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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The use of bioenergy are increasing in many European countries and an important role will be played by biomass produced in willow SRC. Short Rotation Coppice (SRC) willow was developed in Sweden in 1970 and it is cultivated for the production of wood chips. In Romania there are not more than 800 hectares, half of them are in Banat area. In this context assessing the biomass yield in the different experimental trial are very important. Research have been made in three SRC willow experimental trials established in Ghilad, Timis County, Romania. The material consist in willow Inger. All three trails have been established in the year 2011 but harvested in different years. Measurements and observation were made on 15 plants at the end of the 2014 season. One plant from each experimental trial has been harvested and then weight in order to establish their aboveground and underground biomass. Research highlight significant differences according with a number of shoots per stump and shoot diameter according with harvested year. According with stump age and the number of harvests, significant differences were established for quantitative character diameter. There also have been put in evidence the differences between the aboveground and underground biomass for different willow age. This screening about biometric characteristic and aboveground biomass showed high value for willow SRC harvested every year. We have to notice that any economic aspect have not been evaluated

Tilia spp. (lime trees) as ornamental trees have a privileged place in the European mythology and traditions and this is a reason of their constant presence in the urban landscape. Lime trees are in general very resistant to biotic and abiotic stress, although some sanitary problems may occur (e.g. aphids and other related organisms). Tilia spp. are considered a good bioindicator and accumulator of heavy metals. Seasonal accumulations of Pb, Ni, Cr, Mn, Cu and Fe in leaves of Tilia spp. in urban and periurban green areas of Western Romania, under different traffic conditions, were analyzed using atomic absorption spectrophotometry. The results confirmed the direct correlation between the traffic intensity and the accumulation of Pb in leaves. By mitigating the effects of air pollution, especially in terms of heavy metals, Tilia spp. should be further promoted as urban trees.

Tilia spp.