In 2024, record high air temperatures were observed in Central and Eastern Europe. Combined with unfavorable precipitation conditions, this caused serious disturbances in forest water resources, which occurred mainly in 2025. These disturbances affected both groundwater and surface water. Groundwater levels reached their lowest points in all forest habitats (fresh, moist, and swampy), indicating a shift in moisture type by one class and reduced water availability for the tree stands. Surface waters in small catchments did not experience any peaks or inundation throughout 2025. In particular, the absence of spring floods severely limited the water supply to riparian habitats. Surface runoff also decreased to about 15% of normal levels. This led to the drying up of significant sections of watercourses, transforming them into intermittent watercourses, and to a substantial reduction in the supply of water to reservoirs on watercourses, resulting in a marked decrease in the amount of water retained and, in some cases, even their complete drying up. Extraordinary phenomena in 2024-2025 may become normal in Eastern Poland in the future.

Beaver ponds create unique aquatic ecosystems. The activities of beavers promote the growth of biodiversity and enhance water purification but can also lead to the accumulation of harmful pollutants. Water retention in beaver ponds leads to the growth of bacteria and other microorganisms that play a key role in biogeochemical cycling. Stagnation of water can lead to anaerobic conditions and the formation of toxic substances that can limit benthic diversity. Beavers play an important role in shaping these environments, and the study of bacteria in beaver ponds helps to better understand their impact on aquatic ecosystems. A 16S rRNA sequencing revealed the presence of 365 bacterial species in water and sediments, identified in 174 genera and 83 families, 62 of which are present in water and sediments. The main indicator family for the bacteria identified in water samples was the family Xantonomodaceae, while for the sediments, it was the family Planococcaceae. The occurrence of bacterial families was similar in both substrates, but sediments showed greater variability compared to water. The statistical differences in the distribution of families between water and sediments were confirmed by a paired sample T test.IMPORTANCEThis study helps us to understand how beavers shape their environment and influence water quality. By building dams, beavers create wetlands that change the flow of water and influence which bacteria thrive there. Some of these bacteria contribute to the natural purification of water, while others can pose a threat to biodiversity. Knowing how the activities of beavers affect microbial life is important to protect ecosystems and ensure water safety. The results can help scientists, conservationists, and policy makers make better decisions about beaver conservation and water management. By understanding the role of bacteria in these wetlands, we can predict both the benefits-such as improved natural filtration and potential risks-such as the spread of harmful bacteria. This research also provides insights into how nature itself filters and purifies water, which could lead to sustainable water management strategies in the future.

Groundwater is the primary water source for ecosystems, and so changes in groundwater levels, if directional and constant, can cause changes in vegetation and habitat characters. In Białowieża National Park, a significant decline in the water table was observed at the beginning of the 20th century. The question therefore arose as to whether the changes that occurred at that time were permanent. A second question was whether the negative trend would continue so clearly in the following years. The study is based on measurements from 1985 to 2005 and 2022 to 2023 taken in the same monitoring wells. Complete data were collected from 21 monitoring wells. An analysis of groundwater levels between 1985 and 2005 showed an average decline of 0.08 m/10 years in swamp habitats, 0.11 m/10 years in moist habitats, and 0.21 m/10 years in fresh habitats. The measurements in 2022 and 2023 showed that the trend of falling water levels had slowed down in almost the entire study area, with water levels in recent years being similar to those at the beginning of the century. This was also confirmed by comparing years with similar precipitation: 2022 with 1986, and 2002, 2004, and 2023 with 1999. This was due to the higher precipitation after 2005. In the period of 2006–2023, precipitation in the hydrological years was on average 60 mm higher than in the period of 1985–2005. Despite the clear trend toward rising air temperatures, the higher precipitation compensated for the higher evapotranspiration. However, one area showed a systematic decrease in water levels. This occurred at the watershed of the two largest rivers in the Białowieża Forest. The findings indicate that watershed areas are most vulnerable to lowering the groundwater level due to climatic warming.

Ponds created by beavers represent unique aquatic ecosystems that influence hydrological, chemical and biological conditions, including the microbiology of the water. The activity of these animals promotes biodiversity and water purification processes, but can also lead to the accumulation of pollutants. Water retention in beaver ponds promotes the development of bacteria and other microorganisms that play an important role in biogeochemical cycles. Long-term water stagnation can lead to anaerobic conditions and the formation of toxic compounds, which in turn can limit the diversity of benthic organisms. Beavers play a key role in shaping these habitats, and microbiological studies of their reservoirs provide a better understanding of their impact on aquatic ecosystems, self-purification processes and potential biological threats. Metagenomic analysis revealed the presence of 365 bacterial species in water and sediment samples, belonging to 174 genera and 83 families. 83 operational taxonomic units (OTUs) were identified, 62 of which were present in both water and sediments. Although the overall OTU composition was similar in both environments, greater variability was observed in the sediments. The statistical differences in OTU distribution between water and sediments were confirmed using the Wilcoxon test.

Bathymetry, the science concerned with measuring the depth of water bodies and reservoirs and representing them graphically in the form of bathymetric maps, sections, and three-dimensional numerical models, is used in monitoring dynamic, socio-economically important areas. Available methods include satellite bathymetry, sonars or echo sounders. Satellite bathymetry is unsuitable for most inland reservoirs because its turbid waters suppress electromagnetic radiation. For small, inaccessible reservoirs, sonar and echo sounders are most commonly used as measurement methods. This manuscript describes bathymetric surveys conducted using a low-cost method based on the echo sounder Lowrance Hook 5. The bathymetric method was combined with a digital terrain model (DTM) enhanced by real-time kinematic (RTK) measurements. The analysis of the selected reservoir, located in the middle of the forest, shows that the method used fully meets the assumed objectives and can be successfully applied for the purposes of water reservoir used by forest services.

Climate change is leading to an increase in the frequency and intensity of droughts, posing a real threat to forest stands, for which lack of available soil water may limit growth and health. Many authors indicate that properly conducted forest management may contribute to increasing the resistance of stands to drought stress. One of the possibilities offered by forest management is the use of an appropriate thinning method. The aim of this publication is to show how different thinning methods affect soil water resources and the occurrence of soil drought. Model studies of the variability of soil water resources were carried out on the experimental plot in Kozienice Forest District, using meteorological data from 2011-2020 for 9 thinning treatments. These studies demonstrate that in the fresh conifer forest site, the most favourable conditions are created by moderate selective thinning, as well as a low level of thinning that does not permanently disrupt the canopy.

Drought in the forest is not only a prolonged state of water shortage, but also an occasion where interactions between plants and fungi are affected. Water efficiency accelerates a range of pathologies in interactions between organisms, influencing the ecosystems and their interacting biological components. This study focuses on the role of mycorrhizal and endophyte fungi in alleviating the effects of soil water shortage, and on the impact of their altered activity during drought on the health of trees. The issues presented here show the fundamental role of the mycorrhizal mycelium and the mechanism of water transport to the plant in the course of other phenomena (withering, pathogenesis, endophytes biology) that occur in trees under influence of drought, with particular attention on managed coniferous stands. Conclusions resulting from published information on this topic emphasize the negative impact of soil moisture deficiency on the ectomycorrhizal fungi functioning and, in contrast, on the promotion of the growth of some endophytes, pathogens and hemi-parasitic mistletoes (Viscum spp.).

This study aimed to simulate oak and beech forest growth under various scenarios of climate change and to evaluate how the forest response depends on site properties and particularly on stand characteristics using the individual process-based model HETEROFOR. First, this model was evaluated on a wide range of site conditions. We used data from 36 long-term forest monitoring plots to initialize, calibrate, and evaluate HETEROFOR. This evaluation showed that HETEROFOR predicts individual tree radial growth and height increment reasonably well under different growing conditions when evaluated on independent sites. In our simulations under constant CO2 concentration ([CO2]cst) for the 2071-2100 period, climate change induced a moderate net primary production (NPP) gain in continental and mountainous zones and no change in the oceanic zone. The NPP changes were negatively affected by air temperature during the vegetation period and by the annual rainfall decrease. To a lower extent, they were influenced by soil extractable water reserve and stand characteristics. These NPP changes were positively affected by longer vegetation periods and negatively by drought for beech and larger autotrophic respiration costs for oak. For both species, the NPP gain was much larger with rising CO2 concentration ([CO2]var) mainly due to the CO2 fertilisation effect. Even if the species composition and structure had a limited influence on the forest response to climate change, they explained a large part of the NPP variability (44% and 34% for [CO2]cst and [CO2]var, respectively) compared to the climate change scenario (5% and 29%) and the inter-annual climate variability (20% and 16%). This gives the forester the possibility to act on the productivity of broadleaved forests and prepare them for possible adverse effects of climate change by reinforcing their resilience.

Forests play one of the most important roles in the hydrological cycle; as a result, knowledge about the water relations in forest areas should be of great importance in the context of global change. In Poland, the level of groundwater in forest areas has been decreasing for several decades, which negatively affects forest stands. To prevent this, activities have been carried out to increase water resources. Therefore, there is a need to develop a method for prioritizing the locations of retention investment projects. While searching for simple methods to achieve this goal, it was assumed that retention facilities should be located first in the partial catchments with the greatest possible retention capacities. This value, which is called the potential retention of the catchment, can be calculated using the CN parameter, which is used in the soil conservation service–curve number (SCS–CN) method. The CN parameter contains information on the type of land cover, the type of soil, and the moisture content. The source of the obtained land-use data was the Corine Land Cover (CLC) database, which was developed by the European Environment Agency for the area of the European Union. The analyses were carried out on the forest catchment of the Łutownia River, which is located in the Białowieża Primeval Forest.

Climate change affects many elements of the natural environment and strongly influences the hydrology of rivers. In this study, we investigated trends in temperature, precipitation, and the water level characteristics in the small lowland river Lebiedzianka in northeastern Poland for the 50 year long period of observations (1970–2019). We recorded significant increase in air temperature and potential evapotranspiration, but the annual sum of precipitation did not change. We found significant downward trends for annual runoff. The results show a steady decrease in the number of days with high water levels. These changes caused by global warming will have a strong impact on forest habitats associated with high water levels and periodic inundations. In Europe, many of these precious habitats are protected under the Natura 2000 network as sites of high heritage value; nevertheless, their sustainability will be at risk due to the ongoing changes in their hydrological regime.

The Bialowieza Primeval Forest (BF) is one of the well-known forests in Central Europe. The most common tree species in BF was Norway spruce (Picea abies (L.) H. Karst), comprising 26%. However, a mass dieback of spruce has occurred during recent years. The spruce dieback in Bialowieza Forest is directly caused by the spruce bark beetle. However, the mass appearance of this pest can be a consequence of global warming and drought. Changes in air temperature were presented and drought indices were calculated as follows: standardized precipitation index, Palmer drought severity index, climatic water balance and soil water storage deficit. The warming of the climate of Bialowieza from 1950 to 2015 is comparable to that observed throughout central Europe. The temperature increased by 1.27 °C. The occurrence of drought from 1950 to 1966 and from 1985 to 2015 had a similar frequency. From 1963 to 1966, the volume of removed deadwood from the managed part of Bialowieza Forest was 27 thousand m3 but from 2012 to 2016, the volume was more than one million m3.

Raised bogs dominated by the vegetation association Ledo - Sphagnetum magellanici Sukopp 1959 em. Neuhäusl 1969 are a valuable and ecologically important plant community that occurs in Central Europe. They develop in impervious depressions with precipitation as the only water source, and are particularly sensitive to drainage, climate change, eutrophication and overgrowing by trees and shrubs. The high pressure of threat justifies taking protective measures. This research focused on the effects of the removal of birch from two bogs, which were dominated by two birch species ( Betula pubescens , B. pendula ) and also included stands of Scots pine ( Pinus sylvestris ); the bogs are located in northeastern Poland and showed signs of drying. The trees were removed in early spring 2008. To capture the response to tree cutting, vegetation monitoring was performed for 7 years. The results were compared to pre-cutting environmental conditions (precipitation, temperature, air transpiration). At the first site, which was drained at the beginning of the twentieth century, the ground water level initially decreased; then, from 2010 onwards, the level stabilised and exhibited a negative correlation with the average annual air temperature. While the second site exhibited no significant differences in the ground water table, a correlation with the average annual rainfall was found. At both sites, there was an increase in the coverage of species appropriate for raised bogs, Oxycocco - Sphagnatea Br.-Bl. et R. Tx. 1943, whereas only the second site had significant coverage of these species. These actions improved the habitat conditions and initiated the process of raised bog restoration at that site because Oxycocco - Sphagnatea species cover and frequency increased.

The paper reviews the projected impacts of climate change on forest stands in relation to the local conditions in Poland. One of the most urgent challenges for foresters in Central Europe is adapting the stands to the effects of climate change. Warming of the climate will lead to limited soil water availability to forest stands and to the increasing risk of long-term drought. The threat of soil drought depends on the meteorological conditions, but also on the ability of the soil to retain water. In Poland, forests grow mainly on poor sandy soils with low water retention capacity. Additionally, relatively small precipitation less than 600 mm per year occurs in most areas of Poland and long-term periods without precipitation are more and more frequent. In 2015, drought affected large area of the country. The forests are severely exposed to the stress of drought caused by climate change. Polish forests ared comprised of rather small number of tree species. It is considered that drought will threaten the biodiversity of forests. Of all tree species in Poland, Scots pine has the best ability to survive drought and therefore it can be expected that the share of pine in the stands will increase in the future. Pedunculate oak, which is the most common deciduous species in Poland, may retreat because of its vulnerability to drought. Forest management should aim at the adaptation of stands to climate change. The proportion of species resistant to drought stress should be increased. The thinning of forest stand can help to reduce damage. A smaller number of trees contributes to lower interception and consequently increases the amount of water reaching the soil. In some opinions the reduction in the number of trees and the density of the canopy reduces evapotranspiration, but not in Scots pine stands.

Wetlands, along with their biodiversity, have been subject to major threats worldwide. This was the reason to undertake restoration measures in order to cease their deterioration and loss of natural values. Controlled water table management in irrigation channels was said to be vital for maintenance of proper ground water levels on wetland areas that are favourable for wet, low-productive meadows state. We aimed to demonstrate this on a "developing wetland" area, which is part of Calowanie Peatland, consisting of sandy soils. The possible increase in channel water table caused that on 29% of research area (171.6 ha) the ground water depth ranged from 0.3 to 0.45 m., which was found to be indispensable for the development of wet meadows, according to the adopted hydrologic criteria. The evidence was found through ground water modeling and assuming criteria for so-called "hydrologic uniformity", which were still subject to discussions in the literature and herein.

Management for sustainable river valleys requires balancing their natural values against the need for agricultural and recreational development on surrounding lands. The Southern Całowanie Peatland near the city of Warsaw sits on a sandy terrace and has well preserved Carex and Molinia stands existing in part of the area, especially where water tables are less than 1.5 m below the surface. The existing drainage network in this southern part has been poorly maintained and could be reestablished to help raise water levels for restoration of the peatland. Modflow was used to look at influence of drainage channel water levels on the overall water table height in the area. By raising water levels in the drainage system by 0.5 m it was found that 29% of the area would become suitable for increasing Carex and Molinia communities.

Because of more and more frequent droughts and observed climate changes, infrastructural investments in forest are at present targeted at increasing water resources, which is realized under the so-called smallscale water retention. Forest reservoirs located in Pomorze Forest District in the north-eastern Poland, which was selected for research, fits this trend. The constructed facilities were to reduce the indications of habitat dryness and to improve fire prevention. The investment consisting in building 14 objects of water melioration has changed water conditions in the research area. 12 oak dams, stone weir and an earth pond for amphibians have been built. As a result of the realized investment, the level of water has increased and problems with periodical flooding of forest habitats have occurred. At the beginning of 2012, observational and measuring wells were created to monitor all occurring changes of the soil water table. The received data can be useful in clarifying the causes for flooding and in possible suggestions to improve the existing water conditions. This paper presents the analysis of the influence of realized investments on the changes in the level of groundwater between 2012 and 2014.

Vegetation cover affects the amount of precipitation, its chemical composition and its spatial distribution, and this may have implications for the distribution of water, nutrients and contaminants in the subsurface soil layer. The aim of this study was a detailed diagnosis of the spatio-temporal variability in the amount of throughfall (TF) and its chemical components in a 72-year-old pine stand with an admixture of oak and birch. The spatio-temporal variability in the amount of TF water and the concentrations and deposition of the TF components were studied. The components that are exchanged in canopy (H+, K, Mg, Mn, DOC, NH4+) were more variable than the components whose TF deposition is the sum of wet and dry (including gas) deposition and which undergo little exchange in the canopy (Na, CI, NO3-, SO42-). The spatial distribution was temporally stable, especially during the leafed period. This study also investigated the effect of the selected pine stand characteristics on the spatial distribution of throughfall and its chemical components; the characteristics included leaf area index (LAI), the proportion of the canopy covered by deciduous species and pine crowns, and the distance from the nearest tree trunk. The LAI measured during the leafed and leafless periods had the greatest effect on the spatial distribution of TF deposition. No relationship was found between the spatial distribution of the amount of TF water and (i) the LAI; (ii) the canopy cover of broadleaf species or pines; or (iii) the distance from the trunks. (C) 2016 Elsevier B.V. All rights reserved.