The article presents the results of a so far most extensive study on the effect of tree age on variation of the chemical structure of silver birch wood carried out in Poland. Field studies took place in 12 forestry districts distributed throughout the country. In each district, study sites were selected with stands aged approximately 30, 50, and 70 years in fresh broadleaved forest habitats, as well as in five districts in fresh mixed broadleaved forest habitats. Analyses were made of the contents of substances soluble in cold and hot water, ethanol and 1% NaOH, as well as the contents of cellulose, lignin, pentosans and ash, and the pH, of wood from 306 silver birch trees. Tree age was shown to have a significant effect on the contents of cellulose, pentosans, ash, and substances soluble in 1% NaOH. In the case of the other characteristics, age was found to have no significant effect. The cellulose content was lowest in 30-year-old stands and increased with tree age. Similar observations were made regarding ash content. Contents of pentosans and substances soluble in 1% NaOH were highest in the wood of the youngest trees. Since birch wood is used by the pulp and paper, board and energy industries, the knowledge of its chemical composition, depending on the age of the trees, can be of potential practical importance for its further application.

We report on the most extensive study to date in Poland concerning the variability in the chemical composition of silver birch (Betula pendula Roth.) wood depending on the forest habitat type and the location of the forest stand. The research was carried out in 12 forest districts, on two habitat types where silver birch forest stands predominate in respect of coverage area and merchantable volume. Chemical composition analysis was performed on 51 samples from 306 test trees aged approximately 30, 50 and 70 years. In the examined sample material, the sum of the main chemical components for individual locations varied from 89.26 to 91.57%. The content of substances soluble in water and ethanol ranged from 2.30 to 4.03%, and the ash content was measured at between 0.09 and 0.25%. The results showed that the location had a significant influence on the contents of substances soluble in cold water (p = 0.0015), hot water (p = 0.0005), ethanol (p < 0.0001) and 1% NaOH (p = 0.0014), as well as on the contents of cellulose (p = 0.04), lignin (p = 0.002), pentosans (p = 0.04) and ash (p < 0.0001) and on the pH value (p < 0.0001). Notable influence of location on the contents of secondary constituents of birch wood, especially those extractable with water and ethanol, was recorded for the test plots in north-eastern Poland. The obtained results may form a basis for assessment of the industrial utility of birch wood, as well as the optimisation of traditional methods of utilisation and the development of new such methods that are ecological and sustainable.

The most extensive study to be carried out in Poland, and one of only a few worldwide, regarding the influence of location, tree age and forest habitat type on the basic fuel properties of silver birch (Betula pendula Roth.) wood was conducted in 12 Forestry Districts of the Polish State Forests. The field study included trees in three age groups of approximately 30, 50 and 70 years. The research was carried out in a fresh broadleaved forest (FBF) habitat type, where in Poland silver birch stands predominate in respect of coverage area and merchantable volume. Additionally, for five selected Forestry Districts, a comparative study was conducted in a fresh mixed broadleaved forest (FMBF), the second most important habitat of this tree species. A total of 306 test trees were examined. For every sample, calorific value and contents of ash, carbon, hydrogen, nitrogen, sulphur and chlorine were determined. The results indicated a statistically significant influence of location on the calorific value (p = 0.0001) and on the contents of ash (p < 0.0001), carbon (p < 0.0001), hydrogen (p < 0.0001), nitrogen (p < 0.0001) and chlorine (p < 0.0001) in the analysed wood. Moreover, statistically significant differences were observed between values of ash content (p = 0.046) and of calorific value (p = 0.0026) depending on the forest habitat type. Tree age was found to have no significant influence on the calorific value of silver birch wood.

When transporting timber, the high variability of species, assortments and moisture content of the wood raw material does not allow the weight of the transported timber to be precisely determined. This often contributes to the excessive weight loading of the entire truck unit. The aim of the research is to present the variability of the total weight of truck units with wood cargoes (GVW—gross vehicle weight) depending on the weight of the empty unit and the transported timber load, as well as to analyze the changes in GVW, unit loads of wood and load on individual truck unit axles depending on the season. This study analyzes the total weight of truck units for 376 transports of Scots pine timber at different times of the year. The total weight of the truck units depends on the weight of an empty unit and the weight of the load. GVW was determined by using a weighbridge to weigh the vehicles and then the empty unit after unloading. The weight of the load was obtained as the difference between GVW and the tare. It was found that GVW differed significantly depending on the truck unit used, ranging from 43.60–58.80 Mg, often exceeding permissible limits for public roads. The individual axle loads for various truck units were also analyzed. The obtained results indicate that these loads are more equally distributed in the case of five-axle trucks compared to six-axle ones.

This work presents the findings of a study concerning variability in the basic density of silver birch ( Roth) wood, depending on the geographical location of tree stands, the age and thickness of the trees, the forest habitat type, and interactions between some of these factors. The study was carried out on wood from trees aged approximately 30, 50 and 70 years in 12 forest districts located throughout Poland. In total 4777 wood samples, taken from 306 trees from 51 test plots, were measured. The location, the age of the trees, the thickness of the trees and the forest habitat type, as well as interactions between these factors, proved to have a significant influence on the basic density of silver birch wood. The highest mean values of the basic density of the birch wood were found in Sokołów forest district on the FBF habitat type (549 kg m) and in Giżycko forest district on the FMBF habitat type (548 kg m). For the entire set of examined material, the average values of the basic density of wood increase with tree age. For the examined material originating in FBF and FMBF habitats the average values of basic density showed no significant differences; however, in the cases of the forest districts of Giżycko, Łobez and Rudziniec, significant differences in the analysed property were observed.Betula pendula –3 –3

Study analyses coarse (d>2 mm of diameter) roots biomass dynamics in young succession stands of silver birch ( Roth) growing on abandoned farmlands in central Poland. Research material based on 181 sample trees, which were gathered in 20 pure silver birch stands in 5 locations. The age of the trees varied from 1 to 16 years. Coarse roots biomass of the investigated trees ranged from 0.7 to 4305.5 g/tree (422.6 g/tree on average) showing great variability (coefficient of variation equals 185%). A clear dependence of belowground biomass on the age and size of a tree was observed. Root-to-shoot ratio values vary from 0.1 to 1.0 with evidence of a tendency to decrease with increasing age, diameter at the breast height and height of analysed trees. An allometric equation was elaborated for the estimation of belowground biomass based on height or diameter at breast height of young silver birches. The suitability of this formula should be considered for the estimation of biomass accumulation and carbon sequestration by young successional silver birch stands growing on abandoned agricultural lands.Betula pendula