Polish Forests Research Articles

Forest Fire Hazard Forecasting Based on Google Earth Engine Open Satellite Data

Introduction. Forest fires cause significant damage to both the natural fund and the national economy. In recent years, their harmful influence has increased due to global warming, and in Ukraine also due to the armed conflict. Thus, traditional methods of patrolling (ground and air) are not only costly, but also dangerous due to mines and possible shelling of border areas. Therefore, the role of surveillance using satellite systems is increasing. Space monitoring is more efficient and covers a larger area of ??the Earth's surface. Another important advantage is open access to information. The purpose of the paper is to build a mathematical model for determining fire danger based on climatic and biophysical satellite data for the forests of Ukraine, as well as a similar climatic zone with the possibility of further scaling to other climatic regions and types of vegetation cover. To adhere to the principles of open science, Google Earth Engine (GEE), a cloud-based platform that provides open access to dynamic collections of pre-processed Earth remote sensing results, was chosen. Results. Climatic and biophysical data for the forests of Ukraine for the years 2017-2020 were collected using the tools of the Python library for working with GEE data. Further, the obtained data were processed by two methods: linear (PCA) and non-linear (UMAP) in order to obtain statistically independent attributes. Both obtained datasets were subjected to statistical processing using the Bayesian method. Finally, for each point on the map for which information was collected, an indicator was calculated that predicted fire danger if the obtained value was greater than 1 and its absence in the opposite case. The resulting model showed its efficiency on training data. On the test dataset (data on Polish forests for the same period), the results turned out to be worse, in particular, the model using PCA did not predict absence of fire danger, and the model using UMAP generally showed lower performance. This can be due to both the imperfection of the model and the small size of the test dataset or factors unrelated to natural processes (in particular the human factor). Conclusions. An approach to forest fires forecasting based on satellite data is proposed. The obtained results indicate that the model is already effective at this stage, although machine learning methods have not yet been applied. However, it needs further improvement, so work on the model will be continued. Along with improving the quality of forecasts, attention will be paid to the geographic expansion and the creation of a web application. Keywords: fire danger in forests, satellite data, correlation, PCA, UMAP, hard-to-reach areas.

Climate-mediating role of forests in Central and Eastern Europe

ABSTRACT The material-and-energy impact of forests on the environment is significant for climate and public health, depending on their local extent and productivity. The boreal-nemoral forests of Germany, Poland and Ukraine make up more than one-fifth of the production potential of Central and Eastern Europe forests. Forests in Germany with an average annual increment of 10.8 m3timber/ha produce 5.26 t/ha/y of oxygen, transpire 3152 t/ha/y of water and, by evaporation, consume 2.17 GWh/ha/y of thermal energy. Accordingly, Polish forests with an annual increment of 5.7 m3/ha have only half of this environmental potential; and Ukrainian forests with an annual increment of 3.9 m3/ha have a potential one-fifth of those in Germany. Consumption of thermal energy during evaporation cools the 30 m surface layer of air over Germany by 2.09°С, Poland by 1.01°С, and Ukraine by 0.39°С.

Properties of Forest Tree Branches as an Energy Feedstock in North-Eastern Poland

Tree branches from forest tree harvesting for the timber industry are an important energy feedstock. Solid biofuel in the form of wood chips, produced from branches, is an excellent renewable energy source for generating heat and electricity. However, the properties of wood chips as a solid biofuel produced from forest tree branches can vary greatly depending on the species from which they have been produced. Therefore, this study aimed to assess the thermophysical properties and elemental composition of fresh branches harvested from nine tree species (pedunculate oak, silver birch, European ash, common aspen, grey alder, Norway maple, Scots pine, European larch and Norway spruce) over three consecutive years (2020–2022). The branches of the tree species most commonly found in Polish forests (Scots pine) were characterized by the highest heating value (an average of 20.74 GJ Mg−1 DM), the highest carbon content (an average of 55.03% DM), the lowest ash (an average of 0.60% DM) and nitrogen contents (an average of 0.32% DM), and low sulfur (an average of 0.017% DM) and chlorine contents (an average of 0.014% DM). A cluster analysis showed that the branches of all three coniferous tree species (Scots pine, Norway spruce and European larch) formed one common cluster, indicating similar properties. The branches of the European ash were characterized by the lowest wood moisture content (an average of 37.19% DM) and thus the highest lower heating value (an average of 10.50 GJ Mg−1). During the three years of the study, the chlorine and ash contents of the branches of the tree species under study exhibited the highest variability.

Exceptionally Uniform Bat Assemblages across Different Forest Habitats Are Dominated by Single Hyperabundant Generalist Species

Woodland bat assemblages are usually structured in a space according to the distance from the ground, water, and obstacles, features that often define chiropteran hunting tactics. Consequently, the bat species composition differs strongly among various habitats, even within the same forest patch. However, when conducting local bat surveys in Wolin National Park (WPN), we revealed an unexpected uniformity in the qualitative and quantitative structure of bat assemblages, based on mist netting and ultrasound recording. In total, 10 vespertilionid species were detected. Across all methods and sampled habitats, a single species, Pipistrellus pygmaeus, predominated, while no Barbastella barbastellus, an old forest specialist, were detected, despite the abundance of their preferred daily roosts. We also reviewed the literature for mist-netted bat samples in four different habitats in lowland Polish forests. The samples usually clustered based on habitats, and the same habitat classes often clustered very closely despite representing geographically distant forests. The exception was WPN, where all four habitat classes formed a tightly packed cluster. We hypothesize that P. pygmaeus might act as a hyperabundant native species, a successful generalist that reduces the contribution of more specialized taxa in the assemblage. It probably benefits from both forest renaturation and anthropogenic cross-boundary subsidy.

The potential of Polish forests to provide ecosystem services

Polish forests differ in their potential to provide ecosystem services (ES), but it is unclear how and to what extent. We assessed the potential of 35 forest habitat types to provide 17 key ES and showed that the montane mesic broadleaved forest has a high potential to provide the largest number of key forest services (14 out of 17), which gives it the status of a multi-service hotspot. The highest overall potential was found in the forests of mountain regions, slightly lower in the postglacial northern regions, and the lowest in the central lowland regions.

(Non)responsibility for Refugees – Communicating about the Belarusian-Polish Border (2021–2023)

Given that two dramatically different refugee regimens have developed along Poland’s eastern border, this essay explores the social conditions and discourses that facilitate such a radically different treatment of people. The Polish state’s violation of human rights on the Belarusian section of the border and the celebration of these rights on its Ukrainian section have become part of media spectacles. This text analyses both the technical and content-related issues of communication about migrants and refugees from the Global South. It includes typologies of attributional biases in the media towards people on the move, discusses their functions and the ways towards a normalisation of violence. The final section historicises the current negative responses to refugees and sets them in the wider context of the uneasy obligations imposed on the “West” by its professed values. In doing so, this essay touches upon questions not only of a sense of social responsibility, but also of actual responsibility for the people who have died in Polish forests and rivers.

How do stand features shape deadwood diversity?

Saproxylic species from different taxonomic groups often occur only on certain types of deadwood with specific qualitative characteristics. The various types of deadwood are very dynamic elements of forest ecosystems, associated with many site and stand features, as well as with the type of forest management. Using a pool of 29,098 sample plots spread across Poland, we analyzed 30 different deadwood types defined on the basis of three characteristics: position (standing, lying), degree of decomposition, and size. Statistical hurdle models were used to assess changes in the volume of individual deadwood types based on a broad range of independent variables. Depending on the type of management, terrain, site fertility, stand volume, tree density, and stand age, the models revealed substantial differences in the volume of different deadwood types, ranging from 0 to approx. 4 m3 ha−1. It was found that the volume of most deadwood types (except for a few, mostly with diameters under 15 cm) increases with stand age or stand volume. In managed forests at all stages of stand development there is a deficiency of thick deadwood. Both standing and lying deadwood at different decay stages is available continuously, irrespective of the values of individual independent variables, but considerable differences exist. While most lying deadwood exhibits higher levels of decomposition, in standing deadwood the proportions of different decay stages are strongly associated with tree diameter at breast height. The developed models make it possible to predict the volume of individual deadwood types for a broad range of independent variables. The current work presents several examples, with the results showing extremely complex relationships between deadwood diversity and site and stand features at every stage of forest development, with continuous changes in the volume and proportions of different deadwood types. In general, at the landscape level Polish forests contain both standing and lying deadwood at all decay stages in more or less equal proportions. However, in forest management one should pay special attention to the dimensions of retained deadwood. The absence of thick deadwood is particularly conspicuous in lowland managed forests.

„Las to ojciec nasz…”. Inne spojrzenie na historię lasów Polski. Cz. III. Toponimy i antroponimy motywowane borami

Oprócz nazw topograficznych (toponimów), które nawiązują do nieożywionych elementów środowiska (ukształtowanie terenu, typ gleby, obecność rzek, podmokłości itd.), jest wiele motywowanych roślinnością, czyli fitotoponimów, a zwłaszcza dendrotoponimów, gdy funkcję identyfikującą w terenie pełnią drzewa i krzewy. Dominującą rolę odegrały nazwy wywiedzione od lasu, niezależnie od jego typu, oraz drzew i krzewów liściastych. Celem pracy była ocena, w jaki sposób udział i przestrzenne rozmieszczenie jednostek nazewniczych z kategorii odborowych odzwierciedla udział rodzimych gatunków iglastych (sosna, świerk, cis, jodła, modrzew, jałowiec) w dawnych lasach Polski. Z ponad 15 tys. odleśnych nazw miast, miasteczek, wsi i różnych osad tylko 2033 (13,5%) przypada na toponimy borowe. Niemal 2/3 wszystkich nazw miejscowych tej kategorii (1318) posiada rdzeń Bor-/Bór-, najczęściej nawiązujący do boru bądź borówki, a zdecydowana większość z nich skupia się w kilku regionach Polski centralnej i południowo-wschodniej: MAZ, WLP, ŁDZ, MŁP, LBL, PDK i ŚWK. Na tych obszarach jest też najwięcej spośród ok. 340 toponimów (16,8% kategorii borowe), pochodzących od sosny i jej staropolskich bądź regionalnych nazw. Znacznie niższą frekwencję mają nazwy miejscowe motywowane świerkiem – 145 (7,1%), cisem – 112 (5,5%), jodłą – 76 (3,7%) i modrzewiem – 27 (tylko 1,3%), a od jałowca wywodzi się zaledwie kilkanaście toponimów. Analizę toponimów uzupełniono przeglądem odpowiadających im nazw osobowych (antroponimów) w ujęciu historycznym i współczesnym.

The Identification of the Abundance of European Larch Trees in Polish Forests

The purpose of the study was to identify the abundance of European larch trees in Polish forests, taking into account the size of areas and their location. A dendrometric analysis (volume, age of trees) was performed as a source of knowledge on the availability of the raw material base as a response to the production needs of wood products in Poland. The detailed data were made available in 2023 by the Directorate General of State Forests on the basis of a license specifying the conditions of use of the vector record of the forest numerical map and appraisal description data. European larch trees are in areas all around Poland. They grow throughout the country, with most stands located in the southern and northern parts of Poland. Stands with a dominant share of larch in the species composition (i.e., those that are part of trees stands with a minimum area of 0.1 ha) occupy 44,813 ha and occur in 17,553 stand divisions. The analysis of productivity showed that the average height of larch stands in Poland ranges from 5 m to 45 m. Tree stands are predominately 26–30 m in height. Most stands with trees over 30 m high are located in the RDFS Krosno (over 15% of the entire forest area with larch as the dominant species). European larch stands in Poland are characterized by significant differences in the average DBH. They are correlated with the age of the stands.

Challenging the dominant path of forest policy? Bottom-up, citizen forest management initiatives in a top-down governance context in Poland

Forest governance in Poland is characterised by the dominance of public forest ownership and hierarchical, top-down policy-making. These governance arrangements, characteristic of post-socialist countries, have traditionally been challenged by environmental NGOs, advocating stronger protection of old-growths. Recently, institutional stability of the forest policy field has been increasingly influenced by numerous citizen initiatives responding to technocratic local forest management decisions. These initiatives, so far not analysed scientifically, vary in terms of the issues addressed, actions employed, and the local actors involved. In the paper we use a data base of 274 such initiatives to explore their manifestation, actors involved, main postulates, and the responses of forest managers. Based on this, we explored whether these initiatives pose challenges to the traditional forest management and, if so, what kind. We imply that the growth of bottom-up initiatives indicates a growing diversity of beliefs and values regarding forests and the increasing determination of local people to impact local environmental decisions. Furthermore, informed by the institutional theory, we argue that the growth of local initiatives, particularly during and after Covid-19 pandemics, suggests the eroding legitimacy of dominant rules and discourses. This process is particularly visible in sub-urban forests, which are increasingly seen through a ‘well-being discourse’ that highlights cultural, regulative and supportive functions of forests, while putting less emphasis on provisioning functions. We also identify a networking trend among the initiatives that unifies their discursive background and enhances their influence at the national level. Therefore, local activists can be seen as a new advocacy group in the Polish forest policy subsystem. In response to local demands public forest administration has introduced institutional changes enhancing participation but their impact is still to be assessed. We recommend establishing a monitoring programme to track new participatory practices and to identify and promote best practices.

Laboratory of Forest Fire Protection – 60 Years of Research in the Field of Forest Fire Protection

Abstract On 1 April 1963, the Department of Forest Fire Protection was established at the Forest Research Institute, which resulted from the need to develop scientific and organisational bases for building a forest fire protection system that would effectively minimise the growing fire hazard of Polish forests. The Department began its activities by developing a programme that took into account both the immediate but urgent needs of the forestry and the anticipated directions of research. Over the course of 60 years, more than 350 research reports were produced. Among the achievements that have influenced the currently functioning forest fire protection system in Poland there are: the method of forest fire risk assessment, forest fire risk prediction, the creation of fire risk monitoring based on a network of forest meteorological measuring points, the development of forest fuel models, the extensive use of aircraft to detect and extinguish forest fires, the conduct of the first studies on the possibility of using television cameras to detect forest fires, the operation of the National Forest Fire Information System, the purpose of which is to collect data on forest fires and natural non-forest areas, the development of an application for forest fire models and the conduct of the first workshop on controlled heath burn in the country. Among the many projects completed, there were also those dealing with the evaluation and suitability of equipment and chemicals for extinguishing forest fires.

The Forest Fund as an instrument for addressing budget deficit in Polish forest districts

Motives: The forest fund was established to ensure the financial stability of forest districts whose operations are financed by the State Forests National Forest Holding in Poland. However, the main role of the forest fund is to distribute funds from high-income forest districts to districts reporting a budget deficit. Aim: The purpose of this paper was to analyse and evaluate the model of managing forest fund resources in view of the provisions of the applicable legal regulations. Results: Between 2013 and 2020, the allocation of funds to forest districts reporting losses did not contribute to fair and rational distribution of resources, nor did it eliminate differences in the financial performance of forest districts operating under various environmental and economic conditions and implementing nature promotion and social education activities. The mechanism by which timber sales (operating costs that reduce profit) can be deducted from the forest fund raises serious doubt. Districts that benefit from such write-offs can program the amount of deductions in the forest fund. The above violates the principle of tax equality which states that tax laws should be applied in an identical manner to all taxpayers. A decrease in profits posted by forest districts reduces the central government’s revenues in virtue of the taxes paid by the State Forests.

Feasibility of Low-Cost LiDAR Scanner Implementation in Forest Sampling Techniques

Despite the growing impact of remote sensing technology in forest inventories globally, there is a continuous need for ground measurements on sample plots. Even though the newest volume assessment methodology requires fewer sample plots, the accuracy of ground-recorded data influences the final accuracy of forest stand modeling. Therefore, effective and economically justified tools are in the continuous interest of foresters. In the presented research, a consumer-grade light detection and ranging (LiDAR) sensor mounted on iPad was used for forest inventory sample plot data collection—including tree location and diameter breast height. In contrast to other similar research, feasibility and user-friendliness were also documented and emphasized. The study was conducted in 63 real sample plots used for the inventory of Polish forests. In total, 776 trees were scanned in 3 types of forest stands: pine, birch, and oak. The root mean square error was 0.28 m for tree locations and 0.06 m for diameter breast height. Various additional analyses were performed to describe the usage of an iPad in tree inventories. It was contended that low-cost LiDAR scanners might be successfully used in real forest conditions and can be considered a reliable and easy-to-implement tool in forest inventory measurements.

Forest Sustainability: A Force to Recon with in the Phase of Global Environmental Challenges

We live in a moment where so many unimaginable things are happening simultaneously. The most natural formation in our climatic and geological zone today is the forests. They are vital component of ecological stability, continuity of life, landscape, and balance of impurities, subsequently checking ecological dilapidation. Forests, as a type of land use, permit biological production with a market worth and assist with shaping the quality of human life and existence. Poland's timber assets have been consistently expanding, their volume remains at 2.5 billion m3 of gross merchantable lumber. Toward the finish of 2010, Poland's woodland cover estimated by the global appraisal standard added up to 30.4% and was below the European normal (32.2%, except the Russian Organization). Over the years, forests covered practically the entire area of Poland. Due to socio-economic development, however, the forest cover remained at 40%toward the end of the 18th century but dropped to 20.8% by 1945. This cycle was switched during 1945-1970 when nearly a million hectares of land was afforested, which expanded the forest cover to 27.0%. The figure has since then been fluctuating, at the end of 2014 forest area covered 30.7% and today, It 31%. This review evaluates the state of Polish forests in the past, present and suggests a strategy for the way forward through diverse means of sustainable management.

The Effect of the Tree Dieback Process on the Mechanical Properties of Pine (Pinus sylvestris L.) Wood

As a result of the progressing climate changes, there is an increase in the volume of pine deadwood harvested each year from Polish forests. Its presence is an important part of the forest ecosystem; however, there are some indications that the material obtained from dying trees can be characterized by lower quality and properties. Taking into account the growing issue of tree dieback, the volume of pine wood annually harvested in Poland, and the importance of wooden products from an economic standpoint, preliminary research aimed at recognizing the process and its effect on the mechanical properties was conducted. Model trees in Brzeg Forest District were selected based on the crown defoliation. The properties of wood obtained from trees representing three different categories of soundness were determined according to the relevant standards. Based on the results of density, modulus of elasticity, bending strength, and compressive strength, it was found that there were statistically significant differences in wood quality depending on the condition of the tree. The results were particularly interesting in the case of compressing strength, where a healthy tree of lower density showed a similar strength to a dying tree with a much higher density.

The role of socialisation of the forest management system in Poland in the face of the need to mitigate climate change

Abstract Climate change will have a significant impact on forests as most of the factors determining their condition are modified by the effects of the climate change process. Some of these effects are a change in the distribution and amount of precipitation, an increase in the frequency of extreme meteorological phenomena, including hurricane winds, temperature distribution, or a change in the length of the growing season. In order to maintain the productivity of Polish forests and the range of ecosystem services they provide, the forestry sector will have to adapt to these changes. However, forestry will also have to take a part in holding back climate change. Achieving climate neutrality by mid-21st century and ensuring a 55% reduction in greenhouse gas emissions by 2030 will not be possible without using the ability of forests to absorb and permanently store carbon. Polish forestry seems to be insufficiently prepared for the challenges ahead. A new national forestry policy has not been developed in the past twenty years, which results, inter alia, in a lack of any clear indication of the role of Polish forests in climate protection. Adaptation to the effects of climate change is hampered by the lack of up-to-date, detailed scenarios of how this process will affect the climate factors in Poland. Particularly dangerous, in light of the role of forests in climate protection, is a significant decrease in the afforested area, which in turn leads to a reduction in the amount of carbon absorbed by them. Another obstacle to implementation of effective measures may be the growing disparity between the current forestry practice and social expectations, as well as a low degree of willingness from the State Forests to cooperate with stakeholders who present different opinions on how to conduct forest management. This obstacle may lead to disputes about the management of Polish forests at the European Union level and rulings of the Court of Justice of the European Union. The conducted analyses showed that cooperation with a wide range of stakeholders will be the basic condition for the inclusion of Polish forests in the implementation of climate policy objectives on a greater scale. It should help define the role of this sector in this process, implement the necessary adaptative and climate protection measures, and support activities aimed at acquiring new land for afforestation.

Spectral Indices as a Tool to Assess the Moisture Status of Forest Habitats

Measurement of water content in forest habitats is considered essential in ecological research on forests, climate change, or forest management. In the traditional forest habitat classification, two systems of habitat conditions analysis are found: single factor and multifactor methods. Both are laborious and therefore costly. Remote sensing methods provide a low-cost alternative. The aim of the presented study was to find the relationship between the spectral indices obtained from satellite images and the forest habitats moisture indices used traditionally in the Polish forest habitats classification. The scientific hypothesis of the research is as follows: it is possible to assess the variation in the humidity of forest habitats on the basis of spectral indices. Using advanced geographic information system (GIS) technology, 923 research plots were tested, where habitat studies performed with the traditional methods were compared with the analysis of 191 spectral indices calculated for Sentinel-2 image data. The normalized difference vegetation index (NDVI) has proved to be the most useful to the assessing of moisture of forest habitats. The ranking of the most correlated indices was calculated as Eintg—the product of the absolute value of the slope and the mean square error complement, and for the top five indices was as follows: NDVI = 0.248619, EXG = 0.242112, OSAVI = 0.239412, DSWI-4 = 0.238784, and RDVI = 0.236995. The results also highlight the impact of water reservoirs on the humidity and trophicity of forest habitats, showing a decrease in the fertility of habitats with an increase in distance from the water reservoir. The results of the study can be used to preparing maps of the diversity of forest types, especially in hard-to-reach places, as well as to assess changes in the moisture status of habitats, which may be useful, for example, in the assessment of the fire risk of forest habitats. We have proved that NDVI can be used in applications for which it was not originally designed.

Was it really different? COVID-19-pandemic period in long-term recreation monitoring - A case study from Polish forests.

The COVID -19 pandemic posed serious challenge for securing public health worldwide. Public health preparedness and restrictions put in place impacted many aspects of human life, including recreational activities and access to outdoor recreational destinations. Green spaces have become one of the few sources of resilience during the coronavirus crisis due to their restorative effects on psychophysical health and community well-being. The aim of this study is to analyse the impact of the COVID -19 pandemic on forest visitation. The results are based upon long-term visitor data acquired via pyroelectric sensors (Eco-Counter) in three forest districts located in Poland (Browsk, Gdansk & Kozienice Forest Districts). The analysis covers the period between January 01, 2019 and December 31, 2020 and the results confirm changes in recreational use in the studied forest areas during the pandemic compared to the preceding year. However, observed changes in forest visitation vary by pandemic period and study area. The ban on access to forest areas significantly reduced the number of forest visits in all studied areas. The number of visits to sub-urban forests (Gdansk Forest District) and to remote nature-based tourist destinations (Browsk Forest District) increased in the later pandemic periods, especially in the summer months of 2020, while it remained the same in a popular nearby recreation area: Kozienice Forest District. There were only minor temporal shifts in the distribution of weekly and daily visits. The results are important for public health preparedness planning in crisis situations and for provisioning conditions supporting societal health and well-being. Objective data on forest visits are necessary for successful management of forest areas and surrounding amenities. More cross-sector collaboration and public participation would be desirable to create sustainable, resilient, and liveable spaces for the society.Management Implications•Long-term visitation monitoring is crucial for successful management of outdoor recreation destinations and their catchment areas.•Objective numbers concerning forest visitation from the pre-pandemic and COVID-19 pandemic period allow observing trends and making fact-based management decisions during period of crisis.•Changes in the investigated three forest study areas in Poland were not homogenous, which implies the necessity of systematic visitor monitoring in multiple destinations, in order to cover different types of forest areas and also local diversity in recreational use.•More intersectoral, interdisciplinary and transdisciplinary exchange would be desirable to better integrate existing on-site visitor monitoring data into decision making processes related to forest management, urban planning, transportation, tourism and public health.

Skiing Tourist Activity in Polish Forests

The aim of the research was to determine the frequency, motifs and barriers to practicing the hiking ski tourism in Polish forests. Recreational activity in this respect was analyzed in terms of the occupational status of Poles. The research used an original questionnaire carried out among 900 Poles practicing hiking ski tourism, among which 859 respondents were taken into account in statistical calculations after verification. Physically working Poles and freelancers most often use hiking ski tourism in Polish forests. The most important motives for practicing this activity are: contact with nature, clean air, taking care of physical condition, relaxation and taking care of mental health. The largest barriers are: expensive ski equipment, lack of snow, lack of free time, few ski trails, unfavorable weather conditions, short daylight, large distance to the trail, insufficient infrastructure on the forest ski trails and lack of organized forms of hiking ski tourism. Tourist routes and trails are an important place for skiing tourism for Poles due to the proper microclimate, clean air and contact with nature.

Technical methods of preventing and limiting the effects of natural disasters in Polish forests caused by severe weather conditions

Technical methods of preventing and limiting the effects of natural disasters in Polish forests caused by severe weather conditions