Frost Cracks Research Articles

Tree vegetation viability of the Murmansk urban ecosystem

This paper aims to analyze the woody vegetation viability of northern territories. The research objectives were as follows: (1) to study the predominant species of woody vegetation in public gardens and alleys in Murmansk; (2) to identify groups and categories of trees quality conditions; and (3) to calculate the average coefficient of trees condition for the city. To conduct the research, we used the method guidelines for the stand viability assessment in July 2020, and we studied a total of seven sites (1,252 specimens of trees). According to the methodology, we identified three groups of trees conditions. We noted that the public green spaces in Murmansk are within the minimum norm for the cities in the tundra zone, with landscaped objects slightly below the normative values. The predominant trees in the studied public gardens and alleys are Sorbus species. The research showed that most trees are of satisfactory quality and belong to the “weakened category.” We recorded the following types of damage: frost cracks, bare trunk, insufficient leafage, small leaf plates, trunks’ bending and tilting. The main factors affecting the condition of woody vegetation in Murmansk are abiotic factors (wind, frost, heavy rain, hail, sharp temperature fluctuations). Biotic factors and human activity have a lesser impact. The city annually carries out sanitary work to cut down dead branches and give the landscaping objects aesthetic value. The novelty of the research is in the fact that the assessment of the trees in Murmansk in 2020 was carried out for the first time; the previous works are dated 2013–2017.

Multiphysics meshless method for mesoscopic concrete cracking under frost action

Frost cracking in the interior part of concrete in the cold region has a great influence in the concrete durability and the safety of hydraulic structure. In this paper, mesoscopic concrete is investigated taking into consideration the effect of pore water phase change resulting from heat exchange under frost action in the framework of Material Point Method (MPM). For meso-structure in the real concrete consisting of mortar, interfacial transition zones (ITZ) and aggregates, ITZ-embedded method is proposed to reproduce the discontinuity of heat exchange and mechanical simulations in MPM. The relationships between phase transition and stress evolution is incorporated into the constitutive model in MPM by introducing the parameter, liquid phase fraction, to realize the simulations of concrete behavior under frost action. Firstly, the verifications of thermo-mechanical coupling and the phase transition of pore water considering evolution of pore pressure are presented respectively in two homogeneous examples compared to the literature results. A simple concrete model with a polygon aggregate is used to present the rationality of ITZ-embedded method in reproducing the heat exchange discontinuity role of ITZ in the internal part of concrete. The following investigation is conducted in a square concrete model, and the effect of different influencing factors on frost cracking morphologies is systematically discussed for studying the comprehensive mechanism of concrete damage and phase transition under frost action. The aggregate percentage Pagg, heat convective coefficient of ITZ Qh and ice plugging point αp obviously influence length, depth and density of frost cracks in the interior part of the concrete. The results demonstrate the numerical feasibility of multi-field coupling MPM method in the mesoscopic research of concrete initiation and propagation under frost action.

A Step-Wise Workflow for SAR Remote Sensing of Perennial Heaving Mound/Crater on the Yamal Peninsula, Western Siberia

Climate change in the Arctic region is more significant than in other parts of our planet. One of the manifestations of these changes is crater creation with blowouts of a gas, ice and frozen soil mixture. In this context, dynamics studies of long-term heaving mounds that turn into craters as a result are relevant. A workflow for detecting and assessing anomalous dynamics of heaving mounds in the Arctic regions is proposed. Areas with anomalous increase of ALOS-2 PALSAR-2 synthetic aperture radar (SAR) backscattering intensity are detected in the first stage. These increases take place due to sudden changes in local terrain slopes when the scattering surface (mound slope) turns toward the radar. Radar backscattering intensity also rises due to depolarization at newly formed frost cracks. Validation of the detected anomaly is carried out at the second stage through a comparison of multi-temporal digital elevation models obtained from bistatic radar interferometry TerraSAR-X/TanDEM-X data. At the final stage, the deformations are assessed within the detected areas using differential SAR interferometry (DInSAR) technique by ALOS-2 PALSAR-2 data. The magnitude of the heaving along the line of sight (LOS) was 22–24 cm in the period from January 2019 to January 2020. In general, effectiveness for detecting the perennial heaving mounds and the rate assessment of their increase were demonstrated in the suggested workflow.

УГЛЕРОД МИКРОБНОЙ БИОМАССЫ В ПРОФИЛЕ МЕРЗЛОТНЫХ ПОЧВ ЮГА ВИТИМСКОГО ПЛОСКОГОРЬЯ

The cryogenic nature of soils undoubtedly affects the carbon content of microbial biomass. Global climate warming has led to a highly dissected relief in the form of heave mounds and thermokarst depressions, where the first reaction of landscapes to changing environmental conditions is the response of biota. The objects of our research are permafrost soils, brown soils and quasi-clay chernozems. The aim of the work was to determine the carbon of microbial biomass in soils with a dissected relief of the south of the Vitim plateau. We found a strong direct correlation between the carbon content of humus and carbon of microbial biomass in the studied soils. The correlation between the content of C-biomass and soil moisture in the forest cenosis is also noteworthy, here the relationship was (r=0.91) in the humus pocket and less close (r=0.69) in the host horizon. Comparing the carbon content of microbial biomass from frost-breaking cracks (humus pocket) in the soil from the same depths of the host horizon, it should be noted that the entry into the soil of significant amounts of organic matter with plant litter stimulates the soil microflora and even in the lower horizon there is a fairly high content of C-biomass. The indicators of microbial biomass and humus in frost cracks are higher. The obtained data characterize the direction and intensity of microbiological processes along the profile horizons. Such studies in agroecosystems are necessary to assess the influence of natural and anthropogenic factors on the soil microbial complex.

БОЛЕЗНИ POPULUS ALBA L. В БОТАНИЧЕСКОМ САДУ ТУВИНСКОГО ГОСУНИВЕРСИТЕТА

Poplars are used for landscaping residential areas, urban conglomerates and highways. Pathogenic microflora was revealed and studied in the zone of greening of the introduced plant - silver poplar in the conditions of dry steppes of the Republic of Tuva. A detailed examination revealed various types of lesions: leaves, branches, bark and trunk. The species composition of diseases of the infecting plant was up to ten. At the facade of student hostel No. 4, lesions of the tree trunk by the pathogen Cytospora foetida Vl. et For. In mixed crops of silver poplar among plantings of other plants near the facade of the archive, lesions of Septoria populi Desc., Virus VTM., Septoria candida, Desc. In the shelterbelt of the training and experimental field, there were leaf spots of Marssonina populi and Septoria populi Desc. In the façade of the Faculty of Philology, symptoms of Nicola salisus Wint. f. populorum Radh, Melampsora tremulae, Taphrina aurea For., Allocasuarina fraseriana (Miq.) L. A. S. Johnson. Psedomonas guercus Schem., Hypoxylon pruinatum Pon., heavily polluted with soot emissions during the heating season, mechanical damage, frost cracks were found on the facade of the Faculty of Agriculture. The reason is the northeast wind. The microflora of pathogens causing harm to silver poplar showed that the development and spread of diseases are not significant, reaching two points on the damage scale. The value of the index of development of pathogenic microflora indicates the beginning of the process of infection of poplars in the landscaped area of the student quarter of the city of Kyzyl. The annual preventive health measures contributed to the reduction in the development of lesions. Thus, in the green zone of the student quarter of Tuva State University, phytosanitary measures are regularly carried out to improve plantings of silver poplar and other plants.

The propagation and interaction of cracks under freeze-thaw cycling in rock-like material

In cold mountainous regions, the freeze-thaw cycling often leads to rock weathering, which might trigger spalling, significant landslides and rockfalls. In this work, we used combined experimental, theoretical and numerical approaches to investigate the mechanisms of frost cracking as a result of coupled effects of freeze-thaw cycling, confining stress and the interaction of multiple cracks. The experimental facility with a temperature cycling chamber and a high-pressure cell has been developed. We used rock-like materials (rock analogue samples made from cured cement and quartz-sand mixtures) to conduct the experiments. The rock-like samples contain pre-existing single or double initial cracks, which are then water filled and exposed to freeze-thaw cycling. The coupled thermal-hydro-mechanical modeling for analyzing fractures induced by freeze-thaw cycling was achieved by using a code that was previously developed named TOUGH-AiFrac. Good agreements between the TOUGH-AiFrac modeling and the laboratory experiments have been achieved including the exact paths of crack propagation. The experimental and numerical results show that the frost cracks tend to propagate in the direction of maximum principal stress. The results further show that the interaction effect between two frost cracks is significantly influenced by the position, orientation and offset of initial cracks, as well as the orientation of intact rock bridges between the cracks. At last, the stress shadow that was calculated by the TOUGH-AiFrac model between two cracks was discussed.

New data on the problem of the origin of Griva and Lake landscapes in the south of Western Siberia

The characteristic of the upper part of the borehole 486 drilled in 1981 on the Tyumensky Peninsula, located in the center of the Chany Reaches agglomeration is given. The main feature of the section is the presence of a horizon of large frost cracks in the roof of clays of the Lower Pliocene Novostanichnaya Formation, on which the upper Quaternary cover of Griva deposits occurs. The nature of the filling of cracks by the sediments of the overlying layer indicates that they were constantly filled with ice, which had already melted under the influence of the Grosswald Flow. This horizon is important for the reconstruction of the paleoclimate and paleogeography of the region. For the first time, data of palynological study of sediments of a typical Griva in the south of Western Siberia on the example of a section on the Cape Kazantsevsky Peninsula (the northern part of Lake Chany) are presented. Sediments contain pollen of woody and herbaceous plants, single spores of mosses and ferns, as well as microphytoplankton. The presence of cells of colonial algae of the genus Pediastrum suggests the accumulation of sediments in lacustrine conditions.

Thaw Settlement Monitoring and Active Layer Thickness Retrieval Using Time Series COSMO-SkyMed Imagery in Iqaluit Airport

Thaw consolidation of degrading permafrost is a serious hazard to the safety and operation of infrastructure. Monitoring thermal changes in the active layer (AL), the proportion of the soil above permafrost that thaws and freezes periodically, is critical to understanding the conditions of the top layer above the permafrost and regulating the construction, operation, and maintenance of facilities. However, this is a very challenging task using ground-based methods such as ground-penetrating radar (GPR) or temperature sensors. This study explores the integration of interferometric measurements from high-resolution X-band Synthetic Aperture Radar (SAR) images and volumetric water content (VWC) data from SoilGrids to quantify detailed spatial variations in active layer thickness (ALT) in Iqaluit, the territorial capital of Nunavut in Canada. A total of 21 SAR images from COSMO Sky-Med (CSK) were first analyzed using the freely connected network interferometric synthetic aperture radar (FCNInSAR) method to map spatial and temporal variations in ground surface subsidence in the study area. Subsequently, we built an ALT retrieval model by introducing the thaw settlement coefficient, which takes soil properties and saturation state into account. The subsidence measurements from InSAR were then integrated with VWC extracted from the SoilGrids database to estimate changes in ALT. For validation, we conducted a comparison between estimated ALTs and in situ measurements in the airport sector. The InSAR survey identifies several sites of ground deformation at Iqaluit, subsiding at rates exceeding 80 mm/year. The subsidence rate changes along the runway coincide with frost cracks and ice-wedge furrows. The obtained ALTs, ranging from 0 to 5 m, vary significantly in different sediments. Maximum ALTs are found for rock areas, while shallow ALTs are distributed in the till blanket (Tb), the intertidal (Mi) sediments, and the alluvial flood plain (Afp) sediment units. The intersection of taxiway and runway has an AL thicker than other parts in the glaciomarine deltaic (GMd) sediments. Our study suggests that combining high-resolution SAR imagery with VWC data can provide more comprehensive ALT knowledge for hazard prevention and infrastructure operation in the permafrost zone.

The Effects of Frost Cracks and Large Poplar Borer Damage on Stem Rot in Hybrid Aspen (Populus tremula L. × Populus tremuloides Michx.) Clones

Hybrid aspen (Populus tremula L. × Populus tremuloides Michx.) plantations may produce valuable sawlogs for the growing timber market and contribute to carbon sequestration. However, environmental risks such as stem rot, the spread of which is facilitated by insect or frost damage, may reduce the proportion of valuable timber. It is important to understand the various factors affecting the spread of aspen rot to mitigate negative impacts with tree breeding. This study aimed to assess the impact of frost cracks and large poplar borer on stem rot in hybrid aspen clones in two clonal trials in Latvia. Genetic parameters for the traits were also estimated. The presence of insect passages substantially increased the probability of stem rot without distinct clonal differences. A negative and mainly insignificant correlation was observed between rot and stem cracking. The highest broad-sense heritability (H2 = 0.21) and strong site-site genotypic correlation (0.86) showed that the probability of stem rot is genetically determined in the study material. Significant differences in diameter at breast height, the presence of stem rot, and its severity were found among the clones, albeit without undesirable positive correlation between growth and presence of decay. This indicated its potential to improve both productivity and rot resistance.

Assessment of the condition of Balsam poplar trees (Populus balsamifera L.) in a residental area of Bratsk

In this study, we investigated the health status of balsam poplar (Populus balsamifera L.) trees in a residential area of the city of Bratsk (Irkutsk Oblast, Russia). Visual and instrumental assessment of the health status of pruned and unpruned trees was performed. The identified internal defects in the tree were analyzed with a Resistograph device, which enabled the extent of decayed wood to be determined. Visual analysis revealed various types of damage: dried branches, brittle crowns, frost cracks, mechanical damage, curvature of trunks, decay and inclusions of foreign bodies. We compared trees with and without canopy pruning. We found that pruned trees were significantly more damaged than non-pruned trees. Decomposing wood at different stages of development was found in all the trees studied. A tree passport combining the visual and instrumental assessment data was compiled for each tree. The results of the research were used to formulate conclusions and recommendations for improving the management of urban trees in order to restore their ecological and aesthetic functions.

Stem Quality of European Beech in Latvia and Its Effect on Tree and Stand Monetary Value

Abstract Beech is expected to expand its range into the territory of Latvia due to climate change, but we lack information on its stem and wood quality as a measure of its economic importance. We studied external stem quality traits in beech stands with age of 69 to 131 years. Nine trees were cut and sampled to determine internal wood quality and the proportion of peelable cylinder. Tree value was calculated according to buckling by dimensions and buckling accounting for stem and wood defects. Trees of the second generation (69 years) had a significantly lower incidence of frost cracks (22.0% vs. 36.2%), epicormic branches (50.5 % vs. 65.8%), and forks (15.8% vs. 23.5%) as compared to trees from the first generation (115–131 years). All sampled trees had discolouration in the height of the first log. The proportion of the peelable cylinder was positively linked to tree height and ranged from 12% at the stump level to 33.4% at the tree height of 30 m. All analysed phenotypic traits decreased stand monetary value: frost cracks by 6% to 8%, all external traits by 16% to 20%, all external and internal traits by 29% to 33%.

Аналіз дендрофлори парку ім. Т. Г. Шевченка у м. Тернополі

The city of Ternopil is one of the regional centers of Ukraine, the rate of landscaping which is one of the highest. Among the plantations of the city with a large area (22,0 hectares) stands out the park of Taras Shevchenko, located on the banks of the Ternopil pond. V.M. Chernyak, V.O. Burma, I.O. Pyatkivsky, R.B. Dudyn, P.P. Tsaryk, S.M. Pidkhovna and others studied the flora of the city of Ternopil and the region. The dendroflora of the park includes 55 taxa of trees, shrubs and vines, which belong to 38 genera and 24 families. The most numerous in terms of number of representatives are the families Rosaceae and Pinaceae. The total number of woody plants is 1836 specimens. The park is significantly dominated by deciduous trees and shrubs (82%). In general, trees make up 77%, of which conifers – 12,4%. All woody plants of the park are phanerophytes, and mesophanerophytes dominate – 62%. In relation to light, light-loving species predominate (68%). 51% of plants are cold-resistant and only 19% are heat-loving. Most of the park's plants are resistant to environmental pollution (only 10% are not gas-resistant). The results of the study of plants in relation to fertility and soil moisture indicate favorable conditions for their growth and development, as most of them show medium and high demands on habitat conditions: 69% are meso- and mesohygrophytes and 56% – megatrophs. Based on the sanitary assessment of the plantations, it was found that about 8,5% of the park's plants have various damages: frost cracks, core rot, coppice, hollows. 8 dead trees were found, 32 specimens need sanitary pruning. 17 plants are recommended for removal for various reasons.

Assessment of the green spaces' state in the impact zone of the Pechenganikel smelter, the Murmansk region

The study of the state of green spaces in urbanized areas is important due to their sanitary, hygienic and aesthetic role in the harsh climatic conditions of the Arctic. The objects of research were the green spaces of the urban-type settlement Nikel (the Murmansk region). The assessment of the distribution of tree and shrub species by categories of life state was carried out; revealed damage to leaves by atmospheric emissions, insects and fungi. A high degree of damage from pollution was noted in birch, mountain ash and bird cherry; aspen up to 85 % damaged by aphids; mechanical damage to the trunks was noted in about 26 % of the surveyed trees; 5 % of trees have frost cracks in the trunk. In the course of a comparative assessment of the chemical composition of birch leaves growing in the urbanized territory of Nikel and in forest ecosystems along the gradient of atmospheric pollution in the impact zone of the Pechenganikel plant, it was found that the concentrations of pollutants in birch leaves in technologically disturbed areas exceed background values. Birch leaves in the southern direction from the plant accumulate higher concentrations of Ni, Cu, Pb, Co, Fe than in the western and northern directions. In 2019, the concentrations of heavy metals in birch leaves increased compared to the previous study period (2004). In the urban area, the content of pollutants exceeds not only the values of the regional background, but also the levels identified in forest ecosystems along the gradient of atmospheric pollution. Concentration coefficients Cc show abnormally high values for Ni, Cu, Pb, Co, Fe; the maximum Cc values are noted for Ni and Co.

The influence of stress anisotropy and stress shadow on frost cracking in rock

With growing research interest of liquefied natural gas storage in underground frozen host rock cavern, it is the key to have a comprehensive understanding of rock deformation and cracking under freezing and their impact on the stability of the underground storage caverns. In this work, a coupled thermo-hydro-mechanical model is developed in the framework of TOUGH-FEMM simulator to gain such understanding, where complex coupled processes involving water–ice phase transition as well as non-planar frost cracks are rigorously considered. In this model with the TOUGH-FEMM, heat transfer and fluid flow under freezing are simulated using TOUGH2, while mechanical deformation and cracking are simulated using the hybrid finite element-meshfree method (FEMM). The new modelling component for simulating temperature transfer and freezing-induced strain is validated against data from a previous laboratory experiment on sandstone by Neaupane et al. Finally, the influence of stress anisotropy and stress shadow on frost cracking are discussed using a set of experiments and TOUGH-FEMM modelling. The experimental and numerical results show that frost-induced cracks propagate towards to the direction of the maximum principal stress, while the stress shadow between multiple cracks has a significant impact on the damage pattern.

Properties of Oak Roundwood with and without Frost Cracks

The aim of this study was to examine certain properties of sessile oak wood (Quercus petraea (Matt.) Liebl.) with frost cracks, such as density (ρ), modulus of rupture (MOR), modulus of elasticity (MOE), and compressive strength in all anatomical directions and to compare it with control trees without frost cracks. Oak with frost cracks had a higher wood density (ρ = 765 kg × m−3) than the control (ρ = 650 kg × m−3). However, despite its lower density, the control oak was characterized by noticeably better mechanical parameters, with the exception of the compressive strength in radial and tangential directions. Differences in mechanical parameters reached up to 26%. The tests were performed on wood taken from trees with frost cracks that formed over 10 years to several decades ago. Frost cracks can render wood vulnerable to fungi growth, which leads to rotting and discoloration. Differences in strength were found on samples with no visible signs of decay, as they were cut at a distance from the crack. Nonetheless, the observed differences in strength allowed us to conclude that the shreds of fungi, as well as decay, may occur in the entire volume of the frost-damaged log. Such wood is, therefore, of a lower quality than that made of logs without any frost damage. Trees with frost cracks should be progressively be felled during the periodic intermediate cutting, as their wood quality may systematically deteriorate over the years.

Видове багатство дендрофлори та естетичне оцінювання фітоценозів парку смт Магдалинівка

Дендрофлора парку смт Магдалинівка налічує 347 прим., що належать до 19 видів і 15 родин. У насадженнях переважають Aesculus hippocastanum, Ulmus scabra, Betula pendula. Родини презентовані переважно 1-2 видами, за винятком Rosaceae. Родини Hippocastanaceae, Ulmaceae та Betulaceae мають найбільшу представленість за кількістю примірників, порівняно з іншими. Частка видів аборигенної дендрофлори становить 53,32 %. Найбільша частка від загальної кількості інтродуцентів становлять представники з Південної та Південно-Східної Європи. Переважна кількість дерев у насадженні має висоту від 8,1 до 10,0 м (23,3 % щодо всіх рослин). За діаметром штамба переважають дерева зі значеннями цього показника від 22,1 до 26,0 см (16,1 %), чисельними є групи рослин з діаметрами 26,1-30,0; 34,1-38,0 та від 18,1-22,0 см. Діаметр одного з найстаріших дерев парку Populus alba становить 108 см. За життєвим станом дещо більше половини насаджень належить до категорії "здорові", серед них багато примірників Betula рendula, Juglans regia, Ulmus scabra, Tilia cordata. До ослаблених належить 110 дерев, до сильно ослаблених – 43, до тих, що відмирають, – усього 6 шт. Індекс стану деревостану для парку становить 80,14, що характеризує його як здоровий. За екологічними вимогами асортимент парку тільки частково відповідає умовам зволоження території, проте майже повністю – родючості ґрунту. За таксаційно-фітоценотичною шкалою загальна естетичне оцінювання фітоценозу парку становить 31 бал. У парку ростуть дерева з вираженими фітонцидними властивостями, а саме: Acer platanoides, Betula pendula, Syringa vulgaris, а також Tilia cordata, Aesculus hippocastanum та Sorbus aucuparia.

Stratigraphy and chronology of Pleistocene coastal deposits in northern Aquitaine, France: a reinvestigation

Pleistocene deposits exposed along the coast of the Medoc area, south-west France, represent valuable palaeoenvironmental archives that have been the subject of extensive work in the past few decades. To further understand the palaeoenvironmental history and sedimentary dynamics of these deposits, a detailed lithostratigraphic study was performed on a series of new sections. Additionally, new chronological data were obtained from the combination of luminescence (OSL, IR-RF) and electron spin resonance (ESR) dating of quartz and feldspar grains (Kreutzer et al., 2018). The investigated sections comprise estuarine, lacustrine and peaty deposits (Negade Formation, Argiles du Gurp Formation), aeolian sands (Sables du Gurp Formation) and colluvial units (Gres de l'Amelie Formation). The Argiles du Gurp Formation, in which many remains of Palaeoloxodon antiquus were found, support the hypothesis of a progressive replacement of a tide-inluenced marsh by a peaty fresh-water pond during the Holsteinian Interglacial (MIS 11). IR-RF dating of green estuarine clays at L’Amelie, in the northernmost part of the investigated area, strongly suggests that they do not belong to the Argile du Gurp Formation, but were deposited during the MIS 9 sea level highstand. The estuarine deposits are overlain by sandsheets (Sables du Gurp Formation) dated to MIS 10 and MIS 8 at Pointe de la Negade in the southern part of the study area, and to MIS 8 at L’Amelie. Syngenetic frost cracks testify to a periglacial depositional environment. Regional studies show that the Sables du Gurp Formation is a local equivalent of the Sables des Landes Formation, and corresponds to the oldest aeolian phase recorded in south-west France so far. Colluvial material (Gres de l'Amelie Formation) dated to the Weichselian pleni-glacial (MIS 2) ill small palaeo-valleys incised in the Sables du Gurp Formation. Holocene coastal dunes cover the whole sequence.

ОЦІНЮВАННЯ ФІТОСАНІТАРНОГО СТАНУ ДЕРЕВНИХ НАСАДЖЕНЬ ЛАНДШАФТНОЇ ДІЛЯНКИ "СХІДНА БАЛКА" ДЕНДРОПАРКУ "ОЛЕКСАНДРІЯ" НАН УКРАЇНИ

Визначено фітосанітарний стан деревних рослин Східної балки дендрологічного парку "Олександрія" в межах наукової теми "Відновлення та реконструкція історичних ландшафтних ділянок рівнинно-балкового типу в Державному дендрологічному парку "Олександрія" НАН України". Ураження хворобами і шкідниками виявлено на 331 екз. (36,8 % від загальної кількості) деревних рослинах, що належать до 19 видів. Описано основні хвороби і ураження шкідниками у дерев. Розвиток хвороб на деревах та їх фітосанітарний стан визначено за фітоценотичними умовами та екологічними умовами мезорельєфу. Більшість хвороб у деревних рослин протікала в хронічній формі, не призводячи до втрати декоративності дерева і до ослаблення його життєздатності. Гострий характер спричинило короїдне всихання сосни зі супутньою синявою та всихання Fraxinus excelsior L. із симптомокомплексом ознак, характерних для хвороби Chalara fraxinea. Ці ураження призводять до стрімкого всихання дерев, розпаду ландшафтних композицій. Під час планування оптимізації насаджень ділянки "Східної балки" потрібно враховувати фітопатологічний стан дерев, прогнозувати їх відпад, проводити заходи з індивідуального лікування і догляду дерев, профілактичні і захисні заходи.

Морозобойные трещины как специфический патологический признак деревьев дуба рекреационной зоны г. Воронежа

The article is devoted to the most specific to oak pathological signs in the plantations of the recreational zone of the city of Voronezh. These include frost cracks. Regularities of the manifestation of frost-breaking cracks and their significance are analyzed. On the basis of literature sources it is established that frost cracks appear on the trunk of oaks not only in extremely severe, but also in ordinary winters and affect the best, cleaned from the branches, part of the lower trunk, significantly reducing the yield of valuable assortments. The mechanism of crack formation on the trunks of living trees is given, with rapid and significant lowering of the ambient temperature. Occurrence of this feature in the oak forests of the forest-steppe is identified and analyzed. Evaluation of the role of frost crack in the weakening of oak trees is conducted. The causes and regularities of their appearance in various types of plantations are revealed. The data for all frost cracks are recorded with their differentiation into overgrown and unbroken cracks. Variation of this feature in various plantations is shown. Analysis of the structure of frost crack as a result of a disproportionate thermal contraction of the tissues of the outer and inner parts of the trunk is made. The location of the frost cracks is analyzed depending on the sides of the light and depending on the inclination of the trunk. Manifestations of the occurrence of frost cracks are analyzed depending on the combination of the inclination of the trunk and the sides of the light. Comparative characteristic of frost cracks on height of a trunk and extent on trees of other species is made. As a result, the occurrence of frost cracks in all ripening and ripe oak plantations of the recreational zone of Voronezh has been revealed. The ability of frosts to infect oak trees with stem decay and deteriorate the sanitary state of plantations is revealed. It is determined that frost cracks appear in the draft timber facing the north and east and have a well-defined specificity in place of location and extent.

Geochemical characteristics of the infilling of ground wedges at Puerto Deseado (Santa Cruz, Argentina): palaeoenvironmental and chronological implications

Ground wedge structures of cryogenic origin are common in the Quaternary sediments along the coast of the Patagonia, and their formation is related to climatic cold events experienced by this area in the Late Quaternary. The infilling sediments of two wedges generations were analyzed in the area of Puerto Deseado. Bulk chemistry (major elements), X-ray diffraction (XRD), morphoscopic observations with Scanning Electronic Microscope (SEM) and chemical analyses of volcanic glass shards were undertaken to provide indications about infilling sediment provenience, along with chronological constraint for wedge formation. Bulk chemistry and XRD patterns indicate a significant SiO2-enriched composition of the sediment infilling compared to the most of the loess deposits of the North Argentina and the present day dust originated in Patagonia. This was interpreted as due to the nature of the bedrock present over the Deseado Massif. SEM morphoscopic characteristics of glass shards evidence typical aeolian reworking features, with impact structures and indented edges of the volcanic fragments. Chemical analyses of the glass shards indicate that they were probably generated by the H0 eruption (17,300-17,400 cal yr BP) of the Hudson volcano. Volcanological data indicate that H0 eruption dispersed toward NE, but volcanic glasses were available for reworking due to a WNW component in the western wind direction. Over the Deseado Massif structural high the glass shards mixed with sediments enriched in SiO2, and were eventually deflated further to SE reaching the present coastal area and infilling the frost cracks. The age of the glass shards (17,300-17,400 cal yr BP) and that of the sandy layer affected by cryogenic structures (14,670±750 yr BP) well constrain to the Late Glacial both wedge generations.