Assessment of the reproductive capacity of <Emphasis Type="Italic">Pinus sylvestris</Emphasis> trees growing under conditions of chronic exposure to radionuclides of uranium and thorium series

The reproductive capacity of Scots pine (Pinus sylvestris L.) has been estimated in trees from the population growing in an area used to store tailings from uranium ore processing and radium production. Under such conditions, 12- to 15-year-old trees produce seeds of a quality inferior to that in areas with a normal background radiation level. As the weighted absorbed dose rate (at a weighting coefficient of 5) for generative organs increases from 0.002 ± 0.0003 to 0.344 ± 0.059 mGy/day, a proportional increase is observed in the proportion of empty seeds and the frequency of cytogenetic disturbances in the root meristem of seedlings, while the survival rate of seedlings decreases. The minimum absorbed dose rate leading to these changes in the pine population is 0.027 mGy/day, i.e., 12 times as high as the control value.     

Distribution of Fine Roots of Coniferous Trees over the Soil Profile under Conditions of Pollution by Emissions from a Copper-Smelting Plant

The distribution of fine conducting roots of Siberian spruce, Siberian fir, and Scotch pine over the soil profile was studied in the taiga ecosystems polluted with heavy metals and SO₂. Under conditions of heavy pollution, tree roots were not found in the forest litter. Regardless of the level of technogenic load, the largest amount of conducting roots concentrated in the upper layer of mineral soil.     

Postfire succession in a forest of the cryolithozone: The example of central Yakutia

The results of studies on postfire succession in larch forests of the permafrost zone are discussed. The main directions of successional processes in burned-out areas of different ages are described. It has been shown that secondary pyrogenic successions in larch forests follow the scheme of rapid regeneration without tree species replacement and the model of succession tolerance. Groups of plant species with different life strategies and indicator species characterizing different stages of the overgrowing of burned-out areas have been identified.     

Influence of nonsymbiotic and symbiotic parameters of underground organs on the development of aboveground organs in <Emphasis Type="Italic">Pinus sylvestris</Emphasis> seedlings

A method is described for comparing the influences of nonsymbiotic and symbiotic parameters (accounted for by the plant itself and by the plant together with ectomycorrhizal fungi, respectively) of under-ground organs on the development of aboveground organs. The method has been used to analyze 4- to 12-month Scots pine seedlings from 26 habitats. The results show that 24 to 88% (on average, 54%) of total variation in the weight of aboveground organs is dependent on specific structural features of roots and mycorrhizae, with nonsymbiotic and symbiotic parameters of underground organs accounting for 5–73% (on average, 36%) and 3–45% (on average, 18%) of this variation.     

Analysis of consortive relationships between the Siberian stone pine and the nutcracker in the Northern Urals

The data presented have been obtained in the course of long-term stationary quantitative studies on the annual seed reproduction dynamics of Siberian stone pine (Pinus sibirica Du Tour) stands, including the abundance of seedlings, and the local population of the nutcracker (Nucifraga caryocatactes macrorhynchos C.L. Brehm) in forests of the Northern Urals. Statistically significant consortive relationships of the nutcracker population density with the yield of Siberian stone pine seeds and of the abundance of pine seedlings with the yield of seeds and the abundance of nutcrackers over preceding years have been hrevealed for the first time and formalized mathematically.     

Methods and results of studying the geographical trends in the structure of single-tree biomass of larches and two-needled pines in Eurasia

First transcontinental changes in fractional composition of sample tree biomass of larches (Larix Mill.) and two-needled pines (subgenus Pinus) are reported, taking into account their regional differences by age, tree height, stem diameter, and volume, as well as tree density. All components of the tree biomass of larches and pines monotonically increases from the North to the South. Dynamics of pine biomass in the direction from the Atlantic and Pacific coasts to the continentality pole in Siberia is characterized by monotonous decrease of all components, including the roots. The latter is in contradiction with the change of the larch root biomass across the same gradient of climate continentality, which, unlike the mass of pine roots, is not reduced, but increased. The system of the transcontinental dependencies obtained allows its use in estimating forest biomass based on the local data of a tree enumeration per ha.     

Ecological characteristics of Alhagi sparsifolia Shap. seedling roots under different irrigation treatments

An trench profile method was used to study seasonal variation of root ecological characteristics of Alhagi sparsifolia Shap. seedlings under different irrigation treatments. The results indicated the following: (1) Root morphology: under excellent soil moisture conditions, A. sparsifolia seedlings developed many horizontal roots and root sprouts to compete for light; but under poor soil moisture, the vertical root system expanded its resource space into deeper soil. Plasticity of root morphology is an important strategy to capture water and adapt to the hyperarid environment. (2) Root/shoot ratio: root/shoot ratio increased with declining soil moisture, and this trend was more obvious later in the growing season. Increase of root/shoot ratio is a strategy for adapting to drought. (3) Growth of root system: The seedlings prefer to develop roots in shallower surface layers with less water availability. The growth depth and vertical growth rate of roots increased with decreased soil moisture. (4) Accumulation of root biomass: biomass and surface area of the root system decreased with increased soil depth, with the roots distributed in an ??inverted pyramid?? in vertical section view. The formation of root biomass conformed to a logistic ??slow-quick-slow?? growth curve, and total biomass decreased with intensity of soil drought. The findings will provide data useful for effective restoration of A. sparsifolia and better utilization of water resources in hyperarid regions.     

The consequences of chronic radiation exposure of scots pine in the remote period after the chernobyl accident

Long-term observations on Scots pine populations (2003–2012) were performed in areas of Bryansk region radioactively contaminated by the Chernobyl fallout. Throughout the observation period, the frequency of cytogenetic alterations in the root meristem of germinated seeds of pine trees from radioactively contaminated test sites significantly exceeded the control level. Seeds developing under chronic radiation exposure were characterized by high interannual variation in viability. The quality of the seeds and their resistance to additional γ-irradiation showed no definite relationship with the level of radioactive contamination in the site and the radiation dose absorbed by the generative organs of Scots pine.     

Rapid thermal method for early diagnosis of the physiological state of Scots pine trees

Trends in stem temperature of Scots pine trees in different life states are described. Any substantial disturbances of water flow in the roots, stem, or crown have an immediate effect on the stem temperature. This temperature shows a strong inverse correlation with the state of the tree, with the coefficient of determination ranging from 0.710 to 0.974. The method of assessing the physiological state of trees by temperature parameters allows early diagnosis of decline in the viability of conifers.     

Scotch Pine Pollen under Conditions of Environmental Stress

Environmental conditions causing stress have a significant effect on the generative organs of Scotch pine. The parameters characterizing pine pollen are subject to significant interannual variations and are closely connected with weather and climatic conditions in the period of pollen formation. Airborne pollutants affect the quality of pine pollen, which is especially apparent in the years favorable for the formation of microspores. The ability of Scotch pine pollen to germinate and form pollen tubes in the regions with different technogenic loads proved to be significantly lower than in tree stands of the background areas.     

The structure of absorbing roots in invasive and native maple species

Specific structural features of absorbing roots have been studied in Acer negundo (an invasive species in the southern Cisural region), compared to native Acer platanoides and A. tataricum. A comparative analysis of the diameter of fine roots, stele and bark volumes, and the frequencies of roots with retained primary bark, root hairs, arbuscular mycorrhiza, and dark septate endophytes has been performed in the invasive and native species from four habitats (by two habitats in the forest–steppe and steppe zones). The roots of A. negundo have been additionally studied in trees from two monospecific stands. It has been found that the structure of fine roots significantly differs between the invasive and native species: the roots of A. negundo are larger, with relatively poorly developed root hairs and low occurrence of dark septate endophytes. In monospecific stands, the frequency of mycorrhiza in A. negundo roots is very low, with arbuscules and dark septate endophytes being totally absent. It is concluded that specific structural features of the belowground absorbing apparatus in A. negundo are accounted for mainly by traits autonomously formed in a plant, rather than by characteristics of symbiotic relationships, and that they are not consistent with the assumption that the invasive species can utilize soil resources more effectively or more rapidly than taxonomically close native species.     

Thorium uptake by wheat at different stages of plant growth

Data on biogeochemistry of thorium are rather limited. So far little is known about toxic effects of small amounts of the radionuclide on higher plants. In this study the uptake of thorium by wheat seedlings was measured by greenhouse experiments. Germination of wheat seeds for 6 days in the presence of thorium resulted in accumulation of the metal in all parts of the seedlings. When the Th-rich seedlings were transferred to normal soil and were grown there further for 7 days, Th concentrations in roots and leaves decreased significantly (in leaves the Th content decreased up to the level of Th in the control plants). In seeds, however, Th content remained unchanged. An increase of Th content in roots and seeds was also observed as a result of addition of thorium to soil but in this case the concentration of Th in leaves did not change. The accumulation of Th in plants affected the uptake of other elements including essential macro-nutrients. The most strongly affected part of the plants was leaf.     

Species-specific effects of P-solubilizing and N<Subscript>2</Subscript>-fixing bacteria on seedling growth of three salt-tolerant trees

Coastal afforestation suffers from low survival and slow growth due to harsh conditions and lack of robust seedlings. Inoculation of P-solubilizing bacteria (PSB) or N₂-fixing bacteria (NFB) are effective in promoting plant growth and thus potentially helpful for coastal afforestation. However, it remains unclear about the generality and specificity of these plant-growth-promoting-bacteria (PGPB) on the growth of salttolerant trees. We inoculated seedlings of two mangrove trees and one terrestrial salt-tolerant tree with pure cultures of PSB or mixed cultures of PSB and NFB. Plant biomass, height, base diameter and N and P concentrations were determined six months after bacterial inoculation. We found that inoculation of PGPB had an overall promoting effect on the seedling growth of three tree species, but the effects differed greatly (3–280% increase) among plant species and bacterial isolates or bacterial combinations. Only in the terrestrial tree, co-inoculations of PSB and NFB showed greater promoting effects than monocultures of PSB. Root: shoot ratios of seedlings were not changed by bacterial inoculation. Inoculation treatments moderately elevated N concentrations in shoots and roots and P concentrations only in roots of seedlings. Our results suggest that PGPB might have a general promoting effect on the seedling growth of salt-tolerant trees. Nevertheless, the magnitude of promoting effects and the comparative advantage of dual inoculation over single inoculation are species-specific. The generality and specificity of the plant-PGPB relationship are similar to the plantmycorrhizal symbiosis. In addition, tissue nutrient improvement might not be the main mechanism of the promoting effects by PGPB.     

Means for soil nutrient uptake in sedges with different ecological strategies

The prevalence of arbuscular mycorrhizas and nonsymbiotic modifications of absorbing organs (dauciform roots) has been studied in species of the genus Carex with competitive (C) and stress-tolerant (S) types of Grime-Ramenskii’s ecological strategies. The groups of C- and S-strategists do not differ in the ability to form mycorrhizas. Dauciform roots are more frequent in S-strategists, which accounts for a higher diversity of means for soil nutrient uptake in this group, compared to S-strategists.     

Cytogenetic Variation in Populations of Scotch Pine

Cytogenetic variation was analyzed in daughter populations of Scotch pine from the Voronezh Forestry. The dependence of the variation on the method of seed collection (the commercial method; the population method, when seeds from a group of phenotypically normal trees in the center of the forest are collected; or the individual method, when seeds from plus trees are collected) and on the ecological situation at the sampling site (ecologically safe conditions or chemical or physical pollution) was studied. The parameters of the mitotic rate and mitotic pathology were estimated at 7–9% and up to 5%, respectively. These parameters may be considered as normal when estimating the quality of seed progeny in pine and when pine is used as a test object in cytogenetic monitoring. The limits of variation and the spectra of cytogenetic characteristics allowing the pine populations to maintain their homeostasis were also determined.     

Assessment of biological effects in <Emphasis Type="Italic">Plantago major</Emphasis> L. Seed progeny in the zone of impact from a Copper Smelter

The quality of seed progeny was studied in Plantago major from populations growing for a long time in the gradient of chemical pollution around the Karabash Copper Smelter (KCS). The results showed that the range of variation in seed germination and seedling survival rates was wider in background than in impact populations. The lowest values of growth parameters (the number of seedlings with a true leaf and root length) were recorded in the sample from the most polluted plot. Challenging exposure to toxic elements (seed germination in soils from polluted plots) was found to stimulate, to different extents, the rate of leaf formation and suppress root growth in the seedlings. It cannot be stated from these results that the adaptive potential of plants grown in the zone of impact from the KCS is altered, compared to that in other samples. Evaluation of the prooxidant and antioxidant status of seedlings from this zone revealed a decrease in superoxide dismutase and catalase activities (to 60 and 33% of background values, respectively) and an increase in peroxidase activity (to 122%). The prooxidant status of seedlings in samples from the KCS zone was found to be increased, except for the sample from the most polluted plot.     

Forest structure and regeneration along the altitudinal gradient in the Binsar Wildlife Sanctuary,Uttarakhand Himalaya,India

Forest structure and regeneration were studied along the altitudinal gradient in the Binsar Wildlife Sanctuary of Uttarakhand Himalaya in India. Stratified random sampling of tree species was done by placing minimum 15 quadrats of 10 × 10 m at each aspect and altitude. The results reveal that along the altitudinal gradient there were three types of forest communities in the Sanctuary viz., chir pine (Pinus roxburghii), oakchir pine (Quercus leucotrichophora and Pinus roxburghii) and oak (Quercus floribunda and Quercus leucotrichophora). Rhododendron arboreum, Cornus macrophylla and Lyonia ovalifolia were main associates of these forest communities. The oak forests had larger shrub population as compared to chir pine. Myrsine africana was the most dominant shrub across the altitudinal gradient, whereas few shrub species were restricted to a certain altitudinal range. The regeneration of chir pine was best at lower altitude on south and east aspects, which indicates that it mostly regenerates on warm and dry slopes. In general, the regeneration potential in most of the tree species declines with the altitude. The density of saplings and seedlings also represented the dominant species at each altitudinal range, which indicates the cyclic regeneration of forests in the Sanctuary area.     

Density of Scots pine undergrowth after ground fires in a zone of industrial air pollution

The effects of two exogenous factors, ground fires and industrial air pollution, on natural regeneration of Scots pine (Pinus sylvestris L.) cenopopulations have been studied in the Transural region. It has been found that an increased level of air pollution leads to a decrease in the abundance and occurrence frequency of pine undergrowth; as the intensity of ground fire increases, these parameters of the postfire generation of undergrowth increase as well, especially in background areas. As shown by two-way ANOVA, either of these factors and their interaction have a significant effect on the density of pine undergrowth, with this effect being stronger in the case of ground fires.     

Cytogenetic Damage of Human Somatic Cells and Weeping Birch Cells in Voronezh Districts with Different Levels of Anthropogenic Pollution

Cytogenetic parameters (the mitotic rate and the frequency of pathological mitoses) of the seed offspring of weeping birch (Betula pendula Roth.) and the frequency of micronuclei in the buccal epithelium of children living in several raions (districts) of the city of Voronezh differing in environmental conditions were studied. Judging from these parameters, the environmental situation was the worst in the Sovetskii raion. A correlation was found between the frequency of pathological mitoses in the roots of birch seedlings and the frequency of micronuclei in the buccal epithelial cells of children. This indicates that the cytogenetic monitoring data obtained in plants may be extrapolated to man.     

Assessment of radiation impact on <Emphasis Type="Italic">Stellaria graminea</Emphasis> cenopopulations in the zone of the Eastern Ural Radioactive Trace

The seed progeny of the little starwort (Stellaria graminea) growing in the zone of the Eastern Ural Radioactive Trace (EURT) and in background areas was studied. The radiation exposure of this species in the EURT zone was three orders of magnitude higher than in the background. Evidence was obtained for high interannual variation in seed viability and tolerance to additional acute irradiation, but no specific connection was revealed between these parameters and radioactive contamination level in plant habitats. Weather conditions are an important source of variation in seed viability, but significant influence of temperature and precipitation was revealed only for cenopopulations of the EURT. The proportion of seedlings with morphoses in samples from the EURT was found to be increased; additional irradiation facilitated the detection of latent abnormalities. A negative correlation between seedling survival rate and the content of low-molecular antioxidants in the seedlings was revealed in all test areas. The allozyme structure of starwort cenopopulation was analyzed for the first time. A directed switch of allele frequencies at loci Pgi-2 and Fdh was revealed in samples from the EURT.