The paper presents the fuel usage and heating energy efficiency of forest district offices in Poland. This analysis of fuel and energy consumption deals with 197 forest districts, that is 45% of all such forest administrative units in Poland. The results show that almost half (45%) of forest district offices are heated with natural gas or oil. Wood as the only source of heat is used in 18% of forest districts and a similar percentage of forest districts use wood with coal for the production of heat. A quantitative analysis of fuel usage shows that 60% of all the consumed heat comes from wood, whereas a mere 13.12 and 16% comes from oil, gas and coal respectively. Thus oil and gas heating systems prove to be the most energy saving. The forest districts heated with those fuels show the lowest average energy consumption. Up to 52% of heating costs in all the analysed forest districts are fuel costs, while 36% of the total heating costs are running costs. The fact that 60% of all the energy consumed derives from wood combustion, while less than 40% of forest districts use wood for heating purposes, proves that the wood fuelled installations that are used in forest districts are ineffective.

This study presents the analysis of mean tree crown defoliations of different tree biosocial groups belonging to the main stand prepared on the basis of observations from years 1991, 1993 and 1995 in the Zielonka Experimental Forest Division. The objective of investigations was to determine statistically significant or non-significant differences between them. In relation to 1991, an improvement of tree crown condition was observed in successive years of observation in consecutive individual Kraft classes and groups of Kraft classes expressed by a decreasing value of defoliation. A smaller number of evaluated tree crowns in 1993 had a distinct effect on defoliation variability, which was significantly higher than in the remaining two years of observation – 1991 and 1995. The better the condition of crowns, the more statistically significant differences of mean defoliations. This process was more conspicuous in younger stands. The change of tree crown defoliation of the same Kraft classes but different age classes observed in successive years of observation was statistically significant which proves that the improvement in stand condition was apparent and unequivocal. When the thinning was considerable, differences in tree crown defoliations of the same Kraft classes but different age classes in a given year of observation were not statistically significant. The improvement in crown condition initially revealed significance of differences only in the case of groups of Kraft classes (1993) and later also in individual Kraft classes (1995). The obtained results did not give a clear answer as to the usefulness of individual Kraft classes for the evaluation of stand defoliation. In order to obtain a clear answer to the above question, it is necessary to carry out investigations on a wider sample collected from different objects.

During the years 1982-1985 and 1994 12 pairs of beavers from the Mazurian Lake District were reintroduced into the central part of the Polish Carpathian Mountains (Beskid Sądecki and Beskid Niski). In 2000 an inventory was taken of the beavers and the environment where they settled was described. The wanderings and movements of the beavers in their search for new biotropes were analyzed. Based on dens and buildings (lodges, dams) it was estimated that there were 44 animals in the area under study. The nature of feed bases and feed preferences were described. The trees most frequently found were sallow and alder.

Investigations were carried out to estimate the true impact of wild animals on growth of pine cultivations. For this purpose, in newly established cultivations of logging unit 119 d, ten 16-are experimental, square-shaped (40 m side) surfaces were established (Fig. 1). The following different methods of culture protection were applied: treatment with Roundup herbicide and Emol repellent, mechanical cutting of reed grass (Calamagrostis sp.) and fencing. On two experimental surfaces, seedlings were left without any protection. Experiments were conducted in years 1991-1995 measuring the height of seedlings and assessing the extent and causes of damages. Browsing was estimated using a three degree scale elaborated by the Forest Research Institute. The establishment of forest cultures was found to be affected only slightly by browsing by animals from deer family. In the first year after cultivation establishment, only 11% of seedlings were damaged by browsing, of which only 7% were damages of lll degree, whereas 41% of losses were caused by fungi and insects as well as other factors such as: drought and mistakes in planting techniques (Tab. 1). Autumn inventory of 1993 showed that only 7% of seedling losses were caused by browsing and in the following year, this level dropped to only 1%. Other, much more serious causes of damages (27%) included such fungi as: needle cast of pine (Lophodermium pinastri), root-rot fungus (Heterobastidion annosum) and honey fungus (Armillaria spp.). The highest levels of damages caused by deer were observed only in the case of oak admixture, which, 10 years after planting, could only be found on fenced surfaces.

The objective of this study is to specify the characteristics of firs, beeches and pines with the DBH increment under the average in the Świętokrzyski National Park. The fir trees with the DBH increment smaller than the average were in general characterized by a parabolic or flattened top, losses in the crown regularity above 20%, and the mean relative crown length from 29% (for trees 61-80 years of age at b.h.) to 42% (for trees 81-120 years of age at b.h.). The majority of worst growing beech trees was characterized by the light part of the crown confined above 55% in an area, and the relative crown length from 45% (for trees 61-80 years of age at b.h.) to 66% (for trees 21-40 years of age at b.h.). The pine trees with the DBH increment smaller than the average were in general characterized by a parabolic or flattened top.

Authors present recommendations, which can be helpful in fight against black cherry both in the Zielonka Experimental Forest Division and on the area of other regions. They are based on estimation of methods of fight against Prunus serotina within the Zielonka Experimental Forest Division, known up to the present and on the works on forest typology units and on plant communities of the described forest division. Investigations show that physical and chemical methods used till now have only significantly delimited the expansion of that plant. Achieving stand composition consistent with potential vegetation and receiving multilayer structure of stands seem to be the most effective ways of black cherry control. European hornbeam, European beech and notably pedunculate and sessile oaks, as the species shading on forest floor, are of great importance in these processes. Mentioned species should appear naturally on the sites of deciduous fresh forests. The authors suggest increasing their participation on the sites of fresh forest, and with reference to oak and beech on the site of fresh coniferous mixed forest, too. Protecting Scotch pine on these sites within the investigated area is, however, economically profitable, promotes spread of P. serotina. It may cause adverse effects both natural and financial.

The objective of this research project was to estimate the effect of the shape of the cutting link and the value of the inclination angle of the cutting edge of the horizontal blade on machining performance. The performed experiments comprised two types of saw chains with cutting links of chisel and semi-chisel types with the following five variants of the inclination angle: 20°, 25°, 30°, 35° and 40°. Investigations carried out by the author showed a statistically significant influence of both the shape of the cutting link and the size of the inclination angle of the horizontal blade on unit machining output. Higher outputs were obtained by saws with chisel toothing and the best variant in both types of saws was the variant with the 35° angle.

A new method for increase of adhesion of urea-formaldehyde resins to surface of straw particles was presented in the text. Treatment of particles by turpentine before gluing partially removes anti-adhesion wax layer from surfaces of straw particles. In the result, increases the strength of glue joints bonding straw particles in particleboards and improves physical and mechanical properties of boards.

The objective of the study was to compare chemical composition of archeological and contemporary wood as well as to characterize changes in the lignin structure. The investigation was performed for 30 years old elm and 80 years old oak stored in the same environmental conditions for 1000 and 800 years respectively. On the basis of the obtained results distinct differences in the degree of degradation of the both main and extraneous components of wood were found.