Abstract: Knowledge of costs, their structure, and change dynamics are the basis for decision making by forest managers. Furthermore, an understanding of the factors affecting the expenses borne by forest holdings influences forest resource management and is of importance in improving the profitability of silviculture. The objective of this study was to understand the relationships between unit costs of forest management and the attributes of forest districts distinguished on the basis of natural and economic conditions (e.g., forest site type, compatibility between stand species composition and forest site type, silvicultural system, and fragmentation of forest complexes, etc.). This was accomplished using unit costs of forest management in 82 forest districts belonging to the Regional Directorates of State Forests in Białystok, Krosno, and Lublin (eastern Poland) in the years 2005−2009 and 2015−2019. Based on regression analyses, the main forestry activities significantly affecting costs were found to be forest regeneration, tending, protection, investment in infrastructure, as well as timber harvesting and skidding costs. Regeneration costs increased with the degree of management difficulty, while the costs of forest tending were significantly higher in districts managing mountain sites, especially those with fir−beech stands. Outlays on forest protection were significantly greater where the clearcutting system was used and in forest districts with compact forest complexes. Significantly greater bunching and extraction costs were reported by forest districts in mountain areas, where selection silvicultural systems predominated. Cost optimization of forest management can improve the net income of forest holdings, especially in the face of increasing ‘ecologisation’ pressures in forestry and the mounting opportunity costs of nature conservation and biodiversity protection in forests.
Key words: economics of forestry, principal activity costs, costs analysis, natural factors, economic factors

Abstract: Woodpeckers Picinae are recognised as important keystone species in forest ecosystems because many species of animals find shelters or breeding places in cavities woodpeckers excavate. We evaluated the nest tree preference of a European species, the grey−headed woodpecker (GHW), Picus canus Gmel., in the semi−boreal Augustów Forest in northeast Poland, an extensive forest complex covering 114 000 ha, dominated by fresh and mixed fresh coniferous forest. Nest trees made by the GHW were sought within areas identified by the playback of territorial vocalisations and drumming in spring. We found 35 cavities on 31 trees. Twenty−one of these cavities were made in trees of poor health and 14 in dead trees. Only deciduous trees were selected for excavation, specifically aspen Populus tremula L., silver birch Betula pendula Roth., and black alder Alnus glutinosa (L.) Gaertn. Alder was chosen most frequently, but according to Ivlev’s electivity index, the most preferred species was aspen. We found important differences between forest sites used by the grey−headed woodpecker. Most cavities were found in alder forest, with fewer in broadleaf fertile forest, mixed broadleaf forest, and mixed pine forest. Cavity trees were on average 83−years−old (ranging from 45 to 127 years). The average diameter of cavity trees used by the grey−headed woodpecker was 47.4 cm (ranging from 30 to 67 cm), of which the most numerous were trees with diameters between 30 and 40 cm. All cavities were excavated in trunks. Cavity entrances were located at an average height of 8.2 metres (4.5−14 m). The mean height of the first branch on excavated trees was 10.2 metres above ground and was higher than the average height of the cavity entrance. Cavities in birch were placed higher than in other tree species. A linear mixed model explaining cavity height above ground showed important effects for first branch height, which allows for higher placement of the cavities, and tree species, because cavities in aspen and alder were excavated significantly lower than in birch. The GHW preferentially placed cavity entrances on southern and eastern exposures, with entrance aspect related to cavity height above the ground. Our results underline the importance of aspen to GHW and indicate the need to maintain this tree species in managed forests.
Key words: aspen, cavity trees, cavity entrance orientation, habitat preferences, Picus canus

Abstract: The research was conducted in July 2018 in the Barania Góra massif in the Silesian Beskids. Water samples were taken from the springs and watercourses of the Biała Wisełka and Czarna Wisełka Rivers, comprising the headwaters of the largest river in Poland, the Vistula. A total of 69 water samples was collected: 15 from the springs and 20 from the watercourses of the Biała Wisełka; 11 from the springs and 23 from the watercourses of the Czarna Wisełka. Water samples were collected mainly within the Barania Góra nature reserve. The Reserve was established in 1953 to protect and observe the processes taking place in the various climatic and vegetation zones of the Silesian Beskids and to preserve the spring area of the Vistula in its natural state. Laboratory work was performed at the Laboratory of Geochemistry of the Forest Environment and Land Intended for Reclamation of the University of Agriculture in Krakow. In the water samples collected, pH (Elmetron CX−741 multifunction instrument), conductivity (Elmetron CPC−551 conductometer) and concentrations of Ca²⁺, Mg²⁺, SO₄^2–, Cl^–, NH₄⁺, NO₃^–, HCO₃^–, Na⁺, and K⁺ ions were measured (DIONEX 5000 chromatograph). The research aims to explore the differences in the physicochemical parameters and the water quality of the Vistula spring area, including the differences between the Biała Wisełka and Czarna Wisełka supply areas. The spring areas of Czarna Wisełka and Biała Wisełka differ in geological structure, soil type and subtype, topography, exposure, forest habitat type, and tree−stand species composition. Additionally, the spring area of Czarna Wisełka and the upper portions of the spring area of Biała Wisełka were affected by the defeat of the dieback of spruce stands. These environmental factors are apparent in the different chemical compositions of the watercourses and springs of the two catchments. Lower pH, conductivity, and concentrations of Ca²⁺, Mg²⁺, Cl^–, NH₄⁺, NO₃^–, HCO₃^–, Na⁺, and K⁺ ions in both springs and watercourses were recorded in the Czarna Wisełka catchment.
Key words: forest catchments, water chemistry, spruce dieback, Beskidy Mts.

Abstract: Białowieża Forest is an extremely valuable and diverse area in which two approaches to nature conservation are used. On the one hand is passive conservation, a conservative approach whose purpose is to protect natural processes by reducing human intervention. On the other is active conservation, which aims to take steps to protect nature, including by maintaining areas in certain successional stages. Dracocephalum ruyschiana L., a Eurasian continental species with a fragmented distribution, undoubtedly requires active conservation. Its contiguous range extends from the Eastern European Plain to Eastern Siberia. It is found in scattered European sites from the southern Scandinavian Peninsula to the Alps, the Balkan Peninsula, and the Caucasus, and as far the west as the Pyrenees. In Poland, D. ruyschiana has been known to occur in about 50 locations. Most locations were in north−eastern Poland, as far west as the valleys of the Noteć and the lower and middle Vistula rivers. Unfortunately, at the moment, many of these sites were not identified for a hundred years or more. In recent years, D. ruyschiana has been found mainly in north−eastern Poland (Knyszyn Forest, Biebrza Valley, and Wigry National Park). D. ruyschiana was considered extinct in Białowieża Forest until its recent discovery. In Poland, D. ruyschiana is most often found in thermophilic edge communities of the Trifolio−Geranietea class, on exposed sites and in forest gaps, and in fresh mixed broadleaved forest habitats, where vegetation belongs to the thermophilous oak forest, Potentillo albae−Quercetum. The new locality of D. ruyschiana was discovered in the Hajnówka Forest District in Białowieża Forest. The new stand is located in an area of active forest conservation in fresh mixed broadleaved forest (LMśw), oak−hornbeam forest community (9170). D. ruyschiana is located in a 0.35 ha second−growth forest, established in 2017 in a gap created as a result of sanitary cuts carried out in 2012−2015 related to an outbreak of spruce bark beetle. The specimen of northern dragonhead had a height of about 40 cm with 15 generative shoots and 1 vegetative shoot.
Key words: active conservation, critically endangered, flora, Hajnówka Forest District, Northern dragonhead

Abstract: Identification and analysis of proliferated cones in conifers has both theoretical and practical significance, particularly in systematic and taxonomic investigations, but also in the study of population and individual variability within a species. Comparative morphological−anatomical studies of reproductive organs can contribute to solving many issues in phylogeny and can identify abnormal phenomena in cone formation. In light of the value of such information, this paper presents the results of monitoring European larch Larix decidua Mill. cone proliferation in Serbia over a 24−year period, with the aim of studying cone apical meristem activity, which usually is limited. Cone proliferation was confirmed by comparative morphological and genetic−physiological analyses of cones from European larch growing in the Arboretum of the Faculty of Forestry in Belgrade, at ages of 41, 51, and 65 years old.
Key words: genotype, morphogenetic control, teratological phenomenon

Abstract: This study evaluates the effects of season and the length of service of chainsaw operators on the ability to achieve felling guidelines based on Occupational Health and Safety Regulations. The study consisted of measurements of stump cuts on three tree felling plots in two seasons: winter (in the presence of snow cover) and spring. In total, 90 stumps, 30 in each plot, were measured. Plots were similar in species composition, age, and forest habitat type, while variability in the study resulted from the age and occupational experience of saw operators. In addition, escape routes were assessed to evaluate whether they were in accordance with forest management Occupational Health and Safety Regulations. Season had no effect on stump attributes except for stump height, for which there was a significantly greater number of excessively high stumps in winter than in spring. More experienced saw operators were more competent in making precision saw cuts (e.g., depth of the notch cut, width of the hinge) and made fewer errors than a less experienced worker. In contrast, all escape routes prepared by a less experienced saw operator were prepared correctly, while about 8% of the escape routes prepared by longer−serving workers were incorrect. Since the preparation of escape routes depends only on compliance with Occupational Health and Safety Regulations and does not require special professional expertise, incorrect escape routes prepared by longer−serving saw operators probably reflect a disregard for risks caused by not following prescribed safety protocols.
Key words: saw operator's work experience, season of the year, stump attributes, tree felling