Forestry and Forest Melioration

Current radioecological problems if the forestry sector of Ukraine and ways to address them

Fri, 29 May 2026 00:00:00 +0300

Introduction

Forty years have passed since the accident at the Chornobyl Nuclear Power Plant. This period has been marked by significant scientific achievements as well as a number of unresolved problems. The article briefly reviews the history of radioecological research in forest ecosystems of Ukraine. It is shown that scientists of the Ukrainian Research Institute of Forestry and Forest Melioration named after G.M. Vysotsky (URIFFM) and its experimental network were among the pioneers of radioecological research in Ukraine. The study emphasizes that scientific issues in forest radioecology remain highly relevant in Ukraine.

Materials and Methods

The dynamics of radiocaesium contamination were studied in the forests of Narodychi Forestry during two periods: in 1991 for ¹³⁴Cs + ¹³⁷Cs and in 2025 for ¹³⁷Cs. To create map schemes of radioactive contamination for 1991, a database from the Polissya Branch of URIFFM was used. Data for 2025 were obtained by calculation, taking into account radionuclide decay periods: 2,5 years for ¹³⁴Cs and 30,1 years for ¹³⁷Сs. Measurements of ¹³⁷Cs activity concentrations in samples were carried out using an AKP-S spectrum analyzer equipped with a BDEG-20R1 scintillation detector. Isolines of ¹³⁷Cs activity concentration in the soil were constructed using the Distance Weighted Least Squares method, and graphical visualizations were produced using the 3D Contour Plot function in STATISTICA 12.0 software.

Results

As a result of fundamental research conducted in radioactively contaminated forests of Ukraine, scientific foundations and practical recommendations for forest management under radioactive contamination conditions have been developed. Their implementation is aimed at strengthening the multifunctional role of forests and ensuring the safer and more efficient use of forest resources under varying levels of radioactive contamination. It was emphasized that, during the period following the Chornobyl accident, research mainly focused on ¹³⁷Cs in different components of forest ecosystems, whereas ⁹⁰Sr has been actively investigated only during the last decade and remains insufficiently studied. The spatial heterogeneity of radioactive contamination in forest ecosystems has been investigated only fragmentarily, which complicates comprehensive analysis. The study highlights the need to significantly deepen and expand fundamental research on forests growing on radioactively contaminated lands. The necessity of continuing long-term monitoring observations at biogeocenotic experimental plots for investigating ¹³⁷Cs migration was emphasized. In addition, ⁹⁰Sr should be incorporated into monitoring protocols, and a comprehensive state-level forest monitoring system should be urgently implemented. The urgent need to update the database of forest radioactive contamination surveys conducted in 1991–1992 was also demonstrated, taking into account radionuclide decay. On this basis, new maps of radioactive contamination density for the forest fund of Ukraine with ¹³⁷Сs and ⁹⁰Sr should be developed.

Conclusion

The results of later surveys conducted for forest rehabilitation purposes should be incorporated into the national database on forest radioactive contamination. Amendments and additions should also be introduced to the Hygienic Standards for the Content of ¹³⁷Cs and ⁹⁰Sr in Wood and Wood Products. From a practical perspective, it is important to restore the system of radiation monitoring and control of forest products, which has largely ceased to function.

3 Figs., 33 Refs.

Structural and mensurational characteristics of spruce stands in primeval forest communities of the Verkhovynskyi National Nature Park

Fri, 29 May 2026 00:00:00 +0300

Introduction

The study of forest mensurational and silvicultural characteristics was conducted in primeval forest communities formed by Picea abies (L.) Karst. The relevance of this research lies in the investigation of the forest mensurational and silvicultural characteristics of spruce primeval forests as natural models of sustainable ecosystem functioning under current environmental conditions. The study of the productivity of primeval forest ecosystems is an important prerequisite for the implementation of close-to-nature forest management in other spruce stands, since primeval forests can serve as reference systems for the formation of biologically stable and highly productive forest communities. The aim of the study was to investigate the developmental processes of primeval forests involving Picea abies, their forest mensurational and silvicultural characteristics, and the condition of primeval forest communities.

Materials and Methods

The study was conducted between June and September 2025 at three sites of spruce primeval forests located within the Verkhovynskyi National Nature Park. The research covered the altitudinal vegetation belt of spruce forests (Piceeta abietis) within the elevation range of 1000–1600 m above sea level under conditions of the high-mountain humid spruce forest site type. For the purposes of the study, sites were selected in primeval forest stands representing specific phases of their development. The mensurational and silvicultural characteristics of the stands were determined, including the presence of trees approaching the limit of physiological longevity, as well as standing deadwood and fallen deadwood at different stages of decomposition. In addition, the quantitative and species composition, as well as the spatial distribution of the shrub layer, seedlings, saplings, and herbaceous ground vegetation were examined within the study plots. The presence or absence of traces of anthropogenic influence was also assessed at each site. The health condition of the stands was evaluated according to four categories: healthy (without signs of weakening), weakened, severely weakened, and dying. The criteria and indicators applied in the assessment of the investigated spruce forest stands fully correspond to those established for primeval forest communities.

Results

The growing stock of living trees at the site representing the early stage of the ageing phase amounted to 588 m³·ha^-1, at the site representing the late ageing phase – 596 m³·ha^-1, and at the site representing the initial phase of stand breakdown – 545 m³·ha^-1. The volume of standing deadwood was 24, 70 and 121 m³·ha^-1, respectively. The stands are composed of three vertical layers. The first layer is formed by the tallest trees, often with the largest diameters. The second layer is weakly expressed but represented by trees of similar diameter (20–32 cm) and height (12–26 m). The third layer consists of the youngest generation of trees, with diameters of 8–18 cm and heights of 6–15 m. The largest volume of standing dead trees, both in terms of number (10–41 trees·ha^-1) and stock (19–105 m³·ha^-1), was recorded in the first layer, which is also the oldest. In the second (8–32 trees·ha^-1) and third (10–38 trees·ha^-1) layers, the number of standing dead trees was similar or even higher than in the first layer; however, due to the smaller size of the trees, the volume of deadwood was considerably lower (4–13 and 1–3 m³·ha^-1, respectively). The number of regeneration individuals varies considerably and generally depends on the developmental phase of the stand: 4.8 thousand individuals·ha^-1 (early ageing phase), 13.6 thousand individuals·ha^-1 (late ageing phase), and 15.0 thousand individuals·ha^-1 (initial breakdown phase). Another factor contributing to the high variability in regeneration density among the sites is the different intensity of herbaceous ground vegetation development, which depends on canopy closure and the level of light availability within the forest stand. Seedlings and saplings are mainly concentrated on fallen logs at the fourth stage of decomposition.

Conclusions

The studied old-growth spruce stands are characterized by natural origin, uneven-aged structure, the presence of trees approaching the limit of physiological longevity, the occurrence of seedlings and saplings, and fallen deadwood at all stages of decomposition. Trees representing all developmental stages are present, and no signs of anthropogenic disturbance were detected. Thus, these stands exhibit all the characteristics typical of primeval forest communities. The health condition of the stands depends on the developmental phase of the primeval forest community and varies from “healthy” (sample plot 12, early ageing phase) to “severely weakened” (sample plot 13, initial breakdown phase). The study of natural processes occurring in primeval forest ecosystems is an important prerequisite for the implementation of close-to-nature forest management, since primeval forests can serve as reference systems for the formation of biotically stable and highly productive forest communities.

9 Figs., 3 Tables, 26 Refs.

Productivity of sessile oak (Quercus petraea) forest stands located in the Uzh and Latorica river basins

V. P. Kichura, A. V Kichura, V. I. Roman — Fri, 29 May 2026 00:00:00 +0300

Introduction

Research on forest stand productivity is extensive and encompasses various aspects, including general stand growth dynamics, the influence of climatic factors on productivity indicators, and the development of models for strategically planned productivity levels under thinning, sanitary and health-improving measures, reconstruction, reforestation, and other silvicultural activities aimed at forest formation and improvement. At the same time, there remains a need for further studies focused on assessing the influence of factors that have either not been investigated or have been insufficiently studied. One such factor is the effect of river basin location on the productivity of forest stands belonging to the same forest typological category. This study aimed to determine whether differences in productivity exist between sessile oak (Quercus petraea [Matt.] Liebl.) stands growing within the basins of different rivers during the course of stand development.

Materials and Methods

The study is based on data from the baseline forest inventory of the Uzhhorod forestry as of 1 January 2022. Differences in productivity between forest stands located within the Uzh and Latorica River basins were assessed using a comparative approach based on model growth series. Growth dynamics were analysed using a single indicator—total growing stock per hectare of forested land. Approximation of growth trends was performed using a second-order polynomial function. The identification and quantification of productivity differences in sessile oak stands from the Uzh and Latorica River basins were carried out for the most widespread oak forest types within the territory of the Uzhhorod forestry.

Results

It was found that, in the Uzh River basin compared with the Latorica River basin, the total growing stock per hectare of forested land in sessile oak stands aged 30–140 years differed only slightly and remained within the normatively accepted accuracy limits for growing stock estimation. The largest productivity differences were observed at the beginning and the end of the stand development period, whereas the smallest differences occurred between 60 and 100 years old.

Conclusions

Throughout the entire stand development period, the productivity values for sessile oak stands in both the Uzh and Latorica river basins are similar. The observed difference in productivity does not exceed 10%.

4 Figs., 1 Table, 20 Refs.

Stock structure in oak stands of different origin under the conditions of the Left-Bank Forest-Steppe of Ukraine

V. V. Nazarenko, V. P. Pasternak, I. M. Lytsur, A. A. Suska — Fri, 29 May 2026 00:00:00 +0300

Introduction

The condition, structure and productivity of pedunculate oak (Quercus robur L.) stands in the Left-Bank Forest-Steppe of Ukraine remain an important research issue. Oak stands managed by the State Enterprise “Forests of Ukraine” in this region cover approximately 285 thousand ha. Given the importance of assessing the dimensional and qualitative structure of these stands under current conditions, systematic studies are required. The aim of the study was to determine the dimensional and qualitative structure of planted and coppice-origin oak stands.

Materials and Methods

The study was conducted on 20 temporary sample plots (TSPs) located in the Trostianets (Sumy region) and Huty (Kharkiv region) forestry management units. Sample plots were established in the dominant forest types, taking into account stand origin and productivity, in accordance with standard forest mensuration methods. The dimensional and qualitative structure of the stands was assessed using commonly accepted standards. Oak and ash on TSPs 1–5 were of planted origin, whereas on TSPs 6–20 they were of coppice origin; the associated species were of mixed (seed and coppice) origin. On TSPs 10, 14, and 15, a considerable proportion of oak stems was of seed origin. The average age of oak stands ranged from 95 to 126 years.

Results

The distribution of stems by technical suitability categories and the yield of timber by quality classes were evaluated. The average proportion of merchantable stems was 30.4 ± 1.5%, and the proportion of merchantable timber was 38.2 ± 2.4%. In planted stands, the share of merchantable stems averaged 27.4 ± 1.2%, including oak – 70.5%, ash – 27.4%, Norway maple – 7.6%, and small-leaved lime – 14.5%. In coppice stands, the proportion of merchantable stems averaged 31.4 ± 2.0%, with a lower share of oak (67.5%) and higher shares of associated species (ash – 55.4%, maple – 13.7%, and lime – 31.6%). The proportion of merchantable timber amounted to 38.6 ± 1.5% in planted stands and 38.1 ± 2.8% in coppice stands. The proportion of quality class A timber was 4.0% in planted stands and 2.9% in coppice stands, with a maximum value of 6.7%. According to diameter classes, more than 34.5% of timber volume consisted of logs with diameters of 30–39 cm, 26.0% – 40–49 cm, and 21.8% – 20–29 cm. A tendency toward an increase in the share of merchantable timber was observed in stands containing 70–80% oak. The obtained merchantable timber yield (38%) corresponds to the results of previous studies, which reported 40–42% in coppice-origin stands aged 100–110 years with diameters of 34–36 cm, as well as a proportion of large-diameter merchantable timber of 70–75%. The largest share of timber belonged to quality class D (66.0% in coppice stands and 56.7% in planted stands), whereas class C accounted for 22.7% and 30.2%, respectively; the proportions of the remaining quality classes were insignificant. The actual yield of quality classes A and B in harvesting areas was slightly lower because of hidden defects, especially in coppice-origin stands.

Conclusions

The dimensional and qualitative structure of oak stands is primarily determined by stand density, species composition, mean diameter and height, and stem quality. The optimal composition of mature stands is represented by mixed stands containing about 80% oak and 10–20% associated species, particularly ash, which ensures higher productivity and improved timber quality. Given the predominance of coppice-origin stands in the region, regeneration fellings should focus on the formation of seed-origin stands, which are characterized by greater longevity, stability, and timber quality, while maintaining an admixture of associated species in accordance with forest site conditions.

Fellings as an indicator of the condition of high-mountain Norway spruce forests of the Ukrainian Carpathian Mountains

A. A. Novak, O. M. Klymenko, S. L. Kopiy — Fri, 29 May 2026 00:00:00 +0300

Introduction

The dieback of Norway spruce forests in the Ukrainian Carpathians is one of the most pressing challenges in contemporary forestry, as it affects extensive mountain areas and has a systemic character. Norway spruce (Picea abies (L.) H. Karst.) has historically occupied a prominent position in the structure of Carpathian forests, performing important ecological functions, including habitat formation, water and climate regulation, and soil protection.

Materials and Methods

To assess changes in the health and resilience of high-mountain Norway spruce stands within dieback foci, a retrospective analysis of thinning and sanitary fellings carried out in the Brustury Forestry Management Unit was conducted. In this forest district, Norway spruce is the principal and dominant tree species and forms predominantly pure stands. Forest management interventions during the period 2020–2024 were analysed using official forest management reports of the forest district.

Results

The study examined temporal patterns in the volume and intensity of thinning and sanitary fellings in declining high-mountain Norway spruce (Picea abies) stands within the Brustury Forestry Management Unit during 2020–2024. Particular attention was paid to the relative prevalence of tending operations and sanitary interventions, as well as to associated harvesting volumes and felling intensity. Thinnings were characterized by generally stable intensity with only minor interannual variation, whereas selective sanitary fellings demonstrated a noticeable increase in harvested volumes accompanied by a gradual rise in intensity. Monitoring of thinning operations by type revealed considerable differentiation both in their prevalence and temporal dynamics. Throughout the analysed period, thinning from above (commercial thinning) accounted for the largest proportion of interventions, and the treated area increased steadily over time. The proportion of merchantable timber within the assortments obtained from clear sanitary fellings was also analysed as an indirect indicator of stand condition, silvicultural interventions, and management effectiveness. The analysis revealed a consistent decline in the share of merchantable timber within the total harvested volume from clear sanitary fellings over the study period.

Conclusions

In the high-mountain Norway spruce stands of the Brustury Forestry Management Unit in the Ukrainian Carpathians, the study revealed a transition from a crisis state, characterized by the predominance of sanitary interventions, toward gradual stabilization. This shift became evident in 2024, when the area subjected to thinning operations equalled and subsequently exceeded the area affected by sanitary fellings. The increase in the area, volume, and intensity of thinnings, particularly during 2023–2024, indicates the restoration of systematic forest management and a transition from measures aimed primarily at mitigating the consequences of large-scale forest degradation to silvicultural practices focused on the formation and improvement of spruce stands. Overall, the obtained results confirm that felling-related indicators can serve as reliable proxies for assessing forest condition and vitality. They also highlight the importance of their systematic application for detecting degradation processes in spruce forests and for supporting evidence-based forest management strategies.

10 Figs., 25 Refs.

State and productivity of silver fir (Abies alba) stands on the northeastern macroslope of the Ukrainian Carpathians

V. V. Tysiak, L. S. Osadchuk — Fri, 29 May 2026 00:00:00 +0300

Introduction

In recent years, considerable attention has been devoted to the study of the biotic stability, spread of pests and diseases, and degradation processes in Abies alba stands, as well as to the characteristics of their formation, structure, and growth. A comprehensive assessment of the current condition and growth dynamics of silver fir stands is essential for evaluating the adaptive capacity of the species under climate change and for developing scientifically grounded strategies for the targeted formation of uneven-aged forest stands based on close-to-nature silviculture principles.

Materials and methods

The analysis of subcompartments was based on the current forest management database of Ukrderzhlisproekt as of 1 January 2021 and covered the northeastern macroslope of the Ukrainian Carpathians within the Ivano-Frankivsk, Lviv, and Chernivtsi regions. Sample plots were established in the Gorgany mountain range (Vygoda Forestry Management Unit, Shevchenkivske Forestry) within the most widespread forest type – moist beech-spruce mixed forest. Circular sample plots of 500 m² were established in fir stands of different ages and compositions; their number depended on the size and homogeneity of the forest subcompartment in accordance with selective forest inventory standards. The yield tables for silver fir in the study region were developed considering stand composition, site quality class, and forest type, which reflect the specific regional characteristics of fir stand development.

Results

The total area of forest stands containing silver fir on the northeastern macroslope of the Ukrainian Carpathians was estimated at approximately 130.5 thousand ha, representing 8.2% of the total forest area of the studied territory. The largest areas of fir forests are concentrated in the Lviv Region (about 45% of the total fir forest area), followed by the Ivano-Frankivsk and Chernivtsi regions, which account for approximately 30% and 25%, respectively. Exploitation forests predominate within these areas. A high degree of coenotic plasticity of silver fir was identified across 71 forest types grouped into seven typological groups within the region. The species is most widely distributed in fir forest types, where it occurs in 85% of forest stands as a dominant or co-dominant species, forming characteristic phytocoenoses. An imbalance in age structure was observed, with the area occupied by young stands being approximately three times greater than that of mature stands. The analysis showed that the increase in average diameter slows after stands reach 100 years of age. At the age of 140 years, the difference in average diameter between the studied and reference stands was approximately 4.2 cm, indicating enhanced radial growth in more intensively thinned stands. Even greater differences were observed in tree height, with an average difference of approximately 2.7 m, reflecting the potential for increased height growth under improved growing space conditions.

Conclusions

The altitudinal distribution of silver fir on the northeastern macroslope of the Ukrainian Carpathians is determined by the complex interaction of climatic, soil, and orographic factors that define its ecological niche and the boundaries of its natural range in the region. The orographic structure of the territory, particularly slope exposure, directly influences the distribution of fir–beech stands and determines their mosaic spatial structure. In the studied region, Abies alba occurs under highly favourable ecological conditions, enabling the formation of some of the highest standing wood volumes in Ukraine. Fir forests are concentrated mainly in moist beech–fir forest types, where they form highly productive stands. The predominance of site quality class I confirms the high forestry potential of these territories. The identified imbalance in age structure, with the area of young stands being three times greater than that of mature stands, may result in a future reduction in timber harvesting due to the insufficient area of stands reaching final felling age. At the same time, the predominance of young and middle-aged stands (71% of the total area) contributes to intensive carbon sequestration, which is important for climate change mitigation. The potential productivity of forest vegetation is not yet fully realized, and the revealed patterns emphasize the need to optimize forest management practices to achieve more effective utilization of the bioproductive potential of fir forests in the region.

10 Figs., 28 Refs.

Forestry and mensurational characteristics of stands with Picea abies (l.) Karst. in the fir types of forest in the Ivano-Frankivsk region

Ya. S. Forgil — Fri, 29 May 2026 00:00:00 +0300

Introduction

Despite the partial loss of biotic stability associated with climate change, Picea abies (L.) Karst. remains one of the most valuable tree species in the forests of the Ukrainian Carpathians. Even in pure secondary stands, Norway spruce generally remains relatively stable up to the age of 50–60 years and accumulates considerable timber volumes. Researchers characterize Picea abies as a fast-growing tree species under rich forest site conditions. Despite ongoing climate change, spruce stands still possess significant resource potential and remain the main source of timber in the Carpathian region. The aim of the study was to investigate the current state and dynamics of silvicultural and mensurational characteristics of spruce stands of different composition and age in silver fir forest types of the Ivano-Frankivsk region.

Materials and Methods

The analysis of silvicultural and mensurational characteristics of stands containing Picea abies within the forest fund of the studied region was carried out using forest inventory data from 2016–2024 provided by the Lviv State Forest Inventory Expedition. The analysis covered 11 silver fir forest types in which Norway spruce is the dominant tree species in both natural and artificial stands. In total, more than 40 thousand forest inventory subcompartments within silver fir forest types were analyzed. The names of forest types are presented according to Gerushynskyy (1996).

Results

The proportion of spruce in forest stands of silver fir forest types varies widely, ranging from 2 to 10 units in stand composition. The largest share of stands was observed where the coniferous species occurred in the composition at 5 and 6 units (14.6% and 17.4%, respectively). At the same time, the area of pure spruce stands in silver fir forest types (10 units) is relatively high (13.6%). The highest timber volumes are concentrated in stands with spruce participation of 6–10 units (2,031.6–2,297.2 thousand m³, or 15.8–17.8%). The largest proportion of stands containing spruce was observed in the age range of 30–70 years (10.9–23%). The highest share of timber stock (13.6–28.1%) is concentrated in stands aged 50–70 years. Within this age range, 7,801.6 thousand m³ of timber have accumulated. Forest stands containing Picea abies are represented by all age groups, from young stands of the first age class to overmature stands. The largest areas are occupied by mature (12,521.4 ha or 32.3%) and middle-aged (10,768.4 ha or 27.8%) stands; somewhat smaller areas are represented by premature stands (8,850.4 ha or 22.9%), while the smallest areas are occupied by overmature stands (4,615.6 ha or 11.9%) and young stands (1,972.4 ha or 5.2%). It is among mature and middle-aged stands that the highest proportion of high-density stands (relative stocking 0.8 and higher) is observed (18.2% and 21.8%, respectively). The largest proportion of the area is occupied by stands of the highest site classes, I and I^a (41.6% and 26.9%, respectively). Stands of site class II occupy a considerably smaller part (19.3%). The timber stocks of stands growing in site classes I and I^a are the highest (10,079 thousand m³ or 78.3%).

Conclusions

Under the conditions of fir and spruce-fir forest types, pure spruce stands are capable of forming substantial timber stocks within a relatively short period, which creates certain prerequisites for the establishment of spruce forest plantations with a shortened rotation period on limited areas. Reducing the timber-growing rotation in such conditions (to 50–60 years) would contribute to maintaining an adequate level of biotic stability of Norway spruce. The presence of highly productive and stable spruce stands in silver fir forest types, some of which exceed 200 years of age, the relatively high stability of spruce up to the age of 50–60 years, its high growth rate, and the accumulation of significant timber volumes in fir and spruce-fir forest types provide grounds to recommend Picea abies as a promising tree species for the establishment of plantation forest stands.

3 Figs., 5 Tables, 30 Refs.

Assessment of forest damage caused by war-related fires within the Chornobyl Radiation and Ecological Biosphere Reserve in 2022

Ya. P. Didukh, O. A. Borsuk, I. I. Moysiyenko — Fri, 29 May 2026 00:00:00 +0300

Introduction

After the liberation of the Chornobyl Exclusion Zone from occupation, it became possible to assess the environmental impacts of the war. Unfortunately, a large area of forest was destroyed not only by fires, but also as a result of fortification construction, the deployment of military equipment, shelling, and explosions. In addition, a significant part of the territory remains mined, posing a constant threat to wildlife, which may be injured or killed by detonations. The destruction of tree stands, ground vegetation, and forest litter by fires has substantially affected soil properties. The analysis indicates that the fires caused a complex set of severe environmental and economic problems requiring urgent resolution. This study aimed to estimate the ecological damage caused by the loss of the phytobiotic component of forest ecosystems within the Chornobyl Reserve based on an assessment of their functional (regulating and supporting) ecosystem services.

Materials and Methods

An assessment of forest losses in the Chornobyl Radiation and Ecological Biosphere Reserve caused by military actions in spring 2022 was conducted based on functional (regulating and supporting) ecosystem services. Timber stock calculations were performed using forest inventory data from 2016 according to the methodology proposed by Didukh et al. (2024). The phytomass of all ecosystem components, biomass increment, CO? sequestration, O? production, transpiration, soil-forming processes, and the trophic requirements of the heterotrophic component were calculated. The resulting energy indicators were monetized in US dollars.

Results

During 2025, field studies were conducted in the forests of the Chornobyl Radiation and Ecological Biosphere Reserve affected by the indirect impacts of military operations in 2022, including burned areas. Analysis of satellite imagery revealed that 6,403.0 ha of forest were destroyed in 2022, representing 2.8% of the reserve’s total area. The greatest losses were recorded in dry and fresh Dicrano-Pinetum pine forests, which accounted for 40.91% of the affected area and 42.92% of the destroyed timber stock and were identified as the most vulnerable to fire.

Conclusions

According to satellite imagery, forests of the Chornobyl Radiation and Ecological Biosphere Reserve affected by the indirect impacts of military operations in 2022, including burned areas, covered 6,403.0 ha, representing 2.8% of the reserve’s total area. The greatest losses were recorded in dry and fresh Dicrano-Pinetum pine forests, which accounted for 40.91% of the affected area and 42.92% of the damaged timber stock, confirming their high vulnerability to fire. For different forest types, the estimated value of ecosystem service losses ranged from USD 12.2 thousand to USD 14.2 thousand per hectare per year. Losses in pine forests, taking into account the time required for ecosystem recovery, were estimated at USD 2.61 billion, representing 83.75% of the total estimated damage (USD 3.12 billion). Considerable losses were also recorded in widespread secondary birch forests, amounting to USD 387.42 million. The obtained results are important for assessing environmental damage and substantiating compensation claims for the ecological losses caused by the war against Ukraine.

7 Figs., 4 Tables, 52 Refs.

Phytomass and sequestered carbon in the forests of the Poltavske Forestry Management Unit

S. S. Kovalevskyi, V. M. Khryk — Fri, 29 May 2026 00:00:00 +0300

Introduction

Global climate change and the increasing concentration of greenhouse gases drive growing scientific interest in the carbon sequestration function of forest ecosystems. Forests represent one of the most efficient natural mechanisms for CO₂ sequestration; therefore, assessing their bioproductivity at the regional level is of critical importance for the development of adaptive strategies for sustainable forest management. Despite numerous studies on the forest carbon balance in Ukraine, a comprehensive assessment of phytomass stocks and sequestered carbon specifically for the forests of the Poltavske Forestry Management Unit of the Branch “Slobozhanskyi Forest Office”, State Specialized Forest Enterprise “Forests of Ukraine” has remained insufficiently explored.

The aim of the study was to determine total phytomass stocks by major fractions and to assess the carbon potential of the main forest-forming tree species in the studied region of the Left-Bank Forest-Steppe of Ukraine.

Materials and Methods

The object of the study is forest stands of the Poltavske Forestry Management Unit, with a total forest land area of 95,561 ha. The information base consisted of materials from the State Forest Inventory and compartment-level forest mensuration database of the Ukrainian State Forest Inventory Enterprise (VO “Ukrderzhlisproekt”), processed using the specialized software package “PERTA” (National University of Life and Environmental Sciences of Ukraine). The dataset included 1,137 sample plots obtained through sampling-based forest inventory methods and 3,248 relascope plots. Phytomass was estimated according to the methodology developed by P.I. Lakida, using a system of multifactor regression equations to calculate the mass of individual tree components (stem wood, bark, branches, foliage or needles, and root systems) in absolutely dry condition. Conversion of phytomass into sequestered carbon was performed using internationally recognized conversion factors: 0.50 for woody fractions and 0.45 for foliage and understory vegetation. Statistical data processing was carried out using Microsoft Excel and SPSS.

Results

The analysis of species composition revealed the dominance of coniferous tree species (74% of forested areas), among which Scots pine (Pinus sylvestris L.) overwhelmingly prevails (99.9%). Hardwoods (10%) and softwoods (16%) occupy smaller shares. The age structure is characterized by the predominance of middle-aged (37%) and maturing stands (28%); young stands account for 24%, while mature and overmature stands represent only 10%. The average growing stock of stem wood is 218 m³·ha^-1, with an annual increment of 4.0 m³·ha^-1. The total phytomass of forest stands within the super-forestry is estimated at 15,100.59 thousand tonnes of absolutely dry matter, of which 70.4% belongs to coniferous stands. The phytomass structure is dominated by stem wood and bark – 72% (10,876.94 thousand tonnes); root systems account for 17%, branch wood and bark for 6%, assimilation apparatus for 1%, and understory vegetation for 4%. The total amount of sequestered carbon equals 7,513.88 thousand tonnes. The highest carbon density was recorded in hardwood stands—10.7 kg·m^-2, which is 44.6% higher than in coniferous stands (7.4 kg·m^-2). The area-weighted average carbon density across the enterprise is 7.8 kg·m^-2.

Conclusions

It was evaluated that the total biomass of the forest stands in the Poltavske Forestry Management Unit, Branch “Slobozhanskyi Forest Office”, State Specialized Forest Enterprise “Forests of Ukraine” was 15,100.59 thousand tonnes of absolutely dry matter. This volume of organic mass ensures the accumulation of 7,513.88 thousand tonnes of carbon. It was revealed that although coniferous species dominate the enterprise’s forest fund (74 % of the area), the highest specific density of sequestered carbon was recorded in hardwood stands – 10.7 kg·m^-2. In the structural distribution of phytomass, the absolute majority falls on the wood and bark of the trunks (72 %). Root systems accumulate about 17 % of carbon, the crown (branches and assimilation apparatus) – 7 %, and understory vegetation – 4 %. The analysis of the age structure of forests showed a significant predominance of middle-aged and maturing stands (over 65 %), which indicates a high potential for carbon dioxide absorption in the coming years, but requires optimization to ensure uniform forest use. The obtained results have significant practical value for improving the national greenhouse gas inventory system, spatial planning of forestry activities, and the development of bioenergy in the region.

2 Figs., 3 Tables, 21 Refs.

Scots pine radial growth response to surface fire in young stands in Zhytomyr Polissia

Fri, 29 May 2026 00:00:00 +0300

Introduction

Forest fires pose a critical environmental threat, particularly to Scots pine (Pinus sylvestris L.) stands in the Polissia region of Ukraine. Since 2022, full-scale military aggression has drastically increased both the frequency of forest fires and the total burned area. Surface fires cause cambium damage, reduce radial growth, and may lead to tree mortality. Dendrochronological analysis provides an effective tool for assessing the impact of fire on tree vitality. This study aimed to evaluate the response of radial growth in young Scots pine stands to a spring surface fire in Zhytomyr Polissia under current climatic conditions and military-induced pressures.

Materials and Methods

The study was conducted in a 30-year-old Scots pine stand under fresh relatively poor site conditions (B?) in Korostyshiv forestry, Zhytomyr region. A surface fire occurred in April 2022. Two temporary sample plots were established: an unburned control plot (TPP-1) and a burned plot (TPP-2). Mean tree height was 15.8 m on the burned plot and 14.7 m on the control plot, while mean diameter was 18.3 cm and 17.9 cm, respectively. Relative density of stocking was 0.3 on the burned plot following fire-induced mortality and sanitary felling, and 0.7 on the control plot. Fifteen increment cores per plot were collected at breast height (1.3 m) in September 2024 using a Pressler increment borer. Earlywood, latewood, and annual ring widths were measured with a precision of 0.001 mm. Cross-dating and chronology development followed standard dendrochronological procedures. Meteorological data from the Zhytomyr weather station for the period 1995–2024 were analysed using the hydrological year approach. Statistical analysis included descriptive statistics and polynomial regression analysis.

Results

In the fire year (2022), total radial growth on the burned plot decreased by 34% compared to the control plot (0.96 mm vs. 1.46 mm). Latewood width decreased by 28% (0.25 mm versus 0.35 mm), while earlywood width decreased by 27% (0.83 mm versus 1.13 mm). Hydrothermal conditions in 2022 were close to optimal, with precipitation exceeding the long-term average by 7% and air temperature by 0.6°C, which partially mitigated immediate fire stress. However, the severe drought of 2023 (precipitation deficit of 32% and air temperature 14% above the long-term average) prolonged the recovery period. By 2024, earlywood width on the burned plot exceeded that of the control plot by 23% (1.02 mm versus 0.78 mm). This increase was associated with a 57% reduction in stand density following sanitary fellings (from 0.7 to 0.3). Post-fire variability in radial growth increased substantially: earlywood variance on the burned plot reached 0.88 in 2024 compared to 0.22 on the control plot. In 1% of sampled trees, the annual ring for 2022 was absent. Regression analysis revealed significant relationships between radial increment and health condition (R² = 0.44, ? = 0.66), as well as stem diameter (R² = 0.69, ? = 0.83). Trees with larger diameters demonstrated greater fire resistance due to thicker bark and improved cambial protection.

Conclusions

The surface fire of April 2022 caused substantial physiological stress in the 30-year-old Scots pine stand, resulting in a 34% reduction in total radial growth during the fire year. Favourable moisture conditions in 2022 reduced the immediate impact of fire stress; however, the severe drought of 2023 prolonged the recovery process. By the second year after the fire, surviving trees exhibited increased earlywood growth, exceeding control values by 23%, due to reduced competition following a 57% reduction in stand density. Post-fire variability in annual ring width increased markedly, indicating considerable individual variation in fire response. Stem diameter and health condition were identified as statistically significant predictors of post-fire radial growth. Trees with larger diameters demonstrated greater resilience to fire. Overall, surviving trees on the burned plot successfully restored radial growth by the second year following the fire.

7 Figs., 3 Tables, 25 Refs.

Growth of English oak (Quercus robur L.) forest plantations established using planting material of different types and cultivation methods, in the Right-Bank Forest-Steppe of Ukraine

Fri, 29 May 2026 00:00:00 +0300

Introduction

In the plain part of Ukraine, artificial regeneration remains the main method of oak forest restoration, including the establishment of forest plantations using bare-root and containerized seedlings, as well as acorn sowing. It is well known that the proper selection of planting stock type for specific site conditions largely determines the success of artificial reforestation and afforestation. Numerous scientific studies have addressed the selection of planting stock types for artificial regeneration of oak forests, as well as the survival, preservation, and growth performance of plantations established using different types of planting material. However, such studies in the Right-Bank Forest-Steppe of Ukraine remain fragmentary, which determines the relevance of the present research. The aim of this study was to compare the survival, preservation, and growth performance of two-, four-, and five-year-old English oak (Quercus robur L.) plantations established using bare-root seedlings, containerized seedlings, and acorn sowing in the Right-Bank Forest-Steppe of Ukraine.

Materials and Methods

The study of survival rate, preservation, and growth performance of two-, four-, and five-year-old English oak plantations established using bare-root and containerized seedlings, as well as acorn sowing, was conducted in 2025 in the Vinnytsia, Khmelnytskyi, and Cherkasy regions. The survival rate in 1–3-year-old plantations and the preservation rate in older plantations were calculated as the ratio of the number of viable plants at the time of assessment to the initial number of planted individuals, expressed as a percentage. The following growth indicators were determined: average height, height increment, and root collar diameter. Plantation age was determined from the time of seedling planting or acorn sowing. The significance of differences in growth indicators between plantations established using different methods and planting stock types was tested using Student’s t-test at the 5% significance level. The data followed a normal distribution and therefore met the assumptions for applying Student’s t-test.

Results

Higher survival rates were observed in two-year-old oak plantations established using containerized seedlings grown both in polystyrene containers (variant «ЗКС-1») and agrofiber containers (variant «ЗКС-2»), amounting to 94% and 91%, respectively, compared with plantations established using bare-root seedlings (variant «ВКС») – 85%. The differences in average height between plantations in variants «ЗКС-1» and «ЗКС-2» and «ВКС» amounted to 10.8 cm and 20.4 cm, respectively; differences in height increment were 6.0 cm and 12.2 cm, and differences in root collar diameter were 0.9 mm and 1.4 mm. A statistically significant difference in height, height increment, and root collar diameter was found between plantations in variants «ЗКС-2» and «ВКС», whereas between «ЗКС-1» and «ВКС» a significant difference was observed only in height. Higher preservation was observed in four-year-old plantations established using containerized seedlings (variant «ЗКС») – 88%, compared with plantations established using bare-root seedlings (variant «ВКС») – 81%. The differences in average height, height increment, and root collar diameter amounted to 20.6 cm, 10.8 cm, and 4.2 mm, respectively, and were statistically significant for all indicators. Higher preservation rates were also observed in five-year-old plantations established using containerized seedlings (variant «ЗКС») – 89%, compared with plantations established using bare-root seedlings (variant «ВКС») – 81% and acorn sowing (variant «Acorn») – 80%. The differences in average height between plantations in variants «ЗКС» and «ВКС» amounted to 24.8 cm, in height increment – 8.1 cm, and in root collar diameter – 6.7 mm; whereas between «ЗКС» and «Acorn» the differences amounted to 59 cm, 10.9 cm, and 9.9 mm, respectively.

Statistically significant differences in height, height increment, and root collar diameter were found between plantations established using containerized seedlings and those established using bare-root seedlings or acorn sowing. A significant height difference was also observed between plantations established using bare-root seedlings and acorn sowing, whereas differences in height increment and root collar diameter were not significant.

Conclusions

In the Right-Bank Forest-Steppe of Ukraine (Vinnytsia, Khmelnytskyi, and Cherkasy regions), under fresh hornbeam forest and moist hornbeam–oak forest conditions, two-, four-, and five-year-old oak plantations established using containerized seedlings grown both in agrofiber and expanded polystyrene containers demonstrated higher survival, preservation, and growth performance compared with plantations established using bare-root seedlings or acorn sowing. The optimal planting spacing for establishing forest plantations with containerized seedlings is 4.0 x 1.0 m on clear-cut areas without natural regeneration or with insufficient regeneration of dominant and valuable associated species, and 6.0 x 1.0 m on clear-cut areas with satisfactory regeneration of dominant and valuable associated species.

1 Fig., 4 Tables, 26 Refs.

Experience in artificial forest regeneration in the Vyhodsky Forestry Management Unit of the “Carpathian Forest Office” Branch

M. M. Sishchuk, V. M. Hudyma — Fri, 29 May 2026 00:00:00 +0300

Introduction

Global warming and climate change pose a serious threat to the stable functioning of the biosphere. Among vegetation types, forest ecosystems are among the most vulnerable to climate change, as they are highly sensitive to shifts in optimal environmental conditions. Increasing summer temperatures threaten the decline of certain tree species and the spread of new, including invasive, species, which may alter species composition and reduce forested areas. Rising winter temperatures may also contribute to the expansion of pest species and pathogens, such as bark beetles, which are already causing extensive dieback in coniferous forests. Changes in precipitation patterns, intensity, and frequency further negatively affect forest ecosystems, leading to deterioration in forest health, widespread stand decline, and increased wildfire risk.

Materials and Methods

The study of reforestation processes in the forests of the Vyhodsky Forestry Management Unit of the “Carpathian Forest Office” Branch was based on the results of the authors’ own research, departmental records for 2019–2021 covering 270 sites with a total area of 271.4 ha, as well as domestic and international scientific and practical experience in forest regeneration.

Results

The forest regeneration fund consists mainly of recent clear-cuts within beech–fir–spruce, beech–spruce–fir, pure spruce, spruce–fir–beech, and fir–spruce forest types. Their regeneration is planned through either natural or artificial methods. In most cases, the determining criterion is the quantitative and qualitative composition of natural regeneration, including the presence of self-seeded trees and advance growth. Artificial regeneration is carried out on a forest typological basis where natural regeneration is insufficient or where its species composition does not correspond to the target forest type. Forest plantations are established as mixed stands composed mainly of fir, beech, sycamore maple, and larch. Their planting density depends on the amount of existing natural regeneration.

Conclusions

The forest regeneration fund of the Vyhodskyi Forestry Management Unit of the “Carpathian Forest Office” Branch consists mainly of recently harvested areas following final felling (clear-cutting and the final stage of selective felling) as well as clear sanitary felling. During the three-year study period, 30% of the area was regenerated artificially, while 70% was regenerated naturally. In most of the clear-cut areas subjected to artificial regeneration, natural regeneration of mixed species composition was already present; however, its quantity was insufficient to ensure successful stand formation. The tree species introduced into newly established forest plantations included fir, beech, sycamore maple, larch, and spruce. In some cases, spruce accounted for up to seven units in the stand composition, which may be considered excessive under current environmental conditions. Artificial forest regeneration is carried out on a forest typological basis; however, under present conditions, the impacts of climate change must also be taken into account. The analysis of the quantitative and qualitative composition of natural regeneration in areas designated for artificial afforestation demonstrates considerable potential for changing regeneration approaches and increasing the proportion of natural regeneration through the application of close-to-nature forestry principles.

1 Fig., 1 Table, 13 Refs.

Results of the non-native coniferous species testing in the arboretum of the State Biotechnological University

V. G. Grygoryeva , S. A. Los, L. I. Tereshchenko, E. I. Bachevska — Fri, 29 May 2026 00:00:00 +0300

Introduction

Collections of non-native woody plants in arboreta represent important research objects for studying their growth, development, and adaptation to new environmental conditions. Generalization of such research results makes it possible to identify species promising for further testing and to draw preliminary conclusions regarding their suitability for establishing forest plantations of various purposes under specific site conditions. Previous studies of introduced coniferous species in the Arboretum of the State Biotechnological University were conducted by I. Sytnyk, N. Vysotska, Yu. Potashev, and S. Poznyakova. According to the most recent inventory, the gymnosperm collection includes 33 species. Currently, most trees in the arboretum are about 50 years old, allowing for reliable assessment of their growth and development and enabling scientifically grounded conclusions regarding their current condition and future prospects. The aim of the study was to identify the most well-adapted coniferous species in the Arboretum of the State Biotechnological University through a comprehensive evaluation.

Materials and Methods

The Arboretum of the State Biotechnological University was established in 1972. According to soil and climatic conditions, it is located in the southern part of the Left-Bank Forest-Steppe of Ukraine, with forest site conditions classified as fresh fertile sites. The study focused mainly on forest-forming species that are used for timber production in their native ranges and are potentially promising for forestry in Ukraine. The survey was conducted during 2022–2023. Conclusions regarding the prospects of the studied species were based on the results of a comprehensive assessment.

Results

Douglas fir and Engelmann spruce showed the highest average annual diameter increments. These species, together with Siberian larch and Oriental spruce, also demonstrated the greatest average annual height increments. Based on the obtained mensurational and selection indicators, a comprehensive assessment was carried out for species represented by more than 10 trees. Promising species were identified according to the total score obtained. Of the nine studied non-native coniferous species, Larix ? eurolepis, Larix sibirica Ledeb., Pseudotsuga menziesii (Mirb.) Franco, Abies alba Mill., Picea orientalis (L.) Link, and Picea pungens Engelm. were found to be suitable for seed collection and the establishment of forest plantations in the Kharkiv region under fresh fertile site conditions. Among the species identified as promising, some are already well known and have long demonstrated their high adaptive potential. This group includes Douglas fir, Siberian and hybrid larches, blue spruce, and Norway spruce. Our study confirmed the high potential of all these species except Norway spruce. The remaining species are less widespread and insufficiently studied. In particular, Oriental spruce and rough spruce were identified as promising in the present study, whereas according to the research of N. Vysotska (2010), they were not included among the promising species.

Conclusions

The surveyed 15 species of non-native conifers in the Arboretum of the State Biotechnological University were characterized by good or satisfactory condition, and six species were found suitable for establishing forest plantations in the region under D2 site conditions. All studied species have reached the reproductive stage. Natural regeneration was absent in almost all species, except for silver fir, under whose canopy small numbers of 1–2-year-old seedlings were observed. No signs of invasive activity were detected.

3 Figs., 3 Tables, 27 Refs.

Morphological variability of English oak acorns in oak stands in the forest-steppe zone of the Kharkiv region

M. M. Didenko, S. P. Raspopina, V. V. Goroshko, A. Yu. Gordiyashchenko — Fri, 29 May 2026 00:00:00 +0300

Introduction

English oak (Quercus robur L.) is characterized by considerable intraspecific variability in morphological traits, growth intensity, and wood quality, which results from the interaction between genetic factors and environmental conditions. The aim of the study was to assess the variability of morphological and biometric parameters and acorn mass of English oak, and to identify the relationship between these indicators and the origin and density of the stand.

Materials and Methods

The morphological variability of acorns was studied in a fresh maple-lime oak forest within the Mokhnachanske Forestry of the State Enterprise “Skrypaivske Educational and Research Forestry Enterprise” (Southern part of Left-Bank Forest-Steppe of Ukraine). The research was carried out using a transect-based sampling method, where 1 x 1 m sample plots were established along each transect. Transects were arranged parallel to each other at a distance of 10 m, while the distance between sample plots was 5 m. On average, 55 sample plots were established within each study area.

Results

Seven morphological forms of acorns were identified: barrel-shaped, oval-cylindrical, elongated-cylindrical, obovate, ovoid, broadly oval, and cylindrical. A high level of individual variability of these morphotypes was recorded, which further substantiates the effectiveness of using morphological indicators in selection and breeding studies. In English oak stands, the oval-cylindrical and cylindrical forms predominated, accounting for 49% and 16%, respectively, of the total number of examined morphotypes. Other forms were distributed as follows: broadly oval – 8%, obovate – 4%, elongated-cylindrical – 4%, barrel-shaped – 12%, and ovoid – 6%. In seed-origin stands, the proportion of elongated acorn forms was 17% higher than in coppice stands, whereas the latter showed an increased proportion of rounded forms. This confirms that the structural composition of acorn morphotypes varies depending on the regeneration method of stands, which should be considered when organizing forest seed sources and selecting plus trees.The highest proportion of elongated acorn forms was recorded in stands with a relative density of 0.6, where they accounted for 83.8%. In stands with densities of 0.7 and 0.8, this indicator was 72.2% and 72.4%, respectively. A reduction in resource scarcity in medium-density stands affects the selectivity of fruiting in individual trees, which determines the morphological heterogeneity of the crop and leads to a redistribution of the proportions of certain acorn morphotypes.

The highest mean mass was recorded for ovoid and barrel-shaped acorns, at 3.6 g and 3.5 g, respectively, whereas the lowest mass was observed for cylindrical and broadly oval forms (1.7 g and 1.9 g, respectively). A strong positive correlation was found between acorn size and mass parameters: length and mass (r = 0.83), diameter and mass (r = 0.91), and diameter and length (r = 0.84).

Conclusions. The obtained data on individual variability in acorn shape confirm the genetic determination of morphological traits and indicate the feasibility of using them as diagnostic criteria for identifying clones of plus trees of English oak. The detected differences in acorn mass correspond to variations in acorn length and diameter and may have practical significance for evaluating seed quality. The high correlation coefficients between linear and mass parameters indicate their close interdependence, allowing acorn diameter to be considered the most informative indicator for rapid selection of viable seed material.

5 Figs., 1 Table, 17 Refs.