Ash trees are an important component of both forests and the countryside. Emerging new diseases like ash dieback poses new challenges to Fraxinus spp., which not only have to adapt to global warming but also defend themselves against new threats from pathogenic fungi and insect pests. A new species of fungus, Hymenoscyphus fraxineus, has arrived in Europe from Asia and has severely damaged shoots which alters the structure of ash tree crowns. While some older trees have survived, younger trees are dying en masse, so the only hope is that the surviving trees will produce a younger generation that may be more resistant to the new diseases. The fine roots of ash trees are also attacked by pathogenic oomycetes, and others by Armillaria spp. The current stressed condition of ash trees in Europe is exacerbated by a new threat from insects. Agrillus planipennis, emerald ash borer, migrating from the east (from near Moscow airport) towards the borders of the European Union, killing thousands of ash trees on its way. This raises the question of future prospects for ash cultivation in Europe. This article takes a closer look at the information described in the literature.

In natural environments, plants develop adaptive mechanisms at the cellular and molecular levels to cope with many external factors, e.g., insects and soil pathogens. We studied physiological stress induced by different levels of foliage removal (defoliation 30% and 60%) and by infection of root rot pathogen Phytophthora plurivora on the common Polish tree species, Betula pendula, grown in an open greenhouse. This study showed that P. plurivora damaged the root system which negatively impacted all morphological parameters. However the loss of 30% of the leaves had a positive effect on defense responses. Chlorophyll-a fluorescence parameters indicated a decrease in photosynthetic efficiency in defoliated plants, but plants inoculated with the pathogen had a higher performance index showing increased vigor of the infected plant than birches. The study demonstrated the intense immunity response of birch to P. plurivora through the expression of Hsp90 and Hsp83 genes. The trees weakened by P. plurivora became more susceptible to infection by Erysiphe ornata var. ornata.

The condition of Norway spruce ( Picea abies (L.) Karst) in the Białowieża Forest is categorized as a crisis. It is believed that due to the cooling in the Holocene, the then-relict species of the forest, silver fir ( Abies alba Mill.), disappeared from its ecosystems and then spruce appeared. Today’s climate change presents challenges to our civilization, including to forestry. However, there is no information at all about how this affected the silver fir in the Białowieża Forest. In the Polish part of the forest (subcompartment 498 Сi, Białowieża Forest District), for the first time a comprehensive study has been carried out on the condition of mature fir trees planted by man and on their progeny. The results indicate high forestry-taxation indicators of trees, resistance to the abiotic factor and competitiveness. Their constitution corresponds to local environmental conditions. However, the disproportionately small number of adult natural regeneration of old firs indicated some kind of malfunction in the mechanism of natural generational change.

Currently, a change in the species composition of the Białowieża Forest, eastern Poland, is occurring. Parallel to the dying of spruce (Picea abies L. Karst.), caused by Ips typographus (L.), there is a spread of deciduous tree species, among which hornbeam (Carpinus betulus L.) is the most active. Against the background of climate change, it is of interest to consider the possibility of reintroducing relict species in areas occupied until recently by spruce. One of these is silver fir (Abies alba Mill.), which is biologically and ecologically very similar to spruce. The Tisovik tract (the Belarusian part of the Białowieża Forest) is the most northeastern and the only preserved refuge of autochthonous silver fir in the region. Therefore, it is the most suitable source of propagation of this species outside the mountainous part of its range. The target area of our study was a 26-year old artificial stand included in the information system of forest genetic resources conserved in Europe. It was created in 1996 in the Polish part of the Białowieża Forest in the Hajnówka Forest District (Forestry Wilczy Jar) from 10 half-sib families originating from seeds collected in the Tisovik tract. The goal of the study was to assess the influence of provenance factors and spatial structure on productivity and phenotypic variation as measured by diameter (DBH). The study’s initial results showed that the provenance factor’s influence at the pole wood stage manifests itself more clearly than spatial structure. Even within the framework of individual half-sibs, there was a clear differentiation of diameters between investigated trees. Interpretation of the obtained results allowed us to conclude that there is a “threshold value” of the distance between trees in a stand of a given age, which determines the point when its increase no longer contributes to an increase in DBH. The most promising phenotypes were selected for further research and practical actions to reproduce silver fir further.

A long-term introduction experiment conducted in 2009–2016 revealed that in the harshest weather conditions of the northern part of Belarus associated with a difficult environmental situation on a trial area, including weakly-decomposed acid sphagnum peat and the deficiency of artificial watering, lowbush blueberry (Vaccinium angustifolium Ait.) due to the significant tolerance to abiotic factors of the environment completely fulfills its bioproductive potential. It is clear, in particular, through the formation of a continuous berry bush cover and its high resistance to cold. A sustainable cultivated phytocenosis forms. It protects a peat substrate from fires, water and wind erosions, and has a high level of positive dynamism of berry productivity during the whole period of record. It proves the appropriateness of the ecological-biological type of the species to the extreme weather and ecological conditions of the experiment. However, lowbush blueberry needs an optimization of mineral nutrition. The implementation of this condition is a guaranty of successful introduction of the plant on the cutover raised-bog peatlands in the North of Belarus.