Extreme Cold Stress Research Articles

Thermal bioclimate in Greece based on the Universal Thermal Climate Index (UTCI) and insights into 2021 and 2023 heatwaves

The research on the thermal bioclimate is increasingly valuable in the context of climate change. Human well-being is threatened not only from direct exposure to extreme thermal conditions and complications from underlying health issues but also from disruptions of health and social services. This study aims at examining the thermal bioclimate in Greece. Data of ERA5-Land reanalysis dataset were used to estimate the Universal Thermal Climate Index (UTCI, in °C). The analysis covered a 30-year period (1991–2020) examining UTCI climatology and trends. Additionally, the intensity of two recent heatwaves which occurred in summers 2021 and 2023 was assessed. During the period 1991–2020, the UTCI equivalent temperature ranges between -49.8 °C and 51.9 °C [mean ± standard deviation (sd) = 13.3 ± 12.2 °C] classifying thermal stress from ‘extreme cold stress’ to ‘extreme heat stress’. Across the country, the mean UTCI ranges from 7.5 °C to 17.8 °C (mean ± sd = 13.3 ± 2.1 °C), with a decrease of 0.5 °C per latitude degree. Mountainous regions exhibit the lowest UTCI equivalent temperatures, while inland plains display higher UTCI equivalent temperatures, especially in the eastern regions of the country. An increasing trend in mean annual UTCI (mean = 0.05 °C/year) is identified, more pronounced in higher latitude regions. Both the 2021 and 2023 heatwaves were exceptionally severe, with about 99% of the population to experience mean UTCI equivalent temperatures falling within stress categories of ‘moderate heat stress’ and above. The 2023 heatwave set a new record with the highest absolute maximum UTCI (52.1 °C) and number of heat stress hours compared to the period 1991–2020. The bioclimatic maps developed in this study analyze the spatial variability in the thermal conditions across Greece identifying high-risk areas. These findings can contribute to impact studies for tourism, energy efficiency, urban design and public health purposes.

The freeze-avoiding mountain pine beetle (Dendroctonus ponderosae) survives prolonged exposure to stressful cold by mitigating ionoregulatory collapse.

Insect performance is linked to environmental temperature, and surviving through winter represents a key challenge for temperate, alpine and polar species. To overwinter, insects have adapted a range of strategies to become truly cold hardy. However, although the mechanisms underlying the ability to avoid or tolerate freezing have been well studied, little attention has been given to the challenge of maintaining ion homeostasis at frigid temperatures in these species, despite this limiting cold tolerance for insects susceptible to mild chilling. Here, we investigated how prolonged exposure to temperatures just above the supercooling point affects ion balance in freeze-avoidant mountain pine beetle (Dendroctonus ponderosae) larvae in autumn, mid-winter and spring, and related it to organismal recovery times and survival. Hemolymph ion balance was gradually disrupted during the first day of exposure, characterized by hyperkalemia and hyponatremia, after which a plateau was reached and maintained for the rest of the 7-day experiment. The degree of ionoregulatory collapse correlated strongly with recovery times, which followed a similar asymptotical progression. Mortality increased slightly during extensive cold exposures, where hemolymph K+ concentration was highest, and a sigmoidal relationship was found between survival and hyperkalemia. Thus, the cold tolerance of the freeze-avoiding larvae of D. ponderosae appears limited by the ability to prevent ionoregulatory collapse in a manner similar to that of chill-susceptible insects, albeit at much lower temperatures. Based on these results, we propose that a prerequisite for the evolution of insect freeze avoidance may be a convergent or ancestral ability to maintain ion homeostasis during extreme cold stress.

Effects of combined extreme cold and drought stress on growth, photosynthesis, and physiological characteristics of cool-season grasses

Abiotic stress is an important factor affecting turf establishment and limiting the sustainability of the turf industry. To alleviate the effects of combined cold and drought stress in cold- and drought-prone regions, it is essential to select and introduce turfgrass germplasms that are suitable for these conditions for successful turf establishment. Thus, we evaluated the effects of combined extreme cold and drought stress on the morphological, plant leaf functional, photosynthetic, and physiological and biochemical traits of 16 wild annual bluegrass (Poa annua) germplasms. We found that there were significant differences (P < 0.05) among different provenances, combined cold and drought stress, and the main interaction factors. Combined cold and drought stress altered the morphological characteristics of the 16 germplasms to varying degrees. Furthermore, combined cold and drought stress significantly reduced the net photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (Tr), instantaneous water use efficiency (WUE), chlorophyll content, chlorophyll fluorescence parameters, accumulated intercellular CO2 concentration (Ci), and relative electrical conductivity (REC) and malondialdehyde (MDA), proline (Pro), soluble protein (SP), soluble sugar (SS), superoxide anion (O2.-), hydrogen peroxide (H2O2), and hydroxyl radical (·OH) and other active oxygen, and increased the superoxide dismutase activity (SOD), peroxidase activity (POD), catalase activity (CAT), ascorbate peroxidase activity (APX) and glutathione reductase (GR) activities. Comprehensive evaluation using principal component analysis (PCA), membership function analysis, and clustered heatmaps indicated that the ‘HZ’ germplasm had stronger combined cold and drought tolerance, whereas the ‘ZQ’ germplasm was more sensitive to combined cold and drought, which was roughly consistent with the order of morphological damage symptoms. Therefore, it is recommended to use the ‘HZ’ germplasm for planting projects in cold- and drought-prone areas, while the ‘ZQ’ germplasm is more suitable for use under warmer and non-water-deficient conditions.

Changes in biothermal conditions in the Sudetes Mountains and their foreland in relation to the circulation conditions

Abstract Progressing climate change is often reflected in changing biometeorological conditions. The Sudetes Mountains, located in the Polish–Czech border area, are concerned by this phenomenon. The goal of this paper is to evaluate the influence of atmospheric circulation on multiannual changes in biothermal conditions using the UTCI index. In the analysis, data for 1991–2020, from both Polish and Czech meteorological stations, was considered, while the circulation factor was evaluated using the Lityński classification. The research indicated a positive tendency of UTCI values for the majority of circulation types, which consequently contributed to a decrease in the frequency of cold stress categories. In the summits, a decline in the number of days with extreme cold stress was the most characteristic feature, especially under anticyclonic and northern circulation. Tendencies of heat stress occurrence were in most cases statistically insignificant, except for cyclonic and transitional circulation.

Multiomics analyses reveal the mechanisms of the responses of subalpine treeline trees to phenology and winter low-temperature stress.

Withstanding extreme cold stress is a prerequisite for alpine treeline trees to persist and survive. However, the underlying mechanism by which treeline trees sense phenological changes and survive hard winters has not been fully elucidated. Here, we investigated the physiology, transcriptome, and metabolome of the subalpine treeline species Larix chinensis to identify the molecular mechanism of phenological and cold resistance. Calcium and antioxidant enzyme activities (e.g., superoxide dismutase and glutathione peroxidase) are essential for coping with winter cold stress in L. chinensis. Transcriptome analysis revealed that circadian rhythm and phytohormone signalling transduction played important roles in regulating L. chinensis phenological changes and cold stress responses. The variations in the transcriptome identified were accompanied by the specific accumulation of flavones, flavonols, and monosaccharides. The flavonoid biosynthesis and phenylpropanoid biosynthesis pathways played important roles in the adaptation of L. chinensis to the extreme winter environment, and flavone and flavonol biosynthesis was an important pathway involved in bud burst. In addition, temperature and photoperiod had synergistic influences on the formation and release of bud dormancy. Thus, our findings provided new insights into the mechanism of subalpine treeline formation.

Особенности реакции сердечно-сосудистой системы организма человека на погружение в холодную воду

Winter swimming implies extreme cold stress, which can cause respiratory disorders, arrhythmias, and elevated blood pressure even in generally healthy people. Pre-training examinations for athletes practicing winter swimming should include additional criteria evaluating reaction of the cardiovascular system (CVS) to cold water. This study aimed to determine the risk of pathological abnormalities in the examined individuals exhibiting different CVS reactions to immersion in cold water. We assessed reactivity of CVS with the help of a cold-hypoxic test (CHT), following a previously developed algorithm. The subjects of the analysis were CVS reactions to CHT and physical data collected after swimming in cold water. The study involved 255 female and 205 male participants, all of them almost healthy, aged 18–25 years. They participated in testing in a laboratory setting. Poly-Spektr-8/E cardiograph was used to record ECGs, and GraphPad Prism 8 package for Windows 10 for statistical analysis. Findings: in highly reactive and reactive participants, CHT causes lengthening of the PQ interval, with its value in the initial state (IS) equal to 158 ± 7.2, and with CHT — 178 ± 9.1 (p &lt; 0.01); in subjects of he paradoxical type, CHT, against the background of higher pulse, triggered increase of QTc, which in the IS was 405 ± 7.1, with CHT — 420 ± 7.5 (p &lt; 0.05). As for blood pressure, on average, CHT made it grow, SBD by 17.4 ± 4.3 mmHg, DBP by 12.9 ± 3.1 mmHg (p &lt; 0.05). Swimmers adapted to cold, when swimming in cold water, had QTc above normal in 50% of cases: e.g., if IS of QTc was 434 ± 24 s, after swimming it increased to 492 ± 25 s. After a 200 m swim at t = 1.5–2 °C, the average blood pressure in the group, compared to IS, increased, with SBD growing by 16.9 ± 3.1 mmHg, and DBP — by 12.3 ± 2.3 mmHg (p &lt; 0.05). Having analyzed the data, we conclude that CHT can be the basis of additional criteria extending examinations for athletes seeking admittance to cold water swimming.

Comprehensive optimization of urban building cluster morphology based on microclimate: A two-level optimization approach

Building cluster morphology plays a crucial role in shaping urban microclimate. Due to the global warming and urban expansion, urban microclimate environment has encountered several problems, like extreme heat or cold stress events. The practical design of building clusters often involves multi-scale, multi-faceted problems and contradiction points which is always challenging to solve. This paper proposes a “two-level” optimization framework for the layout and form design of building clusters in the aspect of engineering applications. A case design project is used to demonstrate the effectiveness of the proposed framework through detailed seasonal simulation. Results show that, comparing with the base case, the candidate design plan (i.e., Plan C) is attractive given the mean UTCI of the selected locations is lower by 0.73 °C in the cooling season noon and higher by 1.91 °C in the heating season at night. Results also indicate that the layout of a building cluster has greater impacts on the outdoor thermal environment during the heating season than the cooling season. Considering Plan C still has a heat/cold stress, further refinements have been performed on the local micro climate to adjust the wind corridor and solar radiation at the lower-level of architectural form. Finally, comprehensive design strategies have been synthesized for the building cluster design.

Establishing a baseline for thermal stress conditions – A high-resolution radiative perspective

As Earth's climate warms, outdoor thermal conditions that threaten human life are becoming more frequent and severe. To prepare and adapt effectively to this challenge, an understanding of both current baseline thermal conditions and how thermal conditions will change throughout the 21st century is vital. However, current efforts to measure and model baseline thermal conditions have generally ignored the contributions of radiation, and have been performed at coarse temporal and spatial resolutions. In this study, we present the first hourly multidecadal bioclimatology of mean radiant temperature and the Universal Thermal Climate Index, driven by meteorological reanalysis data and processed using the Solar and LongWave Environmental Irradiance Geometry model. This process allows for the calculation of the influence of urban geometry on radiation fluxes at 1 m spatial scale. The results demonstrated that this technique provides significant insight into thermal stress conditions, while also presenting some inherent challenges. The presence of bimodal thermal stress conditions driven by shade, significant variability of heat stress conditions on multiple time scales, and differences in the factors that drive extreme heat and cold stress were revealed. Our study showed that such high-resolution modelling of thermal stress is a feasible technique with the potential to provide significant value in understanding outdoor thermal stress in complex urban environments.

Effect of regional baric systems on the occurrence of bi- oclimatic conditions in Poland

The present study concerns the determination of the characteristics of bioclimatic conditions, as well as the synoptic situations related to the occurrence of thermal stress conditions, in Poland. The study was based on daily data obtained from the Institute of Meteorology and Water Management – National Research Institute from the period 1966–2020 for 37 synoptic stations in Poland. Based on the obtained data, values of the Universal Thermal Climate Index (UTCI) were calculated. The occurrence of heat stress increases from the north to the south, corresponding with the variability of influx of solar radiation, and is modified by factors at a smaller spatial scale. The results of this paper evidently point to the cooling effect of the waters of the Baltic Sea. In circulation conditions favouring strong and very strong heat stress, e.g. in two of the designated circulation types (T1 and T2), the occurrence of an expansive high-pressure ridge in the Atlantic-European area is typical, stretching from the region of the Azores High towards the north- east, with a secondary high developed within its boundaries. In the third of the designated circulation types (T3), the high-pressure area extends from the Azores eastwards, reaching the Black Sea. Each of the three circulation patterns associated with the unfavourable biometeorological conditions of very strong and extreme cold stress in Poland is characterised by strong pressure centres formed in the Euroatlantic region, triggering the airflow from the northern (T4) or eastern (T5, T6) sector.

Evaluation of outdoor thermal comfort conditions: evidence from the Serbian major ski resort over the last 30years.

The study aims to present reliable information about thermal conditions and their impacts on visitors to ski travel destinations. Mountain tourism areas are specific since high altitudes affect the ambient weather conditions which can affect different types of human activities. In this paper, the thermal comfort and its changes in Kopaonik Mountain, the most popular ski resort in Serbia over the last 30years, have been evaluated. Information about thermal comfort is presented by using the Universal Thermal Climate Index (UTCI), physiologically equivalent temperature (PET), and modified physiologically equivalent temperature (mPET) in 3-h resolution for the period 1991-2020. The results indicate prevailing cold stress all year round. Days with moderate, strong, and very strong heat stress were not recorded. Strong and extreme cold stress prevailed during winter, while slight and moderate cold stress prevailed during summer. Transitional seasons were very cold, but autumn was more comfortable than spring. The occurrence of days with neutral and slightly warm/cool conditions is concentrated in the summer months. However, summer is not used enough for tourism because the choice of tourists to stay at Kopaonik is not primarily based on favorable bioclimatic conditions, but on resources for winter tourism. With global warming, the annual number of thermally favorable days has been increasing, while the number of days with extreme and strong cold stress is decreasing. Continuing this trend can significantly influence tourism in the future, and therefore, new strategies in ski resorts will be required to adapt to the changing climate.

Impact of Cold Stress on Physiological, Endocrinological, Immunological, Metabolic, and Behavioral Changes of Beef Cattle at Different Stages of Growth.

The purpose of this study was to investigate the effect of cold stress (CS) on the physiological, blood, and behavioral parameters of beef cattle according to their growth stage. Twelve calves in the growing stages (220.4 ± 12.33 kg, male and non-castrated) and twelve steers in the early fattening stages (314.2 ± 18.44 kg) were used in this experiment. The animals were randomly distributed into three homogenized groups (four animals each) for 14 days, namely threshold, mild-moderate cold stress (MCS), and extreme cold stress (ECS), according to the outside ambient temperature. The feed and water intakes were recorded daily. The physiological parameters, blood parameters, and behavioral patterns were measured weekly. All data were analyzed using repeated-measures analysis. The calves exposed to the ECS decreased (p < 0.064, tendency) their dry matter intake compared to the threshold and MCS groups. The HR and RT increased (p < 0.001) in the ECS compared to the threshold in calves and steers. Moreover, increased (p < 0.05) blood cortisol, non-esterified fatty acids (NEFA), and time spent standing were observed after exposure to ECS in calves and steers. However, the calves exposed to the ECS had decreased (p = 0.018) blood glucose levels compared to the threshold. In conclusion, ECS affects the dry matter intake, HR, RT, blood cortisol, NEFA, and behavioral patterns in beef calves and steers. This phenomenon indicated that beef cattle exposed to CS modulated their behavior and blood parameters as well as their physiological response to maintain homeostasis regardless of the growth stage.

Larval nutritional-stress and tolerance to extreme temperatures in the peach fruit fly, Bactrocera zonata (Diptera: Tephritidae)

ABSTRACTWithin the factors affecting insect tolerance to extreme environmental conditions, insect nutrition, particularly of immature stages, has received insufficient attention. In the present study, we address this gap by investigating the effects of larval nutrition on heat and cold tolerance of adult Bactrocera zonata – an invasive, polyphagous fruit fly pest. We manipulated the nutritional content in the larval diet by varying the amount of added yeast (2–10% by weight), while maintaining a constant sucrose content. Adults derived from the different larval diets were tested for their tolerance to extreme heat and cold stress. Restricting the amount of yeast reduced the efficacy of the larval diet (i.e. number of pupae produced per g of diet) as well as pupal and adult fresh weight, both being significantly lower for yeast-poor diets. Additionally, yeast restriction during the larval stage (2% yeast diet) significantly reduced the amount of protein but not lipid reserves of newly emerged males and females. Adults maintained after emergence on granulated sugar and water for 10 days were significantly more tolerant to extreme heat (i.e. knock-down time at 42 oC) when reared as larvae on yeast-rich diets (8% and 10% yeast) compared to counterparts developing on a diet containing 2% yeast. Nevertheless, the composition of the larval diet did not significantly affect adult survival following acute cold stress (exposure to −3°C for 2 hrs.). These results are corroborated by previous findings on Drosophilid flies. Possible mechanisms leading to nutrition-based heat-tolerance in flies are discussed.

Cold stress triggers freezing tolerance in wheat (Triticum aestivum L.) via hormone regulation and transcription of related genes.

Low temperatures limit the geographic distribution and yield of plants. Hormones play an important role in coordinating the growth and development of plants and their tolerance to low temperatures. However, the mechanisms by which hormones affect plant resistance to extreme cold stress in the natural environment are still unclear. In this study, two winter wheat varieties with different cold resistances, Dn1 and J22, were used to conduct targeted plant hormone metabolome analysis on the tillering nodes of winter wheat at 5 °C, -10 °C and -25 °C using an LC-ESI-MS/MS system. We screened 39 hormones from 88 plant hormone metabolites and constructed a partial regulatory network of auxin, jasmonic acid and cytokinin. GO analysis and enrichment of KEGG pathways in different metabolites showed that the 'plant hormone signal transduction' pathway was the most common. Our study showed that extreme low temperature increased the most levels of auxin, cytokinin and salicylic acid, and decreased levels of jasmonic acid and abscisic acid, and that levels of auxin, jasmonic acid and cytokinin in Dn1 were higher than those in J22. These changes in hormone levels were associated with changes in gene expression in synthesis, catabolism, transport and signal transduction pathways. These results differ from the previous hormone regulation mechanisms, which were mostly obtained at 4 °C. Our results provide a basis for further understanding the molecular mechanisms by which plant endogenous hormones regulate plant freezing stress tolerance.

Examining the impact of urban canyons morphology on outdoor environmental conditions in city centres with a temperate climate

• The relationship between urban geometry parameters and outdoor environmental conditions in urban areas was examined. • The study tested threshold values in urban design guidelines by experiential means. • The findings demonstrated the effect of urban geometry parameters as environmental mitigation measures. The concept of future-proofing cities seeks to minimize environmental impacts and achieve sustainability by utilising various mitigation and adaptation techniques, specifically by improving urban fabric. Different urban forms and parameters have been extensively investigated in hot, arid and humid climates, however, it is less in temperate climates. In the UK, the current local urban design guides meet the needs of designers and urban planners, however, these guides are still considered descriptive and lack in-depth environmental assessment. This study aims to investigate the recommended threshold values in the National Model Design Code against real sites with different urban canyons morphologies to examine their impact on outdoor environmental conditions. The study used quantitative methods by conducting a review study, a survey of UK urban design guides and modelling using simulation via RayMan and IESVE. The study targeted pre-selected sites in Cardiff and Bristol that were identified as zones with urban heat stress. The results showed that the Aspect Ratio and Sky View Factor in two cities have significantly impacted outdoor environmental conditions in urban areas subsequently affecting the Physiological Equivalent Temperature (PET). The results showed that the recommended values have a significant impact on the outdoor thermal performance of the pre-selected urban canyons. The findings demonstrated that modifying the width of streets and changing the Aspect Ratio and SVF resulted in achieving a positive impact during summer when both factors have a direct relationship. However, when the Aspect Ratio and SVF have an inverse relationship, the results showed extreme cold stress during winter. Therefore, maintaining a direct relationship between the Aspect Ratio and SVF would help to improve outdoor conditions.

Identification of QTLs controlling cold tolerance in cucumber (Cucumis sativus L.) seedlings

Cucumber (Cucumis sativus L.), an essential and economically important vegetable crop, is sensitive to cold stress. Cucumber seedlings exposed to extreme cold stress seriously reduce cucumber yield, however, few cold-tolerant genes have been identified yet. In this study, a 186 recombinant inbred lines (RILs) population constructed by crossing two inbred lines, cold-tolerant ‘CG104’ and cold-sensitive ‘CG37’, was used to identify loci associated with cold tolerance in cucumber seedlings. Genetic analysis of the chilling injury index (CII) of the RILs population showed that cold tolerance in cucumber seedlings was quantitatively inherited. One QTL named qCT6.1 was repeatedly detected. It was delimited by two flanking markers (6SSR13741 and 6SSR19970) and explained 6.2% and 11.0% of the phenotypic variation in two different experiments, respectively. Furthermore, the qCT6.1 was delimited to a 271.99 kb region (flanking markers Indel8 and Indel9) using 1500 F2 individuals, containing 41 annotated genes. Via sequence and expression analysis, we speculated that CsaV3_6G042810, encoding AP2/B3-domain, was likely to be the candidate gene regulating cucumber cold tolerance. These results provide insight into the genetic basis of cucumber cold tolerance and lay a solid basis for enhancing molecular breeding.

The Value of Myocardium and Kidney Histopathological and Immunohistochemical Findings in Accidental Hypothermia-Related Fatalities.

Background and Objectives: The post-mortem diagnosis of hypothermia is challenging in forensics. The aim of our study was to detect the kidney and heart histopathological changes that occurred in a group of hypothermia-related fatalities. Materials and Methods: The cohort included 107 cases identified in the database of our department between 2007 and 2021, which have been associated with extreme cold stress. Demographic and clinicopathological data were collected from the medico-legal reports. Archived tissue samples were evaluated to identify the histopathological features, in routine haematoxylin-eosin (H&E), Periodic acid-Schiff (PAS), and Masson's trichrome stainings, while cardiac sirtuin1 (SIRT1) and renal ubiquitin (Ub) immunostaining have been performed. Results: The majority of cases exposed to low temperatures were males (76%) from rural regions (68.2%) during the cold season. Paradoxical undressing was documented in 9.3% of cases. The common comorbidities included alcoholism (50.5%), neuropsychiatric diseases (10.3%), diabetes mellitus (3.7%), and lung tuberculosis (4.7%). The microscopic heart exam revealed areas of myocardial degeneration (100%), contraction bands (95.3%), fatty change (13.1%) and focal wavy contractile myocardial cells. Basal vacuolisation of renal tubular epithelial cells (Armanni-Ebstein lesions) (21.5%), focal tubular necrosis (7.5%), tubular renal cysts (7.5%), interstitial haemorrhages (5.6%), diabetic kidney disease (3.7%), background benign nephroangiosclerosis (42.1%), variable thickening of tubules and corpuscles basement membranes, capsular space amorphous material, and intratubular casts were identified in kidney tissue samples. Myocardial cells displayed SIRT1 weak expression, with a loss of immunopositivity correlated with areas with contraction bands, while a variable Ub expression was observed in renal corpuscles capsules, proximal, distal, and collecting renal tubules, Henle's loops, urothelium, and intratubular casts. Conclusions: In the context of the current concept that death associated with hypothermia is still a diagnosis of exclusion, our findings suggest that the microscopic exam provides relevant data that support the diagnosis of hypothermia-related fatalities in appropriate circumstances of death. A deeper insight into the histopathologic findings in hypothermic patients may lead to new therapeutic approaches in these cases.

Morphological and physiological response of Chinese tallow (Triadica sebifera) to an extreme cold spell in subtropical, coastal forests of China

Acute and extreme weather events can cause considerable damage to the tissues of trees, including stem death and branch or leaf distortion, which may limit their survival and reproduction. In January 2016, a rare cold spell impacted the coastal forests of subtropical China. Using post-hoc assessments, we evaluated the morphological and physiological response of Chinese tallow (Triadica sebifera L.) to the extreme cold spell in two distinct ecoregions, one (Xiangshan, China) representing the cold spell impacted zone and the other (Taizhou, China) representing the non-affected zone. To determine if the extreme cold events impacted the vigor of Chinese tallow, we assessed differences in growth rate, leaf characteristics, and leaf gas exchange. As age may affect tree morphological and physiological response to stress, we grouped subject trees into three distinct cohorts, namely, seedlings (1–2 years old), young-aged (5–6 years old), and middle-aged (10–12 years old). Our results suggest that although tree height and diameter did not differ, leaf area expansion and leaf mass were reduced in the impacted zone. In seedling and young-aged trees, the cold spell significantly reduced leaf net photosynthetic (An), transpiration rates (Tr), stomatal conductance (Gs) and water use efficiency (WUE) while leaf intercellular CO2 concentration (Ci), vapor pressure deficit (Vpd), and intercellular CO2 pressure (Ci-Pa) increased. In contrast, the middle-aged group was less responsive to the cold spell. Across all cohorts, the event did not affect leaf temperature (Tleaf), but the activity of superoxide dismutase (SOD) and peroxidase (POD) decreased. We also detected increases of leaf malondialdehyde (MDA) and free proline (Pro) contents in young-aged and middle-aged groups. Hence, the extreme cold spell caused remarkable negative effects on the morphological and physiological traits of Chinese tallow. Redundancy analysis revealed that the cold spell also impacted the subsequent recovery process of damaged Chinese tallow by reducing the ability of leaf to utilize microenvironmental resources (radiation, air humidity, and CO2) for gas exchange. Results from this study are important to strengthen our understanding of Chinese tallow responding to extreme cold stress within its native range, also be helpful to predict the distributions of Chinese tallow in its invasive range where it has devastating impacts to coastal ecosystems in the southeast US.

Impact of Atmospheric Circulation on the Occurrence of Very Strong and Extreme Cold Stress in Poland

AbstractThe primary objective of the study was the determination of the spatial and multiannual variability of occurrence of days with very strong and extreme cold stress in Poland according to the Universal Thermal Climate Index (UTCI), as well as determination of baric conditions favouring their occurrence. The study was based on data from the years 1966/67 to 2018/19 from the Institute of Meteorology and Water Management – National Research Institute and National Centre for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR). The research showed a statistically significant decrease in the number of days with very strong and extreme cold stress on half of the analysed stations, and a slight tendency or no changes on the remaining stations. The occurrence of days with extreme cold stress in Poland, as revealed by the analysis was primarily related to the presence of high-pressure systems blocking zonal circulation. The study resulted in the designation of three circulation types, i.e. two types related to anticyclonic systems and one cyclonic type.

Effects of Shading Nets on Reactive Oxygen Species Accumulation, Photosynthetic Changes, and Associated Physiochemical Attributes in Promoting Cold-Induced Damage in Camellia sinensis (L.) Kuntze

Climate change and extreme weather affect tea growing. A competitive tea market needs quick, short-term solutions. This study evaluates the effects of various shade nets under mild and extreme cold stress on tea leaf physiology, photosynthetic alterations, antioxidant activities, and physiochemical characteristics. Tea plants were treated with SD0 (0% non-shading), SD1 (30% shading), SD2 (60% shading), and SD3 (75% shading). The 30%, 60%, and 75% shade nets shielded tea leaves from cold damage and reduced leaf injury during mild and extreme cold conditions compared with SD0% non-shading. Shading regulates photochemical capacity and efficiency and optimizes chlorophyll a and b, chlorophyll, and carotenoid contents. Moreover, carbon and nitrogen increased during mild cold and decreased in extreme cold conditions. Shading promoted antioxidant activity and physiochemical attributes. In fact, under 60% of shade, superoxide dismutase, peroxidase, catalase, and ω-3 alpha-linolenic acid were improved compared with SD0% non-shading during both mild and extreme cold conditions. From these findings, we hypothesized that the effect of different shades played an important role in the protection of tea leaves and alleviated the defense mechanism for “Zhong Cha 102” during exposure to a cold environment.

Assessment of bioclimatic comfort of the territories of Krasnoyarsk region by the thermal comfort index

Various bioclimatic indices assess the influence of physical factors in cold or hot climates. The Thermal Comfort Index (UTCI) measures health risk in the ranges from heat-temperature to cold stress. The bioclimatic comfort of the habitat in the subarctic and temperate climate of the Krasnoyarsk Territory was assessed during the periods of determining climatic norms (1961–1990 and 1991–2020). The neutral temperature in a temperate climate was determined for 1 and 2 months, respectively. per year (third month — transitional). Mild cold stress was detected only for 1 month. In August and May, UTCI values indicated warming and a less significant risk of body cooling. The duration of the period of moderate cold stress remained the same: 3 months each. The duration of periods of severe cold stress began to differ by 1 month. In the subarctic, health risks ranging from mild to extreme cold stress have been reported. The same regularity was determined: in general, warming, and by months — the transition according to gradations of degrees of risk to a less significant one. In the subarctic, climate warming was determined within 8 months, in the temperate zone — 9 months. The temperature rise was determined, respectively, by 4.0–9.7 0 С and 1.4–7.1 0 С. In a temperate climate, neutral weather conditions were recorded for periods of 1 and 2–3 months, uncomfortable, respectively 11 months. and 9–10 months. In the subarctic, living conditions are only uncomfortable. The degree of health risk decreased: in a temperate climate in the spring months and August (4 months), in a subarctic climate — in March, April, June, February and October (5 months). Health risk in the form in a temperate climate in the form of mild, moderate and severe cold stress, in the subarctic, in addition, very strong and extreme stress.