of non-native species, the generally allowed and prohibited NNT, approval mechanisms and specific areas or cases where NNT are restricted or prohibited. Our study revealed a very diverse landscape of legal frameworks across Europe, with a large variety of approaches to regulating NNT being pursued and the intensity of restriction ranging from very few restrictions on species choice and plantation surface area to the complete banning of NNT from forests. The main conclusion is that there is a clear need for more co-ordinated, science-based policies both at the local and international levels to enhance the advantages of NNT and mitigate potential negative effects.

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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.

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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. ZusammenfassungEine Kombination unterschiedlicher physikalischer und struktureller Holzkennwerte wurde eingesetzt, um Walnußholz zu untersuchen. Hierzu wurden fünf Probebäume ausgesucht, bearbeitet und definierte Holzproben hergestellt. Die Ergebnis zeigten eine weite Streuung bei den Werten der strukturellen Kennwerte sowie des Wassergehaltes. Die Farbkennwerte waren streng um die Mittelwerte gruppiert. Alle experimentellen Verteilungen wurden an mindestens einem der analysierten Faktoren stratifiziert (der Baum und sein strukureller Aufbau, d.h. longitudinal, radial und tangential). Die radiale Anisotropie war dabei besonders ausgeprägt. Die Stabilität von Dichte und Wassergehalt in longitudinaler Richtung, eine Stabilität der Farbsättigung zwischen den Probebäumen sowie eine Homogenität aller Farbindices im Randbereich konne festgestellt werden. Das Kernholz deckte bis zu 12,5 % des transversalen Abschnittes ab und umfaßte 1-10 Ringe. Die jährliche Bioakkumulationsrate erlaubte eine Trennung von Stadien der radialen Strukturetwicklung auf Basis der Breite der Zuwachsringe: juveniles Holz, die ersten 8-9 Ringe um das Mark umfassend, eine Übergangszone zum reifen Holz (10 Jahrringe) und reifes Holz in Entstehung. Die Holzdichte war kein zuverlässiges Kriterium um Splintholz von Kernholz zu unterscheiden, jedoch konnten Helligkeit, Rötung und hue's Farbe zu diesem Zweck erfolgreich eingesetzt werden.