Abstract: We sought to determine changes in the gene pool in a stand of Scots pine Pinus sylvestris subject to different thinning regimes. The pine stand under study was located in central Poland. The simulations using the ForestSimulatorBWINPro involved six experimental variants representing five virtual thinning regimes, i.e. 1) low thinning of 12% intensity; 2) low thinning of 35% intensity; 3) geometric thinning; 4) selection thinning; 5) high−grading; and 6) the untreated control. We considered the impact of these regimes on stand genetic variability up to 10 years after the given treatment, by reference to eleven SSR sequences. While various changes in the level of genetic diversity of stand were forecast to arise under the different regimes, low thinning of 35% intensity was identified as the method least favourable to maintenance of the initial level of genetic variability in the stand (loss of 22 and 43% of rare alleles in nSSR and cpSSR). High−grading proved most beneficial in the short−term. The selection thinning represented a kind of ‘golden mean’; it turned out to be a method that enables achieving important silvicultural goals and simultaneously only slightly distorts the stand genetic variability. The conducted experiment with the use of ForestSimulatorBWINPro program proved that the software can be successfully used in studied on the genetic variability of trees. Because it was only a preliminary study we suggest larger resampling the populations and genotyping using a larger number of microsatellite markers.
Key words: genetic variation, Pinus sylvestris L., SSR markers, stand tending, thinning simulation

Abstract: Black locust has been known in Poland since the nineteenth century. The aim of the present study was to analyse the variability of selected features of black locust wood of native origin, as despite the long−standing cultivation of this species in forests, little is known about the diversity in the features of its wood. The research was conducted in four tree stands located in southern Poland. One core was taken from 15 trees in each stand. The width of sapwood, the width of annual rings, and the basic density of wood were measured in the cores sections. The average width of sapwood was about 1 cm and its share in the cross−sectional area of the stem amounted to ca. 16%. There were no significant differences in the width of sapwood or in its share between black locust trees of different age classes, or between those growing in different habitats. The average width of the annual rings was 2.95 mm; notably, the black locust trees from the mountain forest habitat had broad−grained wood (average above 3 mm), while the wood of trees growing on the mixed forest habitat was narrow−grained (average below 3 mm). The average share of late wood was 67.5%. The average basic density of wood was 0.608 g·cm^–3; further, it was found that black locust trees growing in the upland forest habitat had a favourable (even) course of wood density values on the radius of the cross−section of the stem.
Key words: annual rings width, basic wood density, share of latewood, width and share of sapwood

Abstract: The photosynthetic efficiency was studied in Robinia pseudoacacia (black locust) as one of the most common forest−forming species in artificially established stands of the northern Steppe of Ukraine. Plantings of this species in the region studied were established specifically to perform protective functions such as soil erosion control, phytoremediation of disrupted landscapes, and the protection of agricultural cenoses from wind erosion. The goal of this study was to investigate (I) how Parectopa robiniella caterpillars affect the photosynthesis system of black locust; (II) what age groups of black locust trees were most vulnerable to P. robiniella attacks. The study was conducted in September 2022; this period corresponded to the greatest activity of the second (more numerous) generation of P. robiniella. The artificially established forest strip of R. pseudoacacia of different ages was chosen as the object of research: I – young trees (up to 15 years old); II – middle−aged (15−25 years old), and III – old parent trees planted at the time of the forest belt creation (50−70 years old). The forest belt was situated near the Mayorka village on the right bank of the Dnieper River in the Dnipro District of the Dnipropetrovsk Oblast; it performs field−protective and anti−erosion functions. The effect of locust digitate leaf miner, P. robiniella, on the plant functioning was assessed by quantifying and comparing chlorophyll fluorescence parameters. The level of the miner exposure was evaluated in trees of three age groups (5−10, 15−25, and 50−70 years old). The study was performed with recording of background, maximum, stationary, and variable fluorescence in live intact and damaged leaves using a ‘Floratest’ fluorometer. The level of photosynthetic activity inhibition in tree leaves damaged by the miner was determined. Data from the analysis of fluorescence indicators showed significant differences between the intact and miner−damaged leaves in trees of all age groups under conditions of field−protective forest planting. A decrease in background, stationary, maximum, and variable fluorescence under the influence of phytophagous insects was recorded. This trend was most pronounced in young trees under the age of 15 years. The results of the research may open up new approaches to an assessment of the black locust plantations in the Steppe zone of Ukraine the establishment of which is aimed at performing specific protective functions.
Key words: black locust, chlorophyll fluorescence, field−protective forest strips, phytophagous, special−purpose forest stands

Abstract: The aim of the study was to assess the losses of dissolved forms of DOC and selected nutrients, i.e. N−NO₃, N−NH₄ and P−PO₄, as a result of their leaching into the soil under deadwood in selected forest reserves. The study was conducted in the following forest reserves of the Białowieża Forest: Władysław Szafer Landscape Reserve, Dębowy Grąd and Lipiny as well as outside these area in Koryciny Reserve. Soil samples were collected in the autumn of 2021 from litter (O) and mineral soils at a depth of 40 cm in several layers (0−5, 5−10, 10−2 and 20−40 cm). The pH in a soil solution of 0.01 CaCl2·dm^–3 (1:10) was measured potentiometrically and the total forms of P, K, Ca, Mg, Mn, Fe and Al were measured using ICP−OES. The water soluble forms of DOC, N−NO₃, N−NH₄ and P−PO₄ (1:5) were determined colorimetrically. Studies have shown that leaving deadwood impairs the slow release of DOC, nitrogen and phosphorus into the soil solution due to the high cellulose content in woody plant tissue. The process of DOC uptake into the soil solution also depended on the amount of carbon (TOC) and nitrogen (N_tot) in the soil as well as the presence of ammonium (N−NH₄) and phosphate (P−PO₄) ions released during mineralisation of soil organic matter. It was shown that the dissolved forms of N−NO₃, N−NH₄ and P−PO₄ can form stable complexes with Al and Fe. Further, it was shown that the content of DOC in soils can be an indicator of carbon fixation and its possible losses as well as changes in the forest soil environment.
Key words: deadwood, dissolved organic carbon (DOC), forest soils, nitrogen, phosphorus

Abstract: With climate change being a pressing issue, the multi−functionality of urban forests can only be ensured by their sustainability, diversity and stable development. Improving our knowledge of the ecological requirements, ecosystem effects and adaptability of non−native tree species in specific urban forest conditions is a foundation for future sustainable forest management. The study involved investigating the impact of selected alien tree species on soil properties in urban forests located in Krakow. Eight tree species were investigated – Douglas fir, Canada hemlock, sweet chestnut, black cherry, horse chestnut, common walnut, box elder, and black locust. The study’s primary goal was to determine the impact of selected species on the quantity and quality of soil organic matter, its physicochemical properties, the C/N/P stoichiometry of soil and enzymatic activity. The analyses confirmed different properties of soil under influence of alien deciduous and coniferous tree species. Properties of soil surface horizons of black locust and horse chestnut were different from other examined alien species. Canada hemlock and Douglas fir exerted the most substantial acidifying effect on the surface soil horizons. These results confirm that growing mixed stands and avoiding conifer monocultures is justified. Additionally, research confirmed that soils of different alien tree species characterized by different biochemical activity expressed by enzymatic activity. Our research confirmed that C/N/P stoichiometry is a valuable tool to assess the nutrient cycle in urban forests and that alien tree species have different effects on the C, N, and P content.
Key words: dissolved organic carbon; ecological stoichiometry; enzyme activity; forest stands; litter characteristics

Abstract: Both natural and man−made forest areas are subject to many changes, the observation of which is necessary to understand their causes, monitor current processes and precisely forecast further changes. Protected areas with preserved natural forests play a special role in research on long−term changes in forest cover height. The presented research presents the processes of changes in forest cover height over the last 30 years in the area of the Białowieża Primeval Forest, the last of the large, natural forest complexes that once covered the lowland part of Europe. For areas with different degrees of protection, data was obtained representing the spatial arrangement of tree crowns in the period between 1982 and 2012. The historical status was determined on the basis of point clouds obtained by processing panchromatic stereoscopic aerial photos. These data were compared with contemporary datasets resulting from airborne laser scanning measurements. This allowed for a precise definition of the range of changes, their dynamics and the nature of these changes in parts of the forest with different conservation regimes. The research demonstrated the usefulness of the proposed method for determining long−term changes affecting forested areas, including not only the range, but also the height structure of vegetation. This enables the identification of events affecting the structure of the forest, both due to normal forest management and to natural causes, along with the possibility of determining the location and approximate determination of the occurrence of a given event in time.
Key words: ALS, Białowieża Forest, historical photographs, LiDAR, natural forests, point clouds, protected areas, stereoscopic image processing