During the years 1998-2002 in investigated forests of southern Poland 99 lightning gaps with 1265 damaged trees as a result of thunder strike were recorded. Among them 99 trees were directly struck by lightning. The lightning gaps were formed in different forest types, mainly in age of VI and V class (74%) as well as in I and II classes of stand quality classification (70%). The lightning gaps appeared most frequently in very strong slope area (slope 18-30°) (39%) at the southern and northern exposition (74%) and at elevation 301-700 m a.s.l. (45% of cases). Beside the damages of single trees, directly struck by lightning, the neighboring trees were also damaged on 64% of lightning gaps (A type). Those, were formed mainly in Norway spruce stands and in forests with the domination of spruce. Among trees species the most frequently damaged was spruce (59% of cases). Damages of a single tree, directly struck by lightning, were evidenced only on 36% of lightning gaps (B type). The lightning gaps B type were formed mainly in fir stands and in forest with the domination of fir. The most frequently struck by lightning tree species was fire (69% gaps B type). Using the statistical Principal Component Analysis (PCA) were shown the multidimensional significant relationships between different distinguished parameters, as: the type of tree stand, elevation, exposition, and site humidity. The relationship between frequency of all lightning gaps and gaps A type and environmental parameters was not present. However, the frequency of gaps B type was primary connected with elevation 301-700 m a.s.l., northern exposition, very strong slope of area, brown soil, age of tree stand within V-VI class and enhanced humidity of site (PCA-1). Next, it was connected with the presence of fir in tree stand (PCA-2).

In years 2002 and 2003, pairs of experimental plots were established in some selected forest divisions in pine stands of the III^rd and IV^th age class and, on each of these surfaces, crown defoliation of 25 trees from the main stand was assessed according to the, so called, European criteria. Mean defoliations were calculated for each experimental plot and this information was used to allocate individual stands to the appropriate defoliation class. Moreover, the author investigated, whether there were statistically significant differences among mean defoliations and referred the findings to the membership of specific pairs of stands to a defoliation class.

The study presents results of investigations in which attempts were made to determine and compare the conventional density and compression strength along wood fibres of Scots pine (Pinus sylvestris L.) developed on former farmland and on typical forest soils. The analyses comprised two forest site types: fresh coniferous forest (FCF) and fresh mixed coniferous forest (FMCF). The conventional density and compression strength along fibres were studied. It was found that the timber conventional density of pines grown in conditions of former farmland was higher than that of the pines derived from typical forest soils. The performed studies revealed distinct correlations between the compression strength along fibres and wood conventions density both in pines derived from the former farmland and from the typical forest soils of both analysed forest site types. The correlation between the examined properties was found stronger in the case of the typical forest soils (FCF r = 0.93; FMCF r = 0.88) and weaker, in the case of the former farmland (FCF r = 0.48; FMCF r = 0.42). It should be emphasised that the heartwood of pine trees which grew on the former farmland in conditions of the FMCF was characterised by different properties. At high density, this wood exhibited low compression strength along fibres. The wood derived from trees developed in conditions of the former farmland did not show differences in its macrostructure in comparison with the wood derived from forest sites.

Results of mixed forest prognosis with use of the FORKOME model on the area of the 135g division of the Kampinoski Forest Department are presented in this research work. 600 hundred years of future possible tree amount and biomass changes are described. The research includes control scenario simulating Pinus sylvestris biomass decreasing and Quercus robur biomass increasing up to reaching the domination level. Scenario 1 (warm and humid) simulates Quercus robur and Tilia cordata biomass decreasing and increasing of Quercus petrea biomass. Scenario 2 (warm and dry) Quercus petraea biomass reaches lower level than in scenario 1 however, slightly higher in the middle of the simulation than in the control scenario. In scenario 3 (cold and humid) FORKOME simulates considerable domination of Pinus sylvestris especially during the first half of the prognosis. Scenario 4 (cold and dry) simulates Tilia cordata and Acer platanoides biomass increasing in the second half of the prognosis. Preceding FORKOME simulations allows ascertaining that forest succession computer research is helpful in estimating climatic changes influence on forest ecosystems. The results clearly state that FORKOME model is very useful for that kind of research.

It was found that mixed stands of the Niepłomice Forest cannot be included among highly productive stands, since their mean biomass amounts to 158.5 t·ha^-1, ranging from 40.1 t·ha^-1 in age class I to 347.2 t·ha^-1 in age class III. The percentage of individual biomass components (underbrush, wood of trees, assimilative apparatus) changes with age, and depends on the main species forming the stand. Biomass of the underbrush is 2.4 t·ha^-1 on the average, and its percentage is significant only in stands of age classes II (3.41%) and III (1.79%). The percentage of wood in the total biomass is 84.4% on the average (from 81.9% in stands of age class II to 86.4% in stands of age class IV and older), while that of the assimilative apparatus is 2.2%. The annual production of the tree layer reaches 8.3 t·ha^-1 on the average. The greatest increment (mean 9.2 t·ha^-1·year^-1) is in stands of age class III, while the smallest one (mean 4.7 t·ha^-1·year^-1) in stands of age class I. Biomass of the assimilative apparatus is of a considerable importance (from 19.2% in stands of age class I to 44.9% in stands of age class V) in the total annual production of biomass.

The paper presents the occurrence of forest fires in Poland in the years 1990- -2003 and factors controlling their spatial distribution. The analysis was conducted by voivodeship. A study was also made of changes that had taken place in the area of fires and their underlying causes. The research showed the number of fires to have an upward rather than downward tendency from year to year. Fire intensity differs spatially. The high fire risk is a result of the increasing penetration of woodland by people and their careless handling of fire in a forest or land bordering a forest. Besides, the predominance of coniferous habitats in forests with their easily drying plant matter lying on the forest floor and the dominance of conifers are favourable to the start and rapid spread of a fire.

In Zielonka Forest District seven Scots pine plantations monitored in 1998-2001 for Armillaria ostoyae and Heterobasidion annosum disease development proved affected mainly by the former pathogen. Observations of 200 trees per plantation (every spring and fall) showed there was no correlation between the morphological features and over ground symptoms and infestation of pines by the pathogens in question and mortality of trees. The young stands were threatened more by Armillaria than by Heterobasidion annosum s.s., yet the infestation by Armillaria decreased with age of trees while the infestation by Heterobasidion increased.

Armillaria root rot is one of the most dangerous infesting diseases of tree roots. Armillaria spp. spread and infest trough rhyzomorph. Four samples were taken out and diploid mycelium was isolated. 28 isolates were chosen in order to examine rhyzomorph. The result of the experiment indicates the division of isolates from particular areas as well as within the areas.

An attempt was made in the study to determine interrelationships between the volume, proportion of manure wood and selected easy-to-determine biometric traits of trees, i.e. breast height diameter, height and stem total volume. The analysis comprised pine stands of the ll, lll, lV and V age classes which developed in conditions of the fresh mixed coniferous forest site type. Correlations were found between the volume and the proportion of mature wood and the selected tree biometric traits. The observed interrelationships were expressed in different ways and with different intensity, depending on the compared traits.

The paper presents results of research on changes of the variation of chosen true form factors of oak stems with age. There were 28 sample trees chosen by Darudt’s scheme in 80 years old oak stand. On these trees, when fallen down, the full stem analysis in five year periods were applied. The results of the analysis were used for calculating following form factors: f_L/15, f_L/10, f_L/9, f_L/8, f_L/7, f_L/6, f_L/5, f_L/4, f_3/10L, f_L/3, f_4/10L and f_L/2 under bark. The value of the b.h. form factor was also calculated for each stem for comparative purpose. The less variable form factors in examined stands were f_L/4, f_L/3 and f_L/5. Average values of their coefficients of variation were, correspondingly 9.01%, 9.08% and 9.09%. The highest variation was found for f_L/2 – 14,84% on average. The correlation between investigated form factors and d.b.h. under bark, tree height so as slenderness quotient have also been analysed. In most cases, the correlation between form factors and tree height, calculated in different periods of life, is weak, often statistically insignificant. Stronger correlation appears in later period of tree life (over 40 years) between true form factors f_L/7, f_L/6, f_L/5, f_L/4, f_3/10L, f_L/3, f_4/10L and d.b.h. under bark and slenderness quotient.

The subject of research was pine bark (Pinus silvestris L.) (at age 17-45 years) and soil from several forest sections of the Moracz Forest District. Both in bark and in soil different contents of organochlorine pesticides were found. Among HCH izomers, γ-HCH (lindan) was distinguished by the highest contents in all samples collection sites. Its maximum level in bark (60.1±80.6 µg·kg^-1 d.m.) was observed in the surroundings of Przybiernów village (section 617), while in soil – 8.2±4.9 µg·kg^-1 d.m., in former Przybiernów state-owned farmlands. In the bark of pines growing on the border of farmlands of Przybiernów village the most of ΣHCH residues was stated (156.8 µg·kg^-1 d.m.), instead in the soil near Moracz village – 9.6 µg·kg^-1 d.m. and in the surroundings of the Rokita railway station – 10.4 µg·kg^-1 d.m. The most of ΣDDT residues were found in the surroundings of the Moracz village, where the maximum contents in the soil – 159.5 µg·kg^-1 d.m. and in the pine bark – 252.2 µg·kg^-1 d.m. were stated. Within the whole examined area, both in bark and in soil, the greatest percentage participation among izomers and DDT metabolites obtained pp'-DDT (over 40%).

The Darzybór ecological site is a protected object which plays exceptionally important economical and recreational as well as ecological functions. Despite changes caused by anthropo-pressure, Darzybór belongs to objects distinguished for their remarkable floristic value. The total of 540 taxons of vascular plants, from 78 families and 282 genera grow here. It is one of the last refuges in the city giving shelter and protection to rare and endangered plant species, of which 12 are under legal protection and 8 are considered as threatened species in the region of Wielkopolska. 174 species can be found on red lists of which 166 are considered as species threatened for the city of Poznań. The total of 14 trees with monumental dimensions, 13 – with dimensions close to monumental and 60 trees described as ‘splendid’ trees were inventoried. Eleven most valuable trees were proposed to be placed under legal protection as nature monuments.

Some of the most important factors decreasing the life span of trees are pathogenic fungi causing wood decay. To protect old, monumental trees it is necessary to investigate a new methods of their conservancy. In this paper some results of the systemic fungicides applying to living trees were presented. Three applying methods were tested: to the ground, to the leaves and straight to the wood (using hydrostatic injections). The last method appeared as the most effective. Wood from trees protected with systemic fungicides by hydrostatic injections were decayed much slower by testing fungi in laboratory conditions. It was also proved that the fungicide applied in this way to the wood was transported both up and down in the stem, protecting all the tree. According to this results hydrostatic injections of systemic fungicides seem to be a new promising method of protecting trees against fungal wood decay.

The study presents results of the investigations on the influence of the presently produced furniture on the development of concentrations of volatile organic compounds and formaldehyde in air of rooms. The volatile organic compounds were analyzed with the use of the gas chromatography method together with mass spectrometry. The obtained results showed differences in type as well as in amounts of the identified compounds depending on the type of the applied materials for finishing furniture surfaces.