Abstract: The aim of the study was to identify changes in species composition and structure of European beech Fagus sylvatica communities occurring at the limit of their natural range, in response to current climate change. The investigations were carried out in the Dębowo Nature Reserve (NE Poland; N 53.929468, E 20.997331), using a set of permanent research plots. On two occasions (in 1974 and 2019), the diameter at breast height (DBH) of all trees with DBH≥5 was measured by assigning a species, and seedlings and saplings were counted. Phytosociological reléves were taken in 1962 and 2016. Between 1974 and 2019, a significant decrease of tree density, from 845 ±165 trees/ha to 350 ±52 trees/ha, was observed. The basal area increased consistently with the age of the stand. A significant increase in the share of European beech was observed (from 85% to 92%). The mean density of seedlings and small saplings increased significantly, from 117 to 7,907 trees/ha, and beech became the dominant species in the regeneration layer. Cover of shrubs and saplings increased almost fivefold, but is still below 5%. Cover of the herbaceous layer decreased significantly from 60% to 37%. The spontaneous regeneration and vitality of young trees suggest that beech at the north−eastern limit of its range can form stable stands in the future.
Key words: beech stands, distribution edge, forest regeneration, forest reserve, natural processes, permanent plots

Abstract: Trees adapt to fluctuating environmental conditions by regulating the allocation and mobilisation of non−structural carbohydrates (NSCs) and proteins, particularly during winter dormancy and the transition to spring growth. NSCs serve not only as energy reserves but also contribute to osmoregulation, cell membrane stability, and stress resistance, whereas proteins support metabolic activity and structural reorganisation. This study investigated winter−to−spring changes in the contents and spatial distribution of soluble (SP) and insoluble proteins (IP), soluble carbohydrates (SC), and starch (S) in one−year−old seedlings of common beech Fagus sylvatica and pedunculate oak Quercus robur sampled in January, February, and March 2022. We analysed compounds in shoots, main roots, and fine roots, with shoots and main roots further divided into upper, middle, and lower sections. The results revealed distinct species−specific patterns in the seasonal allocation and distribution of storage compounds. In both species, starch accumulated predominantly in the main root. Beech showed more pronounced temporal and spatial changes in the distribution of proteins and carbohydrates among organs and within individual shoot and root sections, indicating more dynamic resource redistribution. In contrast, oak exhibited a more conservative pattern, with storage compounds remaining more strongly associated with particular organs and showing less pronounced changes in their spatial distribution. Significant differences among the upper, middle, and lower sections of shoots and main roots further demonstrated that storage compounds were not distributed uniformly within individual organs. These findings indicate that beech and oak differ in both the localisation and seasonal dynamics of storage compounds and suggest species−specific strategies of resource management during winter dormancy and preparation for spring growth.
Key words: carbon storage, nitrogen reserves, non−structural carbohydrates, soluble sugars, winter dormancy

Abstract: The analysis of strategic groups in tender procedures enables the classification of contractors according to similarities in their market strategies, competitive behaviour and operational scope. The aim of this study was to identify strategic groups participating in tender procedures for forest management services within the Regional Directorate of State Forests (RDLP) in Zielona Góra, with particular emphasis on the geographical scope of the services provided, and to determine patterns of intra−sectoral mobility among companies between 2011 and 2025. The study covered all entities submitting bids in tenders conducted across 20 forest districts administered by the RDLP in Zielona Góra. A comprehensive database of contractors was developed based on 407 tender procedures, using “Information on the Opening of Tenders” documents, which listed all companies submitting bids. Each entity was analysed in terms of the spatial relationship between the location of its registered office and the forest districts in which it submitted bids. On this basis, strategic groups were identified, and annual strategic group maps were constructed to trace changes in group composition and patterns of mobility over time. For nearly two−thirds of the analysed period, the most numerous strategic group consisted of companies based within the RDLP in Zielona Góra area that submitted bids in only one forest district. However, from 2020 onwards, the dominant group shifted towards locally based companies operating across a broader geographical area, submitting bids in two or more forest districts. Among companies located outside the RDLP in Zielona Góra area, the prevailing group throughout the study period comprised entities submitting bids in only one forest district, although their overall presence in the market increased over time. These findings indicate a gradual transformation of the regional forestry services market from a predominantly local, stable and predictable system towards a more open, competitive and mobile structure. The increasing participation of non−local firms and the expansion of the geographical scope of operations among local companies reflect greater market dynamism and changes in competitive strategies. Understanding the composition and evolution of strategic groups provides valuable insights for forest administration units. This knowledge can support the design of tender packages aimed either at enhance competition or strengthening the position of local contractors, depending on the policy objectives.
Key words: enterprise, forest market, public procurement, strategic groups, tenders

Abstract: This paper examines the impact of discrepancies between the national definition of forest in Poland and the harmonised definition mandated by the European Environmental Economic Accounts (EEA) Regulation on reported forest areas in European Forest Accounts (EFA). Harmonisation ensures comparability of environmental−economic statistics across EU Member States. Key differences include Poland’s minimum forest area threshold of 0.1 ha (vs. 0.5 ha under EEA) and the EEA’s canopy cover criterion, non−existent in national law. With the use of National Forest Inventory (NFI) data as of end 2022 and end 2023, the study identifies and quantifies NFI sample plots both in small forest patches (0.1−0.5 ha) and areas registered as forest but used for non−forest purposes. Data regarding National Forest Inventory sample plots were first verified with orthophotomaps and other geospatial sources for these both categories and then were extrapolated nationally by ownership categories. Results show that the needed adjustment is minor (<1% of total forest area in both years) but visible while considering ownership forms: it is larger in fragmented private forests and sectors where forestry is a secondary activity, and marginal in forests managed by the State Forests. Despite the small overall effect, adjustments could enhance data consistency and comparability across the EU, which justifies their application in forest accounts reported by Poland.
Key words: definition of forest, Eurostat, forest accounts, forest area, harmonisation, Poland

Abstract: Oak species are widely distributed throughout Azerbaijan and have significant symbolic, ecological, and economic value for the country. Therefore, assessing the adaptive potential of oaks and conducting biological and ecological studies are important for the conservation of oak biodiversity. Despite the widespread distribution of the genus Quercus across various regions of Azerbaijan and its important ecological role, the morphological polymorphism of acorns and the influence of environmental factors on acorn morphological variation in oak species have not been comprehensively investigated using statistical approaches. In this study, the diameter, length, diameterto−length ratio, volume, and weight of acorns from five oak species representing 14 populations under different ecological conditions were measured. The data were analysed using analysis of variance (ANOVA), correlation analysis, and cluster analysis based on Euclidean distances. The results revealed pronounced intra− and interspecific variation in acorn morphological traits, indicating substantial phenotypic polymorphism among the studied populations. Acorn weight and volume showed the greatest variability and were among the most informative traits for distinguishing the studied groups, whereas diameter exhibited relatively low variability and limited discriminatory power. The observed variation was further examined in relation to environmental factors. Altitude was associated with variation in acorn development, particularly in Q. petraea ssp. iberica, Q. macranthera ssp. macranthera, and Q. robur ssp. pedunculiflora. In contrast, precipitation appeared to be associated with variation in acorn size and weight in Q. castaneifolia and among populations growing at similar altitudes. The findings of this study may contribute to oak taxonomy and afforestation practices by providing information on species−specific responses to environmental factors.
Key words: acorn morphometric traits, adaptive capacity, environmental factors, morphological variation, Quercus

Abstract: Tree−related microhabitats (TreMs) are widely used as indicators of forest biodiversity and in assessments of the conservation status of forest habitats. Despite their growing importance in forest monitoring and conservation, relatively little attention has been paid to the workload associated with TreM surveys. The aim of this study was to quantify the workload associated with TreM surveys in Sub−Atlantic and medio−European oak or oak−hornbeam forests of the Carpinion betuli (habitat type 9160) and to determine whether survey duration was associated with field team, plot sequence, and stand characteristics. Factors associated with TreM abundance and type richness were additionally examined to account for the potential interdependence between survey effort and TreM detection. The study was conducted on 94 circular plots (400 m²) systematically distributed across the Polish range of habitat type 9160 within the National Forest Inventory grid. All trees with DBH≥70 mm were inspected using a catalogue of 49 TreM types. Survey duration ranged from 3 to 50 minutes per plot, with a median of 22 minutes. Multivariable analysis showed that survey duration differed among field teams, decreased with the cumulative plot sequence within a team, and increased with the number of trees and the number of dead trees. TreM abundance and type richness were associated with stand characteristics, while the within−day plot sequence was negatively associated with TreM abundance and, together with field team, improved the TreM type−richness model. Both TreM abundance and type richness increased with mean DBH and tree−layer cover, whereas Scots pine abundance was negatively associated with both metrics. TreM abundance additionally increased with the number of trees and dead trees, while type richness increased with tree−species richness. The results show that TreM survey workload varies considerably among plots and cannot be reliably estimated from plot number alone. Readily available stand characteristics, particularly the numbers of trees and dead trees, may help refine fieldwork estimates. At the same time, associations of TreM metrics with field team and within−day plot sequence indicate that recorded abundance and richness may partly reflect variation related to the survey procedure. Workload estimates should therefore be interpreted in relation to the habitat and survey protocol used.
Key words: conservation status, field sampling, forest biodiversity, Habitats Directive, National Forest Inventory, survey effort