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Halting the unprecedented rate of decline in global biodiversity belongs to most important problems and challenges of the contemporary world. For a long time, various activities and efforts have been run and taken to achieve this goal. Generally, the undertaken measures go in two major directions. One direction, historically older, is based on the principle of segregation. This direction is generally about spot− and area−based activities. The second direction, on the other hand, seeks to integrate conservation activities into broader natural resource and environmental management plans that assume their use in a sustainable manner. The goal of this paper is to critically analyse the advantages and disadvantages, benefits and limitations of both approaches and their practical effectiveness, taking into account contemporary environmental and social conditions. A particular emphasis is placed on analysing the implications of recent trends and proposals falling under the first of the two aforementioned directions (segregative approach) and stemming from the European Commission’s Biodiversity Strategy for 2030. The essence of segregative approach is the setting up a system of protected areas as a basic means of attaining the conservation goals. However, in the light of many examples, it is now becoming increasingly clear that nature cannot be effectively protected by enclosing it within protected areas (reserves, national parks, or wilderness areas) and by drawing a line around them and leaving them alone. The paper presents numerous data and facts showing that efficient conservation of forest biodiversity calls nowadays for integrative approaches, represented by such concepts as an idea of ecosystem approach derived within the scope of Convention of Biological Diversity and/or an idea of sustainable forest management developed within the Ministerial Conference on Protection of Forest in Europe (currently: Forest Europe). The considerations end in a conclusion, that the real challenge of the time is not to further increase the area of protected areas and increase the area under strict protection, but to improve and implement as widely as possible in practice the methods of forest management favourable to maintaining the truly multifunctional character of forests, at the smallest possible spatial scale, as well as to ensure the economic effectiveness of forest management and to prepare forest ecosystems for the challenges which are already appearing and which are to be expected in the near future from the changing climate and other environmental factors., Sylwan 166 (7): 470-490

The paper describes changes, which took place over the last 30 years in old−growth forest stands occupying two permanent research plots, established in the Kaliszki and Sieraków strict protection areas in the Kampinos National Park (central Poland). Both plots have a form of ecological transects. The Kaliszki plot is 20 m wide and 700 m long (1.40 ha), while the Sieraków plot (total area of 2.56 ha) consists of two parts: main (40×460 m) and side (40×180 m) transect. In the Kaliszki plot, the stand measurements were conducted in 1993, 2007, and 2017, while in the Sieraków plot – in 1989, 1994, 2006, and 2017. For every tree with breast height diameter (DBH) 5 cm, species identity, DBH and spatial coordinates were determined. Starting from the second census, all trees which had died (‘losses’), as well as trees which exceeded the DBH threshold (‘gains’) since the previous record were noted, as well. The major tree species occurring on sample plots are Scots pine (emPinus sylvestris/em), pedunculate oak (emQuercus robur/em), silver and downy birch (emBetula/em sp.), and black alder (emAlnus glutinosa/em). During the study period, the overall tree density declined by ca. 50%. The diminishing trends occurred for all dominant tree species. In contrast to major, dominant tree species, the demographic status of a group of minor tree species (lime, hornbeam and maple) was much more stable. One may even speak about some expansion in this case. Particularly, hornbeam density increased rapidly in the period 2006−2017 in some areas of the main transect located in the Sieraków plot. The future studies will show if this tendency will be maintained and will include other regions of sample plots. Assuming a lack of significant disturbances, one may expect that the stands growing on research plots will rather slowly change in the nearest future. Most dynamics will have a quantitative and not qualitative character. One may anticipate, for example, a growing role of pedunculate oak at the expense of Scots pine, however, considering that the two species are rather long−living, they will probably for a long time keep their dominant roles in the stand canopies., Sylwan 164 (5): 392-403

Two fundamental demographic processes (tree recruitment and mortality) are analyzed for forest stands growing on permanent study plots located in strictly protected Scots pine−dominated, old−growth stands of Kampinos National Park (central Poland). The major implications of the observed demographic trends for the general shape of tree size distributions are determined, as well. During the past ca 30 years, in the stands sampled, there was a pronounced lack of balance between mortality and recruitment processes. Mortality rate was eight times higher than recruitment rate. Eventually, there was a net significant decline in population density, observed for all major tree species, including Scots pine, pedunculate oak, silver and downy birch, and black alder. As mortality processes affected mainly smaller trees, there was also a significant deterioration of the general demographic status of most important tree species. This effect was shown by the change of the overall shape of diameter distributions over the study period: from reverse J−shaped to flat curves running nearly parallel to X−axis. The values of recruitment rates were markedly lower, and the values of mortality rates – significantly higher, than analogous values characterizing comparable forests (e.g., those obtained for the natural stands of Białowieża National Park). Low recruitment rates, as obtained for Kampinos stands, suggest that presently, in the local, Scots pine−dominated, old−growth stands, the general conditions for forest regeneration and for maintaining a long−term demographic stability are unfavorable. Most probably, the regeneration of this type of forest has an episodic, ‘wave−like’ character and corresponds to the ‘catastrophic’ model, according to which the successful regeneration of current dominants (especially Scots pine, silver and downy birch, black alder) must be preceded by a stand−initiating (stand−replacing) disturbance, leading to total or partial, but heavy, destruction of the currently existing stand. At the moment, it would be difficult to predict, however, if and when such a disturbance will affect the stands under investigation. Thus, we predict that in the nearest future at least, the state of overall demographic unbalance will continue or even increase., Sylwan 164 (6): 443-453

Climate change creates a big challenge for forest science. One of several problems calling for urgent solution concerns the elaboration of the scientific foundations for determination of the species composition of forest stands under changing environmental conditions. This problem is particularly acute in case of declining Norway spruce stands in the Sudety Mountains (SW Poland). The paper presents the main principles used to develop a model allowing determination of the most desirable species composition for any given forest stand occurring in the Sudety region. These principles include: 1) an assumption that a basis for species composition planning should be a forest site type, corrected by means of site index of the currently existing forest stand, 2) a supposition that one should broadly consider present processes taking place in Sudety stands, particularly, an intense forest dieback caused by recurring drought periods and strong winds, 3) a postulate that one should consider the differences between tree species in respect to their reaction to particular abiotic factors, 4) an assumption that majority of stands should consist of several different tree species, 5) an assumption that introducing on a wide scale Douglas fir, well−adapted to the conditions of the Sudety Mountains, is allowed, 6) an idea that one should take into account differentiated production potential and varied timber quality of particular tree species, 7) an assumption that one should consider the main features of topography (altitude, exposition, slope) as well as 8) fine elements of micro−topographical situation, as a basis for introduction of different tree species. The results obtained by means of the model based on the above mentioned principles are presented on the example of two forest districts: Lądek−Zdrój (fig. 4a, b) and Szklarska Poręba (fig. 5a, b). In both cases, a necessity to diminish the share of Norway spruce and to increase the share of such species like common beech, silver fir, Douglas fir and European larch is demonstrated. One may expect that projected compositions, taking into account the most appropriate tree species and their most suitable localizations, will allow establishment of forest stands which will be more resistant to drought and wind and, thus, will be more able to fulfill several important forest functions (related to water and soil protection, protection of forest biodiversity and timber production)., Sylwan 164 (6): 454-466

The ability of spatial expansion and conquering of new locations, suitable for growth, is one of the most important properties enabling different plant species (including forest trees) a permanent existence in a constantly changing (in space and in time) environment. In the course of evolution, plants developed several adaptations and mechanisms enabling them to capture new localities appropriate for life. The key role in this process is played by so called propagules, i.e. differently built spores, seeds and fruits. The main sources of forces and major transportation vectors for propagules are such mechanisms as: power of gravity (barochory), wind (anemochory), water (hydrochory), animals (zoochory) and man (antropochory). Among them, in case of tree species producing large seeds, containing bulky amounts of food resources, the most important role is played by zoochory. The special variant of zoochory is ornitochory, i.e. dispersion of plant propagules by birds. One of the best known and documented examples of ornitochory is dispersal of oak acorns by jays (Garrulus glandarius). The contemporary research shows that during a vegetation period one single bird is able to deposit even several thousends of acorns within the area of 10 to 100 ha. The dispersal distance in case of acorns distributed by jays is variable and depends on several factors, first of all, climatic conditions and degree of environmental heterogeneity. On average, acorns are distributed within a distance of several hundred meters from seed trees; sometimes they are disseminated at a distance of several (4−8, maximum 20) kilometers. As a rule, only a part of deposited acorns is uncovered and consumed by birds, thus at least some of them can germinate and produce new oak seedlings. It was also recently demonstrated that jays preferably put down acorns under the stand canopies composed by tree species other than oak, for instance, under Scots pine trees. Under favourable conditions, this initiates natural successional processes and leads to a significant conversion of tree stand composition. Considering a large scale and commonness of this phenomenon, it deserves an interest and attention, not in the case of natural forests only, but in the case of managed forests as well, in which the quasi−natural, successional processes, initiated by jays, can considerably contribute to a greater compositional and structural diversity of tree stands., Sylwan 163 (6): 479-488

The aim of this study was to quantify 4−year growth and increment of 11− to 15−year−old, artificially regenerated hornbeam (Carpinus betulus L.) playing the role of the tending (nursery) species in the oak stand of the same age, after the silvicultural treatments aimed at reducing its competition against the oak. The study included three types of experimental treatments: decapitating of all hornbeam trees (OG), schematic reduction of hornbeam density (R50, removal of every second hornbeam in a row) and control (K, without treatment). The trial stand is located in Rogów (51.827023° N, 19.922315° E) and was established in 2004 on a moderately fertile site. The experiment was carried out in the spring 2013 (9 years after planting). Height and breast height diameter (dbh) of trees were measured every two years. During the study period, the height increment of decapitated trees was significantly larger than in R50 and K variants, while the dbh increment of trees in R50 variant was significantly larger than in K and OG variants. The height increment of hornbeam in R50 and OG variant and the dbh increment in R50 variant were positively correlated with height and diameter of trees before the treatment, while the dbh increment after decapitating was negatively correlated with tree dimensions before treatment. The decapitating treatment reduced the competitive ability of hornbeam more effectively than the schematic thinning removing 50% of hornbeam trees. After 4 years in the first case, oaks were on average 1 m higher than hornbeams, and in the second case, there was an opposite situation. In order to improve the effectiveness of the thinning treatment, a selective cutting should be performed (removal of the largest hornbeams), and in order to slowdown the regeneration of hornbeams after decapitating, the treatment should be carried out during the top of the growing season., Sylwan 163 (3): 179-187

Since several years already, a massive infestation of bark beetle has taken place in the Białowieża Forest, decimating a local Norway spruce population. In consequence, many open areas appeared, practically deprived of trees and other forest vegetation. The existence of such areas has a very negative impact on multiple values of the Białowieża Forest: natural, social, economical and landscape−aesthetic values. The local forest administration prepared a strategy aimed at active restoration of diverse woodland communities typical for the Białowieża Forest in all places, where bark beetle infestation wiped up the spruce stands. Those plans were criticized by representatives of the environmental organizations who blamed the foresters for transforming the Białowieża Forest into ‘plantation’ and claiming that such measures are inconsistent with the existing forest management and protection plan. The postulate of environmentalists is that the recovery of woodland communities should proceed completely naturally. Taking into account the above mentioned controversies, in this paper we examine the issue of natural regeneration in the Białowieża Forest in detail. In particular, we try to determine to which extent this method of forest reproduction enables re−establishment of compositionally diverse woodland communities, distinguished by a high level of biological diversity and able to provide a wide range of commodities and benefits important for today’s society. Based on an extensive literature review we show that a combination of different (abiotic and biotic) factors, influencing establishment and subsequent growth of seedlings and saplings in the Białowieża Forest has long been strongly unfavorable for many tree species. In this regard, one should particularly emphasize the negative role of large herbivores, especially red deer, which is present in the Białowieża Forest since the end of 19 th century, when it became a private hunting ground for Russian tzars. The devastating effect of deer browsing on natural regeneration is a well−documented phenomenon and widely recognized problem in the forestry practice. The fencing of young forest generation against game pressure is an indispensable measure, needed to secure the continuous existence of several tree species (first of all those palatable and vulnerable to browsing). Very strong arguments for an active approach to the described problem delivers also a long−term study on natural forest dynamics conducted since 1936. It shows that under conditions of strict protection the regeneration capacity of the Białowieża tree species is very variable. These differences lead to the compositional simplification and impoverishment of many tree stands, with numerous negative consequences for local biodiversity. We underline that an active management strategy is a basic prerequisite for maintaining a diverse character of the Białowieża stands and their ability to provide all important ecosystem services on a sustainable basis. Such a strategy should include, beside of the phase of establishment, also the subsequent developmental stages of new forest generations. The general goal of such a strategy should be to secure a possibly high diversity of tree composition and to enable the development of tree species representing a full range of life−history strategies and playing different successional roles: from typical pioneer species, through intermediate, to climax species., Sylwan 162 (11): 883-896

The Białowieża Forest (BF) is in many respects an exceptional object, of a great importance for nature protection and forest management, at the international scale. The BF plays also a key role from the point of view of regional development and welfare of local community. In the last period, a big threat for multiple values of the BF has arisen, as a result of enormous bark beetle infestation, which started in 2012 and has killed 1.4 million m 3 of spruce trees. In the paper, first, a brief overview of the general history of the BF and an account of long−term human impacts on its functioning and structure is provided. Next, the history of bark beetle infestations in the BF is analysed. It is shown that, in the period 1992−2007, the average volume of spruces killed by bark beetle amounted on average to 20,000 m of wood annually. During that period practically all dead trees were removed from the forest by means of salvation cuttings. Starting from 2008, more and more trees infested by European spruce bark beetle were left in the forest, in a result of a pressure exerted by environmental groups. In 2012, Minister of Environment decided to reduce the allowable cut, determined in forest management plans elaborated for the managed part of the BF, from 107,000 to 48,500 m/year. This decision, along with several other regulations and restrictions, made in practice impossible to stop the development of a current bark beetle infestation, which started in 2011 and intensified during the next 6 years (solely in 2016 bark beetles killed 480,000 m of spruce trees). In the paper, the most important implications and consequences of the current situation are briefly summarized and discussed. A special attention is given to the problems concerning: 1) protection of Natura 2000 species and sites (endangered by bark beetle outbreak), 2) a negative influence of large amounts of spruce deadwood on forest soils, 3) threats caused by pathogenic fungi, 4) question of public safety, 5) fire hazard, and 6) economical dimension. The legal and socio−economical foundations of the functioning of Hajnówka, Browsk and Białowieża forest districts comprising the managed part of the BF, as well as their most important environmental and social consequences are discussed too. Among others, it is indicated that, under current conditions of the BF, human intervention plays a key role in maintaining stable and compositionally diverse woodland communities. Finally, several suggestions and recommendations are provided, aimed at, in the short term, breaking off the current bark beetle outbreak, and, in the long term, at maintaining a multifunctional character of the BF and its ability to provide all important ecosystem services on a sustainable basis., Sylwan 162 (5): 373-386

The long−term changes of vegetation cover at the level of woodland community taking place between 1959 and 2016 on the permanent study plot located in the compartment 319 of Białowieża National Park are discussed. In 1959 two distinctive woodland community types occurring on sample plot were distinguished: subboreal mixed pine−oak forest (Serratulo−Pinetum) and hornbeam−lime forest (Tilio−Carpinetum). The phytosociological investigations, carried out almost 60 years later, revealed that in case of both communities, significant, directional changes of their floristic composition took place. Particularly high rate of change occurred in case of the phytocoenosis representing the Serratulo−Pinetum community. In 1959 it contained a full set of characteristic plant species. During the study period, this community type representing the Vaccinio−Piceetea class, was replaced by the initial form of lime−hornbeam forest belonging to the Querco−Fagetea class. Also, in case of the previous Tilio−Carpinetum association, the significant changes in the floristic composition occurred, although not as large as in case of Serratulo−Pinetum community. 60 years ago this community type contained several plant species typical for thermophilous oak forests. Nowadays, it represents a typical form of lime−hornbeam association. The changes in both community types were mainly related to the strong expansion of lime and hornbeam, which took place during the study period and involved the whole study plot. As a result, the vegetation occurring on the study plot is much more homogenous now than it was ca. 60 years ago. The maintenance of Serratulo−Pinetum phytocoenoses distinguished by a high floristic diversity calls for active protective measures in all cases where such measures are allowed and where this community type can potentially develop., Sylwan 162 (11): 907-914

Growth and mortality of oak (Quercus robur L.) in young mixed stands with various admixture of hornbeam (Carpinus betulus L.) in the period of 9−13 years after planting were examined. The trial stand is located in central Poland (51.827023° N, 19.922315° E). It was established in 2004 on a moderately fertile site. Four experimental variants with different participation of oak (O) and hornbeam (H) were established: W1 – an oak monoculture (control variant, 100% O), W2 – a mixed stand consisting of two rows of oak and one row of hornbeam (67% O, 33% H), W3 – a mixed stand consisting of one row of oak and one row of hornbeam (50% O, 50% H), W4 – a mixed stand characterized by a single tree mixture, with three oaks and one hornbeam alternately occurring in each row (75% O, 25% H). During the first two years of the study period the height increments of oak trees were significantly larger in the study variants with hornbeam (the biggest in W3 variant), while during the next two years, the largest values of height increments occurred in the control variant (W1). Through the second part of the study period, the most pronounced, negative effect of hornbeam on the dbh increment of oak trees took place in the W3 variant. During the first nine years after planting the survival rate of oak trees in the variants with hornbeam were similar (82−94%) as in the control variant (85%). However, during the next four years, three times more oaks died in W3 variant (16,5%) than in other variants (5−7%). In general, the results obtained suggest that in order to create mixed oak stands with hornbeam as a nursery species, the share of hornbeam should not exceed 20−25% of all planted trees. The above value appears to be acceptable from the point of view of the negative competitive effects of hornbeam on oak trees during the initial stages of stand development., Sylwan 162 (12): 989-997

The paper describes current (in years 2007−2017) changes of basic parameters of forest stands that constitute the managed part of Białowieża Forest (ca. 53,000 ha), divided into three forest districts: Białowieża (12,600 ha), Hajnówka (19,700 ha) and Browsk (20,400 ha). The investigated tree stands represent different phases of ecological succession, modified by silvicultural treatments and other human activities. The course of the succession processes is varied, depending, first of all, on local site conditions, consisting mainly of fresh sites (ca. 60%) – particularly fresh broadleaved forest, and encompassing exceptionally high fraction of wet and swamp sites (40%) – especially wet broadleaved forest site type. Most stands represent the intermediate, highly productive phase of succession, with spruce and oak as the dominant tree species. In particular, such stands are common in Białowieża and Hajnówka forest districts. Recently, the share of the mentioned stands is declining, most intensely in the Browsk Forest District. In 2017 alone, 430 ha of highly productive forest stands disappeared from the Białowieża Forest. The process of decay involved mixed stands; besides of spruces which were killed by a current bark beetle infestation, also many oaks, pines, birches, alders as well as rare and valuable minor tree species (such as ashes and maples) died. Dying spruce and, more often, oak stands are often replaced by low−productive hornbeam trees, occupying earlier lower stand strata in such stands. The resulting hornbeam stands are often distinguished by low crown closure and low productivity. Tree stands occurring in the Białowieża Forest are among the most endangered by wind damage stands in Poland. It means that in case of strong winds, several trees will be broken and/or uprooted. The intensity of such phenomena will be further increased by the high tree volume of stands as well as by the presence of many gaps in forest canopy, caused by a massive mortality of spruce trees. In general, one may expect that in the nearest future many stands occurring in the Białowieża Forest, built by different tree species, will be subject to a massive decay. The list of factors contributing to this process is long and involves, among other things, recurring droughts during the growing season, unfavorable changes in ground water table and increased frequency of strong winds. All these factors negatively influence the health status of trees, which further favours the development of parasitic fungi and insects. In consequence, there is a high probability that many areas in the Białowieża Forest will, for a long time, retain a treeless character and/or will be occupied by low-productive and single species hornbeam stands., Sylwan 162 (11): 897-906

Changes in the herbaceous layer (vascular plants), taking place between 1959 and 2016 on the permanent study plot in the compartment 319 of the Strict Reserve in the Białowieża National Park are presented. Zaręba [1972] presented phytosociological research carried out in 1959 on the 1.2 ha plot. The author established 10 relevés (size between 100 and 400 m), in which in total 91 different species of vascular plants were noted. In 2016, the similar study was conducted, using slightly modified methods (the inventory of plants involved the total area of the study plot). The comparison of data recorded during both investigations revealed that the total number of plant species declined from the initial 91 to current 83. During the ca. 60−year long period, 43 plant species disappeared completely and were replaced by 35 new species. In the declining group, almost the half (20) were species important from the point of view of nature conservation, including four Red List species (emArnica montana/em, emGoodyera repens/em, emLathyrus laevigatus/em, emTrolius europaeus/em), 10 plant species protected by law, and several other precious species related to rare and declining woodland community types. The obtained results confirm the findings of other authors describing unfavourable changes in the flora of the Białowieża Forest during the past several tens of years. The floristic richness is an important part of the overall biodiversity of Białowieża Forest. It appears that strict protection does not secure the maintenance of this key component. Thus, an attempt to preserve diverse values of Białowieża Forest on a sustainable basis should, first of all, look for a proper balance between strict and active protection. The later can (and should) be integrated within the multifunctional forest management, conducted on the prevailing area of the Białowieża Forest., Sylwan 162 (12): 980-988

The paper presents the main results of the comprehensive inventory of monumental trees in the Strict Reserve of the Białowieża National Park, which was conducted in years 2002−2017 on an area of ca. 4700 ha and included all live trees with diameter at breast height (dbh) exceeding a minimum threshold value ranging from 60 cm for hornbeam to 120 cm for oak. For every tree fulfilling this condition, species identity, circumference at 1.3 m (measured with tape), geographical coordinates (GPS record) and health status (five classes) were determined. In total, 9190 trees from eleven different species were inventoried. Hornbeam, oak, maple, lime, ash and aspen were the most abundant with their total share in the amount of monumental trees equal to ca. 96%. The average density of monumental trees in the Strict Reserve was approximately 2 ind./ha. The majority (88%) of monumental trees were found in different subassociations of Tilio−Carpinetum community: T−C. calamagrostietosum, T.−C. typicum, T.−C. circaeaetosum alpine, T.−C. caricetosum remotae and T.−C. stachyetosum. As a rule, the fraction of particular species in the amount of monumental trees did not correspond to their fraction in the total pool of trees with dbh 5 cm. Particularly high over−representation characterized oak, maple, ash and aspen. On the other hand, such species like spruce and, to a lesser degree, hornbeam, lime, alder and birch played much smaller role in the group of monumental trees than among all trees with dbh 5 cm. The monumental trees of particular species were distinguished by a high diameter differentiation. In this respect, oak clearly prevailed over the other ones. In contrast, the smallest dimensions were typical for hornbeam. The results obtained suggested the need of revision of minimum threshold values of circumference (and of corresponding dbh), used to classify a given individual as a monumental tree. This problem was particularly acute in case of pine, spruce, alder and birch. We suggest that the current minimum values of dbh for these species should be reduced by 10−20 cm. Further, the comparison of the recorded values of dbh for some species with maximum values of dbh provided in the literature indicated the necessity of correction of the last values, both ‘in plus’ as well as ‘in minus’. For alder, aspen and maple, the current values should be increased by ca. 20−30 cm. On the other hand, for pine, the recent value should be reduced by at least 30 cm. We point out that the definition of large (monumental) tree is, to a large extent, an arbitrary issue. The various growth potential of particular tree species, occurring within a given area, implies that this definition should be used flexibly. It means a necessity of using different thresholds for different species and varied environmental conditions. Also, because of the relative rarity of large trees, the reliable estimation of their density can only be obtained on the basis of sufficiently large sample size. Some high values of density of large trees, which can be found in the existing literature (10−20 trees per hectare and more), may be the result of too small sample sizes., Sylwan 162 (11): 915-926

Dominacja użytkowej funkcji lasu podporządkowanej produkcji drewna utrzymała się w Europie do końca XIX w. Największe jej nasilenie miało miejsce w dwóch okresach. Pierwszy z nich był reakcją na nienotowany wcześniej wzrost popytu na drewno w związku z rozwojem budownictwa po zakończeniu wielkiej wędrówki ludów (V – VIII). Drugi okres, nazywany epoką drewna, trwał od schyłku średniowiecza do XIX w. i związany był również z rozwojem budownictwa, ale zarazem z rozwojem rzemiosła, przemysłu, transportu i górnictwa oraz towarzyszącego im wzrostu uciążliwej dla ludności iśrodowiska emisji dymów, gazów i sadzy. Postępujące nasilenie konkurencji między użytkowaniem lasu a degradacją środowiska przyrodniczego doprowadziło pod koniec XIX w. do zamierania lasu w niektórych regionach Europy. Inicjatywa pionierskich badań nad procesami zamierania lasu przypisywana jest Akademii Leśnej wTharandcie, która na zlecenie rządu Saksonii podjęła analizę oddziaływania zakładu hutniczego we Freibergu pod Dreznem na roślinność przylegających pól i lasów. To właśnie dzięki tym badaniom poznano mechanizmy szkodliwego wpływu dwutlenku siarki na rośliny, dokonano podziału uszkodzeń drzew oraz opracowano stosowane do dziś progowe wartości stężenia zanieczyszczeń powietrza przez SO2. Wyniki wymienionych badań przyczyniły się do podjęcia odpowiednich działań na rzecz poprawy czystości powietrza. Miało to miejsce m.in. w Anglii, w której odpowiednie ustawy ograniczyły zawartość kwaśnych substancji w dymach fabrycznych. Podobne podejście limitujące stężenie SO2 wpowietrzu zastosowano w Niemczech. W Austrii natomiast wprowadzono wpołowie XIXw. odszkodowania za szkody leśne spowodowane przez ruch kolejowy. Naogół jednak dochodzenie odszkodowań za szkodliwe oddziaływanie przemysłu na lasy miało małe szanse powodzenia. Dotyczyło to m.in. trwającego wiele lat starania o odszkodowanie w katowickim procesie rządowym za rozpad około 2 tys. ha lasów na Śląsku. Przez wiele lat ubiegłego stulecia szkody w lasach występowały regionalnie. Skutki jednak były coraz dotkliwsze–aż do ostatecznego zakończenia procesu życia (rozpadu) drzewostanu. Daje temu wyraz pojęcie „zamierania (obumierania) lasu”, które pojawiło się w 1908 r. najpierw wodniesieniu do jodły, następnie w 1934 r. do świerka i w roku 1961 wodniesieniu do buka. Wpołowie XIX w. obserwatorzy odkryli nieznane wcześniej oddziaływanie na znaczne odległości emisji gazów spalinowych na lasy. Zrealizowane na początku XX w. badania wykazały, że w uprzemysłowionych krajach, jak np. w Saksonii, duże nasilenie kwaśnych deszczów doprowadziło w20. latach ubiegłego stulecia do powstania lokalnych szkód leśnych wodległości do 25 km od źródeł emisji gazów spalinowych. Stwierdzona przez specjalistów zbotaniki na początku XX w.niespodziewanie duża koncentracja dwutlenku siarki w powietrzu, odczuwana w odległości 10 km od jego źródła, była dużym zaskoczeniem, podobnie jak kilka dekad później w Szwecji. W1960 r. pochodzący z Europy Środkowej i Wielkiej Brytanii gaz oraz kwaśne deszcze wSkandynawii uznane zostały za problem międzynarodowy. W 1980 r. w Niemczech Zachodnich obumarłe drzewa stały się przedmiotem debat na temat przyczyn i skutków zamierania lasu. Przeprowadzone badania wykazały, że głównym sprawcą zamierania roślin był dwutlenek siarki. Powodowane przez niego szkody wywoływały zmianę kolorystyki drzew widoczną praktycznie w całych Niemczech. Ekosystemowe podejście do lasu doprowadziło jeszcze w 1920 r. do popularyzacji metod gospodarki leśnej, opartych na ekologii i zbliżonych do natury zasadach hodowli lasu. Negatywnie oceniono w tym kontekście zręby zupełne imonokultury, które prowadziły do naruszenia ekosystemowych procesów życiowych lasu. Gwałtowny wzrost szkód przemysłowych w lasach Europy nastąpił w 70. i 80. latach ubiegłego wieku i dotyczył około 6 mln ha lasów, które wykazywały szkody na skutek imisji gazów i pyłów przemysłowych. Wymienione rodzaje szkód obejmują obecnie około 10% powierzchni leśnej naszego kraju (867 tys. ha). Zamieranie lasu na przełomie XX i XXI w. łączy się ze zmianami klimatu, które uznane zostały za główny czynnik sprawczy ryzyka w gospodarce leśnej. Do najczęściej wymienianych sprawców szkód należą liczne huragany, wtym: huragan Gudrun w Szwecji, który w 2005 r. uszkodził 75 mln m3, a wraz z huraganem Peer z 2007 r. 87 mln m3drewna na pniu, huragan Cyryl w Polsce, który w 2007 r. zdewastował 2,5 mln m3 drewna na pniu. W Niemczech w okresie od 1990 r. do 2014 r. 9 huraganów zniszczyło drzewostany o łącznej miąższości 160 mln m3. Głównym problemem obecnej gospodarki leśnej jest minimalizacja ryzyka, którego przeciętny koszt szacowany jest na 20% kosztów ogółem gospodarki leśnej. Ograniczaniu klęsk żywiołowych w lasach oraz procesów zamierania lasów i eliminacji ryzyka wgospodarce leśnej sprzyjają zbliżone do natury metody zagospodarowania lasu. Nie należy przy tym zapominać o towarzyszących produkcji drewna świadczeniach funkcji publicznych, realizowanych w interesie ogółu społeczeństwa, a nie tylko wybranych jego podmiotów. Niektóre z tych funkcji już obecnie zyskały atrybuty funkcji rynkowych, co podniosło ich ekonomiczną rolę.

Habitat preferences of capercaillie Tetrao urogallus in the Augustowska Forest (NE Poland) were evaluated using classification trees. Data were collected on 1033 circular sampling plots localized on leks and in their vicinity with 1 km radius. Gathered information described tree stands (site conditions, age, species composition, tree density, closure, vertical structure, lower strata coverage (saplings and shrubs) and blueberry coverage (Vaccinium myrtillus) as well signs of capercaillie presence. The analysis shows that for capercaillie of key importance are tree stands growing on fresh or wet coniferous sites, more than 100 years old, with density less than 446 trees/ha, with anthill and situated more than 150 from a road., Sylwan 158 (4): 267-276

The paper presents preliminary results and experiences concerning promoting diverse structures in forest stands dominated by light demanding tree species, i.e. those that prevail under conditions of Polish lowlands. Data was collected in the ‘Control Unit Browsk 28C', established in 2002 in the managed part of the Białowieża Forest (eastern Poland) and surveyed again in 2011., Sylwan 157 (8): 597-606

In the paper, an assessment of tree population dynamics in the old−growth stands of the managed part of the Białowieża Forest is presented. Data from five permanent sample plots with a total size of 9.3 ha and six inventories that cover the period 1949−2006, were used. Depending on the dynamic status, determined on the basis of changes in a number of individuals per hectare, basal area and quadratic mean diameter, three major groups of tree species were distinguished: 1) an increasing group, containing only hornbeam and lime; 2) a stable group, involving alder and spruce and 3) a declining group consisting of oak, ash, maple, pine, birch, elm and aspen., Sylwan 156 (9): 663-671

The BDq method, a tool of stocking control in uneven−aged stands, with a special reference to the problem of determining diameter structure of cuttings, is introduced. Both theoretical foundations, as well as a practical application of the BDq method are presented on the example of conversion of two−storied stands, consisting of silver fir and Scots pine, to stands characterized by a plenter−like structure., Sylwan 155 (9): 589-598

Major results of the 45−year−long study on the dynamics of strictly protected forest stands, using 3 permanent study plots, 25×100 m each, located on a former narrow strip clear cut established in the beginning of the 20th century on the northern slopes of the Mt. Łysica (the Świętokrzyskie Mountains, Central Poland) are presented. The general development of forest stands is analysed, including change of overall density, tree mortality rate (general and by species), dynamics of basal area and average tree diameter, competitive ability as well as changing role of particular species (mainly European beech, silver fir, sycamore and Norway spruce) in formation of the general stand structure. The results of the study are compared with other investigations of similar type., Sylwan 155 (8): 518-529

Sylwan 149 (4): 21-33

Sylwan 149 (10): 11-19

Sylwan 148 (7): 3-10