Ukrainian National Forestry University

Currently, wood remains a primary material for construction and finishing applications due to its inherent advantages, including accessibility, environmental sustainability, ease of processing, and renewability. However, the structural application of wood is constrained by several limitations: low resistance to mechanical, atmospheric, thermal, and biological stressors; susceptibility to degradation; and the aesthetic disparity between affordable and premium species. To mitigate these disadvantages while maintaining environmental integrity, thermal modification is employed. This process enhances biological durability and ensures the dimensional stability of wood products during operational cycles. The study utilized radial samples of spruce wood with a rectangular cross-section 35 × 12 × 0.6 mm. These samples underwent thermal modification at temperatures of 180°C and 210°C within a nitrogen-controlled environment. The viscoelastic behavior (creep) under constant loading was analyzed using a Gabo Eplexor 25N Dynamic Mechanical Analyzer (DMA). The experimental protocol was governed by a software module based on the Burgers model. Primary data acquisition and processing were conducted via the GABO software suite. Viscoelastic characteristics were evaluated in tensile mode using "Time Sweep" and "Temperature Sweep" modules at a quasi-static load frequency (f = 0...0.01Hz). The investigation established the correlation between thermal modification temperature in nitrogen, medium and the resulting changes in viscoelastic characteristics and creep modulus. Analysis of deformation kinetics under load indicates that thermal modification significantly alters the mechanical stability of the material. This effect demonstrates a distinct gradational dependence on the treatment temperature. The comparative analysis of deformation ranges between modified and unmodified spruce wood provides a quantitative basis for evaluating the impact of thermal treatment on the material's rheological properties. It has been demonstrated that modification at a moderate temperature of 180°C results in a relatively minor increase in the material's deformability, within the range of 13-15% compared to the control group. This indicates the initial stage of structural transformations, where the degradation of hemicelluloses does not lead to a substantial loss of stiffness. Increasing the treatment temperature to 210°C induces a sharp shift in rheological behavior and leads to a reduction in the mechanical stiffness of the thermally modified European spruce. Consequently, the deformation rate increases by 52-57%, and the difference in ultimate deformation values between the unmodified and high-temperature thermally modified wood reaches 45-47%. It has been established that the thermal modification of wood at 210°C, despite improving biological durability and dimensional stability, leads to a significant reduction in resistance to sustained loading. The intensification of creep processes and the increase in residual deformations restrict the application of such wood in load-bearing building structures. It is recommended to either optimize the thermal treatment parameters or account for the actual decrease in the modulus of elasticity when designing structural elements. The findings offer a quantitative assessment of how temperature influences the structural integrity of spruce wood. Based on the established viscoelastic profiles, practical recommendations are proposed for the industrial application of thermally modified spruce wood in environments requiring high dimensional and mechanical stability.

Forests play a vital role in ecology, economy, urban planning, and social well-being, emphasising the importance of monitoring forest cover and its changes. The study evaluates the ecological impact of the military conflict on forest ecosystem in Ukraine using a time series of Sentinel-2 data and machine learning algorithms. Forest losses following the beginning of the war were derived using a change detection method across the study areas. Two types of forest loss were delineated: conversion of woody areas to non-woody cover, and burnt forest. Before the war, forest loss was predominantly due to the conversion of woody to non-woody cover, accounting for 74% of total changes, while forest fires represented the remaining 26%. Following the outbreak of the conflict, the total area of forest loss doubled. Notably, the proportion of forest converted to non-woody cover decreased to 66%, while the proportion of burnt forest increased to 34%, evidencing the severe impact of military operations on forest ecosystem. Of interest, the area of forest converted to non-wood cover doubled between, possibly reflecting an increased demand for wood due to the conflict, potentially driven by a rise in legal and illegal logging as a result of weakened governance and reduced enforcement of environmental regulations.

The study focused on analysing the species diversity of woody plants and the taxonomic structure of the dendroflora in park plantings in small towns of Western Ukraine (The Transcarpathian region – Khust City Park in the town of Khust; Ivano-Frankivsk region – Kyrylo Trilovskyi Park in Kolomyia and Apollinaris Tarnavskyi Park in Kosiv; Lviv region – Horodok City Park in Horodok and Pustomyty City Park in Pustomyty; Chernivtsi region – Yuriy Fedkovych Park in Vyzhnytsia). The species diversity of the dendroflora was investigated using a combination of general scientific and specialised biological methods. The species composition of the dendroflora, the quantitative representation of woody plants, and the structural characteristics of plant communities within the park plantings were determined through field surveys conducted using the route method. The dendroflora of park phytocoenoses in small towns of Western Ukraine was found to comprise 95 species and forms of woody plants belonging to 59 genera, 28 families, and 22 orders. According to the study findings, the species diversity of the dendroflora in historic parks of Western Ukrainian towns is significantly richer than that recorded in newly established park plantings. The biomorphological structure of the park plant communities is dominated by trees, which account for 83.2% (79 species and forms) of the total dendroflora, whereas shrubs comprise 16.8% (16 species); woody lianas were absent. Woody plant species of the division Magnoliophyta predominate in the park plantings, representing 80.0% (76 species and forms) of the total species diversity, while species of the division Pinophyta account for only 20.0% (19 species and forms). In the dendroflora of the studied park ecosystems, the proportion of native woody species is slightly higher (52.6%) than that of introduced species (47.4%). An analysis of the distribution of the total number of woody plants within the park phytocoenoses revealed that the most abundant species were Acer platanoides L. (4.23%), Picea abies (L.) Karst. (4.26%), Cornus alba L. (4.30%), Fraxinus excelsior L. (5.23%), Aesculus hippocastanum L. (5.26%), Thuja occidentalis L. (6.57%), Robinia pseudoacacia L. (7.32%), Carpinus betulus L. (7.86%), Tilia cordata Mill. (8.13%), Ligustrum vulgare L. (8.67%), and Malus sylvestris (L.) Mill. (9.72% of the total number of woody plants). The species Acer platanoides L., Acer pseudoplatanus L., Aesculus hippocastanum L., Fraxinus excelsior L., Picea abies (L.) Karst., Prunus divaricata Ledeb., Robinia pseudoacacia L., and Tilia cordata Mill. were recorded in all of the investigated park ecosystems of the small towns. Enhancing the biodiversity of the dendroflora of park phytocoenoses and enhancing the aesthetic appeal, ornamental value, and attractiveness of plant compositions in the park ecosystems of small towns in Western Ukraine can be achieved by increasing both the abundance and species diversity of coniferous woody plants, expanding the proportion and species richness of shrubs in the parks' dendrological collections, introducing various species of woody lianas into park plant communities, and increasing the quantitative representation of highly ornamental woody plant woody plant species.

The physical principles underlying the formation of protective and decorative coatings based on modified linseed oil have been investigated. The wetting behavior of wood substrates with linseed oil was investigated in comparison with that of an alkyd varnish. The latter is widely used to create protective and decorative coatings for joinery. Linseed oil modified with rosin was used in the study. Previous studies have demonstrated that rosin improves the performance characteristics of coatings made from oil-based materials. The investigations showed that rosin-modified oil increases the film hardness and reduces the ability of the oil to diffuse into the wood substrate. Consequently, the thickness of the protective and decorative film increases. The wetting and spreading of a coating material over the wood surface is a prerequisite for the formation of a uniform coating. It is well known that the ability of coating materials to wet wood substrates and spread evenly over their surfaces plays a crucial role in determining the appearance, mechanical strength, adhesion, and protective properties of protective and decorative coatings. The surface tension was determined using a Rebinder apparatus. It is based on the maximum bubble pressure method, the maximum pressure required to detach an air bubble from the test material. For a comparative evaluation of the surface tension of rosin-modified linseed oil with varying rosin contents and alkyd varnish as structured (Bingham) fluids, their surface tension values were compared with that of distilled water as an (unstructured) Newtonian fluid. The surface tension value also significantly affects the ability of coating compositions to spread across the substrate surface. In order to conduct experiments aimed at determining the surface tension of oil compositions and alkyd varnish, the contact angle, and the penetration depth of the aforementioned materials into the wood substrate of English oak, European beech, and European ash, linseed oil was modified with rosin in amounts ranging from 1.0 to 3.0 parts by weight. The studies were carried out at a temperature of (20 ± 2)°C and a relative humidity of 70%. According to the results of the study, rosin-modified linseed oil can be used for the formation of protective and decorative wood coatings. The introduction of rosin as a modifier in amounts up to 3.0 parts by weight does not significantly increase the surface tension of the composition. However, when determining the surface tension, the lowest values were demonstrated by the modified linseed oil within the range of 1.0-2.0 parts by weight, which is a positive aspect. The wetting behavior of wood substrates with coating and oil compositions is influenced to a greater extent by the type of wood substrate than by the surface tension of the coating material. In the study of wetting wood substrates with modified oil compositions and alkyd varnish, the best indicators of the coating material's ability to spread over the substrate surface were found for European beech. Rosin-modified linseed oil provides better wetting of wood substrates compared to alkyd varnish. The results of the study on the penetration of rosin-modified linseed oil into wood substrates indicated that increasing the rosin content decreases the penetration depth while correspondingly increasing the thickness of the resulting coating. The penetration depth of the modified oil exhibits a 16% lower penetrating capability compared to natural oil.

As of today, the boundaries of the Pokuttia-Bukovyna Carpathians have been defined based on physical-geographical, geobotanical, and geomorphological criteria, whereas the forest typological and forestry-purpose characteristics of the territory remain insufficiently studied. In particular, the analysis of the species composition of forest stands, considered in terms of forest fund user organizations, the features of their spatial distribution, and the areas by dominant tree species has been conducted only approximately. The lack of such data limits the possibilities for a comprehensive assessment of the region’s forest fund. From this point of view, the present study is highly relevant. The aim of the study is to determine the forest fund areas of forestry enterprises by land categories operating within the subdistricts of the Bukovyna low-mountain and mid-mountain areas of the Pokuttia-Bukovyna Carpathians subregion. The hierarchical units of physical-geographical zoning for the study region are adopted according to Ya. S. Kravchuk (2021) as follows: region – the Skibovi Carpathians; subregion – the Pokuttia-Bukovyna Carpathians; districts – low-mountain and mid-mountain terrain areas of the Pokuttia-Bukovyna Carpathians; subdistricts – Pokuttia and Bukovyna low-mountain areas, and Pokuttia and Bukovyna mid-mountain areas. In the Pokuttia-Bukovyna Carpathians, forestry and nature-conservation activities are carried out by 37 forest districts and five nature-conservation research units. Considering the variations in altitude, terrain features, and forest vegetation composition, the affiliation of the forest fund to forestry units within the subregion is characterized separately for two subdistricts – the Bukovyna low-mountain and mid-mountain areas. In terms of the total area covered by forest vegetation in the Pokuttia Carpathians, the Pokuttia mid-mountain and low-mountain subdistricts occupy approximately the same areas – 19.7 and 22.7 thousand hectares, respectively. In the Bukovyna Carpathians subregion, the mid-mountain part of forestry-purpose land (45.7 thousand hectares) is slightly larger than the low-mountain part (39.8 thousand hectares. The area covered by forest vegetation in the Bukovyna low-mountain and mid-mountain areas amounts to 78.6 thousand hectares, while non-forested areas cover 5.4 thousand hectares, non-forest lands – 1.5 thousand hectares, and lands designated for forestry purposes – 85.5 thousand hectares. The areas of forested and non-forested land in the Pokuttia-Bukovyna Carpathians subregion are 120.9 and 7.4 thousand hectares, respectively, while the area of non-forest land is 1.9 thousand hectares. The total area of forestry-purpose lands of the subregion amounts to 130.2 thousand hectares. The area of artificial plantations within the forest fund of the Pokuttia-Bukovyna Carpathians subregion amounts to 34.9 thousand hectares. In this context, the share of forest plantations in the Pokuttia Carpathians subdistrict is slightly lower than in the Bukovyna Carpathians, being 20.5% and 33.4%, respectively. The distribution of forest fund lands within the subdistricts of the Pokuttia-Bukovyna Carpathians carried out in this study enables the implementation of a differentiated approach to forest management, particularly in the context of forest renewal, taking into account forest site types, forest types, and the species composition of forest stands.