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.

Various studies have established possible threats posed due to pollution using ecological risk indices, but most have focused strictly on anthropogenic areas, so the data from these studies are less comparable with those obtained from natural forest sites, which was the focus of this current study. The main reason for this focus could be attributed to the commonly agreed reference provided by natural forest parks, which are assumed to be uncontaminated. The aim of this research was to determine if the Kampinoski National Park (Poland) could be considered a geochemical referencing ecosystem for Pb, Cd, and Ni levels. The specific purpose was to conduct a soil-background-based evaluation of metal contamination with a focus on geochemical indices as normative tools for assessing similar forest ecosystems at local and international levels. The toxicity response factors indicated some specific metal features that seemed highly magnified for Cd compared with Pb and Ni. The use of geochemical indices when assessing the contamination status of various ecosystems, either natural or strongly anthropogenic, is recommended to enable worldwide comparison, rather than only assessing metal contents. This approach considers the background metal concentrations for local on-site targets as well as pre-industrial reference levels for international referencing.

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.

In 2015 in Kampinos National Park (KNP), monitoring of tree crown condition was conducted in specimens of the Scots pine, which is the dominant tree species in the park (73.3%). The monitoring was aimed at providing information about the health of pine trees in the national park area. The monitoring was conducted on 26 plots throughout the park. The stands where the pine is not a dominant species were omitted. On each plot, 20 trees were subjected to assessment. In total, 520 pine trees were examined. The monitoring was conducted by the assessment of tree crowns based on the adapted forest monitoring methodology conducted as part of National Environmental Monitoring. On the basis of the monitoring, it was found that 75.4% of the trees are characterised by slight defoliation and 94.4% of the specimens were not found to have discoloration of the assimilation apparatus. No differences were found between areas situated closer and further from the administrative borders of Warsaw. On the basis of the monitoring, it was found that the pine trees in KNP are in a good health condition. Dendrometric measurements show that the average diameter at breast height (DBH) of the analysed trees is 26.6 cm. The average height of the trees is 20.4 m. The average age of the examined tree stands is 84. The monitoring will be continued in subsequent years in order to record the changes taking place in tree crowns.

Pines are generally fire-resistant trees. There is a shortage of research on the behaviour of Scots pine after surface fire in older stands. The aim of the work was to describe the effect of the surface fire intensity on the mortality of pines of various diameter at breast height (DBH), including older trees. The research was conducted in Peucedano-Pinetum oligotrophic Scots-pine forest in Kampinos National Park (KPN, central Poland) on the area of two adjacent surface fire sites originated in spring 2015 in 60- to 200-year-old stands (site area: 10,92 ha). There were 45 (28 burned and 17 control) permanent plots established after the fire. The share of not burned, superficially burned and completely burnout organic horizon of the soil was determined within all of them. DBH and location of pine trees were measured within all of the plots on the area of 200 m2. For all of the trees for which full information about soil organic horizon damage was mapped, the prevailing type of disturbance in their close neighbourhoods with radii of 1 and 2 m was assessed. The mortality of trees was assessed after each vegetation period up to 2017, basing on the presence of green needles on the trees. The influence of fire intensity on the survival of trees was examined on whole permanent plot level as well as on individual tree level. Strong linear correlation was observed between Scots pine mortality and the share of plots area with damaged organic layer, especially at the end of the third vegetation period after fire. Logistic regression models constructed for individual trees suggest that bigger tree diameter (hence, thicker bark) diminished the odds of mortality only after two vegetation periods from the fire. After the third vegetation period, only the intensity of surface fire in the close neighbourhood of trees influenced (negatively) the chance on survival. The size of trees did no matter in this case. Nearly all of the trees that were located within burnout organic matter areas died. The results did not support the commonly known mechanism of enhancement of bigger Scots pine tree survival after surface fire because of thicker bark responsible for heat protection. Probably, the main cause of observed mortality was not overheating of cambium but it was rather connected to massive fine root loses. Scots pines growing on oligotrophic arid sites modify their root system to explore topsoil layers with higher proportion of shallow roots, growing even in organic litter layer. This corresponds with massive (regardless of size) pine mortality within sites characterised by complete burnout of organic matter layer and very high survival in those ones with only surfacely burned litter layer. The results can improve the assessment of surface fires consequences in managed Scots pine stands growing in oligotrophic conditions.