In the context of global change, the integration of non-native tree (NNT) species into European forestry is increasingly being discussed. The ecological consequences of increasing use or spread of NNTs in European forests are highly uncertain, as the scientific evidence is either constraint to results from case studies with limited spatial extent, or concerns global assessments that lack focus on European NNTs. For either case, generalisations on European NNTs are challenging to draw. Here we compile data on the impacts of seven important NNTs (Acacia dealbata, Ailanthus altissima, Eucalyptus globulus, Prunus serotina, Pseudotsuga menziesii, Quercus rubra, Robinia pseudoacacia) on physical and chemical soil properties and diversity attributes in Europe, and summarise commonalities and differences. From a total of 103 publications considered, studies on diversity attributes were overall more frequent than studies on soil properties. The effects on soil properties varied greatly among tree species and depended on the respective soil property. Overall, increasing (45%) and decreasing (45%) impacts on soil occurred with similar frequency. In contrast, decreasing impacts on biodiversity were much more frequent (66%) than increasing ones (24%). Species phylogenetically distant from European tree species, such as Acacia dealbata, Eucalyptus globulus and Ailanthus altissima, showed the strongest decreasing impacts on biodiversity. Our results suggest that forest managers should be cautious in using NNTs, as a majority of NNT stands host fewer species when compared with native tree species or ecosystems, likely reflected in changes in biotic interactions and ecosystem functions. The high variability of impacts suggests that individual NNTs should be assessed separately, but NNTs that lack European relatives should be used with particular caution.

Climate change is increasingly affecting forest ecosystems. Modifying the species composition towards species mixtures with a higher potential to mitigate the negative effect of climate change is one of the basic silvicultural measures. Potential economic and production impacts of these actions need to be assessed. This study therefore aims to evaluate the economic and production effect of species composition change as a result of the adaptation of forest ecosystems to climate change. The differences between the value production of Norway spruce (Picea abies /L./Karst.), Douglas fir (Pseudotsuga menziessi/MIRBEL/FRANCO) and European beech (Fagus sylvatica L.) on fresh soils (represented mainly by mesotrophic cambisols), and soils affected by ground water (mainly pseudogley forms of cambisols and pseudogleys) were evaluated. The study was conducted on the area of the forest enterprise of the Czech University of Life Sciences (UFE) situated in the Central Bohemia region. For a model comparison of height and volume growth of Douglas fir and Norway spruce in this area, all stands (pure and mixed) with both species represented were analysed using the data from the current forest management plan and Korf’s growth function. The course of current and mean height increments over time is very similar, yet with constantly higher annual increments for Douglas fir. In 100 years, the mean stand height of Douglas fir is 6 m larger than that of Norway spruce. Production and economic potential were also evaluated. At the rotation age, the volume and value production of Douglas fir was 30% to 50% higher than that of Norway spruce. A higher share of Douglas fir in the total forest area would lead to an important value increment of the forests in the study area. Different results were achieved by comparing the yield potential of Norway spruce with European beech, which most often substitutes spruce at middle altitudes. Beech potential yield is only 40–55% of the spruce yield level.

Mixed lowland forests reserved for natural succession are sparse in the Czech Republic. However, their development provides essential insights into the natural processes of these forests and recommendations for forest management in a changing climate. The research describes the dynamics, productivity, structure, diversity, dead wood, and radial growth of hornbeam-oak groves and calcareous beech-dominated forests in the Karlštejn National Nature Reserve (Czechia) based on inventory in 2002, 2008, 2014 and 2020. The objective was to evaluate changes in differently managed stands (high forest, coppice with standards, and coppice) after leaving the stands to spontaneous development in 2004. The tree density increased by 2–10% from 2002 to 2014 and decreased by 6–18% in 2020. In the high forest, an increase in the stand volume was observed during the whole period, while in the coppice with standards and coppice, only until 2014. The stand volume ranged from 190 (coppice) to 630 (high forest) m³ ha−1 in 2020 and increased by an average of 28% over 18 years. Overall diversity of tree layer showed an uneven structure in the high forest and a substantially diverse structure in the other variants. The deadwood volume has been steadily increasing (18–35 m³ ha−1 in 2020), accumulating an average of 1 m³ ha−1 yr−1. A lack of precipitation and high temperatures from June to August were the main limiting factors of the radial growth of tree species, while the number of negative pointer years has increased in the last decade. European beech (Fagus sylvatica L.) was the most sensitive tree species to climate compared to the resilient European ash (Fraxinus excelsior L.). The lowest fluctuations in the diameter increment were recorded in Norway maple (Acer platanoides L.) and the highest in beech in the temperature cycles of 7–15 years. Over the last 20 years, sessile oak [Quercus petraea (Matt.) Liebl.] showed an increase in radial growth by 7%, while other tree species reported a decrease with a maximum in beech (by −38%). The forest stands managed as high forest, characterized by a higher production potential and lower diversity, had slower dynamics when compared to coppice with standards and coppice.

We studied the effects of magnesium (Mg) NPK fertilizer applied in 2000 to maturing Norway spruce (Picea abies /L./ Karst.) stands with yellowing symptoms and situated on poor acidified soils in the Šumava mountains (the Czech Republic). Long-term defoliation, nutrient content in the foliage and diameter increment were evaluated in three specific variants: yellowing trees, trees without yellowing symptoms and fertilized trees. The results indicate differences in soil characteristics, nutrient content and radial growth with response to climate. Fertilization increased Mg content and base saturation in the soil and decreased the amount of exchangeable aluminum and hydrolytic acidity. Differences were significant especially in magnesium, calcium and phosphorus contents in the foliage of yellowing trees. There was also significant difference in manganese content; yellowing trees showed deficiency in comparison with both fertilized and unfertilized healthy trees. Two years after the initial fertilization (to present), defoliation and yellowing symptoms in the unfertilized yellowing trees were more pronounced compared to other variants. These symptoms were more influenced by fertilization than foliation. The duration of significant positive effects of fertilization on diameter increment lasted for a shorter time than the effect on foliage. Simultaneously, higher sensitivity to climatic factors was observed in the fertilized trees.

Douglas-fir ( Pseudotsuga menziesii [Mirb.] Franco) is the most common utilized introduced tree species in the tem-is the most common utilized introduced tree species in the temperate zone, planted in many European countries. Also, in the Czech Republic it represents the most planted exotic species as well. Its planted area exceeds 6,000 ha and represents 0.25% of the forest area of the country. In the last years, this species is supposed as convenient substitution for declining Norway spruce ( Picea abies [L.] Karst.) stands under current climatic change (extreme drought, bark beetle outbreak). The changed species composition affects also soil dynamic processes, including litter decomposition and transformation. In the presented study, the respiration rate and nitrification intensity were compared in the stand parts dominated by Norway spruce and Douglas-fir in comparable site conditions (410 m a.s.l., 650 mm, 8 ºC, gleyic Luvisol, fresh oak-fir site with Oxalis acetosella, age 97 years). Analyses were performed in laboratory conditions by standard methods determining actual (basal) and potential respiration activity and intensity of ammonia and nitrate ion production. Admixture of Douglas-fir considerably intensified decomposition activities (soil respiration) and profoundly increased the nitrification rate in the surface humus and uppermost mineral soil layer – Ah horizon. Increased interest in the Douglas-fir silviculture needs increased care for forest soil dynamics with respect of nitrogen balance.