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The present work addresses the systematic accurate fabrication and design of biphilic surfaces having superhydrophobic circular islands surrounded by a hydrophilic background by investigating their condensation frosting and defrosting behavior. A significant delay in frost formation is observed on samples with higher superhydrophobicity ratio A*, defined as superhydrophobic area to total area ratio. As the superhydrophobic island diameter D increases from D = 500 µm to D = 700 µm (A* from 19.62% to 38.46%), a 50% improvement/delay is observed in terms of frost formation or densification. Besides delaying icing/frosting, the presence of superhydrophobic areas empowers the formation of porous and nonuniform frost structure, which facilitates ice removal during the defrosting process. To this end, as the surface is recovered the ambient temperature, almost complete passive cleaning performance within only 23 s is observed on the biphilic design having superhydrophobic islands with the diameter of D = 500 µm, that is, a superhydrophobicity ratio A* of 19.62%. This work concludes on the optimum biphilic ratio, which is not only effective as a passive method by hindering frosting but also leads to a slush/water free surface after defrosting eased by the Laplace pressure gradient which is imposed by the different biphilic wettability patterns. [ABSTRACT FROM AUTHOR]

Computed tomography (CT) is an excellent tool to solve certain engineering problems connected to material science (such as sulfate swelling, internal degradation due to freezing, and alkali silicate swelling) and to understand specific processes (frost peeling, acid action). Albeit borne and mostly used in the medical domain, CT is increasingly used in the examination of the internal structure of building materials, where degradation processes occur to the detriment of their mechanical performance and durability. This paper presents five engineering problems concerning concrete freezing and thawing, concrete at high temperatures, timber charring, spalling in asbestos‐cement pipes, and deterioration in prestressed concrete pipes due to the corrosion of metallic inserts. In each case, the degradation processes are monitored via CT, something that may be crucial in the renovation and preservation of historical structures. [ABSTRACT FROM AUTHOR]

Rapidly changing permafrost landscapes are a potential key terrestrial source of greenhouse gases (GHGs) at a global scale, yet, remain poorly characterized regarding GHG origins and environmental controls on emissions. Subsurface ice wedges, commonly found across many permafrost landscapes, harbor GHG‐rich gas bubbles. Analyzing these bubbles aids comprehension of subzero temperature GHG formation in permafrost. The Batagay megaslump, Earth's largest known thaw slump in northern Yakutia, provides an opportunity to study mixing ratios and isotopic compositions of both GHGs and non‐GHG in ice wedge samples from two stratigraphic units: the Upper Ice Complex (UIC) and the Lower Ice Complex (LIC). The Ar/N2/O2 compositions and bubble shapes indicated that the studied ice wedges were likely formed through dry snow and/or hoarfrost compaction, and microbial activity remained active after ice wedge formation. The high CO2 and CH4 mixing ratios and carbon stable isotope values suggested that CO2 and CH4 primarily originated from microbial sources. N2O showed an "exclusive relation" with CH4—meaning that high N2O is observed only when CH4 is low, and vice versa—and N2O mixing ratios vary at different depths. These findings suggest that GHG formation in ice wedges is not solely controlled by physiochemical conditions, but involves a complex interplay between microbial activity and environmental conditions. Our study contributes to a better understanding of the dynamics involved in GHG formation within degrading permafrost landscapes. [ABSTRACT FROM AUTHOR]

Given difficulties with modelling radiation fog and the similarity of meteorological conditions linked to dewfall and frost we investigated the formation of dew, frost and fog. For a site in the UK seven years of data were analysed representing high‐resolution atmospheric profiles and dew meter measurements for radiation nights with stable conditions. Classical dewfall occurs by condensation when the surface is below the dew point and cooler than the air above. However, the profiles show that, in the absence of fog, typically dew and frost form with the surface warmer than the immediately overlying air due to lifted temperature minima (LTMs) at about 0.15 m. Observations of aerosol number density and average hydrated radii show that aerosol optical extinction (and hence their radiative effect) is weakly but significantly correlated with the intensity of LTMs. Low wind speed on stable nights allows settling of aerosols which radiatively cool the air near the ground more quickly than the surface cools – thus creating LTMs. In the presence of LTMs typically dew and frost form not by condensation, but by occult deposition of water droplets onto the canopy and ground. Among radiation fog observations, 91% are associated with light near‐surface winds and LTMs. When the rate of removal of suspended water droplets by occult deposition generating dew or frost is too slow, then build‐up of droplets in the air just above the surface leads to the formation of radiation fog. Future modelling should allow for the accumulation of near‐surface aerosols and their radiative effects during stable nights to represent the formation of LTMs. Modelling of typical dew and frost will require representation of occult deposition. Assessing rates of occult deposition compared to rates of generation of suspended water droplets is needed to forecast the onset of radiation fog formed near the ground. [ABSTRACT FROM AUTHOR]

The evolutionary dynamics of tree species are influenced by their specific climatic environments, and their ability to persist is determined by adaptive strategies such as broad climate tolerance, phenotypic plasticity or genetic differentiation. Biogeographical predictions indicate that populations located at the edges of their ranges are more likely to experience heightened vulnerability to climatic fluctuations due to approaching tolerance limits. However, if local phenotypic acclimation or genetic adaptation has taken place, trees near the edge of their range could demonstrate comparable sensitivity to freeze and drought as the rest of the sampled population. Nevertheless, there remains uncertainty regarding the extent of developmental and evolutionary adjustments in climate sensitivity across the entire ranges of many tree species.Here, we document the biogeography of tree growth sensitivity to freeze and soil water and vapour pressure deficits during 1950–2018 using an extensive multi‐species tree‐ring dataset of 35,784 trees at 4535 sites covering boreal, temperate conifer and temperate deciduous forests of Canada. We quantify the relationships between tree radial growth increment and seasonal climate variables and explore factors driving the observed patterns of annual growth and climate sensitivity such as species, regional climate and local site conditions, and tree age and size.Freeze and drought had widespread impacts on tree growth that were contingent on the presence of focal species in interaction with tree size. An indirect growth thermal limitation towards cold/wet edges, occurring through the site moisture conditions, was observed in seven widespread species (e.g. Picea glauca, Picea mariana and Larix laricina). Moreover, six species had negative drought impacts more strongly expressed towards their warm/dry edges (e.g. Abies balsamea, Betula papyrifera and Pseudotsuga menziesii). However, widespread Picea, Pinus and Populus species showed no indication of increased sensitivity to soil water conditions at these edges.Synthesis. Our findings support the idea of evolutionary or acclimatization adjustments in the development of populations in response to long‐term climate conditions experienced in their respective locations. This underscores the importance of incorporating phenotypic and genomic data into future analyses of climate change impacts, which would enhance our ability to predict potential ecological shifts. [ABSTRACT FROM AUTHOR]

Surfaces capable of delaying the frosting passively and facilitating its removal are highly desirable in fields where ice introduces inefficiencies and risks. Coalescence‐induced condensation droplets jumping (CICDJ), enabled on highly hydrophobic surfaces, is already exploited to slow down the frosting but it is insufficient to completely eliminate the propagation by ice‐bridging. The study shows here how the self‐ejection of single condensation droplets can fully frustrate all the ice bridges, resulting in a frost velocity lower than 0.5 µm s−1 and thus falling below the current limits of passive surfaces. Arrays of truncated microcones, covered by uniformly hydrophobic nanostructures, enable individual condensation droplets to grow and self‐propel toward the top of the microstructures and then to self‐eject once a precise volume is reached. The independency of self‐ejection on the neighbor droplets allows a fine control of the droplets size and distance distributions and thus the ice‐bridging frustration. The truncated microcones with the smallest heads area fraction maximize the percentage of self‐ejecting droplets and minimize the frost velocity. The ice bridges frustration also implies a small frost area coverage, highly desirable in aeronautics and thermal machines. [ABSTRACT FROM AUTHOR]

Frosting occurs due to the freezing of condensed water droplets on a supercooled surface. The nucleated frost propagates through interdroplet bridges and covers the entire surface, resulting from the deposition of highly supersaturated vapor surrounding tiny droplets. While inhibition of the formation of frost bridges is not possible, the propagation of frost can be delayed by effectively removing tiny droplets. Passive technologies, such as superhydrophobic surfaces (SHS) and hydrophobic slippery liquid‐infused porous surfaces (SLIPS), rely on static growth and direct contact with densely distributed droplets. However, use of these approaches in delaying frost propagation involves challenges, as the interdroplet distance remains small. Here, we report a new approach of spontaneous droplet movement on hydrophilic SLIPS to delay the formation of interdroplet frost bridges. Surface tension forces generated by the hydrophilic oil meniscus of a large water droplet efficiently pull neighboring droplets with a diameter of less than 20 μm from all directions. This causes a dynamic separation between water droplets and an adjacent frozen droplet. Such a process delays the formation and propagation of interdroplet frost bridges. Consequently, there is significant delay in frosting on hydrophilic SLIPS compared to those on SHS and hydrophobic SLIPS. [ABSTRACT FROM AUTHOR]

Priming plants with chemical agents has been extensively investigated as a means for improving their tolerance to many biotic and abiotic stresses. Earlier, we showed that priming young avocado (Persea americana Mill cv. 'Hass') trees with sodium hydrosulfide (NaHS), a donor of hydrogen sulfide, improves the response of photosynthesis to simulated frost (cold followed by high light) conditions. In the current study, we performed a transcriptome analysis to gain insight into the molecular response of avocado 'Hass' leaves to frost, with or without NaHS priming. The analysis revealed 2144 (down-regulated) and 2064 (up-regulated) differentially expressed genes (DEGs) common to both non-primed and primed trees. Non-primed trees had 697 (down) and 559 (up) unique DEGs, while primed trees exhibited 1395 (down) and 1385 (up) unique DEGs. We focus on changes in the expression patterns of genes encoding proteins involved in photosynthesis, carbon cycle, protective functions, biosynthesis of isoprenoids and abscisic acid (ABA), as well as ABA-regulated genes. Notably, the differential expression results depict the enhanced response of primed trees to the frost and highlight gene expression changes unique to primed trees. Amongst these are up-regulated genes encoding pathogenesis-related proteins, heat shock proteins, enzymes for ABA metabolism, and ABA-induced transcription factors. Extending the priming experiments to field conditions, which showed a benefit to the physiology of trees following chilling, suggests that it can be a possible means to improve trees' response to cold stress under natural winter conditions. [ABSTRACT FROM AUTHOR]

Most trees die as seedlings, with harsh environmental conditions, such as early‐spring frosts and summer heat waves, being important drivers of early mortality. However, it remains unclear whether tolerance to different environmental extremes (e.g. frost vs. heat) trades‐off, or covaries synergistically and how stress tolerances relate to growth rates and life history strategies. Given the likely role of extreme environmental conditions as environmental filters, the ability to tolerate different stressors at the seedling stage could shape the occurrence and composition of present and future forests.We explored the relationships between different leaf‐level stress tolerances, functional traits and geographic distributions across 22 species of temperate European tree seedlings. We measured indicators of tolerance to frost, drought and heat and related these values to growth rates and to important functional traits (e.g. leaf mass per area and stem‐specific density). Finally, we explored the links between measured seedling stress tolerances and climatic niche limits inferred from adult trees' distributions.We found that seedlings of most species were either moderately tolerant to all three stressors, or susceptible to all of them. Moreover, higher stress tolerances were associated with traits describing slower growth and lower competitive ability. However, seedling tolerances to climatic factors were unrelated to the environmental limits of their adult geographic distributions.Synthesis. Our results suggest that temperate tree seedlings might not experience trade‐offs when facing an increase in multiple extreme climate stressors, but may experience trade‐offs related to growth rate and competitive ability in the establishment phase. The lack of correlation between leaf‐level stress tolerances and the environmental limits of adult geographic distributions suggests that predicting species' current or future geographic distributions in Europe will require a more nuanced understanding of how climatic tolerances at juvenile and adult stages influence range limits. A better understanding of the interaction between survival in extreme climate, leaf‐level stress tolerances of seedlings and the factors driving species distributions is needed to understand future forest responses to climate change. [ABSTRACT FROM AUTHOR]

Observed climate change in northern high latitudes is strongest in winter, but still relatively little is known about the effects of winter climate change on tundra ecosystems. Ongoing changes in winter climate and snow cover will change the intensity, duration and frequency of frost events. Bryophytes form a major component of northern ecosystems but their responses to winter climate changes are largely unknown.Here, we studied how changes in overall winter climate and snow regime affect frost damage in three common bryophyte taxa that differ in desiccation tolerance in a subarctic tundra ecosystem. We used a snow manipulation experiment where bryophyte cores were transplanted from just above the tree line to similar elevation (i.e. current cold climate) and lower elevation (i.e. near‐future warmer climate scenario) in Abisko, Sweden. Here, we measured frost damage in shoots of Ptilidium ciliare, Hylocomium splendens and Sphagnum fuscum with the relative electrolyte leakage (REL) method, during late winter and spring in two consecutive years. We hypothesized that frost damage would be lower in a milder climate (low site) and higher under reduced snow cover and that taxa from moister habitats with assumed low desiccation tolerance would be more sensitive to lower temperature and thinner snow cover than those from drier and more exposed habitats.Contrary to our expectations, frost damage was highest at low elevation, while the effect of snow treatment differed across sites and taxa. At the high site, frost damage was reduced under snow addition in the taxon with the assumed lowest desiccation tolerance, S. fuscum. Surprisingly, frost damage increased with mean temperature in the bryophyte core of the preceding 14 days leading up to REL measurements and decreased with higher frost degree sums, that is, was highest in the milder climate at the low site.Synthesis Our results imply that climate warming in late winter and spring increases frost damage in bryophytes. Given the high abundance of bryophytes in tundra ecosystems, higher frost damage could alter the appearance and functioning of the tundra landscape, although the short and long‐term effects on bryophyte fitness remain to be studied. [ABSTRACT FROM AUTHOR]

Zygnematophyceae, a class of freshwater green algae, exhibit distinctive seasonal dynamics. The increasing frequency of cold snaps during the growing season might challenge the persistence of some populations. The present study explored the frost hardiness of two Mougeotia species isolated from different elevations and habitats. Additionally, a phylogenetic (rbcL sequence), ultrastructural and physiological characterization was performed. Both species, grown under standard culture conditions and cold acclimated cultures (+4°C), were exposed to freezing temperatures down to −9°C. Furthermore, ultrastructural‐, hydrogen peroxide (H2O2)‐ and photosynthetic pigment analysis were performed on cells exposed to −2°C, with and without induced ice nucleation. The alpine M. disjuncta showed a higher frost hardiness (LT50 = −5.8°C), whereas the lowland M. scalaris was susceptible to ice. However, frost hardiness did not improve after cold acclimation in either species but rather decreased significantly in M. disjuncta (LT50 = −4.7°C). Despite darkness, prolonged sub‐zero temperatures or freezing induced the activation of the xanthophyll (VAZ) cycle in M. scalaris. Our results demonstrate that frost hardiness varies within the genus Mougeotia and that the VAZ cycle can be activated in the dark under subzero temperature‐ and freezing stress but does not necessarily increase frost hardiness. As highly frost hardy cell types are usually formed at the end of the growing season, the ability of young cells to survive ice formation in the upper subzero temperature range represents a crucial survival strategy in populations exposed to late spring frosts. [ABSTRACT FROM AUTHOR]

Frost events are a climatic phenomenon of great severity, exerting profound impacts on agricultural production and human endeavours. From 1961 to 2017, China experienced a reduction in frost days (FDs) and elongation of frost‐free periods (FFPs) across most regions. Many factors contribute to the variation of frost events, highlighting the urgent need to scrutinize the intrinsic factors driving these climatic frost events' inter‐annual and interdecadal fluctuations. This work analysed the temporal and spatial attributes of FDs and FFPs, using statistical methods to dissect daily minimum temperature data collected from ground observation stations from 1961 to 2017. The results reveal a declining trajectory in annual FDs and an ascending trend in FFPs. However, the interannual and interdecadal variations do not consistently align with the climatological course. The spatial distribution of the first four modes of EOF exhibits a persistent variation, north–south, monopole and east–west pattern for FDs and FFPs. In comparison, the modes of FFPs exhibit many complexities and diversities. Moreover, this study considers geographical location, altitude and proximity to the ocean, as well as atmospheric circulation factors, including circulation indices, ocean indices and other relevant indices, to elucidate their influence on frost events. In conjunction with the role of greenhouse gases in propelling global warming, we elucidate that the intensity of the Atlantic–European polar vortex, the area of the Indian Ocean warm pool, and the spatial positioning and extent of the subtropical high emerge as preeminent internal oscillations instigating interdecadal shifts in frost events. This study provides valuable scientific insights into the formation mechanisms and evolving patterns of frost events. [ABSTRACT FROM AUTHOR]

Kurzfassung: Im Winter wird überwiegend das Salz NaCl zur Aufrechterhaltung der Verkehrssicherheit auf Straßen und andere Infrastrukturbauwerke gestreut. Die in der Eisschmelze vorhandenen Chloridionen dringen in den Stahlbeton überwiegend durch die Transportprozesse Diffusion und Konvektion ein. Durch die Exposition Frost (XF) kann es zur Koppelung der Transportprozesse kommen und den Chlorideintrag in Hinblick auf die eingetragene Menge und Tiefe erhöhen. Betone, die bereits im CDF‐Test mit NaCl beaufschlagt wurden, werden zu verschiedenen Zeitpunkten im Migrationstest auf die Widerstandsfähigkeit gegenüber erneutem Ioneneindringen (Bromidionen, RBM‐Versuch) getestet. Dadurch kann der Einfluss der Frost‐Tausalz‐Wechsel (FTSW) des CDF‐Versuches auf das Bromideindringen im anschließenden Migrationsversuch (RBM) untersucht werden. Die Quantifizierung der Chlorid‐ und Bromidgehalte erfolgt mit der Laser‐Induzierten Breakdown Spektroskopie (LIBS). Ergänzende Untersuchungen wie die Fluoreszenzmikroskopie liefern weitere Erkenntnisse, die auf das Wirken von Frost in der Konvektionszone zurückzuführen sind. Durch die Kombination der Laborversuche CDF‐ und Migrationsversuch (RBM) können unter Einbezug der LIBS‐Analyse Kennwerte ermittelt werden, die den Frosteinfluss auf den Chloridtransport in Beton quantifizierbar machen. [ABSTRACT FROM AUTHOR]

The freeze–thaw cycles are a process that dominate entire landscapes with different intensity and magnitudes that are strongly changing in the current climate change conditions. In particular, the diurnal frost heave (FH) and needle ice creep (NIC) are two poorly studied processes, especially in the field, despite their effects on the sediment transportation and vegetation colonization on Alpine slopes. In a site of the Central Alps, we applied photogrammetry, thermal imaging, manual measurements and thermistors logging to improve the knowledge of the driving parameter for the formation and accretion of needle ice, of the relations of their spatial distribution with cooling rates and the frost creep modelling change in the presence of the bending process. Among the driving factors, we demonstrate that very local conditions govern the development of the needle ice, like the air cooling rates, the deepening of the freezing front and the surficial cooling rates. Especially low cooling rates are necessary for an intense process. Also the grain size influences the development of the needle ice with higher needle ice development under fine sediment than under small clasts due to a differential thermal conductivity. Moreover, the bending of needle ice has proved to be dependent on its length, age and type of heaved sediment. Therefore, potential frost creep formulas needed to be ameliorated considering the bending angle. Subsequently, a question about the role of slope gradient in NIC is treated. [ABSTRACT FROM AUTHOR]

Summary: Urbanization can affect the timing of plant reproduction (i.e. flowering and fruiting) and associated ecosystem processes. However, our knowledge of how plant phenology responds to urbanization and its associated environmental changes is limited.Herbaria represent an important, but underutilized source of data for investigating this question. We harnessed phenological data from herbarium specimens representing 200 plant species collected across 120 yr from the eastern US to investigate the spatiotemporal effects of urbanization on flowering and fruiting phenology and frost risk (i.e. time between the last frost date and flowering).Effects of urbanization on plant reproductive phenology varied significantly in direction and magnitude across species ranges. Increased urbanization led to earlier flowering in colder and wetter regions and delayed fruiting in regions with wetter spring conditions. Frost risk was elevated with increased urbanization in regions with colder and wetter spring conditions.Our study demonstrates that predictions of phenological change and its associated impacts must account for both climatic and human effects, which are context dependent and do not necessarily coincide. We must move beyond phenological models that only incorporate temperature variables and consider multiple environmental factors and their interactions when estimating plant phenology, especially at larger spatial and taxonomic scales. See also the Commentary on this article by Zhu & Song, 239: 2057–2059. [ABSTRACT FROM AUTHOR]

Introduction: The "Introduction" analyses the mechanisms of concrete frost damage and describes standard methods for determining the frost resistance of lightweight and cellular concrete. Research methods: The frost resistance at different freezing temperatures was carried out on samples of autoclaved cellular concrete of D400 to D600 density. Specimens with dimensions of 100 × 100 × 100 mm were cut from prefabricated parts in accordance with EN 771‐4. During the experiment, frost resistance of ААС samples was determined at a standard temperature of −18 ± 2°C, as well as at temperatures from −5°C to −40°C4. Results and discussion: In the paper, frost resistance of concrete at various freezing temperatures was evaluated by the experimental‐analytical method, which is based on the assumption that frost resistance, expressed in the number of cycles (F) should be inversely proportional to the volume of frozen water at this temperature. The frost resistance of concrete was evaluated experimentally and analytically at different freezing temperatures, assuming that the frost resistance (F), expressed in the number of cycles, should be inversely proportional to the volume of frozen water at that temperature V(t). Determination of the rate of ice spreading front and moisture diffusion in building materials by conductometric method during one‐sided freezing allows a more detailed study of the mechanisms of frost failure of building materials. Conclusions: The proposed experimental‐analytical method for evaluating AAC frost resistance at different freezing temperatures allows, with a small expenditure of time, to obtain more complete information on the material behavior in freezing temperatures than it is provided by the existing standard methods. The analysis of the dependence of freezing resistance on temperature also allows revealing the regions of temperature where it changes most strongly, and to shift, if necessary, these regions towards lower or higher temperatures by adjusting the composition and technology of AAC production. The developed combined method of independent measurements of moisture diffusion kinetics and ice content makes it possible to determine the speed of diffusion of ice formation front and moisture conductivity depending on the composition (capillary‐porous structure) of samples and their initial storage conditions. This information can give a more reliable picture of the behaviour of AAC under alternating temperature loading under varying initial moisture conditions. [ABSTRACT FROM AUTHOR]

Mars Orbiter Camera Wide Angle images were taken from late 1999 through most of 2006, in both red and blue, providing nearly daily, nearly global coverage of Mars for approximately four Mars Years. Significant work has been published from those data, but there did not exist in a public archive a uniform, full time series of the processed data for easier analysis. The companion work to this (Robbins, 2023a, https://doi.org/10.1029/2022EA002673) presents that processing and quality control of the data, producing the full time series in both colors, in equirectangular and polar stereographic projections, in mosaics that have been binned into four different time intervals (daily, ΔLs = 2°, 5°, and 10° [≈4 through 19 days]) and as approximately true‐color composites. The multidimensional data set can be mined for surface and atmospheric variations on Mars. To demonstrate agreement with past work, several well‐known trends are demonstrated in a review‐style narrative format in Supporting Information S1, including changes after a global dust storm, seasonal frost variations at the poles, and surface variations. The data are analyzed further in the main text to demonstrate new qualitative and quantitative analyses of atmospheric and surface features: the North Polar Hood can form earlier than previously demonstrated, Acidalia has significant seasonal brightness variations that can be quantified, and the seasonal frost deposition and sublimation of Hellas can be quantified and shown to vary from year‐to‐year. These different investigations represent a small slice of what can be done now that these data are made available and easily accessible. Plain Language Summary: The first modern craft to orbit Mars was NASA's Mars Global Surveyor, which had the Mars Orbiter Camera. A wide‐angle component of that camera took daily global red‐ and blue‐color images during the camera's lifetime, from 1999 through 2006. That data set has been reprocessed with more attention to data quality control, mosaicked, and grouped into several different time intervals for different types of scientific investigations, and an approximate true‐color set of mosaics was also created. Those recently released mosaics reveal a dynamic world of huge cloud systems, changing surface patterns, seasonal changes in frost and ice cover, and vast polar cloud systems as each hemisphere slips into winter. To validate this new work, the reprocessed images are investigated and shown to reveal numerous broad types of surface and atmospheric changes that have been previously demonstrated by other researchers. To show new science that can be done with this work, the data were also examined to study how polar clouds merge together during winter, how the brightness of some features changes seasonally, and how frost builds and declines in a vast crater in winter. Key Points: A new archive of Mars Orbiter Camera Wide‐Angle mosaics is mined to show several known variations of Mars' surface and atmosphereA new atmospheric study identifying the earlier onset of Mars' North Polar Hood formation than previously observed is demonstratedNew studies showing brightness variations in Acidalia and the growth and decline of seasonal frost in Hellas are described and quantified [ABSTRACT FROM AUTHOR]

Forests are increasingly exposed to extreme global warming‐induced climatic events. However, the immediate and carry‐over effects of extreme events on forests are still poorly understood. Gross primary productivity (GPP) capacity is regarded as a good proxy of the ecosystem's functional stability, reflecting its physiological response to its surroundings. Using eddy covariance data from 34 forest sites in the Northern Hemisphere, we analyzed the immediate and carry‐over effects of late‐spring frost (LSF) and growing season drought on needle‐leaf and broadleaf forests. Path analysis was applied to reveal the plausible reasons behind the varied responses of forests to extreme events. The results show that LSF had clear immediate effects on the GPP capacity of both needle‐leaf and broadleaf forests. However, GPP capacity in needle‐leaf forests was more sensitive to drought than in broadleaf forests. There was no interaction between LSF and drought in either needle‐leaf or broadleaf forests. Drought effects were still visible when LSF and drought coexisted in needle‐leaf forests. Path analysis further showed that the response of GPP capacity to drought differed between needle‐leaf and broadleaf forests, mainly due to the difference in the sensitivity of canopy conductance. Moreover, LSF had a more severe and long‐lasting carry‐over effect on forests than drought. These results enrich our understanding of the mechanisms of forest response to extreme events across forest types. [ABSTRACT FROM AUTHOR]

Frost is damaging to plants when air temperature drops below their tolerance threshold. The set of mechanisms used by cold‐tolerant plants to withstand freezing is called "hardening" and typically take place in autumn to protect against winter damage. The recent incorporation of a hardening scheme in the demographic vegetation model FATES opens up the possibility to investigate frost mortality to vegetation. Previously, the hardening scheme was used to improve hydraulic processes in cold‐tolerant plants. In this study, we expand upon the existing hardening scheme by implementing hardiness‐dependent frost mortality into CLM5.0‐FATES to study the impacts of frost on vegetation in temperate and boreal sites from 1950 to 2015. Our results show that the original freezing mortality approach of FATES, where each plant type had a fixed freezing tolerance threshold—an approach common to many other dynamic vegetation models, was restricted to predicting plant type distribution. The main results emerging from the new scheme are a high autumn and spring frost mortality, especially at colder sites, and increasing mid‐winter frost mortality due to global warming, especially at warmer sites. We demonstrate that the new frost scheme is a major step forward in dynamically representing vegetation in ESMs by for the first time including a level of frost tolerance that is responding to the environment and includes some level of cost (implicitly) and benefit. By linking hardening and frost mortality in a land surface model, we open new ways to explore the impact of frost events in the context of global warming. Plain Language Summary: Frost can lead to partial or full mortality of a plant, unless it has evolved a tolerance to cold weather to avoid the formation of ice crystals in its tissues. Frost mortality is poorly represented in most advanced dynamic vegetation models, which are our primary tools for predicting climate change and to understand its effects on the biosphere. In one of those models, the functionally assembled simulator (FATES), a minimum temperature threshold is assigned to each plant type to represent the limit at which it will start to incur frost injury. In this study, we focus on making the fixed temperature threshold of FATES variable in time and space—depending on the local conditions of temperature and light. Our results show that the new frost mortality scheme can simulate autumn and spring frost mortality, also for cold‐adapted species, and increases mid‐winter frost mortality due to variable winter weather—especially at warmer sites. This is in contrast to the original frost mortality scheme, which was only applicable to predict the distribution of plant types across climate zones. The implementation presented here opens up new ways to explore the spatial evolution of frost occurrences and intensities under changing climatic conditions. Key Points: We compare the original freezing mortality implementation in FATES (based on hard‐coded temperature thresholds) to a more dynamic approach (based on hardening)In contrast to the original approach, a new frost scheme is able to predict the damaging effects of extreme winter events and late spring frost eventsWe show that autumn and spring frost mortality is large, especially at colder sites, and that mid‐winter frost mortality increases with global warming [ABSTRACT FROM AUTHOR]

The kinetic hypothesis of biodiversity proposes that temperature is the main driver of variation in species richness, given its exponential effect on biological activity and, potentially, on rates of diversification. However, limited support for this hypothesis has been found to date. I tested the fit of this model to the variation of tree‐species richness along a continuous latitudinal gradient in the Americas. I found that the kinetic hypothesis accurately predicts the upper bound of the relationship between the inverse of mean annual temperature (1/kT) and the natural logarithm of species richness, at a broad scale. In addition, I found that water availability and the number of days with freezing temperatures explain part of the residual variation of the upper bound model. The finding of the model fitting on the upper bound rather than on the mean values suggest that the kinetic hypothesis is modeling the variation of the potential maximum species richness per unit of temperature. Likewise, the distribution of the residuals of the upper bound model in function of the number of days with freezing temperatures suggest the importance of environmental thresholds rather than gradual variation driving the observable variation in species richness. [ABSTRACT FROM AUTHOR]

Panolis flammea is an important pest whose populations intermittently outbreak in Europe. The species overwinters as pharate moths in the pupal stage in soil.Details on the metabolic activity and cold hardiness of P. flammea during the overwintering period have not been published. Therefore, we assessed O2 consumption and the supercooling point (SCP) of P. flammea in late November, mid‐February, and mid‐March and the influence of soil humidity under fluctuating temperatures and with brief exposures to two increased temperature regimes (10 and 20°C).The respiration pattern indicated diapause termination in mid‐February. A threshold of 0.169 μl O2 h−1 mg−1 fresh weight indicated potentially activated pre‐emerging moths. Drought increased respiration rates.The SCP was lowest in mid‐February (−22.2°C) and was negatively correlated with pupal mass. The frost tolerance tended to increase with low substrate humidity, especially at the end of the overwintering period.Our results indicate that P. flammea requires more energy during dry and mild winters than in wet and cold winters. Winter diapause termination and post‐diapause development may therefore be accelerated as environmental warming and drought increase. [ABSTRACT FROM AUTHOR]

Negative extreme anomalies in vegetation growth (NEGs) usually indicate severely impaired ecosystem services. These NEGs can result from diverse natural and anthropogenic causes, especially climate extremes (CEs). However, the relationship between NEGs and many types of CEs remains largely unknown at regional and global scales. Here, with satellite‐derived vegetation index data and supporting tree‐ring chronologies, we identify periods of NEGs from 1981 to 2015 across the global land surface. We find 70% of these NEGs are attributable to five types of CEs and their combinations, with compound CEs generally more detrimental than individual ones. More importantly, we find that dominant CEs for NEGs vary by biome and region. Specifically, cold and/or wet extremes dominate NEGs in temperate mountains and high latitudes, whereas soil drought and related compound extremes are primarily responsible for NEGs in wet tropical, arid and semi‐arid regions. Key characteristics (e.g., the frequency, intensity and duration of CEs, and the vulnerability of vegetation) that determine the dominance of CEs are also region‐ and biome‐dependent. For example, in the wet tropics, dominant individual CEs have both higher intensity and longer duration than non‐dominant ones. However, in the dry tropics and some temperate regions, a longer CE duration is more important than higher intensity. Our work provides the first global accounting of the attribution of NEGs to diverse climatic extremes. Our analysis has important implications for developing climate‐specific disaster prevention and mitigation plans among different regions of the globe in a changing climate. [ABSTRACT FROM AUTHOR]

Investigations on freeze‐thaw stressing of TWIST components In the experimental building CUBE – a flagship project of carbon concrete construction –, two double‐curved components made of shotcrete are visible. There are increased demands on its appearance and especially on the quality of the exposed concrete of the building envelope. A special feature is the production technology of the shell structures made of shotcrete. Due to the special shape of the components, there are increased moisture stresses and the resulting damage potential due to frost. Computational studies show significantly higher frost loads on inclined exposed concrete surfaces compared to wall surfaces. The generally higher water content of inclined concrete surfaces means that the water contained in the pore spaces freezes at temperatures just below 0 °C. In the case of wall surfaces, the water contained is more frequently stored in very fine pores. The capillary pressure prevailing here means that ice only forms at temperatures below –20 °C. [ABSTRACT FROM AUTHOR]

Blockfields remain enigmatic regarding their origin, internal structure, surface processes, and glaciological implications. In Scandinavia, blockfields are found on high‐elevation, low‐relief mountains (plateaus) across the Arctic and Subarctic. In this study, we present a 1D numerical model that uses near‐surface temperatures measured between summer 2018 and summer 2020 to calculate frost‐cracking intensities (FCI) within the ground column in three different blockfields in Norway and Svalbard. Eighty‐nine miniature temperature loggers were distributed on Tron Mountain (1650 m a.s.l.) in Alvdal, Gamlemsveten (780 m a.s.l.) near Ålesund in southwestern Norway and on Platåberget (460 m a.s.l.) near Longyearbyen, Svalbard. We modelled FCI by scaling the time spent in the frost cracking window (between −3 and −8°C) with the temperature gradient and a penalty function for distance to available water. At Tron and Gamlemsveten, ground temperatures never reached the frost cracking window at one third of our sites due to insulation by a thick snow cover in depressions and on the lee sides of summits. The highest FCI (0.05–0.4 K m) are obtained where the subsurface consists of boulders and stones in a matrix of relatively fine sediment (sand, silt, gravel). In contrast, very low FCI (0.003–0.02 K m) were modelled for blocky layers with large air‐filled pores because of the low water availability. On Platåberget, all sensors reached the frost‐cracking window during the annual temperature cycle, but FCI are extremely low (0.0004–0.15 K m) as water availability is limited due to (i) permafrost and (ii) near‐surface temperatures remaining below the frost‐cracking window for 3/4 of the year. This indicates that boulder‐rich blockfields with air‐filled hollows are preserved in very cold climates, whereas warmer, maritime settings with higher availability of fine interstitial material place blockfields in the fast lane for frost weathering. [ABSTRACT FROM AUTHOR]

Femtosecond laser ablation has been demonstrated to be a versatile tool to produce micro/nanoscale features with high precision and accuracy. However, the use of high laser fluence to increase the ablation efficiency usually results in unwanted effects, such as redeposition of debris, formation of recast layer, and heat‐affected zone in or around the ablation craters. Here this limitation is circumvented by exploiting a thin frost layer with a thickness of tens of microns, which can be directly formed by the condensation of water vapor from the air onto the exposed surface whose temperature is below the freezing point. When the femtosecond laser beam is focused onto the target surface covered with a thin frost layer, only the local frost layer around the laser‐irradiated spot melts into water, helping to boost ablation efficiency, suppress the recast layer, and reduce the heat‐affect zone, while the remaining frost layer can prevent ablation debris from adhering to the target surface. By this frost‐assisted strategy, high‐quality surface micro/nano‐structures are successfully achieved on both plane and curved surfaces at high laser fluences, and the mechanism behind the formation of high‐spatial‐frequency (HSF) laser‐induced periodic surface structures (LIPSSs) on silicon is discussed. [ABSTRACT FROM AUTHOR]

We studied local variations in temperature from winter to spring, and interpopulation variations in leaf out phenology (the day and the temperature sum for budburst and leaf expansion) of Siebold's beech (Fagus crenata) canopy trees. We focused on local topographic variation associated with the late frost regime for the canopy trees using 5–10 years of in situ observation of the temperature at 12 sites and leaf out phenology of two populations inhabiting a basin (basin populations) and 4 populations inhabiting hillside slopes (hillside slope populations) in the Hakkoda Mountains, northern Japan. The late frost regime differed between topographies; late frosts occurred during warmer periods in the basin compared to hillside slopes. The basin populations exhibited a larger temperature sum for leaf out than the hillside slope populations, regardless of altitude, suggesting that local variation in the late frost regime is an abiotic factor causing local variations in leaf out phenology. The six studied populations exhibited earlier days and smaller temperature sum of budburst in years with longer chilling duration. However, the extent of phenotypic plasticity in the temperature sum was small for the basin compared to hillside slopes. The temperature sum of leaf expansion in the hillside slope populations also negatively correlated with chilling duration, whereas that of the basin populations responded in the opposite direction. The safety margin from the last frost differed between the topographies, but not that from the last fatal frost, suggesting local adaptation to the late frost regime in each habitat. [ABSTRACT FROM AUTHOR]

Phenological shifts in response to changing climatic conditions is a key acclimation process for the persistence of perennial plants in temperate and boreal climates. The optimal time to leaf‐out is the result of an evolutionary process determined by the trade‐off between minimizing the risk of freezing damages and herbivory pressure while maximizing resource uptake to increase competitiveness against the other plants.We quantified the penalty exerted by frost damage at the time of leaf emergence on plant development (reduction in leaf area, canopy duration and growth) over the potential gains without frost (increased biomass and non‐structural carbohydrate reserves), depending on when leaf‐out occurs. To this purpose, we exposed 960 saplings of four temperate deciduous tree species with contrasting cold hardiness to two frost intensities shortly after leaf emergence, which was artificially induced at four occasions to reflect the whole range of natural leaf‐out dates.One year above‐ground biomass (AGB) increments following the frost revealed a clear ranking among the species depending on their strategy to cope with damaging frosts. Prunus avium (−41% of AGB‐increment compared to control saplings) resprouted from the stem base, Quercus robur (−62%) rapidly produced new leaves from dormant reserve buds, Fagus sylvatica (−98%) showed highest chlorophyll content in autumn and delayed senescence together with Carpinus betulus (−105%), which overcompensated NSC reserves after the growing season but showed highest mortality (up to 32%). In all species, NSC reserves recovered rapidly to control levels at the expense of growth.The timing of leaf‐out (advanced and delayed artificially) significantly affected the performance and recovery (regreening and growth) of both frozen and non‐frozen saplings, with the lowest performance found at the most delayed leaf‐out date. We propose that the potential to recover from frost damages is an important component of a tree's performance, particularly at the juvenile stage. The ability to recover may become even more decisive in the future with the predicted increase of false springs in many extratropical regions. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Synthetic surfaces engineered to regulate phase transitions of matter and exercise control over its undesired accrual (liquid or solid) play a pivotal role in diverse industrial applications. Over the years, the design of repellant surfaces has transitioned from solely modifying the surface texture and chemistry to identifying novel material systems. In this study, selection criteria are established to identify bio‐friendly phase change materials (PCMs) from an extensive library of vegetable‐based/organic/essential oils that can thermally respond by harnessing the latent heat released during condensation and thereby delaying ice/frost formation in the very frigid ambient that is detrimental to its functionality. Concurrently, a comprehensive investigation is conducted to elucidate the relation between microscale heat transport phenomena during condensation and the resulting macroscopic effects (e.g., delayed droplet freezing) on various solidified PCMs as a function of their inherent thermo‐mechanical properties. In addition, to freeze protection, many properties that are responsive to the thermal reflex of the surface, such as the ability to dynamically tune optical transparency, moisture harvesting, ice shedding, and quick in‐field repairability, are achievable, resulting in the development of protective coatings capable of spanning a wide range of functionalities and thereby having a distinctive edge over conventional solutions. [ABSTRACT FROM AUTHOR]

In theory, canopy openings can influence tree species establishment and resulting distributions over environmental gradients, but evidence concerning the magnitude and direction of such effects remain scarce. In this study we examine how canopy openings influence seedling persistence and growth and resulting elevation range limits. We transplanted 1360 seedlings of eight woody species (trees Trichilia habanensis, Persea caerulea, Cedrela tonduzii, Cornus disciflora,Quercus salicifolia, Q. bumelioides, Q. costaricensis and the shrub Hypericum irazuense) under the forest canopy and in open areas with understorey vegetation removed in a replicated design along a 2900 m elevation gradient in Costa Rica. We recorded survival, stem diameter and height over 18 months. We used hierarchical generalized additive models to examine relationships of seedling survival and growth with elevation and treatment (inside forest versus open area). We found a clear effect of open versus forest conditions on survival across the elevation gradient for six species. Species planted into open areas with full light exposure survived 100–1000 m below (~ 0.5–5°C warmer), and in one case 300 m above (~ 1.8°C colder) their observed ranges. Above 2900 m, survival of all species was markedly greater under the forest canopy versus open sites, suggesting facilitation from the forest, as frost occurred in open areas above this elevation. The resulting upper range increased between 200 and 1160 m (~ 1–6°C colder) compared to their observed range. At lower elevations, severe insect herbivory occurred on some species likely influencing lower range limits. Open areas influenced how seedling survival and growth varied with elevation for all the studied species. All species survived and grew outside the elevation ranges where they are typically observed. We suggest that the influence of forest gaps and clearings over extended gradients offers novel insights into tree range dynamics, limits and conservation. [ABSTRACT FROM AUTHOR]

Under climate change, the increasing occurrence of late frost combined with advancing spring phenology can increase the risk of frost damage in trees. In this study, we tested the link between intra‐specific variability in bud phenology and frost exposure and damages. We analysed the effects of the 2021 late frost event in a black spruce (Picea mariana (Mill.) BSP) common garden in Québec, Canada. We hypothesised that the timing of budbreak drives the exposure of vulnerable tissues and explains differences in frost damage. Budbreak was monitored from 2015 to 2021 in 371 trees from five provenances originating between 48° and 53° N and planted in a common garden at 48° N. Frost damages were assessed on the same trees through the proportion of damaged buds per tree and related to the phenological phases by ordinal regressions. After an unusually warm spring, minimum temperatures fell to −1.9°C on May 28 and 29, 2021. At this moment, trees from the northern provenances were more advanced in their phenology and showed more frost damage. Provenances with earlier budbreak had a higher probability of damage occurrence according to ordinal regression. Our study highlights the importance of intra‐specific variability of phenological traits on the risk of frost exposure. We provide evidence that the timings of bud phenology affect sensitivity to frost, leading to damages at temperatures of −1.9°C. Under the same conditions, the earlier growth reactivation observed in the northern provenances increases the risks of late frost damage on the developing buds. [ABSTRACT FROM AUTHOR]

Alternative water uptake pathways through leaves and bark complement water supply with interception, fog or dew. Bark water‐uptake contributes to embolism‐repair, as demonstrated in cut branches. We tested whether bark water‐uptake could also contribute to supplement xylem‐water for transpiration. We applied bandages injected with 2H‐enriched water on intact upper‐canopy branches of Pinus sylvestris and Fagus sylvatica in a boreal and in a temperate forest, in summer and winter, and monitored transpiration and online isotopic composition (δ2H and δ18O) of water vapour, before sampling for analyses of δ2H and δ18O in tissue waters. Xylem, bark and leaf waters from segments downstream from the bandages were 2H‐enriched whereas δ18O was similar to controls. Transpiration was positively correlated with 2H‐enrichment. Isotopic compositions of transpiration and xylem water allowed us to calculate isotopic exchange through the bark via vapour exchange, which was negligible in comparison to estimated bark water‐uptake, suggesting that water‐uptake occurred via liquid phase. Results were consistent across species, forests and seasons, indicating that bark water‐uptake may be more ubiquitous than previously considered. We suggest that water taken up through the bark could be incorporated into the transpiration stream, which could imply that sap‐flow measurements underestimate transpiration when bark is wet. Summary Statement: We applied bandages soaked in isotopically enriched water to intact branches of Pinus sylvestris and Fagus sylvatica and measured isotopic composition of transpiration and tissue water. Our experiments showed that water taken up through the bark could be incorporated into the xylem and feed transpiration. [ABSTRACT FROM AUTHOR]

Climate model simulations' outputs are prone to biases compared to observations; furthermore, climate projections can be very different in modelling future temperature characteristics. One possible solution for reducing uncertainty and eliminating possible systematic errors within climate projections is the bias‐adjustment of the raw climate model data. We used the quantile mapping method for bias‐adjustment of a mini ensemble consisting of 8‐member high‐resolution (0.11°) regional climate model simulations provided by the CORDEX community. As the method requires a reliable observational dataset serving as reference data, we used the quality controlled and homogenized observational dataset: CARPATCLIM. Quantile mapping bias‐adjustment technique was applied on the following variables: daily mean, minimum and maximum temperature. We analysed changes in mean temperature characteristics and of climate indices for future periods of 2021–2050 and 2070–2099 with respect to the reference period 1976–2005 for the Carpathian Region. The selected climate indices are based on minimum (frost days, FD) and maximum daily temperature data (summer days, SU). Our bias‐adjusted RCM results suggest a similar degree of mean temperature change as the raw RCMs' data. Bias‐adjusted and raw RCM data project a remarkable annual temperature increase on average under the RCP8.5 scenario (1.4°C and 3.9°C by 2021–2050 and 2070–2099, respectively). The highest temperature increase is likely to occur in summer: it is 4.3°C on average by the end of the 21st century. More pronounced differences were found for the projected changes of the number of summer and frost days based on the bias‐adjusted and the raw RCM data. Our results draw attention to the fact that bias‐adjusted RCM data are crucial for the provision of regional climate change impact and adaptation studies for the Carpathian Region. [ABSTRACT FROM AUTHOR]

Coarse sand‐sized (0.5–1.0 mm) grains of vein quartz were subjected to frost‐induced stress under controlled laboratory conditions. A total of 1,000 freeze–thaw (FT) cycles, simulated under different (low, high) water mineralization conditions in the temperature range from −5°C up to +10°C, were used to test effects on collected samples. Scanning electron microscopic (SEM) microtextural analysis of grain surfaces was performed at 0 (start) and after 50, 100, 300, 700, and 1,000 FT cycles. The results indicate that variable frost‐induced microtextural imprints encountered on quartz grain surfaces prior to and following analysis depend largely on the mineralization (dissolved solute content) of water involved in the weathering process. The higher the water mineralization, the greater the intensity of mechanical weathering. Two predominant outcomes in the course of these micro‐scale frost weathering tests have been identified: a physical (mechanical) aspect manifested by the occurrence of conchoidal fractures and breakage block microtextures dominating up to 300 FT cycles, and a chemical aspect resulting in the occurrence of precipitation crusts and obliteration of grain microrelief. Moreover, three additional stages of microtexture development may be distinguished with the evolution of frost‐induced microrelief on the surface of quartz grains: (i) initial cracks of large‐sized conchoidal fractures, (ii) increasing frost cycles yielding additional small‐sized conchoidal fractures, and (iii) advanced breakage blocks. Frost‐induced exposure of fresh, unweathered grain surfaces leads to refreshing of the grain surface. [ABSTRACT FROM AUTHOR]

Temperature‐dependent frost cracking is a major weathering process that dominates sediment supply and hillslope erosion by reducing shear strength and conditioning slopes to be more failure‐prone in cold mountain regions. Landslides are a common erosional process in such landscapes. The linkage between these two processes has been proposed but many of the mechanisms remain to be investigated. In this study we compile a landslide inventory in the Eastern Qilian Mountains including 2482 rockfalls and 5373 elongate transport zone footprints. We use a widely accepted frost cracking model to explore this weathering process as a mechanism of paleoclimate control on the modern landslide distribution. The results show that landslides concentrate in a narrow altitudinal range and that this elevation dependence varies with slope aspect. Based on the paleoclimate record, we calculate the time‐averaged frost cracking intensity (Fci) since Last Glacial Maximum (LGM) and adopt different parameters for two slope aspects. We find that time averaged Fci is a good predictor of the landslide elevation distribution for both aspects. We then introduce two slope‐based landslide initiation and runout models (i.e., SHALRUN and FCIRUN) to examine the relative roles of slope versus temperature in determining the landslide probability in space. The FCIRUN model, which incorporates Fci as a measure of sediment supply, consistently outperforms the SHALRUN model. This result suggests that frost cracking determines the pattern of landslide initiation, although topography still controls their runout path. Our study highlights the potential of introducing Fci into slope‐based landslide prediction models to improve model skill in identifying hazardous areas (e.g., rockfall) across weathering‐limited landscapes like the Qilian Mountains. [ABSTRACT FROM AUTHOR]

Sorghum [Sorghum bicolor (L.) Moench] is a multipurpose crop that is highly susceptible to low temperature stress. Early season cold (ESC) greatly affects seed germination, seedling vigor, and root architecture, whereas late‐season frost (LSF) reduces fertility, yield, and nutrition quality and content in sorghum. Here, an association mapping study was conducted to delineate the genetics of ESC and LSF tolerance in sorghum. A total of 10 single nucleotide polymorphisms (SNPs) and 17 quantitative trait loci (QTL) were identified for ESC, and 40 SNPs were identified for LSF. The diversity panel exhibited extensive variation for plant traits measured for their association with ESC and LSF tolerance. Two QTL colocalized with the classical tannin genes Tan1 (S4_61580203) and Tan2 (S2_7777693) were identified for ESC tolerance. We also identified additional putative candidate genes such as Sobic.001G157100 (Nonphototropic hypocotyl 3, NPH3), Sobic.001G156600 (Lectin receptor‐like serine/threonine kinase), and Sobic.006G061100 (Sucrose nonfermenting 1 related protein kinase 1, SnRK1) for ESC tolerance and Sobic.006G139900 (UDP‐glucoronosyl and UDP‐glucosyl transferase), Sobic.002G187400 (Serine/threonine protein kinase), and Sobic.004G333700 (Ca2+/calmodulin‐dependent protein phosphatase) for LSF tolerance. Tan1 and Tan2 play a major role in seed dormancy and induce resistance against soil‐borne pathogens under cold and wet soil conditions. Seed tannin content may be used as an indirect selection marker for identifying cold tolerant germplasm for breeding. NPH3 and SnRK1 regulate seed germinability under cold stress in various crops. Candidates identified in this study could be further exploited to develop low temperature tolerant cultivars as proxies in marker‐assisted breeding, genomic selection, and genetic engineering. Core Ideas: Low temperature stress early and late in the season affects sorghum productivity tremendously.Association mapping study was conducted to uncover genes involved in low temperature tolerance.Our study identified a total of 50 SNPs and 17 QTLs for low temperature tolerance in sorghum.Two QTLs were colocalized with the classical tannin genese Tan1 and Tan2. [ABSTRACT FROM AUTHOR]

Crop cycles in spring canola (Brassica napus L.) and carinata (Brassica carinata A. Braun) are controlled by temperature and photoperiod. In the central region of South America, which accounts for 90% of South American rapeseed crop production, farmers seek to sow as early as possible to maximize yield even though early sowing dates expose crops to a higher probability of frost occurrence that had not been quantified before. Our objective was to model phenology for one spring cultivar of canola ('Rivette') and one of carinata ('Avanza 641') and assess the probability of frost occurrence during flowering and grain filling in the central region of South America. For the estimation of frost risk, we modeled phenology resulting from 15 April to 15 August sowing dates at 12 locations (from 31.16° to 34.20° S latitude). We assumed that the critical period spans from 100 to 500 growing degree days (GDD) after flowering. Under early sowing dates, carinata tends to have a longer cycle (200 GDD more than canola) although both crops had a similar cycle length under a late sowing date. Predicted and observed flowering dates showed an average difference of 1.6 and 0.95 d for canola and carinata, respectively. Carinata has a lower probability of suffering frost events, and early sowing dates result in a greater exposure to frost damage. The results of this work will enable farmers and stakeholders to know the potential frost risk when defining a sowing date for canola and carinata. Core ideas: Carinata is more sensitive to photoperiod than canola.Carinata has a longer cycle than canola especially in early sowing dates.Early plantings of both Brassicas species aimed for early harvests exposes crops to high frost risk. [ABSTRACT FROM AUTHOR]

In flowering plants (angiosperms), the herbaceous habit has evolved repeatedly from the ancestral woody state and herbs evolved repeatedly back to woody plants. Yet, how common these transitions were and which ecological conditions promote the herbaceous habit is poorly known. Several hypotheses exist, postulating an advantage of the herbaceous growth form to better cope with frost, drought, fire and shade and in allowing a fast life strategy, but their evaluation has been hitherto limited and support equivocal. We aim to evaluate these hypotheses by testing the difference between woody plants and herbs for a set of variables related to these hypotheses.We compiled and integrated data for up to 21,581 species representing 359 families from public databases. We estimated the minimum number of evolutionary transitions between both growth forms. We assembled data on frost, drought, fire and shade tolerances, clonality and specific leaf area and we tested individual hypotheses by comparing herbaceous and woody angiosperm growth forms globally and within selected biomes and clades using phylogenetic comparative analyses.We found 1656 evolutionary transitions from woody towards herbaceous growth form and 2111 transitions in the opposite direction. In agreement with our expectations, herbs were more tolerant to frost and shade than woody plants and had higher specific leaf area. However, the growth forms did not differ in their fire tolerance and clonality. Furthermore, contrary to our expectation, woody plants were more drought tolerant than herbs. The majority of the differences were robust to the choice of biome or clade.Synthesis. Both herbaceous and woody habits evolved many times making the evolution of growth forms a well‐replicated event and suggesting that conditions favourable for either of the growth forms emerge often and plants respond to them. Apart from standard explanation by low temperatures, the success of herbs was likely enabled also by biotic interactions—by their fast life strategy, which is beneficial in seasonal and early successional habitats, and by their ability to tolerate shade. [ABSTRACT FROM AUTHOR]

Icing and frosting on transparent surfaces compromise visibility on various optical equipment and transparent infrastructures. It remains challenging to fabricate energy-saving coatings for harvesting solar energy while maintaining high transparency. Here, transparent, photothermic, and icephobic composite surfaces composed of photothermal nanomaterials and polyelectrolytes via layer-by-layer assembly are designed and constructed. The positively-charged polypyrrole nanoparticles and negatively-charged poly(acrylic acid) are assembled as exemplary materials via electrostatic attractions. The optically transparent photothermal coatings are successfully fabricated and exhibited photothermal capabilities and light-transmittance performance. Among the various coatings applied, the seven-bilayer coating can increase the temperature by 35 °C under 1.9-sun illumination, maintaining high transmittance (>60%) of visible light. With sunlight illumination at subzero temperatures (> -35 °C), the coatings show pronounced capabilities to inhibit freezing, melt accumulated frost, and decrease ice adhesion. Precisely, the icephobic surfaces remain free of frost at -35 °C as long as sunlight illumination is present; the accumulated frost melts rapidly within 300 s. The ice adhesion strength decreases to -0 kPa as the melted water acts as a lubricant. Furthermore, the negatively-charged graphene oxide and positively-charged poly(diallyldimethylammonium chloride) show their material diversity applicable in the coating fabrication. [ABSTRACT FROM AUTHOR]

Climate warming is modifying the movement of air masses over Northern latitudes, producing warming and cooling events across the boreal regions. These new conditions changes may mismatch plant phenology from weather conditions, and affect the growing period of trees. Understanding the processes of local adaptation in bud phenology can help to predict the response of plants to these rapid and unexpected environmental changes.Our study monitored bud burst and bud set weekly during four growing seasons in black spruce [Picea mariana (Mill.) B.S.P.] saplings planted in a common garden and originating from five provenances representing the whole latitudinal distribution of the closed boreal forest in Quebec, Canada. We compared the variance in bud phenology among populations and years, and analysed the relationships with temperatures at the origin sites.Bud burst and bud set occurred in mid‐May and mid‐July, respectively, with a large variability among provenances and between the study years. A delayed bud phenology was observed in the provenances from warmer sites, with bud burst and bud set being 1.1 and 1.4 days later for every additional degree in mean annual temperature at the origin site respectively. Populations with earlier bud bursts also showed earlier bud sets, thus the growing season was similar among provenances. The heritability of bud set was higher than that of bud burst, with estimates of 0.26 and 0.21 respectively. On average, variance in bud phenology among provenances reached 5.3%, which was higher than that within provenances (2.6%). The factor year explained 37.7%–69.7% of the variance in bud phenology.Synthesis. The findings demonstrate the evolutionary response to climate variations in the boreal biome. Endogenous and environmental components have different effects on the phases of bud burst and bud set. This complex interaction among drivers of bud phenology may prevent reliable predictions of changes in the growing season under changing climate. An earlier growth reactivation due to higher spring temperatures could result in higher frost risks to the developing buds. Despite a longer period for photosynthesis expected for the evergreen black spruce under warmer conditions, the period spent for bud development could remain unchanged. [ABSTRACT FROM AUTHOR]

Charon's exosphere may exhibit extreme seasonal dynamics, with centuries of quiescence punctuated by short lived (∼4 earth years) exospheric surges near the equinoxes, as spring sunrise bi‐annually drives frozen methane off the polar night zones. Charon's pole‐centric red spot has been proposed to be the product of Ly‐α photolysis of frozen methane into refractory hydrocarbon "tholins", but the role of exospheric dynamics in the red material's formation has not been investigated. We show with exospheric modeling that methane "polar‐swap", in which exospheric CH4 sublimated from the spring polar zone is rapidly re‐frozen onto the autumn hemisphere, deposits ∼30 μm polar frosts too thick for Ly‐α light to penetrate. Ethane, the primary methane photoproduct under these conditions, may unlike methane remain frozen decades after polar sunrise under solar wind exposure. Solar wind radiolysis of polar ethane frost synthesizes higher‐order refractories that may contribute to the coloration of Charon's polar zones. Plain Language Summary: Charon's thin methane atmosphere undergoes "explosive" pulsations owing to the Pluto‐Charon's systems' near sideways tilt to the Sun, according to new computer simulations that we present here. Spring sunrise may drive polar methane frozen during the centuries long winter night back into Charon's atmosphere, causing the whole atmosphere to briefly and drastically surge in pressure by a factor of almost 1000 every equinox. During these exceedingly brief episodes, taking place just a few years out of the Pluto‐Charon system's 248 year orbit around the Sun, polar caps of methane frost tens of microns thick may be suddenly swapped between north and south, evaporated and then re‐frozen from the spring to the autumnal polar zones. Charon's polar red spot, seen by the New Horizons spacecraft, is suspected to be material synthesized from frozen methane by backscattered solar ultraviolet light. However we find that Charon's polar caps are frozen too fast and thick for synthesis of much material more complex than ethane. Nevertheless ethane, being less volatile than methane, stays frozen to Charon's surface for decades after spring sunrise, and may under exposure to solar wind be converted to permanent red‐colored surface deposits that contribute to the origins of the red spot. Key Points: Surges in Charon's exosphere, driven by spring‐sunrise sublimation of polar methane, produce "flash frozen" CH4 frost at the autumn polePolar frost grows too thick and fast for efficient Ly‐α CH4 photolysis to hydrocarbons past C2H6 that may contribute to Charon's red spotOrigin of Charon's polar red material may be in part solar wind radiolysis of photolytic ethane remaining surface‐bound past spring sunrise [ABSTRACT FROM AUTHOR]

Before dawn on the dustiest regions of Mars, surfaces measured at or below ∼148 K are common. Thermodynamics principles indicate that these terrains must be associated with the presence of CO2 frost, yet visible wavelength imagery does not display any ice signature. We interpret this systematic absence as an indication of CO2 crystal growth within the surficial regolith, not on top of it, forming hard‐to‐distinguish intimate mixtures of frost and dust, that is, dirty frost. This particular ice/regolith relationship unique to the low thermal inertia regions is enabled by the large difference in size between individual dust grains and the peak thermal emission wavelength of any material nearing 148 K (1–2 μm vs. 18 μm), allowing radiative loss (and therefore ice formation) to occur deep within the pores of the ground, below several layers of grains. After sunrise, sublimation‐driven winds promoted by direct insolation and conduction create an upward drag within the surficial regolith that can be comparable in strength to gravity and friction forces combined. This drag displaces individual grains, possibly preventing their agglomeration, induration, and compaction, and can potentially initiate or sustain downslope mass movement, such as slope streaks. If confirmed, this hypothesis introduces a new form of CO2‐driven geomorphological activity occurring near the equator on Mars and explains how large units of mobile dust are currently maintained at the surface in an otherwise soil‐encrusting world. Plain Language Summary: Surface CO2 ice forms at all latitudes on Mars with a strong seasonal control. In this study, we show that diurnal CO2 ice is not observed in visible wavelength imagery in dusty terrains, where diurnal frost preferentially forms. We interpret this situation as the indication of the presence of hard‐to‐distinguish dirty frost, where ice crystals grow within the surficial regolith, not on top of it, resulting in apparent soil‐like dark ice. At sunrise, sublimation‐driven winds within the regolith are occasionally strong enough to displace individual dust grains, initiating and sustaining dust avalanches on steep slopes, forming ground features known as slope streaks. This model suggests that the CO2 frost cycle is an active geomorphological agent at all latitudes and not just at high or polar latitudes, and possibly a key factor maintaining mobile dust reservoirs at the surface. Key Points: Near dawn, diurnal frost is not apparent on cold, dusty, low thermal inertia terrainsThese observations are consistent with a model of dirty diurnal CO2 frost, fluffing up the surface layer when it sublimesThis mechanism could trigger dynamic phenomena on the Martian surface and lead to the formation of slope streaks [ABSTRACT FROM AUTHOR]

Late spring frost stress is one of the major environmental limiting factors for apricot in the warm zone in China. Investigation of frost exposure of apricot is of particular interest for estimating the frost risk, thus representing the potential damage for apricot production. In this study, daily minimum temperature (Tmin), disaster and phenological data of apricot from 1981 to 2020 in the warm zone were integrated to explore the temperature threshold on apricot at young fruit, facilitating the assessment of apricot frost exposure (E) under the background of climate warming. The daily Tmin was firstly extracted according to the historical disaster records, to identify the per‐ and ongoing weather conditions of the low‐temperature events. The overall accuracy and Receiver Operating Characteristics curve (ROC) were combined to identify the trigger threshold of apricot frost. 1.9°C was identified as the apricot frost trigger threshold in regional assessment, with relatively higher correct rate for disaster (90.2%) and lower incorrect rate for none‐disaster (23.4%). An area under the ROC curve (AUC) of 0.88 was obtained, demonstrating a good performance of Tmin as the trigger factor in discriminating between apricot frost and no frost. High frequency of days suffered from apricot and frost exposure at young fruit were mainly found in the northwestern and middle parts of the region, with frequencies of more than 2 days and E more than 3. Regional days suffered from apricot frost and E were found to have a negative trend with slope −0.0317 and −0.789, respectively, whereas the northwest and middle part of the study region were found to have an increasing trend. The results can provide technical and theoretical support for targeted apricot frost detection and risk assessment, and measures for apricot frost prevention and mitigation can be implemented according to the threshold‐based results. [ABSTRACT FROM AUTHOR]

Subsurface pipe failures in cold regions are generally believed to be exacerbated by differential strain in shallow soils induced by seasonal freeze and thaw cycles. The transient stress–strain fields resulting from soil water phase change may influence the occurrence of local buried pipe breaks including those related to urban water mains. This work proposes that freezing‐induced frost loading results in uneven stress–strain distributions along the buried water mains placing them at risk of bending, breaking, and/or leaking. A coupled thermal‐hydraulic‐mechanical (THM) model was developed to illustrate the interactions among moisture, temperature, and stress–strain fields within variably saturated freezing soils. Several typical cases involving highly frost‐susceptible and lower frost‐susceptible soils underlying roadbeds were examined. Results show that the magnitude of frost‐induced compressive stress and strain changes between different frost‐susceptible soils can vary significantly. Such substantial differences in stress–strain fields would increase the breakage risk of water mains buried within different types of soils. Furthermore, even water mains buried within soils with low frost‐susceptibility are at risk when additional sources of soil water exist and are available to migrate to the freezing front. To reduce the risk of damage to buried pipe‐like infrastructure, such as municipal water mains, from soil freezing phenomena, the selected backfill material should have fairly consistent frost susceptibility or a broad zone of transition should be considered between materials with significantly different frost susceptibility. In addition, buried pipes should be kept as far away from external sources of subsurface water as possible considering the potential for the water source to exacerbate the level of risk to the pipe. Key Points: Subsurface pipe failures in cold regions are exacerbated by freezing‐induced differential stress–strain fieldsLocal sources of water available to feed ice growth increases the breakage risk of water mainsThe magnitude of frost‐induced compressive stresses and negative strains may vary significantly between different intermingled soil types [ABSTRACT FROM AUTHOR]

Chemical glass frosting processes are widely used to create visual attractive glass surfaces. A commonly used frosting bath mainly contains ammonium bifluoride (NH4HF2) mixed with hydrochloric acid (HCl). The frosting process consists of several baths. Firstly, the preliminary bath to clean the object. Secondly, the frosting bath which etches the rough light scattering structure into the glass surface. Finally, the washing baths to clean the frosted object. This is where the constituents of the preceding steps accumulate and have to be filtered from the sewage. In the present contribution, phosphoric acid (H3PO4) was used as a substitute for HCl to reduce the amount of ammonium (NH4+) and chloride (Cl−) dissolved in the waste water. In combination with magnesium carbonate (MgCO3), it allows the precipitation of ammonium within the sewage as ammonium magnesium phosphate (MgNH4PO4). However, a trivial replacement of HCl by H3PO4 within the frosting process causes extensive frosting errors, such as inhomogeneous size distributions of the structures or domains that are not fully covered by these structures. By modifying the preliminary bath composition, it was possible to improve the frosting result considerably. To determine the optimal composition of the preliminary bath, a semi‐automatic evaluation method has been developed. This method renders the objective comparison of the resulting surface quality possible. [ABSTRACT FROM AUTHOR]

Frost damage is an important deterioration parameter for reinforced concrete (RC) structures in cold and humid environment, which usually acts simultaneously with sustained load caused by self‐weight, immobile weight, and so forth. This article conducts a thermo‐hydro‐mechanical simulation on the structural behavior of RC beams under the coupled effect of frost damage and sustained load. This simulation approach starts from the microscale material‐based frost damage model of multicomponent substance to the macroscale structural‐based performance evaluation of RC beam. On the basis of this approach, the damage accumulation of RC beam model under both frost action and sustained load is simulated. Afterward, flexural bending load is applied to investigate the structural performance of the RC beam which has suffered coupled damage. Laboratory experiments also show a satisfactory agreement with numerical simulation. Parametric study is also conducted to further evaluate the influence by different parameters on the structural deterioration, for example, reinforcement arrangement, water to cement ratio, and so on. Finally, the equivalent frost‐damaged strength with respect to the damaged region is adopted to calculate the flexural capacity according to the design code, and a simple method is proposed to verify or predict the properties of RC beam under the coupled effect of frost damage and sustained load. [ABSTRACT FROM AUTHOR]

Freezing stress is a critical environmental factor affecting survival, distribution, and evolution of plants. Although there is evidence that nitrogen (N) affects frost tolerance of juvenile conifers, the magnitude and direction of such effect can diverge among species. The influence of the N source on frost tolerance has been barely studied. Particularly, how organic N sources could affect the cold acclimation dynamics of seedlings is poorly understood. We studied morpho‐physiological responses to organic N supply (amino acids) in comparison to inorganic N in seedlings of two Mediterranean pine species: Pinus halepensis and P. sylvestris. Fertilization was applied at low and high N doses (30 and 130 mg N seedling−1) in the first growing season. Then, tolerance of seedlings to freezing stress was evaluated through the cold season. This study confirmed that organic N supply promotes growth of both species as effectively as inorganic N sources. At low N availability, seedlings had acute phosphorus deficiencies when grown with inorganic N, but not with organic N. Likewise, high organic‐N availability improved chlorophylls concentration. Both species increased their frost tolerance through time, especially during late autumn. Although organic N supply did not show clear benefits on frost tolerance, it seemed to enhance cold acclimation via increases of compatible solutes, such as soluble sugars and proline, particularly in P. halepensis. Thus, the effects of organic N supply could depend on the extent that such osmolytes contribute to the dormancy strategy of the species. Other species‐specific mechanisms to cope with freezing stress are further discussed. [ABSTRACT FROM AUTHOR]

American cranberry (Vaccinium macrocarpon Ait.) is a perennial woody plant that produces buds on short vertical branches known as uprights. These buds must overwinter to acquire adequate winter hardening for protection against frost damage in the spring. Once buds have broken dormancy, the plant requires protection from cold temperatures and desiccating winds. In this study, we evaluated three thermal time models, or growing degree day (GDD) models, as decision tools for initiating spring frost protection, and two methods for applying irrigation for spring frost protection (conventional vs. cycling). We found that the WI(30‐5) thermal time model provided the most accurate estimates of the phenology of buds in both normal and abnormal spring temperature years. Although irrigation cycling resulted in slightly higher bud damage, it did not reduce fruit yield. This finding is consistent with bud damage localized in one to two floral initials, with the remaining two to four initials producing flowers and berries comparable to beds with conventional irrigation. In addition to not differences in fruit yield, water savings of up to 35% were obtained in cycled frost irrigation compared with conventional frost irrigation. Core Ideas: We evaluated approaches for timing and applying irrigation for cranberry production.The WI(30‐5) thermal time model mostly accurately predicted bud phenology.Cycling irrigation provides adequate frost protection for cranberry production.Frost irrigation cycling also reduces nutrient leaching, energy use, and labor costs. [ABSTRACT FROM AUTHOR]

Questions: Forest–grassland boundaries in the tropics are primarily interpreted as driven by fire and herbivory. So far, frost has received little attention as driver of tropical vegetation boundaries. Here, we study mid‐altitudes in south‐central Africa and ask the following questions: (a) is there a lower treeline between grasslands and forests on the Angolan Plateau; (b) if so, do topoclimatic differences play a role in it; and (c) what do our results imply for tropical highlands globally? Location: The Angolan Plateau (10°–16°S and 13°–21° E). Methods: We mapped vegetation by applying a supervised support vector machine‐based classification on a Landsat satellite image. We used a 1,000‐m spaced point grid to extract the mean vertical distribution of the vegetation units from a digital elevation model. The topographic position of each point was calculated using a channel network approach. Microclimatic data were collected across topographic gradients at two sites along the Plateau. Analyses focussed on the number of nights where temperature dropped below 0℃, median and minimum temperatures, and diurnal temperature ranges. Results: Lower treelines separate Miombo forests from geoxyle grasslands in all major valley systems. Treelines are located 150–200 m below the headwater divides. Nocturnal outgoing net long‐wave radiation and resulting cold‐air pooling cause frequent frosts in the valleys during the dry season. Topography controls frost patterns, with minima of down to −7.5℃ and diurnal temperature amplitudes up to 40℃. Conclusions: The results show that vegetation patterns in central Angola are shaped by frost. The processes causing frost depend on air humidity. Drier atmosphere and lower global temperatures indicate a longer frost season, lower minima and frost extending to lower elevations and latitudes for the Pleistocene. Pleistocene forest fragmentations and the rise of endemism‐rich grasslands in comparable tropical highlands worldwide may be explained by crossing thermic thresholds via increasing seasonal aridity. [ABSTRACT FROM AUTHOR]

In order to secure a specified preload level, suitability tests for preloading of HV and HR high‐strength structural bolting assemblies according to EN 14399‐4 and EN 14399‐3 are mandatory according to the specifications given in EN 14399‐2. However, in EN 14399‐2 and EN ISO 16047 actual working conditions and processes on the construction site are disregarded: influences of high and low temperatures as well as storage conditions under changing wet/dry conditions, both summarized as weathering impacts, are not covered in the suitability test. Consequently, this leads to a lack of knowledge regarding the effect of weathering impacts on the basic preloading and tightening behaviour of HV and HR bolting assemblies. From practical experiences it is known that different extreme temperature conditions as well as moisture on the threads of the bolting components have an influence on the tightening behavior, which led to failures of the bolting assemblies during the assembly in the past. The presented contribution intends to provide a first insight into the influence of weathering impacts on the tightening behaviour of HV‐ and HR‐bolting assemblies for preloading on the basis of tightening tests of HV and HR bolting assemblies under various temperatures (‐20 °C, +23 °C, +50 °C) and moisture conditions (dry, hoarfrost, little direct/indirect rain impact, changing dry/wet condition etc.). [ABSTRACT FROM AUTHOR]

Questions: Cold temperatures and freezing may hinder the process of forest expansion in moist climate regions, as predicted by the frost hypothesis. We examined the role of frost on the survival and regrowth of tree saplings under field conditions of open grasslands. Location: Cambará do Sul, Rio Grande do Sul. Methods: We established a field experiment protecting one of two groups of saplings of forest species from frost in grassland areas during the winter. We monitored 672 saplings from a total of seven species for 56 days. Saplings were brought back to the laboratory to evaluate regrowth rate and height. Survival curves of the two groups were compared using a Kaplan–Meier estimator. Correlation analysis was undertaken to estimate the relationship between survival and regrowth rate and a variance analysis was used to compare plant height between both groups. Results: Species respond distinctly to frost incidence, with some not being affected by frost (two gymnosperms and Myrcianthes pungens). Most protected saplings had a higher above-ground survival rate than unprotected ones (96.4% and 73.2%, respectively). Moreover, saplings that were damaged by frost showed differences in regrowth and height according to species identity, notwithstanding the fact that those from protected plots showed higher regrowth and height (88% and 25.65 cm compared to 68% and 17.15 cm). Conclusions: Our results showed clear negative effects of frost on the survival rate of aerial parts of saplings during the winter and the regeneration of damaged plants. Species-specific traits can offer frost resistance; however, together with other disturbances, frost may hinder the establishment of forest trees over grassland areas where frost events are common during the winter. [ABSTRACT FROM AUTHOR]