Dynamics and ecological-genetic variability of cytogenetic disturbances in Scots pine populations experiencing technogenic impact

Scots pine (Pinus sylvestris L.) populations in the vicinity of nuclear industry facilities were monitored. Aberrant cells occurrence in root meristem of germinated seeds from the impacted pine populations was found to be significantly above the reference level during all six years of observations. In the reference population, changes of cytogenetic disturbances with time appeared to be cyclic while in the impacted populations, technogenic stress was strong enough to destroy the natural regularities. The increase in cytogenetic disturbances was accompanied by growth of fluctuations magnitude; deviations of basic oscillation parameters from the reference values rose along with technogenic impact level. Variability in cytogenetic response increased under technogenic stress. Inter-family component of variability predominated, though its contribution slightly decreased in impacted populations. A tendency for destabilization of a repetition coefficient dynamics was found under technogenic impact. A portion of the seeds was exposed to 15 Gy of gamma-rays, and higher radio-resistance in the impacted populations was observed. In the reference population, a family-related analysis of cytogenetic variability components after acute y-exposure revealed significant contributions of "family" and "germination conditions" factors as well as their interactions. On the contrary, in populations existing under chronic stress, considerable modifications in the structure of ecological-genetic variability were found, their degree increasing with technogenic impact severity.     

Population variability of cones and seeds of scots pine by phenes of color and traits-indices in the south of Siberia

Studies of the phenotypic variability of cones and seeds of trees in terms of five index and six qualitative traits in the populations of Scots pine in the south of Krasnoyarsk krai, Khakassia, Tuva, and Buryatia are carried out using techniques of A.I. Vidyakin (2004). The population level of seven traits and validity of their use as markers of genetic variability in Southern Siberian pine populations is confirmed.     

GEOGRAPHICAL VARIATION IN THE INBREEDING DEPRESSION OF SCOTS PINE

The magnitude of inbreeding depression caused by recessive mutations in a population is dependent on the mutation rate and on the intensity of selection against the mutations. We studied geographical differences in the level of early inbreeding depression of Scots pine in a common garden experiment. The mean abortion rate of experimentally self-pollinated seeds was significantly lower (75.4%) among trees that originated from northern populations (66–69°N) than among trees from more southern (60–62°N) populations (86.5%). Thus, the number of embryonic lethal equivalents was lower in the northern populations (4.5) than in the southern ones (6.9). The outcrossing rate at the mature seed stage was slightly lower in the northern populations (average 0.93) than in the southern one (0.99). The estimated selfing rate at the zygote stage varied from 0–0.28 in the populations. The reduction in the magnitude of inbreeding depression in the north may have been caused by increased levels of self-fertilization in the northern populations. The proportion of self-fertilized seedlings and adults was very small in all populations (F ≈ 0), indicating high inbreeding depression also in later life stages. The high level of inbreeding depression in the partially selfing Scots pine can be explained by mutation-selection balance only if the mutation rate is high.     

Temporal variation in breeding and cone size selection by three species of crossbills Loxia spp. in a native Scots pinewood

The breeding biology and cone size selection of crossbills was studied mainly during 1995 to 2002 at Abernethy Forest, Scotland, an ancient native Scots pine Pinus sylvestris wood, where only a single crossbill species, the Scottish crossbill Loxia scotica, was assumed to occur and to be adapted to feed on seeds in Scots pine cones. However, three crossbill species (common Loxia curvirostra, Scottish and parrot crossbills Loxia pytyopsittacus) nested in some years, with the parrot crossbill being the most abundant. Most nests were in old large pines, with the three crossbill species not differing in their use of tree size or stand density for nesting. The mean clutch and brood sizes were 3.8 and 2.9, and their mean survivals were 86 and 74%, respectively, with no significant differences among species. The timing of breeding differed between species, with parrot crossbills breeding earliest (median date 21 March, including second attempts) and common crossbills breeding last (median date 21 April), probably in response to the differing accessibility of Scots pine seeds to these species. The difference in the time of breeding may reduce mixed mating. Crossbills foraged preferentially on trees with small cones when the cones were closed. Small cones had thinner scales than large cones, suggesting that the preference for small cones was related to higher feeding rates on these cones when cones are closed. Such a preference was also found for captive crossbills with the Scottish crossbill showing a more pronounced preference for smaller cones than the larger‐billed parrot crossbill. However, crossbills selected larger cones within trees and trees with larger cones once the cones opened in April. Such a shift occurred presumably because variation in scale thickness has little impact on seed accessibility once cones open, and larger cones have larger and more seeds. The greater ability of parrot crossbills to exploit seeds in closed Scots pine cones allowed parrot crossbills to start breeding earlier and to have young when seeds were most accessible. Only after the cones opened were the smaller‐billed common crossbills able to easily access seeds and to start breeding. The time of breeding of Scottish crossbills was intermediate between common and parrot crossbills, and they probably had an intermediate ability to exploit Scots pine cones. The reason why there were few Scottish crossbills nesting in Abernethy Forest remains a puzzle, considering that native pine wood is assumed to be the ancestral habitat to which the Scottish crossbill is adapted. The breeding season for all crossbills ended in June, when most of the seed from a given cone cohort was shed. This is when starved broods were found, not associated with bad weather.     

Seed predation and dispersal in relict Scots pine forests in southern Spain

For two years, the seed rain and magnitude of seed losses due to predation were evaluated in Scots pine forests in southern Spain. The Crossbill was the most important pre-dispersal predator, consuming more than 80% of ripening seeds. In addition, other birds, mainly Tits and Siskin, also consumed seeds just before seed dispersal, reaching values of 16 and 51% losses in 1996 and 1997, respectively. Seed rain was monitored in different microhabitats (under pine canopies, under shrubs and in open areas), and was most intense under the canopy of mother plants both years. Post-dispersal seed predators (rodents and birds) consumed up to 96% of seeds reaching the ground. Both pre- and post-dispersal seed predators preferentially harvested filled seeds. Post-dispersal predation was similarly intense in all microhabitats, so predators did not change the spatial distribution of the seed rain. These high predation rates were constant between years, localities and habitats (woodland and treeline). We hypothesize that this high rate of seed predation is a major factor limiting the regeneration of these relict populations of Scots pine in its southernmost limit.     

Patterns of Forest Decline and Regeneration Across Scots Pine Populations

To predict future changes in forest ecosystems, it is crucial to understand the complex processes involved in decline of tree species populations and to evaluate the implications for potential vegetation shifts. Here, we study patterns of decline (canopy defoliation and mortality of adults) of four Scots pine populations at the southern edge of its distribution and characterized by different combinations of climate dryness and intensity of past management. General linear and structural equation modeling were used to assess how biotic, abiotic, and management components interacted to explain the spatial variability of Scots pine decline across and within populations. Regeneration patterns of Scots pine and co-occurring oak species were analyzed to assess potential vegetation shifts. Decline trends were related to climatic dryness at the regional scale, but, ultimately, within-population forest structure, local site conditions, and past human legacies could be the main underlying drivers of Scots pine decline. Overall, Scots pine regeneration was negatively related to decline both within and between populations, whereas oak species responded to decline idiosyncratically across populations. Taken together, our results suggest that (1) patterns of decline are the result of processes acting at the plot level that modulate forest responses to local environmental stress and (2) decline of adult Scots pine trees seems not to be compensated by self-recruitment so that the future dynamics of these forest ecosystems are uncertain.     

Variability of the cytological parameters of Pinus sylvestris L. seeds from the unique Hrenovskoy pine forest

Hrenovskoy pine forest is a unique island stand at the boundary of the species range of Scots pine Pinus sylvestris L. This object is of exceptional economic value, because it serves as a forest-seed base for the Voronezh oblast and some other regions of Russia; therefore, the stand and seed qualities have to be monitored constantly. The results of the first cytogenetic study of the seed progeny of P. sylvestris from the Morozov Grove, a high-quality stand in a reserved site within the Hrenovskoy pine forest, are reported. The studies have been performed in order to obtain a more correct assessment of seed quality based not only on their germination and energy of germination (traditionally used by forest breeders), but also on their genomic stability. The latter may be estimated by the stability of chromosome number in the somatic cells of seedlings and the regularity of mitotic divisions, because they also characterize the state of the generative system of parental forms and may serve as an integrated estimate of the stand development homeostasis. Therefore, the chromosome number, mitotic and nucleolar activities, and the number and spectrum of pathological mitoses (PMs) have been determined. Seedlings have been obtained from 240 seeds (collected from 12 trees) that resulted from free pollination. The cytological analysis of the rootlets of these seedlings has not detected any deviations from the chromosome number typical of the species P. sylvestris L. (2n = 24). However, considerable variation has been found in each family with respect to the mitotic index (MI) (from 4.2 +/- 0.36 to 8.1 +/- 0.39%) and the number of PMs (from 0.5 to 2.1%); micronuclei have also been found in each family (from 0.01 to 0.05%). In general, the phenotypic characteristics and the variation pattern of cytological parameters of the progeny of the trees studied in the Hrenovskoy pine forest, together with the high germination rate of seeds (90-98%), indicate that the current state of pines in the Hrenovskoy pine forest can be considered to be satisfactory. However, the presence of micronuclei in all variants and the decrease in MI in some individual plants (which was, on average, 6.1 +/- 0.03% in the sample studied, i.e., significantly lower than that of P. sylvestris from the Usmanskii pine forest (7.3 +/- 1.2%), where the conditions are optimal for this species) may serve as the bioindicators of the deterioration of both the state of trees themselves and the ecological conditions in the Hrenovskoy pine forest. Therefore, the population structure of this valuable autochtonic stand should be reproduced urgently.     

Growth patterns in relation to drought-induced mortality at two Scots pine (Pinus sylvestris L.) sites in NE Iberian Peninsula

Drought-related tree mortality has become a widespread phenomenon. Scots pine (Pinus sylvestris L.) is a boreal species with high ecological amplitude that reaches its southwestern limit in the Iberian Peninsula. Thus, Iberian Scots pine populations are particularly good models to study the effects of the increase in aridity predicted by climate change models. A total of 78 living and 39 dead Scots pines trees were sampled at two sites located in the NE of the Iberian Peninsula, where recent mortality events have been recorded. Annual tree rings were used to (1) date dead trees; (2) investigate if there was an association between the occurrence of tree death and severe drought periods characterized by exceptionally low ratios of summer precipitation to potential evapotranspiration (P/PET); and (3) to compare the growth patterns of trees that died with those of surviving ones. Mixed models were used to describe the relationships between tree growth (in terms of basal area increment, BAI, and the percentage of latewood, LW%) and climate variables. Our results showed a direct association between Scots pine mortality and severe drought periods characterized by low summer water availability. At the two sites, the growth patterns of dead trees were clearly distinguishable from those of the trees that survived. In particular, the BAI of dead trees was more sensitive to climate dryness (low P/PET_summer, high temperatures) and started to decline below the values of surviving neighbors 15–40 years before the time of death, implying a slow process of growth decline preceding mortality.     

Flavonoids from Pinus sylvestris needles and their variation in trees of different origin grown for nearly a century at the same area

Flavonoids in needles of Scots pine planted in 1912–1914 in Poland from seeds originating from different parts of Europe, were isolated, chemically characterised and analysed by HPLC. It was shown that flavonoid profiles were similar in all tested populations and were different from those previously reported for Scots pine seedlings. They included taxifolin, taxifolin 3′-O-glucoside, quercetin as well as quercetin 3-O-glucoside and 3′-O-glucoside. The quercetin 3-O-glucoside could be found only in a trace amount in all samples and quercetin 3′-O-glucoside appeared in all samples regardless their origin. The relative concentration of taxifolin 3′-O-glucoside, quercetin, taxifolin and total flavonoids showed dependence on the origin of seeds; needles from high latitude populations contained smaller amounts of these compounds. Presented data clearly indicate that Scots pine contain glycosidases specific for glycosylation at C-3′ rather than at C-3. Besides, they indicate that long lasting influence of similar environmental factors is not able to change genetic regulatory systems responsible for flavonoid biosynthesis.     

Temperature and soil fertility as regulators of tree line Scots pine growth and survival—implications for the acclimation capacity of northern populations

The acclimation capacity of leading edge tree populations is crucially important in a warming climate. Theoretical considerations suggest that adaptation through genetic change is needed, but this may be a slow process. Both positive and catastrophic outcomes have been predicted, while empirical studies have lagged behind theory development. Here we present results of a 30‐year study of 55,000 Scots pine (Pinus sylvestris) trees, planted in 15 common gardens in three consecutive years near and beyond the present Scots pine tree line. Our results show that, contrary to earlier predictions, even long‐distance transfers to the North can be successful when soil fertility is high. This suggests that present northern populations have a very high acclimation capacity. We also found that while temperature largely controls Scots pine growth, soil nutrient availability plays an important role—in concert with interpopulation genetic variation—in Scots pine survival and fitness in tree line conditions. These results suggest that rapid range expansions and substantial growth enhancements of Scots pine are possible in fertile sites as seed production and soil nutrient mineralization are both known to increase under a warming climate. Finally, as the ontogenetic pattern of tree mortality was highly site specific and unpredictable, our results emphasize the need for long‐term field trials when searching for the factors that control fitness of trees in the variable edaphic and climatic conditions of the far North.     

GENETIC VARIATION IN A FUNGAL PATHOGEN: RESPONSE TO HOST DEFENSIVE CHEMICALS

In response to infection by shoot infecting pathogens, Scots pine releases cortical resin into affected tissues. The resin contains a mixture of monoterpene compounds (α-pinene, β-pinene, 3-carene, β-myrcene, limonene and β-phellandrene) that retard the growth of a range of pathogens. The proportion of each monoterpene in the resin shows substantial variation among trees within a population. Thus pathogens on different trees encounter quite different monoterpene environments. To investigate the evolutionary response of pathogens to the chemically heterogeneous environment provided by Scots pine, isolates of the ascomycete canker pathogen Crumenulopsis sororia were collected from trees within a range of natural Scots pine populations. Growth rates of these isolates were measured in the presence and absence of five host monoterpenes. Substantial heritable variation for growth rate in the presence and absence of monoterpenes, and for monoterpene tolerance was recorded, suggesting the potential for the evolution of chemically specialized pathogen subpopulations on different trees within a wood. However, genetic correlations between growth rates in different monoterpene environments and between tolerance of different monoterpenes were either positive or non-significant, and there was no evidence of “tradeoffs” in performance under different monoterpene regimes. The results suggest that, on its own, the presence of monoterpene variability within Scots pine will not lead to disruptive selection on the C. sororia population. The relationship between defensive chemical diversity and pest resistance is discussed in the light of these results.     

Radial growth of Scots pine in urban and rural populations of Ekaterinburg megalopolis

Eleven stands of Scots pine (Pinus sylvestris L.) from the city of Ekaterinburg and its surroundings were sampled and analyzed using dendrochronological methods to detect the effects of climate, biotic and anthropogenic factors on the annual growth of trees. Tree-ring chronologies were developed for six sites within the city and for five control sites. All chronologies were highly and positively correlated before the 1940s. However, after this period, there was a significant decrease in the correlation among chronologies from urban and rural sites. Divergence lasted about 20 years. This firstly has an anthropogenic cause, mainly due to the evacuation in 1941 of more than 60 industrial factories to Sverdlovsk (now Ekaterinburg), which generated a significant increase in air pollution. Environmental pollution seems to negatively affect tree growth. In the early 1950s, trees in the region also suffered from severe droughts. The results of climate and historical data analysis suggest that the trees on urban sites were weakened by both climate and air pollution factors, which led to a massive nun moth (Lymantria monacha L.) infestation of trees. Defoliation led to a drastic reduction in tree-ring width and, in some cases, to the complete loss of annual rings. The recovery period lasted 10–15 years on average. Rural populations were much less affected by the insect outbreak. After urban populations of pine recovered in the 1960s, radial growth of urban and rural populations became synchronized again.     

Genetic consequences of irradiation in a scots pine <Emphasis Type="Italic">Pinus sylvestris</Emphasis> L. population

The genetic consequences of irradiation were studied in a Scots pine population from a region contaminated as a result of the Chernobyl meltdown. Mutations of isozyme loci were not detected in seeds collected from trees of the first post-meltdown generation in 2004. The frequency of cells with chromosome aberrations in the root meristem of seedlings grown from the seeds did not differ from the control level. A deviation from the expected ratio 1: 1 was observed for some isozyme alleles in endosperms of seeds obtained from heterozygous trees.     

Effects of male fecundity, interindividual distance and anisotropic pollen dispersal on mating success in a Scots pine (Pinus sylvestris) seed orchard

Quantifying the effect of pollen dispersal and flowering traits on mating success is essential for understanding evolutionary responses to changing environments and establishing strategies for forest tree breeding. This study examined, quantitatively, the effects of male fecundity, interindividual distance and anisotropic pollen dispersal on the mating success of Scots pine (Pinus sylvestris), utilizing a well-mapped Scots pine seed orchard. Paternity analysis of 1021 seeds sampled from 87 trees representing 28 clones showed that 53% of the seeds had at least one potential pollen parent within the orchard. Pronounced variation in paternal contribution was observed among clones. Variations in pollen production explained up to 78% of the variation in mating success, which was 11.2 times greater for clones producing the largest amount of pollen than for clones producing the least pollen. Mating success also varied with intertree distance and direction, which explained up to 28% of the variance. Fertilization between neighboring trees 2.3 m apart was 2.4 times more frequent than between trees 4.6 m apart, and up to 12.4 times higher for trees downwind of the presumed prevailing wind direction than for upwind trees. The effective number of pollen donors recorded in the seed orchard (12.2) was smaller than the theoretical expectation (19.7). Based on the empirical observations, a mating model that best describes the gene dispersal pattern in clonal seed orchards was constructed.     

Sirex noctilio in North America: the effect of stem‐injection timing on the attractiveness and suitability of trap trees

• 1 Sirex noctilio Fabricius, an invasive woodwasp responsible for severe economic damage to pine industries in the southern hemisphere, is now established in the northeastern U.S.A. and portions of eastern Canada.
• 2 Parts of North America are considered to be high risk for S. noctilio invasion. Effective detection tools, including trap trees, are needed to monitor and survey S. noctilio populations.
• 3 The present study was conducted to determine the optimal time to chemically stress a tree when aiming to attract the most S. noctilio to the host substrate, as well as to determine which timing produced the most adult progeny. Both of these measures (host attraction and host suitability for development) support the main objectives of the study by offering improved methods for monitoring and management of S. noctilio.
• 4 Red pine (Pinus resinosa) and Scots pine (Pinus sylvestris) were treated with Dicamba at three time intervals. Multiple funnel lindgren traps were placed on these trees and, at the end of the flight season, the treatment trees were felled and brought into the laboratory. The number of S. noctilio caught in the traps (host attraction) and the number of S. noctilio emerged from the treated trees (host suitability) were determined.
• 5 Optimal timing of the chemical girdle was dependent on host species. Significantly more female S. noctilio were captured on trap trees prepared 1 month before flight (red pine and Scots pine) or prepared at flight (Scots pine) compared with other treatments. There were also significantly more females reared from Scots pine trap trees prepared at flight and red pine trap trees prepared 1 month before and/or at flight.
• 6 By the beginning of August, most (79%) of the S. noctilio for the flight season were caught in the traps at the trap trees. The sex ratio (males : females) was closer to 1 : 1 than previously reported in studies from other countries.
• 7 The results obtained in the present study demonstrate that timing is important when creating a trap tree with herbicide in North America, whether for the purpose of detection or as part of a biological control effort.

     

The recovery of damaged pine forests in an area formerly polluted by nitrogen

An area in Lithuania containing coniferous stands of Scots pine and Norway spruce that were dead or damaged due to nitrogen pollution by a nitrogen fertilizer plant (JV Achema) was found to have expanded between 1974 and 1989 to a distance of 20 to 25 km northeast of the plant in the direction of prevailing winds. Over the last 10 years, when nitrogen pollution by the plant had decreased, a clear process of recovery of the damaged ecosystems could be observed. The following features of this process as it occurred in damaged Scots pine stands are discussed: (1) refoliation (or decreased defoliation) of damaged trees, where a clear positive trend could be observed; (2) changes in the species composition and in the covering by ground vegetation, where small changes and indication of less-nitrophilous species coverage could be detected; and (3) chemical and acidity changes in Luvisols and Arenosols, where a significant decrease could be seen especially concerning nitrate concentrations.     

Levels of damage of Scots pine and Norway spruce caused by needle miners along a SO2 gradient

Needle damages caused by mining insects on Scots pine and Norway spruce were studied in the vicinity or a pulp mill. The abundance of needles mined by the pine bud moth Exoteleia dodecella (Lepidoptera: Gelechiidae) on Scots pine Pinus sylvestris , and the spruce needle miner Epinotia tedella (Lepidoptera: Tortricidae) on Norway spruce Picea abies had a significantly peaked response curve on logarithmic distance scale. For pine bud moth, the maximum expected population density was estimated to be at the distance of 1.35 km from the factory. The maximum expected population density for the spruce needle miner was at the distance of 1.53 km from the factory. However, for both species the curves were significantly different among transects. Both species had a peaked and significant response to sulphur level in needles as well. The maximum expected density in pine was at 1270 ppm, and in spruce at 1070 ppm sulphur concentration in pine needles. The results are consistent with earlier reports demonstrating that these mining insects frequently attack trees suffering from air pollution. The nonlinear response of both species to distance from the pulp mill suggests that E. dodecella on pine and E. tedella on spruce are rather indicators of the zone of intermediate air pollution than of strongly polluted or nearly unpolluted sites. This also agrees with the plant stress-insect performance hypothesis indicating that insect response varies with the magnitude of stress, and at very high stress levels a tree no longer provides the insects with relevant food.     

Nitrogen metabolism of Douglas fir and Scots pine as affected by optimal nutrition and water supply under conditions of relatively high atmospheric nitrogen deposition

Nitrogen metabolism of the needles of 40-year-old Douglas fir and Scots pine trees, growing in two forest stands on cation-poor and acidic sandy soil with a relatively high atmospheric nitrogen deposition was studied. The composition of the free amino acid (FAA) pool, the concentrations of total nitrogen and soluble protein and the activities of glutamine synthetase (GS) and glutamate dehydrogenase (GDH) were determined in the needles. An excessive nitrogen supply by a high atmospheric nitrogen deposition in both forest stands was indicated by the high concentrations of total nitrogen and the amino acids arginine, glutamic acid, glutamine and aspartic acid in control trees. In addition the effect of optimal nutrition and water supply (fertigation) on the needle nitrogen metabolism was evaluated. The total concentration of the FAA pool in needles of both tree species was lower in the fertigated than in the non-fertigated (control) trees, except for 1-year-old needles of Scots pine, in which the concentration after fertigation did not differ from the control. The lower total FAA concentration in the fertigated trees could be attributed to arginine, the concentration of which was on average 60% lower than in the control. Neither the concentration of soluble protein nor the activity of GS were influenced by fertigation. The activity of GDH in fertigated trees only differed significantly from the control in October. Scots pine needles had higher concentrations of protein (50%) and higher activities of GS (44%) and GDH (25%) than Douglas fir needles. Possible explanations for the lower vitality of Douglas fir compared to Scots pine are given.     

Scots pine seed dynamics on a waterlogged site

Scots pine (Pinus sylvestris) grows some 400 km south of its current native limit at Wybunbury Moss, Cheshire, UK, on a peatland around a small floating bog (Schwingmoor). Cone and seed production of trees, which have been growing on the site for just over 100 years, were investigated over 3 years. Cones matured between September and March and seed shedding began in early April. The number of cones produced per reproductive tree ranged between 31 and 2,418, with a total average of 685 cones tree^?1 y^?1. A strong relationship was found between tree diameter and seed production which allowed the prediction of annual seed production. Scots pine on this peatland produced between 766,874 and 950,000 seeds ha^?1 annually with a germination percentage of 64%. The predicted number of seeds reaching the central bog (maximum of 120 m from the trees) every year was c. 16,000.     

Seasonal changes in antioxidant level of scots pine (Pinus sylvestris L.) needles exposed to industrial pollution. I. ascorbate and thiol content

Current and previous year needles from three 16 years-old populations of Scots pine (Pinus sylvestris L.) trees were seasonally collected at the three experimental areas: Luboń- close to the phosphate fertiliser factory, Głogów — close to the copper foundry and Kórnik — control site. Głogów is the most polluted site, where at 1998 monthly mean daily concentrations of different pollutants were: SO₂ - 17 μg·m⁻³, NO_x - 12 μg·m⁻³ and dust containing heavy metals as Cu, Pb, Cd - 29 μg·m⁻³. Trees growing in Luboń were influenced for many years by high concentration of SO₂ and fluor compounds. A few years ago emissions were markedly reduced, but low pH of soil and high concentration of aluminium ions still influence the growth of trees. Seasonal changes of ascorbate and thiol content were observed in each needle class and population, with the maximum in the winter and minimum in the summer. In needles from trees growing on polluted sites higher level of ascorbic acid and thiols comparing to control site was observed. Significant differences appeared in each population of Scots pine growing under higher pollution stress in the Głogów site. In needles from trees growing in Luboń significant differences in ascorbic acid and thiols content were evidently less numerous. Needles from polluted sites in some seasons contained significantly more malondialdehyde (MDA) and those was more frequent in Głogów than in Luboń. The results indicated that in the Głogów site trees are more influenced by pollution stress than in Luboń and the defense reaction measured as an increase of the antioxidant level is more evident.