László Zoltán

Understanding forest development following the cessation of management remains a key challenge in forest ecology. Gap dynamics, a driver of structural and compositional change, might serve as an important indicator of progression toward old-growth conditions. This study investigates and compares the long-term gap dynamics of two Central European forest reserves (Kékes—old-growth and Őserdő—long untouched) dominated by European beech (Fagus sylvatica L.) over a 42–45-year period, using aerial imagery. Our aim was to assess how historical management legacies influence gap size, formation, persistence, and closure, and to evaluate these processes relative to the forests’ naturalness levels. Gap fractions ranged between 4.9%–9.9% in Kékes and 2.3%–10.7% in Őserdő. These values are mostly consistent with previous reports for primary European beech forests. In Kékes, smaller gaps (<200 m2) predominated, while in Őserdő, following a sequence of recent disturbances, gaps of 200–499 m2 became dominant. Statistical analyses revealed a significantly steeper increase in total gap area in Őserdő, reflecting greater sensitivity to exogenous disturbances, likely due to its more homogeneous stand structure and residual management effects. Site conditions, browsing pressure, and topography might have further contributed to the observed divergence. Our results indicate that the fine-scale endogenous dynamics, typical of old-growth forests (characterized by small, recurring gaps of endogenous processes), develop only several decades after the last human intervention. The study highlights that gap dynamics might serve as an indicator of forest naturalness and can guide restoration planning. Promoting structural heterogeneity and mimicking natural gap processes may accelerate recovery toward old-growth characteristics in formerly managed forests.

The study of bark morphology reveals significant although not absolute relationships between bark types, tree species, and their environmental conditions. This paper aims to review the inter- and intraspecific ecological and evolutionary drivers that seem to have shaped the macromorphological features of bark, especially in temperate forest ecosystems and especially in Europe. Extensive literature research shows that various factors influence bark thickness, structure, color, and morphology, including solar radiation, climate, adaptation to various disturbance regimes, site conditions and biotic factors, reflecting together long-term selective pressures during evolution. Bark’s simultaneous multiple functions and its ontogenetic changes often complicate the identification of the individual selective agents of the adaptive mechanisms and morphologies. An evolutionary perspective can clarify why certain bark types are common in specific environments, how some traits persist as secondary functions, or why diverse bark forms coexist not only in the same site, but also in various ontogenetic stages and positions of the same individuals. Intraspecific variation shaped by both genetic and environmental influences often results in phenotypic plasticity, enhancing species’ environmental and age/size related adaptability. We suggest that further research examine current and historical climate, site, and biotic conditions to understand their influence on bark structure and morphology.

Accurate identification of deciduous woody species in winter is challenging, and the misidentification can lead to ecological and management damage. This study aims to substantiate a diagnostic system for woody species based on macromorphological bark characters. First, we reviewed the literature on bark-based species identification to assess existing approaches and their limitations. Building on this, we identified informative macromorphological features of bark through both literature analysis and our experiences. These characters cover all developmental phases, including twigs, young bark, and mature bark, and are supported by new diagnostic terminology. Using this framework, we compiled a character set for 115 Central European woody taxa, providing practical, primarily qualitative traits that can be applied directly in the field. Finally, we developed and tested “Single-access Keys” as an alternative to conventional dichotomous keys, demonstrating their effectiveness in enabling flexible and rapid species recognition, even under atypical conditions or when only partial observations are possible. Our results highlight the value of bark macromorphology as a diagnostic tool and emphasize its potential for advancing thematic identification keys, as well as digital applications in forestry, taxonomy, and ecological monitoring.

The use of proxies in habitat assessments has become widespread in recent decades. We used forest state descriptive data from a large-scale project (SCP) as proxies to investigate the occurrence of habitats suitable for some protected saproxylic beetles. We searched for pre-defined tree-related microhabitats (TreMs) suitable for saproxylic beetles in 1 ha quadrats in the Börzsöny Mts., Hungary. We compared the frequency of each microhabitat type with the aggregated values of the forest state proxies. Our results suggest that the average number of snags with DBH = 21–50 cm and the frequency of lying deadwood with Ø > 35 cm can adequately represent the occurrence of all beetle microhabitats studied. In most cases, the frequency of plots with species richness of live canopy trees with DBH > 35 cm and the amount of lying dead wood were also good indicators. The TreM indicators of the SCP alone can detect the presence of specialist beetles requiring cavities. The stands with a better forest state had more protected saproxylic beetles. The practical implementation of our work is based on the optimization of the resources required for monitoring. In surveys prepared to cover large areas, it is easier to monitor the habitat of saproxylic beetles with the help of individual proxies.

Egységes európai módszert természetesség-becslés céljából még nem dolgoztak ki. Minden országnak és kutatócsoportnak megvan a saját (erdő)természetességmérő, illetve értékelő módszere. Csehország jogszabályait és módszerét példaértékűnek tartjuk, ezért ezt részletesen bemutatjuk. Magyarországon az erdőtermészetesség-értékelésnek több évtizedes története van, amelyet áttekintünk munkánk során. A módszereket röviden bemutatjuk, illetve a változókészletüket részletesen összevetjük. Az irodalomkutatás során azt találtuk, hogy először a botanikusok cönológiai mutatók segítségével adtak információt a vizsgált területek degradáltságáról. Az erdészek a gazdálkodási szempontokat is bevonták a saját módszereik kidolgozásába. A Magyarországi erdők természetességének vizsgálata (TERMERD) projektben csúcsosodtak ki a módszertani törekvések, hiszen ez rendelkezett a legátfogóbb változókészlettel és legnagyobb (országos szintű) tényleges terepi adatgyűjtésen alapuló értékeléssel. Szinte minden ezt követő új módszer a TERMERD kisebb-nagyobb mértékű átdolgozásából, fejlesztéséből, tömörítéséből állt. A TERMERD projekt hatására a 2009. évi Erdőtörvény óta minden erdőrészletről kötelező megállapítani annak Természetességi Mutatóját (TERMMUT). A TERMMUT módszere nincs gondosan publikálva, számítása jelentős szubjektivitással terhelt. A csehországi jogszabályokkal összevetve azt tapasztaltuk, hogy az alkalmazott nómenklatúra nincs összeegyeztetve a nemzetközi szabványokkal. A TERMMUT kapcsán felmerülő problémák feloldása az lehetne, ha más, kellő mértékben validált módszerrel értékelnénk országos szinten az erdeink természetességét, és ennek eredményeit kommunikálnánk külföldre.

Ungulate populations have surged to unsustainable levels in multiple areas in recent decades due to human intervention, making forestry and conservation practices arduous. The population of ungulates is also currently displaying a rising trend in Hungary, prompting decision-makers to commence substantial reduction efforts. Our study examined the ungulate impact in three forested regions of Hungary, employing field survey sampling plots on almost 50,000 hectares. Our findings revealed that regeneration browsing and soil disturbance were evenly high in these areas, while the cover of the regeneration layer was extremely low. Ungulate pressure was suspected as the cause of the lack of regeneration. Based on habitat and vegetation conditions, we divided our sample as favourable and unfavourable for regeneration. The cover of the regeneration categories was not significantly different between the two sets. The evidence of the direct indicators, including browsing and soil disturbance, coupled with the lack of regeneration, leads us to infer indirect signs of ungulate pressure. The absence of older and taller vegetation in the area also suggests long-standing ungulate pressure. Our investigation suggests that the high ungulate population can cause low abundance, even the lack of regeneration, not only locally but also at a regional scale.

In December 2014 a catastrophic ice disturbance affected the forests of the Börzsöny Mts., Hungary. Planning salvage logging is an urgent task after such events. The use of Earth Observation (EO) data in near real-time could facilitate such planning at a critical time. However, conventional remote sensing studies apply data of passive multispectral sensors, hence the earliest post-event canopy cover damages could be examined only after foliation. Synthetic Aperture Radar (SAR) is an active remote sensing technique, which could be used for the detection of forest disturbances even outside the vegetation period. Due to its 12 days revisit time Sentinel-1 may play an important role in the fast detection of the damaged forests in the case of such events. In this work, we analyze the potential of Sentinel-1 SAR data in mapping natural disturbances in forests, through the 2014 ice break event.We made 4 classifications with the different combination of the following variables: radar backscatter coefficients, polarimetric descriptors, interferometric coherence and optical data. We put great emphasis on the reference datasets: 3 types of field-based reference datasets were used, which include re-surveys (explicit data on changes). Based on the field data and orthophoto comparison the damaged patches were delineated manually as the most reliable reference.We have found that none of the classifications were suitable for identifying the crown loss damages properly, but all of them were capable to detect the uproot damages. The classification using all of the variables proved to be the most reliable. The interferometric coherence with the polarimetric radar data provided the best information compared to the classification including optical data.

In 2014 a catastrophic ice storm occurred in the forests of Börzsöny Mts., Hungary. In this study we analyzed the potential of Synthetic Aperture Radar (SAR) data, complemented, and compared with optical imagery, in mapping this event. Great emphasis was put on reference data: three types of field-based reference datasets were used and the damaged patches were delineated manually based on the visual interpretation of pre- and post-event orthophotos. Four classifications with different set-ups were carried out by applying the eXtreme Gradient Boosting method. Combinations of radar backscatter coefficients, polarimetric descriptors, interferometric coherence, and optical data variables were tested. All classifications were suitable for identifying uprooted trees properly (1–11% underestimation), but none of them could detect crown loss accurately (55–58% overestimation), based on the validation of the most damaged area. Proper differentiation of healthy forests with various levels of canopy closure in the reference data seems crucial for accurate canopy loss estimation. In the case of methods using only Sentinel-1 imagery, interferometric coherence together with polarimetric descriptors provided the best results (OA: 65.7%). This setup can be useful for immediate uproot damage detection for planning salvage logging if a natural disturbance happens outside the vegetation period.