Issues

Although the relationship between site productivity and stand structure has been extensively studied, there is limited research specifically addressing how site productivity influences structural diversity in mixed stands. The aim of this work was to analyse the effect of site productivity on the structural diversity of the Pinus sylvestris–Fagus sylvatica stands in the central part of the Rhodope Mountains in north-eastern Greece. Data from 35 plots of 500 m2, established in mixed P. sylvestris–F. sylvatica stands, representing two site productivity types, were used. For each plot, the tree diameters were classified into 4-cm diameter classes. Using diameter at breast height (DBH) data, the following diversity indices were calculated for each sampling plot: Richness, Gini-Simpson, Gini-Simpson equitability, and Berger-Parker index. In most cases, the studied distributions exhibited high diversity. Overall, in P. sylvestris–F. sylvatica stands of the study area, F. sylvatica diameter distributions tended to exhibit higher structural diversity in good-productivity sites than in medium-productivity sites, although this trend was not consistent across all developmental stages. Further research in mixed P. sylvestris–F. sylvatica forests, as well as in different other species mixtures, is needed to draw more robust conclusions.

Received: 06 October 2025 / Accepted: 12 January 2026 / Available online: 26 January 2026

Open Access: This work is distributed under the Creative Commons Attribution 4.0 License.

Peatlands in South Sumatra are increasingly degraded due to anthropogenic activities and climate change. Effective restoration therefore requires broad consensus on conserving biodiversity and carbon stocks through the planting of native peat species, such as rumbia palm (Metroxylon sagu Rottb.). This study aimed to evaluate the suitability of peatlands for rumbia palm cultivation and to identify the main limiting factors affecting its development. The research combined field observations, laboratory analyses, and environmental assessments to evaluate the physical and chemical characteristics of local peatlands. Results indicated that rumbia palm is closely linked to the cultural history of the Sriwijaya Kingdom in Palembang, yet has become marginalised due to widespread conversion of peatlands into industrial plantations. Soil acidity, nutrient levels, and peat depth were found to be the primary limiting factors influencing cultivation potential. Overall, the study shows that peatlands in South Sumatra have high potential for rumbia palm cultivation under proper management practices, such as soil improvement, fertilisation, and groundwater regulation. The novelty of this research lies in positioning rumbia palm cultivation as an indigenous, biodiversity-supporting, nature-based solution for restoring ecological functions of tropical peatlands.

Received: 06 October 2025 / Accepted: 16 January 2026 / Available online: 26 January 2026

Open Access: This work is distributed under the Creative Commons Attribution 4.0 License.

Our study aimed to develop and provide forest practitioners with a reliable tool for estimating the breast height diameters of the plantation-grown Scots pine trees for restoration of their dimensions when the stems have been removed or destroyed. We applied a number of modelling approaches and developed a simple and a multiple fixed-effects models, a mixed-effects model, and a mixed-effects model with calibrated random parameter components. We compared their goodness of fit and contrasted the accuracy of their predictions with that of the currently applied table. A fixed-effects linear function of the basal tree diameter and the respective linear mixed-effects relationship showed an overall best model performance. Specifying the mixed-effects model to the particular stand by calibrating the random-parameter components with a breast height-basal diameter pair of measurements of one average-sized tree, was recommended. Our models perform better than the currently applied table, which systematically overestimates the breast height diameter, and consequently the volume of the largest portion of the tree trunk. Both model versions are executable in a few simple steps in the user-friendly environment of the MS Excel-based simulator DbhRestore, which is distributed free of charge on the Internet.

Received: 08 December 2025 / Accepted: 27 January 2026 / Available online: 03 February 2026

Open Access: This work is distributed under the Creative Commons Attribution 4.0 License.

Plana Mountain, a water-poor and dry massif in Western Bulgaria, hosts a diverse mosaic of forest communities shaped by environmental gradients and long-term human activity. The objective of this study is to make a syntaxonomic analysis and to create a comprehensible classification. Vegetation surveys, comprising 15 forest communities, were analysed using Braun-Blanquet` s approach. Nine associations and 6 plant communities have been identified, assigned to 5 classes, 8 orders and 9 аlliances. Oak forests dominate on xeric, steep slopes with nutrient-poor soils and are represented by specific associations. Beech forests include mesophytic communities that grow on moderately rich soils with varying moisture. Scots pine forests occupy southern slopes on shallow, eroded soils. Ravine forests develop on steep canyon slopes with xerophilous composition. Riparian stands dominate on wet soils along streams and riverbanks. Historical data indicates that coniferous forests were more widespread prior to anthropogenic disturbance. Current successional trends include upward replacement of Pinus sylvestris L. forests and Corylus avellana L. shrublands by mesophytic beech forests on shady slopes and gradual progression of xerophilous oak forests on sunny slopes.

Received: 11 December 2025 / Accepted: 10 February 2026 / Available online: 18 February 2026

Open Access: This work is distributed under the Creative Commons Attribution 4.0 License.

In Bulgaria, the fungus Biscogniauxia cinereolilacina (J.H. Mill.) Pouzar has been firstly reported based on herbarium material. In recent years, the pathogen has been recorded in urban green areas in Northeastern Bulgaria. The present study provides data on three newly identified localities of B. cinereolilacina on Tilia tomentosa Moench in various regions of the country. The aim of this study was to identify the causal agent of the observed dieback of T. tomentosa through morphological examination of stromata, perithecia, and ascospores, and to characterise the obtained isolates in culture. Our results indicate that, since its initial record in 1983, the species has significantly expanded its distribution, likely as a result of extreme temperature and precipitation fluctuations observed in recent years. Although B. cinereolilacina does not currently pose a serious threat to linden trees, continuous monitoring of their health is necessary to allow timely implementation of appropriate conservation measures.

Received: 12 January 2026 / Accepted: 27 February 2026 / Available online: 02 March 2026

Open Access: This work is distributed under the Creative Commons Attribution 4.0 License.

Cryptomeria japonica (Thunb. ex L.f.) D.Don is a conifer species native to Japan that has been tested in several European trials, including in Germany, due to its high growth potential. However, its adaptability to emerging climatic conditions and its response to extreme events such as drought and late frost remain poorly understood. Therefore, we studied trees of C. japonica originating from the northern part of the natural distribution in Japan and planted at a trial site in northern Germany. Using dendroecological methods, we analysed growth responses to extreme drought and late frost events, assessed variation among trees, and examined growth patterns in response to short- and long-term climate variability. Tree growth was primarily limited by moisture availability in February rather than summer drought, yet individuals showed strong sensitivity to extreme years. Within the analysis period, we identified three extreme drought years and one late frost year. Resistance to late frost was lower than to drought, and relative resilience components differed between spring and summer drought events. Although C. japonica achieved high growth rates with diameters up to 58 cm at age 54, its growth in northern Germany was clearly constrained by climatic conditions. Given projected increases in drought and frost extremes, this species may face increased vulnerability under future climate change.

Received: 06 August 2025 / Accepted: 06 March 2026 / Available online: 12 March 2026

Open Access: This work is distributed under the Creative Commons Attribution 4.0 License.

Mangrove biomass production is influenced by both structural attributes and leaf level physiological processes. However, empirical field studies linking these components at the stand scale remain limited. This study explored associations among leaf chlorophyll content, foliar damage, biomass accumulation of Sonneratia caseolaris (L.) Engl., and sediment nutrient conditions in the Segara Anakan Mangrove Lagoon, Indonesia. Three sampling stations were established, and field surveys were conducted from May to June 2023. Aboveground and belowground biomass were estimated using established species-specific allometric equations. Chlorophyll concentrations were determined spectrophotometrically, and foliar damage was quantified by the Bioleaf application on a smartphone. Positive associations were observed between biomass estimates and chlorophyll concentrations in both intact and partially damaged leaves, reflecting potential photosynthetic capacity. However, correlation analyses were based on plot-level data (n = 15) with limited replication. Therefore, the results should be interpreted as indicative ecological patterns rather than statistical evidence of causal relationships. Stations with relatively higher biomass also exhibited higher sediment nitrogen concentrations, suggesting a possible role of nutrient availability in supporting structural growth. Despite a high proportion of visibly damaged leaves across stations, measurable chlorophyll levels were maintained, indicating that partial tissue damage does not necessarily correspond to complete physiological impairment. Overall, the findings suggest that leaf-level physiological indicators may contribute to understanding spatial variability in mangrove biomass when interpreted within ecological and methodological constraints. Integrating structural and physiological measurements may support improved assessment of mangrove condition in dynamic estuarine environments.

Received: 24 December 2025 / Accepted: 06 March 2026 / Available online: 12 March 2026

Open Access: This work is distributed under the Creative Commons Attribution 4.0 License.

Challenges of our time require in-depth studies of the carbon cycle and, consequently, information about its stocks in soils. Soils play a leading role in the sequestration and emission of carbon. Boreal forests account for nearly 30 % of Earth’s forests. Therefore, the purpose of this study was to establish the features of carbon accumulation in the soils of the southern taiga area within the territory of the supersite ‘Ural-Carbon’ in the Sverdlovsk Region, in the Urals. Geobotanical studies of a profile across the watershed and terrace showed that, despite the similarity in the floral composition and structure of forest communities, with a predominance of dark coniferous trees, there are more spruce trees in the upper site of the studied profile. Additionally, there is an increased proportion of tallgrass species. The soils exposed in 24 pits were classified as Luvisols with a high proportion of clay particles in the particle size distribution. The stocks of organic carbon in the supersite, determined based on the bulk density values obtained for each individual profile, were 9.06 ±3.86 t·ha-1 for the litter layer, 78.11 ±22.41 t·ha-1 for the upper 0–30 cm layer, 96.22 ±30.9 t·ha-1 for 0–50 cm layer, and 111.06 ±37.5 t·ha-1 for 0–100 cm layer. At the same time, soils in the lower site of the profile had significantly higher carbon content compared to those in the upper site, and the differences were statistically significant for the mineral horizons. Obtained data on carbon stocks indicate the heterogeneity of the soil cover and are generally consistent with the available estimates for soils in dark coniferous forests in other regions. These data can be used to create models of carbon stocks in old-growth southern taiga dark conifer forests that form in similar conditions, as well as for climate projects.

Received: 29 December 2025 / Accepted: 18 March 2026 / Available online: 16 April 2026

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This study investigates the development of transverse oak canker, examines key factors influencing its spread, and evaluates potential ecosystem threats. The results provide a basis for developing recommendations for monitoring and preserving oak stands within Kyiv region of Ukraine. During the study, typical symptoms of tree damage were described, confirming three types of lesion morphogenesis: open, transitional, and closed. A gradation analysis was conducted based on trunk diameter and the number of cankers detected. It was established that the highest proportion of trees with minor damage occurred in the 12–32 cm diameter class, where this indicator exceeded 50.0 %. In trees with a diameter of 48–56 cm, a consistently high level of minor damage was maintained alongside a low share of severe damage (up to 13.0 %), suggesting potential genetic resistance or adaptive defence mechanisms in older age groups. Conversely, the smallest trees (4–8 cm) exhibited the highest percentage of medium and severe damage, indicating a high vulnerability in young plants. The results demonstrate that the severity of oak canker damage is closely correlated with trunk diameter and tree age – factors that must be considered when developing monitoring, prevention, and control strategies.

Received: 08 February 2026 / Accepted: 31 March 2026 / Available online: 16 April 2026

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Rapid land-cover change in Tallo Watershed, driven by urbanisation and population growth, has intensified environmental degradation. This has increased drought risk, particularly under ongoing climate change and growing pressure on water resources. This study aims to assess spatial drought conditions and formulate adaptive land-use directions in Tallo Watershed. Landsat 8 OLI/ TIRS imagery from 2014 and 2023 was analysed using a band combination of SWIR-1 (band 6), NIR (band 5), and Red (band 4), and drought conditions were evaluated using Normalised Difference Latent Heat Index (NDLI) as primary spatial indicator. Standardised Precipitation Evapotranspiration Index (SPEI) was applied as a climatic classification framework to support interpretation of NDLI-derived drought severity. The results indicate a clear increase in drought-affected areas, reaching 1,253 ha between 2014 and 2023, with distinct spatial patterns across upstream, midstream, and downstream zones. Land-cover change was dominated by expansion of settlements (+1,964 ha) and reduction of rice fields (−1,699 ha), reflecting rapid urban development. Areas experiencing intensive land-cover conversion consistently corresponded with higher drought severity, highlighting strong influence of anthropogenic land transformation on drought dynamics. Compared with recent studies that primarily focus on meteorological drought indicators, this study demonstrates added value of integrating remote sensing-based NDLI for capturing spatial variations in drought linked to land-cover change. Based on drought levels and regional biophysical characteristics, adaptive land-use directives were developed to enhance resilience to climate change. Findings provide critical spatial information for watershed management and adaptive land-use planning in rapidly urbanising regions.

Received: 25 August 2025 / Accepted: 02 April 2026 / Available online: 16 April 2026

Open Access: This work is distributed under the Creative Commons Attribution 4.0 License.