Scots pine (Pinus sylvestris L.) is a widespread species in Eurasia, but its natural range can be significantly altered by a variety of stressors. The ability of pine to regenerate naturally is significantly reduced by its occurrence in unsuitable habitats. The processes of natural selection of pine from select habitats can be followed in stands of national parks where forestry activities are excluded. The possibility of pine regeneration is influenced by the following factors: characteristics of produced seeds, competition, and genetic characteristics. In the present study, selected factors associated with limiting the natural regeneration potential of pine were analysed. The present work generated important information related to the natural regeneration potential of pine in Central and Eastern Europe. The main objective of the analyses was to discuss the possibility of the natural regeneration of pine stands without human intervention. In addition, the genetic diversity of naturally germinating seedlings was analysed. The obtained results confirmed the high reproductive potential of pine despite the advanced age of the studied trees. The obtained seeds produced by old growth Scots pine trees had high viability, while a significant difference was observed in terms of the average number of cones per dominant tree between studied stands. Thus, the number of cones was the main element determining the regeneration potential of the stands. It should be emphasised that the number of cones did not influence the occurrence of natural regeneration. Based on the obtained results, the regeneration potential of pine stands depends mainly on the habitat and the competitive pressure. In addition, a correlation between genetic parameters and the regeneration potential of stands should be established, which may be the beginning of further research on the process discussed in this publication.

Biodiversity at the species and individual levels is one of the fundamental elements characterizing an ecosystem. It is assumed that the greater the level of biodiversity, the more tolerant the environment is to changes in external conditions. In recent years, dynamic climate change has negatively impacted the health of many forest trees across Europe, in particular Scots pine. Tree health is commonly characterized by crown defoliation. The study presented here describes and correlates crown defoliation with biodiversity indicators at the species and individual tree levels. Research was conducted in two national parks in Poland (Kampinoski and Bory Tucholskie). Since stands have been under legal protection for many years and forest management is not practiced there, stand development processes taking place there are similar to natural ones. This study provided empirical data on ecosystem response to external stresses based on species and genetic structure. The results confirm differing health of the populations, which results from, among other factors, stand age and the environmental conditions in which they grow. Pine stands in both national parks are genetically diverse but with low genetic variability. Differences in stand health are related to the number of alleles forming the genetic pool. This conclusion is supported by a high correlation coefficient for interactions between defoliation, the number of alleles, and the Shannon index for genotypes. This suggests that greater gene diversity is likely to provide a wider range of phenotypic responses to environmental change.

The seed orchards (SO) serve possibilities to collect seeds from the selected genotypes or to create artificial population throughout the controlled crossing of the target genotypes. Therefore, the seed material obtained from the clonal and seedling seed orchards offers unique opportunity to improve the genetic value of seeds. Thus, the seed orchards are considered as an important part of the forest seed base being the key object for both modern forestry and forestry research. This paper outlines the forest breeding activities associated with the seed production in the seed orchards in Ukraine over the last 70 years. During this period, the different aspects related to the establishment and management of the seed orchard were studied. In these processes, many failures had occurred, their causes and consequences were described. These main breeding activities were reported considering plain and mountain regions of Ukraine as well as specific aspects of the reproduction of the main forest tree species. As of 2019, the total area of the clonal seed orchards (CSO) reached 1040.3 ha, while seedling seed orchards (SSO) only 273.7 ha. The results of research on the growth, reproductive development, the morphology of the plus trees clones in the SO were generalized. The article on the current problems and challenges for Ukrainian forestry mainly related to forest tree breeding and there was also focus on forest seed industry. For the main forest trees species (Scots pine, English oak and other), targeted breeding programs should be developed. It is relevant to create the genetic bank of the forest seeds.

Fraxinus excelsior L. is threatened by a variety of environmental factors causing a decline of the species. The most important biotic factors negatively affecting the condition of the F. excelsior population are fungi such as the pathogen Hymenoscyphus fraxineus. Abiotic factors with potentially harmful effect to the F. excelsior population are the accumulation of heavy metals and salinity in soils. Thus, the aim of this study was to investigate the impact of selected biotic and abiotic stress factors to determine which of them pose a threat to European ash. The study was conducted using in vitro techniques based on callus and seedlings regenerated via indirect organogenesis. Tissue cultures exclude the influence of other factors, including the environmental impact on ash extinction. The results confirmed very strong pathogenic potential of H. fraxineus in which after 14 days the callus tissue cells died as the tissue failed to activate its defense mechanisms. Experiments showed the high toxicity of cadmium in concentration of 0.027 mmol/L. Salinity caused the activity of oxidation enzymes to vary among seedlings and calluses in the control suggesting the enzymes play a role in controlling the morphogenetic development of tissue cultures.

The introduction of tree species raises the question of whether they find suitable conditions in their secondary range and whether they can successfully adapt to the new conditions in the context of an unstable climate. Stem secondary growth of trees and the changes in xylem cell structure make it possible to trace the adaptation process to the new climate on an inter- and intra-seasonal scale. The objective of this study was to determine whether the seven non-native conifer species in Central Europe differ in climate sensitivity and to what extent late frost and spring-summer drought can influence xylem changes. In our study, we investigated the growth pattern and xylem cell structure modifications of seven introduced conifer species Pseudotsuga menziesii, Pinus strobus, Tsuga canadensis, Abies grandis, Pinus banksiana, Pinus rigida, Pinus nigra, growing under uniform conditions in Poland. To determine species-specific temporal variations in climate sensitivity, we used stationary and non-stationary correlations of ring width with daily climate variables: mean, minimum, and maximum temperatures, precipitation sum, and SPEI, supported by a pointer-year analysis. Changes in xylem structure (frost rings and intra-annual density fluctuations) were analyzed using light and fluorescence microscopy. Warming of the winter-spring period benefits both southern European and North American introduced conifers, as reflected in the extended responsiveness period. However, as the growing season warms and the risk of late frosts increases, the potential for acclimatization of non-native species decreases, especially with respect to their juvenile growth phase. Negative precipitation and evapotranspiration balance at spring-summer period can lead to reduced growth and anomalies in earlywood xylem structure, commonly referred to as intra annual density fluctuations. P. strobus, the species that loses both frost-induced cambium damage and drought-induced xylem anomalies in summer is the fastest growing non-native species, along with P. menziesii. Although the results presented here show the potential and the limitations in the acclimatization of coniferous species, the obvious limitations related to local environmental conditions and the different ages of the trees make us cautious in generalizing the conclusions. Therefore, we call for the creation of a pan-European dendro-network of sites of non-native coniferous species.