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The Świnia Góra nature reserve (51°03'24" N, 20°42'21" E) with an area of 51 ha is one of the few forests in Poland operating under strict protection for many decades (formally since 1953). Its stands are dominated by fir and beech – two species that are currently showing high growth dynamics and are important in the face of expected climate change. The purpose of the study was to: (1) investigate the state of the forest regeneration layer of the reserve, (2) relate the characteristics of the tree regeneration to certain characteristics of the structure of the canopy layer, and (3) describe, using selected characteristics, the competition between young firs and beeches. The empirical data was collected on 95 concentric sample plots made up of three areas of size related to the dimensions of trees. The average density of trees of the young generation on the whole site was 7226 ±2383 ind./ha (±33.0%) and the sum of their height was 6552 ±1046 m/ha (±16.0%). There were 14 tree species, the most numerous being silver fir (46 ±9%) and beech (35 ±8%). The species compositions of the regeneration layer and the canopy layer partly differed (Morisita index=0.90). In the regeneration, two numerous species of the canopy layer – larch and pine – were missing. The share of species changed with the dimensions of trees (fig. 2). The density and sum of the height of young trees (fig. 3) and the species composition (fig. 4) did not differ much between stands classified into individual natural developmental phases. The influence of the canopy cover on the sum of the height of the regeneration of trees was more pronounced (fig. 5). Also the species composition of the young generation of trees changed with the degree of crowns cover, with this relation in the case of small saplings (h=0.3−1.3 m) being different than in the case of large saplings (d=0.1−6.9 cm) (figs. 7 and 6, respectively). For small saplings, the probability that the tree was a fir and not a beech was low (fig. 8). The periodical increment of the length of the leader shoot changed with the height of the tree and the degree of cover by the crowns of the canopy layer, whereas under the same conditions beech grew faster than fir (fig. 9). In the Świnia Góra nature reserve, the fir seedling (h, Sylwan 165 (1): 30-40

Successful tree regeneration is a key process in ensuring forest sustainability and one of the most crucial investments made in silviculture. In the case of silver fir stands, optimum growth performance and stand health are strictly linked to a diverse vertical structure. This structure is usually achieved by natural regeneration and more close���to���nature, complex silvicultural systems. However, there are also stands where silver fir is missing for various historical reasons, and its restoration by artificial regeneration is required. We present results of the application of two planting methods in the Bieszczady Mountains (SE Poland) to convert pure grey alder stands into silver fir dominated mixed stands. Since 2001 in the Cisna Forest District, where a traditional row planting method is often used, a novel, group planting method (which is similar to the oak cluster planting) has also been applied: i) to reduce damage caused by deer, ii) to facilitate weed control, and iii) to promote natural regeneration of additional tree species among groups. We established a grid of 18 sample plots (each plot consisting of 4 groups of 17 seedlings in each) in three circa 20 year���old silver fir stands, as well as 15 plots (15 rows of 16 seedlings in each) representing one traditional stand (row method) in close proximity. For each tree (silver fir or admixed species) we determined the diameter at breast height, the total height and crown base height. We also assessed the silvicultural quality based on the current health status (including fungi and deer damage), as well as crown shape in the vertical and horizontal profile. To quantify the differences in growth performance we used a linear mixed���effects model approach, available in the R Statistics package (nlme). We found that height and diameter growth were higher and more uniform for the row method, but there were no statistical differences in the height of living crown base or tree slenderness. The silvicultural quality was only slightly better when using the row method. The tree species diversity (the number of admixed tree species present and their abundance) was significantly higher in stands regenerated using the group planting method. Therefore, we conclude that the group planting method could be recommended for tree species conversion on eutrophic sites, because it is likely to decrease establishment costs and creates a more diverse tree species composition and vertical structure, although it may lead to slower growth rate of silver fir up to 20 years. Due to this response, we expect higher resilience of such forest stands to the future biotic and abiotic disturbances under observed environmental changes., Sylwan 165 (7): 542-553

The aim of the study was to characterize the state and dynamics of dead wood resources in the stands of the Świnia Góra strict forest reserve, which was excluded from use for a longer period of time (from 1938/1953), and to compare the results with the state and dynamics of living trees resources. The reserve covers 51 hectares of an upland forest in the Świętokrzyska Forest (central Poland). Data was collected in 2000, 2007 and 2014 on 95 systematically distributed 500 m sample plots. The location and dimensions of living trees, standing dead trees (snags, including stumps) and downed trees (logs) on each sample plot were determined and measured. The decay stages of dead wood were estimated using a four−point scale classification. The average volume of dead wood was 198 ±32 m/ha (43 ±8% of living trees) in 2000 and 138 ±17 m/ha (24 ±3%) in 2014 (fig. 1). The ratio of the volume of snags to logs decreased from 30 ±5% in 2000 to 24 ±6% in 2014. Silver fir was the dominant species among both living and dead trees (fig. 2). The share of dead wood volume in decay stages 1 and 2 was the highest among snags, while in stages 2 and 3 – among logs. The number of highly decomposed wood increased in the period 2000−2014 (fig. 3). The decay rate of wood calculated over a 7−year period was more rapid for logs (fig. 4). In the period of 14 years, 119 ±23 m/ha of dead wood underwent a complete decomposition. Volume of trees that died within that period was 59 ±10 m/ha (fig. 5). The complete decomposition of snags amounted to 64 ±10% and logs to 58 ±5% of the initial dead wood volume. The dead wood resources in the investigated period were not balanced: the amount of decayed wood was larger than the amount of wood replenishing the resources. The lack of this balance was due to the lack of the balance of living trees – dead wood resources were insufficiently replenished by trees that had died during analysed 14 years. The dead wood resources at a level of approximately 200−230 m/ha might be balanced via their continuous replenishment by newly died trees in the amount close to the current volume increment., Sylwan 162 (4): 295-304

The size−class growth model is an empirical model applicable for the prediction of the dynamics of natural forest growth. It is based on the following assumptions: (1) changes in the forest condition are determined on the basis of the sum of the changes that take place in individual size classes, (2) the trees in a given class are represented by single average tree, (3) the calculation of the future tree density distribution in size classes (fig. 1) is the main element of the prediction, and (4) the future tree density distribution is estimated on the basis of the initial structure, actual growth and mortality of trees in individual size classes. The aim of the research was to develop a size−class growth model to be used for the preparation of a medium−term forecast of natural forest dynamics. The study site is located on the Bukowa Góra Mt in the Roztoczański National Park (SE Poland). For the analyses we took all uneven−aged stands (128 ha in total) composed mostly of silver fir and European beech. The material was collected on 65 permanent sample plots every five years in the period 1991−2011. Trees with the breast height diameter (DBH)8 cm were measured on each sample plot (500 m), while smaller trees – on three smaller concentric plots. We calculated, separately for fir and beech, the relationship between the mortality of trees and their diameter (fig. 2), the relationship between the diameter increment of trees and their DBH (figs. 3−4), the rate of saplings (emh/em=0.3−1.3 m) growth into the first DBH class (DBH=0.1−1.9 cm). On the basis of these data, we elaborated a size−class growth model that we used to predict the development of timber resources (trees with DBH8 cm) at 10−year intervals in the period 2001−2041. In 2011, the predicted average standing volume was lower than the one actually measured. The forecast indicated an increase in the average standing volume (fig. 5), a reduction in the volume of ingrowth (fig. 6), an increase in the proportion of beech in the standing volume and ingrowth (figs. 5 and 7) and the maintenance of a similar density structure (fig. 8) throughout the period 2001−2041. The low accuracy of the prediction after 10 years (in 2011) was caused by the difference between the predicted and actual values of tree growth and mortality in the period 2001−2011., Sylwan 160 (3): 207-218

Numerous examples of silver fir stands growing outside its geographical range in northern Poland suggest that this species could be used in a greater extend in creation of managed forest stands. Climatic conditions could potentially constrain the use of this species in some parts of country. The objective of this work was to determine the potential climatic range of Abies alba in Poland. The bioclimatic envelope models were used to identify areas in which selected climatic variables show the same range of variability as observed within natural range of this species. Climatic data with 10' spatial resolution were used. The outcome of the analysis depends to large extent on the demarcation of natural range (in which the variability of tolerable climatic conditions is assessed). The model basing on the climatic conditions in whole natural range of silver fir in Europe suggest that almost whole area of Poland is suitable to fir, but models basing only of climatic conditions in Polish part of its natural range are much more conservative. In the last case the difference in extent between natural range and potential climatic range was smaller. As genetic variability of Polish fir populations is rather low, they are supposed to have constrained adaptative abilities. Forest managers should not focus on planting silver fir outside its natural range, but they rather should consider reintroduction of fir in parts of natural range from where it retreated in 20th century., Sylwan 160 (6): 519-528

The study concerns the secondary sunny crown of silver fir trees, its length and density as well as the relationship between the length of primary and secondary crown between the radial increment and secondary crown characteristics. It also discusses the importance of secondary crown in the life and population growth of silver fir., Sylwan 158 (2): 90-98

The paper deals with problems concerning silvicultural planning in silver fir stands in Zagnańsk Forest District (central Poland) that are characterized by complex structure. Based on a detailed inventory using 98 permanent circular sample plots in four control units the BDq method was employed for determining the future silvicultural activities of the current forest management cycle. The equilibrium model is based on diameter distributions and has the following parameters: B=35 m/ha/em; D=63 cm and emq/em−factor=1.28., Sylwan 158 (9): 651-660

The paper presents an analysis of height growth phases of silver fir from the Świętokrzyskie Mountains. Basing on bilateral relations between average and current height increments, age of their culmination and duration of main (juvenile and sprouting) phases was determined. Empirical data consisted of 61 sample trees that were subjected to the stem analysis. Juvenile stage of fir height growth lasts 30 years, while sprouting phase is quite long as it lasts 45 years on average. Mean age when analyzed trees reach the culmination of current and average height increment equals 50 and 70 years respectively. Course of height growth of fir resembles this of beech, which can be explained by shade tolerance of these species., Sylwan 156 (7): 511-517

The paper describes the changes in the current annual volume increment of fir stands in the Forest Experimental Station in Krynica in 1971−2011. The research material are the results of five−fold measurements of stands on 238 control sample plots using an inventory and control method based on the statistical and mathematical system. On average, current annual volume increment in the 1970s amounted to 6.10 m/ha/year, while in the 1980s to 8.46 m/ha/year, in 1990s to 10.52 m/ha/year and to 13.42 m/ha/year in the last decade (2001−2011)., Sylwan 156 (12): 908-913

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

The paper presents the analysis of relations between diameter increment and climatic factors in silver fir stands in the Zagnańsk Forest District (central Poland). Despite growth rate similar to the observed in other parts of Poland, firs form the Świętokrzyskie Mountains show different climatic driving forces of the increment process. Temperature in March, late summer and September as well as precipitation in May and summer in the year of tree−ring formation, and in August of the previous year turned to be the most important factors that shape diameter increment of analysed trees., Sylwan 154 (7): 463-470

Preliminary studies on frost−hardiness of the current year shoots of silver fir were conducted between the autumn of 1999 and the spring of 2000 on the 20−25 year old saplings, collected in 13 sample plots distributed throughout the Świętokrzyski National Park.The diffusion of electrolytes from shoots and needles kept in a freezer at the temperature of −33°C was analysed using the Dexter's (1932) method. The highest degree of frost−hardiness of shoots and needles was found in February. In spring the resistance to low temperatures declined faster in shoots than in needles.The investigations showed significant differences in the frost−hardiness of young silver firs from different sample plots., Sylwan 147 (8): 84-92

The paper provides information concerning the growth of pine, spruce, oak, beech and fir stands based on the research conducted by the European Forest Institute in a number of the European countries and in Poland. Noteworthy i.a. is the increase in volume increment of spruce and pine in some stands in Germany up to 250% of the values given in the yield tables. Since the early fifties of the past century beech and sessile oak in Bavaria have exhibited an increase in the height growth and volume increment. Their values markedly exceed those provided in the tables. Fir, similar to spruce, pine and beech shows the reduction in the increment and dieback in the regions under heavy industrial pollution. However in other regions under the impact of air pollution the response of pure and multispecies stands with the share of fir was positive. In Poland, a rapid decline in the dbh increment in three tree species (fir, spruce, pine) in the seventies was greater than in the sixties. In 1981−1989, fir showed a favourable growth in diameter; this positive tendency was noticed in the whole range of fir distribution in Poland, though the increment did not return to the level before its decline. The pine increment regenerated after 1990. The poorest increment was found in spruce in the eighties following its collapse in the seventies (Żywiecki and Śląski Beskid)., Sylwan 147 (6): 99-106