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Canopy gaps in two virgin beech forest reserves in Slovakia

Authors:
Lars Drössler at State forest enterprise Thuringia (Thüringenforst)
Lars Drössler
  • State forest enterprise Thuringia (Thüringenforst)
Burghard von Lüpke at Gesellschaft für wissenschaftliche Datenverarbeitung mbH Göttingen
Burghard von Lüpke
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Abstract and Figures

The formation, size distribution and percentage of gaps in two virgin deciduous forests are presented in two case studies. Gaps are defined as openings in the canopy above 2/3 of stand height. These gaps comprise 16% of the forest area in Havešová Reserve and 14.6% of the forest area in Kyjov Reserve. The estimated turnover time is 220 years. More than half the gaps were caused by the death of one tree, and 80% of the gaps were due to the death of up to 3 trees. The largest gap in Havešová Reserve was 0.40 ha, resulting from the death of 56 trees over the last 40 years. The area of the largest gap in Kyjov Reserve was 0.44 ha. It was caused by the death of 80 trees over the last 40 years. Such large gaps are scarce. 85% of the gaps are smaller than 250 m². A correction of the bias towards the over-abundance of large gaps by line-transect sampling was made by estimating the percentage area of gaps of different size from the percentage length along the transects. In Havešová an attempt was made to date the death of trees that were still visible in the gaps. 1/5 of the trees initiated gaps by their death, while 4/5 of the trees extended gaps. While uprooted trees dominate in Havešová, breakage is most common in Kyjov.
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All content in this area was uploaded by Lars Drössler on Dec 11, 2015
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446 J. FOR. SCI., 51, 2005 (10): 446–457
JOURNAL OF FOREST SCIENCE, 51, 2005 (10): 446–457
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dulosae-FagetumCarici pilosae-
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
Institute of Silviculture, University of Göttingen, Göttingen, Germany
              
              
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                    
                         

  




J. FOR. SCI., 51, 2005 (10): 446–457 447
   Dentario glandulosae-Fagetum 

 
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
   
      
Acer pseudoplatanusA. plata-
noidesFraxinus excelsiorUlmus glabra
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
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 
448 J. FOR. SCI., 51, 2005 (10): 446–457
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    
    
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   
    
    
J. FOR. SCI., 51, 2005 (10): 446–457 449
    
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                   
             
      
450 J. FOR. SCI., 51, 2005 (10): 446–457
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             
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     
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           
J. FOR. SCI., 51, 2005 (10): 446–457 451
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452 J. FOR. SCI., 51, 2005 (10): 446–457
       
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     
     
     
     
     
     

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   
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R
J. FOR. SCI., 51, 2005 (10): 446–457 453
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          
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
Fagus sylvatica
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          
    
 
454 J. FOR. SCI., 51, 2005 (10): 446–457
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J. FOR. SCI., 51, 2005 (10): 446–457 455
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yxx∈ 
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456 J. FOR. SCI., 51, 2005 (10): 446–457
             
  
67–68
 

86
  
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  
67–68
   
       
     
126
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22
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  
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     

               

70

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    

70
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
78
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 Fagus crenata
140
  
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


  




J. FOR. SCI., 51, 2005 (10): 446–457 457


Institute of Silviculture, University of Göttingen, Göttingen, Germany


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lars.droessler@web.de

Supplementary resource (1)

JFS 10 446-457[1] Canopy gaps 2005
Data
December 2015
L. Drößler · Burghard von Lüpke
... However, we observed only a few transitions between the DS during the study period, and the developmental trajectory varied partly between (Petráš and Pajtík, 1991) transformed into biomass using biomass expansion factors ( Požgaj et al., 1997) the plots. The low number of observed shifts is not surprising because the length of the cycle can be 200-220 years for beech forests (Drößler and Von Lüpke, 2005) and over 350-400 for mixed mountain forests of beech, spruce, and fir (Korpeľ, 1995;Leibundgut, 1978) in the Western Carpathians. To overcome the decades of observations, we established plots in the well-differentiated and homogeneous patches. ...
... The shift between the optimum and disintegration stages was observed when a large gap was created on the plot nr. 8. In a gap larger than 500 m 2 , which exceeds the common gap size known for Carpathian beech forests (Drößler and Von Lüpke, 2005), the herbaceous understorey responded with rapid development during the first two years and shifted to become similar to the plots established in gaps 19 years ago. This stage of understorey development, characterised by the highest herb frequencies and species richness, is distinguished by eutrophic to nitrophilous and more heliophilous plants, as well as by a higher proportion of therophytes (Šamonil and Vrška, 2008;Ujházy et al., 2005). ...
... Unlike the overstorey dynamics, which can be estimated for specific cyclic patterns of one to three prevailing tree species (Drößler and Von Lüpke, 2005;Korpeľ, 1995;Leibundgut, 1978), development of species rich herbaceous understorey is more complex. The herb layer responds rapidly to disturbances, which limit tree competition and provide microhabitats for understorey organisms (Zemlerová et al., 2023). ...
Effects of tree canopy on herbaceous understorey throughout the developmental cycle of a temperate mountain primary forest
Article
  • Aug 2023
  • FOREST ECOL MANAG
Temporal dynamics of temperate montane primary forests were described based on data from Central-European nature reserves in the 20th century as a long-term cycle involving tree regeneration, growth, maturation, and disintegration. However, the lack of chronosequences focusing on the herbaceous understory has limited our understanding of plant community dynamics within this developmental cycle. To address questions regarding whether the herbaceous understory follows the cyclic trajectory of the tree layer and if the properties of the tree layer drive the dynamics of the herbaceous understory, we investigated a 19-year chronosequence in ten plots (with five sampling periods) within an unmanaged primary beech-fir forest in the Western Carpathians. The vegetation data from the resampled plots, including herb species frequencies and dendrometric variables, covered a significant portion of the developmental cycle of a single plant community type. The results confirmed the cyclical nature of herbaceous understory development in terms of species composition and diversity trajectories, demonstrating transitions between developmental stages. Diversity was highest during the disintegration stage, with a rapid decline towards the growth stage, followed by a slow recovery as it progressed towards the optimum stage. Temporal responses of individual species, along with ordination analyses, allowed for the separation of taxa associated with the disintegration, growth, and optimum stages, as well as the most stable ones throughout the entire cycle. The proportion of therophytes slightly increased after gap-opening events during disintegration, geophytes were most represented during the growth stage, and hemicryptophytes culminated during the optimum stage. The composition of herb species was significantly affected by the above-ground tree biomass (AGTB), which explained 21.4% of the temporal variability. The sum of the diameter at breast height (Sum of DBH) described an additional 7.2%. The relationship between the frequency of the herbaceous understory and AGTB followed a “U” shape, while the relationship with Sum of DBH was negative and linear. The relationship between the herbaceous understory and the tree overstory is likely driven by competition for light, water, and nutrient resources. These findings provide new insights into the temporal relationships between the herbaceous understory and tree layer development, and they may inspire future studies and management strategies aimed at conserving or enhancing biodiversity in temperate forests.
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... However, we observed only a few transitions between the DS during the study period, and the developmental trajectory varied partly between (Petráš and Pajtík, 1991) transformed into biomass using biomass expansion factors ( Požgaj et al., 1997) the plots. The low number of observed shifts is not surprising because the length of the cycle can be 200-220 years for beech forests (Drößler and Von Lüpke, 2005) and over 350-400 for mixed mountain forests of beech, spruce, and fir (Korpeľ, 1995;Leibundgut, 1978) in the Western Carpathians. To overcome the decades of observations, we established plots in the well-differentiated and homogeneous patches. ...
... The shift between the optimum and disintegration stages was observed when a large gap was created on the plot nr. 8. In a gap larger than 500 m 2 , which exceeds the common gap size known for Carpathian beech forests (Drößler and Von Lüpke, 2005), the herbaceous understorey responded with rapid development during the first two years and shifted to become similar to the plots established in gaps 19 years ago. This stage of understorey development, characterised by the highest herb frequencies and species richness, is distinguished by eutrophic to nitrophilous and more heliophilous plants, as well as by a higher proportion of therophytes (Šamonil and Vrška, 2008;Ujházy et al., 2005). ...
... Unlike the overstorey dynamics, which can be estimated for specific cyclic patterns of one to three prevailing tree species (Drößler and Von Lüpke, 2005;Korpeľ, 1995;Leibundgut, 1978), development of species rich herbaceous understorey is more complex. The herb layer responds rapidly to disturbances, which limit tree competition and provide microhabitats for understorey organisms (Zemlerová et al., 2023). ...
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... Veľkosť, rozloženie a štruktúra porastových medzier vznikajúcich po narušení má väčšinou menej ako 150 m 2 (Drossler, von Lüpke 2005;Zeibig et al. 2005;Nagel et al. 2017;Orman, Dobrowolska 2017;Feldmann et al. 2018). Dynamika tvorby malých a stredne veľkých porastových medzier býva označovaná za hlavný faktor pri tvorbe štruktúry a podoby bukovo-jedľových lesov mierneho pásma (Splechtina et al. 2005;Šamonil et al. 2009;Firm et al. 2009;Trotsiuk et al. 2012;Hobi et al. 2015). ...
... Prírodné disturbancie s vyššou intenzitou sa vyskytujú taktiež, ale s menšou frekvenciou. Drossler, von Lüpke (2005) zdokumentovali, že 10 % porastových medzier tvorili tie s rozlohou 250 až 1000 m 2 a boli s veľkou pravdepodobnosťou spôsobené atmosférickými procesmi. Ďalšie štúdie detekovali stredne silné narušenia so 40% odstránením korunového zápoja v Dinárskych vrchoch alebo v Karpatskom oblúku, kde boli zaznamenané aj disturbancie s vysokou severitou Kameniar et al. 2023). ...
Druhové zloženie a synchronizovanosť disturbancií v primárnych lesoch s dominanciou buka lesného (Fagus sylvatica L.) v strednej Európe
Article
  • Jul 2024
Natural disturbances such as windthrows and bark beetle outbreaks are essential in the formation of natural forest ecosystem structures in Central Europe. Therefore, evaluating disturbances’ spatial and temporal extent and synchronicity is critical for understanding of forest dynamics. This study aimed to evaluate the long-term natural disturbance history of primary mixed-beech forests and investigate the species composition-temporal synchronisation relationship. We collected a unique dataset of > 6,000 tree cores across 14 forest stands on 174 study plots, and using dendroecological methods we reconstructed 200-year-long plot-level disturbance histories and evaluated synchronicity within the stands. Subsequently, we used GLMs to evaluate the tree species diversity-synchronicity relationship. The results showed substantial temporal variability of natural disturbances and a prevalence of low and moderate severity disturbances. Disturbance synchronisation was higher in the Western than in the Eastern Carpathian forests, which have a lower proportion of admixture tree species. Moreover, the GLMs showed a strong positive dependence of synchronicity on tree species richness. The results contradict the general assumption that mixed-species forests have higher resilience to disturbances than monospecific forests. The reason behind these findings can be attributed to the substantial admixture of Norway spruce, and its vulnerability to disturbances such as windthrow and bark beetle outbreaks.
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... V rovnorodom bukovom pralese Rožok neboli potvrdené žiadne disturbancie veľkého rozsahu, čo sa prejavilo vo významnom náraste biomasy v poslednom období. Tieto výsledky spolu s doteraz publikovanými poznatkami výskumov v pralesoch s dominantným zastúpením buka v strednej Európe potvrdzujú, že maloplošné disturbancie zohrávajú dominantnú úlohu v produkčnom a vývojovom režime týchto pralesov (DRÖSSLER, LÜPKE 2005;ZEIBIG et al. 2005;OHEIMB et al. 2005;NAGEL, SVOBODA 2008;KUCBEL et al. 2010;SANIGA et al. 2011). Podobne prales Skalná Alpa sa v napriek vysokej nadmorskej výške nedostáva do plošnej disturbančnej dynamiky. ...
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... A number of studies to date have examined stands of old-growth beech forests [2,[8][9][10][11][12], and most have taken a traditional approach to describing structural properties and mapping development phases. Newer research is taking an approach to understanding the effects of natural canopy gaps on forest development dynamics [13][14][15][16][17][18][19], while others have applied time series data [20][21][22]. ...
The Dynamics of Stand Structure Development and Natural Regeneration of Common Beech (Fagus sylvatica L.) in Plitvice Lakes National Park
Article
Full-text available
  • Feb 2024
The authors investigate the structural characteristics, regeneration processes, growth, development, and survival of a young generation of common beech (Fagus sylvatica L.) based on three periodic measurements (1998, 2009, and 2018). The studied forest community (Lamio orvale-Fagetum sylvaticae (Ht. 1938) Bohridi 1963) is situated within a forest reserve in Plitvice Lakes National Park, Croatia. Monitoring was carried out according to UN/ECE (2000) for systematic and repeated research. The basic structural indicators, structural canopy elements, and appearance of the young generation were measured as the basic conditions of natural restoration in repeated phytocenological surveys (1980, 1988, 2004). The distribution of the number of trees of the first two measurements (1998–2009) indicates a distribution with pronounced right asymmetry. The structural dynamics observed during the surveys and alongside vegetation surveys indicate the dynamics of the growth and development of beech. The results show that the main drivers of development dynamics in protected forest ecosystems are structural breaks (gaps) that occur in stands due to the action of abiotic and biotic factors. The passive management model in effect in the national park should be replaced with a more active approach to facilitate natural processes with the aim of preserving and renewing the forest ecosystem.
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... The emergence of seedling banks, the dynamics of their development, their disappearance due to the canopy closing, and the interspecific and intraspecific competitive interactions that occur within the seedling banks are segments that reflect the overall dynamics of old-growth beech forest regeneration. These segments continuously intertwine, thus sustaining the process and maintaining its balance (Dröβler and von Lüpke, 2005;Madsen and Hahn, 2008). In addition, beech proves to be an extremely dominant species in its habitats, suppressing the presence of other broadleaved trees and thus preserving its composition (Petrovska et al., 2023). ...
Key drivers affecting the spatial heterogeneity of the regeneration process in old-growth beech forests in southeastern Europe
Article
Full-text available
  • Nov 2023
Understanding the processes occurring in old-growth forests and identifying their key aspects can significantly enrich modern forestry practices with innovative ideas and concepts. The natural regeneration process in beech old-growth forests exhibits distinct spatial heterogeneity and temporal variability. To define the key drivers that influence the spatial heterogeneity of regeneration processes and their effects, research was conducted in three beech old-growth forests situated in Serbia, Southeastern Europe: Felješana, Vinatovača, and Kukavica. In each old-growth forest, a network of circular sample plots with an area of 0.1 ha (totaling 45 plots) was established to gather data on structural characteristics and ecological conditions. Within each circular sample plot, data on the regeneration layer were collected on four square sample plots of 1 m 2 (180 in total). Using linear mixed models, the key drivers of spatial heterogeneity of regeneration processes in beech old-growth forests were analyzed. Based on the results, several key factors contribute to the highly heterogeneous distribution of seedlings, including the canopy, the presence of a middle layer comprising young trees, ground vegetation, and soil stoniness, while a significant influence of the combined effect of the canopy and the presence of a middle layer of young trees is also defined. The spatial heterogeneity of the regeneration process is also represented through the assessment of the ratio between the abundance of one-year-old and older seedlings. The dominance of one-year-old seedlings intensifies with increased canopy density (in instances of very dense canopy (1.0), the ratio of one-year-old and older seedlings is 70:30%). Seedling growth characteristics are shaped by multiple factors, including the influence of the canopy, the presence of the middle layer of young trees, slope, and soil stoniness, with a substantial combined influence of the canopy and the middle layer of young trees. This indicates that the spatial variability of the regeneration process in beech old-growth forests is primarily driven by factors with a substantial individual influence, which may also act combined. It is of paramount importance to understand these factors and determine their influence on the regeneration process in managed beech forests.
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... The contribution of gaps in the total forest area of beech-dominated forests is given in the literature as 3-19 % (Nagel and Svoboda, 2008;Kenderes et al., 2009;Petritan et al., 2013;Feldmann et al., 2018). These gaps also occur in the course of natural processes of a beech forest due to the death of one or more trees (Drössler and von Lüpke, 2005;Bottero et al., 2011;Hobi et al., 2015). It can be assumed that the removal of individual trees or groups of trees resemble these "natural" processes in managed forests. ...
Stem shape and structural complexity change in beech forests along a management gradient
Article
Full-text available
  • Sep 2023
  • FOREST ECOL MANAG
For about half a century, attempts have been made to manage forests as close to nature as possible. This management targeted the creation of structures that resemble those found in primary forests. Laser scanning provides the opportunity to quantify such structural "naturalness" and allows to evaluate which management practices come closest to forest structures found in primary forests. In this paper, European beech (Fagus sylvatica L.) forests with different management intensity were compared to primary forests in terms of their structural complexity and the shape of tree stems. For this purpose, data from mobile and terrestrial laser scans (MLS and TLS) of managed forests, of forests whose management has been abandoned, and of primary forests was used. We found that management intensity influenced the distribution of plant material in the forest stand and thus the structural complexity on stand level. Also, management affected the shape of the stems. Here, it is important to consider the management history of the forest stands and the forest development phase in which management was abandoned. The stem shapes of trees in primary forests were significantly different (larger stem diameters and longer branch free boles) from those of the other investigated forests. Nevertheless, our results showed that it is possible to achieve old-growth-like structures such as high standing volumes, a multi layered canopy, high number of large trees and high variation in tree size and age through targeted silvicultural treatments in order to accelerate the close-to-nature development of forests. The present study illustrates the possibility of using mobile and terrestrial laser scanning to objectively compare and evaluate the structural effects of different silvicultural concepts.
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... Average stand-level canopy openness varied between 9.6-21.0% in SDPF and 2.4-6.2% in BDPF stands. Other studies also report low gap proportions, a variable more frequently used to represent canopy openness in BDPF; 1.2% at a Slovenian locality (Bončina 2000), 2.7 and 4.2% at two primary forest localities in Poland (Orman and Dobrowolska 2017) and 7-8% (or 15-16%, depending on gap characterisation) at two localities in the Slovakian part of the Eastern Carpathians (Drössler and von Lüpke 2005). We are not aware that comparable numbers have been published from SDPF. ...
Spruce- and beech-dominated primary forests in the western Carpathians differ in terms of forest structure and bird assemblages, independently of disturbance regimes
Article
Full-text available
  • Jun 2023
Mountain spruce- and beech-dominated forests (SDPF and BDPF) are of major importance in temperate Europe. However, information on the differences between their historical disturbance regimes, structures, and biodiversity is still incomplete. To address this knowledge gap, we established 118 circular research plots across 18 primary forest stands. We analysed the disturbance history of the last 250 years by dendrochronological methods and calculated disturbance frequency, severity, and timing. We also measured forest structure (DBH, tree density, volume of deadwood, and other parameters). Breeding bird populations were examined by point count method during the spring seasons 2017–2018 (SDPF) and 2019–2020 (BDPF). Using direct ordination analysis, we compared the disturbance history, structure and bird assemblage in both forest types. While no differences were found regarding disturbance regimes between forest types, forest structure and bird assemblages were significantly different. SDPF had a significantly higher density of cavities and higher canopy openness, while higher tree species richness and more intense regeneration was found in BDPF. Bird assemblage showed higher species richness in BDPF, but lower total abundance. Most bird species which occurred in both forest types were more numerous in spruce-dominated forests, but more species occurred exclusively in BDPF. Further, some SDPF- preferring species were found in naturally disturbed patches in BDPF. We conclude that although natural disturbances are important drivers of primary forest structures, differences in the bird assemblages in the explored primary forest types were largely independent of disturbance regimes.
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БУКОВИ ГОРИ ВЪВ ФАЗА НА СТАРОСТ -СТРУКТУРА И ПРИРОДНА ДИНАМИКА
Book
Full-text available
  • Dec 2023
We collected and analyzed structural and tree-ring data in Steneto and Boatin Natural Reserves and studied tree response after disturbances (ice and wind damages and fires) in North Dzhendem, Steneto and Sokolna reserves in the Central Balkan National Park, Bulgaria. Our aim was to contribute to the understanding of the structural variability of unmanaged old-growth Fagus sylvatica forests on different spatial scales. A grid permanent circular plots (1500 m2) were established in Steneto and Boatin forest reserves, in total, 14 and 28 plots respectively. This work was done within the framework of project REMOTE-Primary forest (https://www.remoteforests.org/ ) The total number of live trees with the DBH>6 cm for the whole studied forest patches ranged between 269 (patch Steneto 1) and 367 trees/ha (Boatin). The volume of alive trees was about 400 m3/ha, of the dead standing trees 6-20 m3/ha, of the dead lying wood about 50-70 m3/ha. The forests were dominated by European Beech with few other species. The DBH structure resembled Reverse-J in all forests. The age varied strongly, between 100 and 500+ years. The highest concentration of old trees was found in Steneto 1 forest patch, where there were many trees over 300 years. In Steneto 2 patch dominated trees below 250 years. In Boatin reserve there was a peak of trees between 200 and 250 years with oldest ones above 500 years. After disturbances the tree reactions were varying strongly, but were not only releases. There were also suppressions and especially after the fires the post-disturbance mortality was very high.
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Natural disturbance regimes in northeastern North America - Evaluating silvicultural systems using natural scales and frequencies
Article
Full-text available
  • Jan 2002
  • FOREST ECOL MANAG
Many scientists and foresters have begun to embrace an ecological, natural disturbance paradigm for management, but lack specific guidance on how to design systems in ways that are in harmony with natural patterns. To provide such guidance, we conducted a comprehensive literature survey of northeastern disturbances, emphasizing papers that studied late-successional, undisturbed, or presettlement forests. Evidence demonstrates convincingly that such forests were dominated by relatively frequent, partial disturbances that produced a finely patterned, diverse mosaic dominated by late-successional species and structures. In contrast, large-scale, catastrophic stand-replacing disturbances were rare, returning at intervals of at least one order of magnitude longer than gap-producing events. Graphing the contiguous areas disturbed against their corresponding return intervals shows that these important disturbance parameters are positively related; area disturbed increases exponentially as the return interval lengthens. This graph provides a convenient metric, termed the natural disturbance comparability index, against which to evaluate both single and multi-cohort silvicultural systems based on their rotations or cutting-cycles and stand or gap sizes. We review implications of these findings for silvicultural practice in the region, and offer recommendations for emulating natural disturbance regimes.
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Relation of dead wood course within the development cycle of selected virgin forests in Slovakia
Article
Full-text available
  • Dec 2002
Following measurements of dead wood (20 to 40 years) at various developmental stages of the life cycle of selected virgin forests of the 1 st to 7th altitudinal zone the relation of its course was derived. The dynamics and course of dead wood in the life cycle of virgin forests were best represented by a polynomial of the third degree. An analysis confirmed that virgin forests consisting of stable tree species with approximately the same physical age (Boky) showed small differences between maximal increase and decrease in necromass during the whole development cycle. Virgin forests at sites rich in nutrients consisting of several tree species with various physical age had high values of necromass during their whole development cycle. Spruce stands at the upper forest boundary also had a relatively high ratio of necromass at the advanced optimum stage.
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Patterns of Disturbance in Some Old-Growth Mesic Forests of Eastern North America
Article
  • Jun 1983
To characterize the disturbance regime of one type of vegetation, study areas in which relatively small-scale disturbance predominates were chosen in several old-growth mesic forests in the eastern United States. Canopy openings covered 9.5% of total land area. New gaps were formed at an average of 1% of total land area per year; old gap area closed at a similar rate primarily by sapling height growth. With increasing gap size, vegetation within gaps increased in woody species diversity, total basal area, and total number of stems. Stems also showed accelerated growth into larger size classes. As gaps aged, stems grew into larger size classes and basal area increased. Species responses to canopy gaps varied. Some species survived and became established in fairly small gaps (50-100 m^2). Although in large gaps (up to 2009 m^2 in the present study) these species usually increased in total number of stems and basal area, they declined in importance relative to species which rarely survived in small gaps but grew rapidly in large gaps. The disturbance regimes in the forests studied favored tolerant species but allowed opportunists to persist at low densities.
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Fifteen Years of Canopy Dynamics Analyzed by Aerial Photographs in a Temperate Deciduous Forest, Japan
Article
  • Mar 1997
Aerial photographs were used to analyze long-term canopy dynamics over 15 yr in a large area (25.25 ha) for a mixed deciduous forest in the Ogawa Forest Reserve, central Japan. Digital elevation models of canopy surface were made from aerial photographs taken in four summers at 5-yr intervals from 1976 to 1991. A digital elevation model of ground surface was also made from the aerial photograph taken in winter 1991. The canopy height at each location was calculated from the elevational difference between the canopy add the ground, and the 'vegetation profile technique' was applied to quantify canopy dynamics. The size distributions of gaps at each observation time and of gaps that were created between observation times followed a power function model. While the rates of gap formation and closure throughout the whole period were nearly balanced, they showed large temporal variations among the observation periods. Spatial distribution of newly created gaps was significantly biased toward the edges of old gaps. Probability of repeated gap creation was also significantly high. Analysis of changes in the canopy height profile by a transition probability matrix showed that gap area distribution of this forest may be nearly in a steady state.
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Long-term variability of thunderstorm occurrence in Poland in the 20th century
Article
  • Jul 2003
  • ATMOS RES
The main aim of this study was to present thunderstorms' occurrence in Poland in the 20th century. The paper also attempts to assess the impact of atmospheric circulation on the variability of number of days with thunderstorms and estimate synoptic conditions conducive to the formation of thunderstorms. The analysis was based on thunderstorm observations from 56 synoptic stations in Poland in the period 1951–2000 and 7 stations for the years 1885–2000. In the second part of the study, the types of synoptic situations elaborated by Osuchowska-Klein, the types of synoptic situations by T. Niedźwiedź, indices of atmospheric circulation by Z. Ustrnul and index of North-Atlantic Oscillation (NAO).As a result, it was determined that during the analysed period, no tendency was found in the multi-annual course of mean yearly number of days with thunderstorms in Poland, and the values usually do not differ much from the value typical for the climatic–geographical region in which Poland is situated. Synoptic situations have less influence on thunderstorm occurrence than that usually suspected. The eastern advection has the largest influence on the occurrence of the days with thunderstorms, especially in southern Poland. The analysis of relations between the variability of number of days with thunderstorms and the changes of the circulation indices proved these regularities.
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