Sub-freezing Temperatures Research Articles

Storing sunlight at low temperatures?

Artificial leaves that convert sunlight to fuels could provide a sustainable energy future. But several challenges must be overcome to improve their economic viability. Publishing in Energy & Environmental Science, Kölbach, Rehfeld, and May describe the potential of decentralized hydrogen production using thermally integrated architectures that operate under sub-freezing temperatures. Artificial leaves that convert sunlight to fuels could provide a sustainable energy future. But several challenges must be overcome to improve their economic viability. Publishing in Energy & Environmental Science, Kölbach, Rehfeld, and May describe the potential of decentralized hydrogen production using thermally integrated architectures that operate under sub-freezing temperatures.

A model for freeze-thaw-induced plastic volume changes in saturated clays

A new model is proposed for describing freeze-thaw-induced plastic volume changes in saturated clays based on microscopic inhomogeneities inherent in the soil structure and the pore water transfer between them. It is shown through a simple inhomogeneous mesostructure model that the equilibrium state reached after freezing serves as an important reference state for interpreting the volumetric behaviour. The soil state evolution towards this freeze equilibrium state describes many features seen in the experimentally observed freeze-thaw behaviour, such as the existence of a limiting stress level above which no plastic volume change occurs. The process of freezing/thawing is modelled as a rate process approaching the freeze equilibrium line (FEL) and representing the eventual equilibrium states at a particular sub-freezing temperature, exploiting a newly defined state parameter, ψfe. The model offers a mesoscopic three-dimensional yield surface in the specific volume – effective stress – temperature space, expressed by a simple equation. Although the model’s essence is encapsulated in only two simple equations, it can simulate well the experimentally observed volume change accumulation with freeze-thaw cycles under different stress levels and densities (or over-consolidation ratios). As the model is formulated in an incremental rate form, it can be applied to general freeze-thaw problems, even those with irregular temperature and stress history – a feature not seen in existing models.

Determination of subfreezing temperature and gel retrogradation characteristics of potato starch gel

The freezing properties and retrogradation of potato starch gels were studied. The freezing points of the starch gels decreased with increasing starch concentration and ranged from −0.7 °C to −1.4 °C. The water in the gel was partially frozen at −3 °C and was essentially frozen at −6 °C. The glass transition temperatures of potato starch gels increased with the increase of starch concentration and ranged from −3.69 °C to −3.23 °C. Therefore, −3 °C was selected as the subfreezing temperature for potato starch gel, and the retrogradation characteristics of gel with 8% potato starch concentration (w/w) were investigated at this temperature. The results showed that the hardness of starch gel stored at −3 °C was stronger than that at other temperatures, and the relaxation times T23 and T24 were shorter. Potato starch gel stored −3 °C had better rheological properties and higher relative crystallinity than those of the other gels, and still exhibited B-type crystallinity according to X-ray diffraction analysis. Thus, potato starch gel has a higher retrogradation rate and better gel-related properties at subfreezing temperatures than those at other temperatures, which represents a new approach for the aging of potato starch products.

Longevities of Adult Chironomidae (Diptera) from Two Streams in Iceland

Mean annual air temperatures are predicted to increase by several degrees in the Arctic. This increase in temperature will likely impact organisms adapted to current conditions. Studies of longevities of winter-active Chironomidae from cold, groundwater-fed streams in Minnesota demonstrate that winter-emerging species are long-lived as adults when incubated at cold or sub-freezing air temperatures post emergence. It is unknown if this holds for species emerging in sub-arctic latitudes during warm months, or if warm air temperatures affect the adults of species emerging from cold and geothermally heated streams. The goal of this study was to determine the effects of exposure to air temperatures predicted by climate change models on the longevities of Chironomidae emerging from both cold and geothermally heated larval environments. Chironomidae were trapped at emergence from two groundwater-fed streams with contrasting (warm and cold) thermal regimes at the Hengladalir valleys in the Hengill alpine geothermal area in southwestern Iceland over 4 days in July 2018. Adults (N=102) were randomly divided into two treatments and incubated at either 20°C or 6°C for 28-32 days to determine influence of source stream and incubation temperature on adult longevity. These temperatures were selected to simulate current and predicted water and air temperatures that adult chironomids are likely to be exposed to with climate change. Adults incubated at 6°C survived longer than adults incubated at 20°C irrespective of source stream. All adults incubated at 20°C died within 1-5 days post-emergence. Longevities of taxa incubated at 6°C ranged from 13 to more than 32 days. Species of Diamesa exhibited the greatest longevities, with 41.7% surviving more than 28-32 days post-emergence at 6°C. We were unable to determine maximum longevity for Diamesa within the 6°C treatment because surviving adults had to be sacrificed at the termination of the experiment on day 32. However, the minimum longevity we report is similar to longevities determined for other Diamesa species and indicates that Diamesa species in Iceland are also long-lived under cold air temperatures. We suggest there may be a difference in longevity between sex, with females living longer than males at cold temperatures. By contrast, we found that both sexes of Diamesa and all other chironomid taxa that we tested are susceptible to warm air temperatures regardless of stream of origin. Therefore, warming climatic temperatures could potentially lead to shortened adult lifespans for these sub-arctic taxa.

Fluid Flow With Three Upstream Configurations in Freezing Tubes

AbstractThe accumulation of frozen liquid around a central passageway of melt as it flows through a freezing region can make calculations very challenging. To both illustrate and to quantify some of these challenges from freezing, a model equation is developed. It simplifies the solution of Holmes (2007, https://gfd.whoi.edu/wp-content/uploads/sites/18/2018/03/MHolmesGFDReport_30151.pdf) for low Reynolds number single component liquid flow through a long tube that has a wall kept at subfreezing temperature. This model equation is used in conjunction with three different upstream configurations, each with parameters expressing their behavior. Analytical and numerical results give the parameters that have criteria for: the freezing of a compressible upstream reservoir that includes oscillatory behavior; the freezing of flow fed through a constriction with a large upstream pressure, just like a dripping water faucet during winter; the evolution of flow in multiple tubes connected by an upstream manifold, where some tubes end up with full flow and others freeze shut. Numerical runs with 1,000 tubes give a formula for the spacing between actively flowing (non‐frozen) tubes over wide ranges of the two upstream parameters (flow rate and manifold resistance). Results have implications in various areas in earth science. Some are: oscillatory and freezing shut criteria for flow of magma from a compressible region, a criterion for wintertime ice accumulation at natural springs, and the spacing between volcanos.

The biogeographic history of eelpouts and related fishes: Linking phylogeny, environmental change, and patterns of dispersal in a globally distributed fish group

Modern genetic data sets present unprecedented opportunities to understand the evolutionary origins of diverse taxonomic groups. When the timing of key events is known, it is possible to investigate biogeographic history in the context of major phenomena (e.g., cooling of a major ocean). In this study, we investigated the biogeographic history of the suborder Zoarcoidei, a globally distributed fish group that includes species inhabiting both poles that produce antifreeze proteins to survive chronic subfreezing temperatures. We first generated a multi-locus, time-calibrated phylogeny for the group. We then used biogeographic modeling to reconstruct ancestral ranges across the tree and to quantify the type and frequency of biogeographic events (e.g., founder, dispersal). With these results, we considered how the cooling of the Southern and Arctic Oceans, which reached their present-day subfreezing temperatures 10–15 million years ago (Mya) and 2–3 Mya, respectively, may have shaped the group’s evolutionary history, with an emphasis on the most speciose and widely distributed family, eelpouts (family Zoarcidae). Our phylogenetic results clarified the Zoarcoidei taxonomy and showed that the group began to diversify in the Oligocene ~31–32 Mya, with the center of origin for all families in north temperate waters. Within-area speciation was the most common biogeographic event in the group’s history (80% of all events) followed by dispersal (20%). Finally, we only found evidence, albeit limited, for ocean cooling underpinning diversification of eelpouts living in the high Antarctic over the last 10 million years.

DIRECT NUMERICAL SIMULATION STUDY OF WATER DROPLETS FREEZING ON A HORIZONTAL PLATE

We present the numerical results of the solidification process of water droplets on a cold plate with different wetting angles. The numerical method used is an axisymmetric front-tracking technique. The water droplets are assumed as a spherical cap and placed on the cold plate which is kept at a subfreezing temperature. At the end of solidification, we obtain a small protrusion shape at the top of the frozen water droplet and its height is also higher than that of the initial water droplet. The frozen water droplets are also compared with the corresponding experimental ones reported in the literature.

Glucose and glycerol temperature-pressure correlations for the design of cryopreservation protocols in an isochoric system at subfreezing temperature

There is growing interest in the use of isochoric (constant volume) freezing for cryopreservation of biological matter. The goal of this study is to generate fundamental experimental data on the pressure temperature relation during the freezing of an isochoric system of aqueous solutions of two compounds, glucose and glycerol. Glucose and glycerol are commonly used as cryoprotectants in conventional isobaric (constant pressure) cryopreservation protocols. Earlier studies have shown that the increase in pressure during isochoric freezing is detrimental to biological matter and limits the range of temperatures in which isochoric freezing can be used for preservation to temperatures corresponding to pressures below 40 MPa. In physiological saline solution this pressure corresponds to a temperature of - 4 °C. Our new experimental data shows that the addition of 2 M glycerol to the saline solution lowers the temperature at which the isochoric freezing pressure is 40 MPa to −11 °C, 3 M glycerol to – 16.5 °C, and 4 M glycerol to – 24.5 °C, thereby substantially expending the range of temperatures in which cryopreservation by isochoric freezing can be practiced.

Suction measurement in freezing soils using pore pressure transducers

Frost heave is major problem for infrastructures build in cold regions. Frost heave occurs due to suction (negative pore water pressure) generated due to the freezing process close to the frost line, i.e., at the frozen fringe. To understand and predict these negative pore water pressures is a key factor to accurately calculate the segregation heave, i.e. heave related to the formation of ice lenses. Segregation heave is the major part of the total heave and also the most challenging to predict. Many attempts have been presented in literature where the generated suction during freezing is related to temperatures, temperature gradients, grain size of the freezing soil etc. Very few laboratory tests have been presented in which the actual suction is measured during the ice lens formation process and compared with theoretical estimations. One reason is that these measurements are challenging. This paper presents results from laboratory measurements of generated suction during freezing. Laboratory tests were conducted on a silty soil sample and suction was measured at the frozen fringe using small pore pressure transducers (PPT’s). The samples were subjected to one-dimensional freezing from top to bottom in an open water system at a constant temperature gradient. Temperatures were measured at various points along the height of the soil sample while suction was measured at middle of the sample. Test results have shown that PPTs do not show pressure change in long-term static pressure test under sub-freezing temperature. For suction measurement at the frozen fringe, pore pressure readings should be measured at various points along the sample height.

Experimental and numerical analysis of anti-icing a GLARE laminate

Abstract This study aimed at developing a numerical model to estimate the power consumption of a GLAss fiber REinforced aluminum-based electro-thermal ice protection system for anti-icing. The GLAss fiber REinforced aluminum laminate was embedded with recurred S-shaped copper meshes thermally energized by a surface power density. The model determined the influence of a forced convective heat loss and copper-mesh dimension on anti-icing. As a test case, the numerical model addressed the anti-icing performance of a GLAss fiber REinforced aluminum 5A-3/2 laminate at a sub-freezing ambient temperature of 267.95 K. The model demanded a surface power density of 13.03 kW/m2 in order to keep the temperature of the outer aluminum-skin at 285.44 K, which was clearly beyond the water freezing point. The numerically predicted power consumption for anti-icing was in excellent agreement with that from the experiment. The experiment was conducted in a miniature icing wind tunnel by incorporating the comparable icing condition of the numerical analysis. In the experiment, an infrared thermography camera determined the spatio-temporal temperature history of the outer aluminum skin in contact with the free-stream. The infrared thermography camera measurements of surface temperature collapsed in close proximity to that from the numerical analysis. The outcomes of this study will consolidate the confidence of aircraft manufacturers on the proposed anti-icing system.

Effect of sub-zero versus sub-freezing temperature on chloride diffusion and binding in concrete

Effect of temperature on chloride diffusion in concrete has been extensively studied by others and it is found to follow Arrhenius law. However, the lowest exposure temperature studied to date has been −4 °C, but due to supercooling the concrete pore solution is not expected to freeze at −4 °C. It is hypothesized here that below the supercooling temperature, some of the pore water will freeze and pore ice will form, which increases the pores tortuosity, and reduces their connectivity, resulting in reduced diffusivity. To test this hypothesis, concrete samples are subjected to natural diffusion in a 10% NaCl solution under 5, 0, −5, or −15 °C for 3 and 6 months. It is discovered that Arrhenius law can capture the effect of temperature on chloride diffusion, but when the temperature falls below the supercooling temperature, the effect of pore ice must be also considered. A method is proposed for capturing the latter effect. The diffusion coefficients of the frozen specimens computed by the proposed method differ maximum 15% from the corresponding experimental values.

Preliminary assessment of environmental performance of ice formwork production method for irregular architectural elements of concrete

The present article communicates knowledge in sustainability of a method of digital fabrication in precast concrete production. The method, known as Ice Formwork, serves in production of ultrathin lightweight architectural elements – a novel design typology that has emerged with the development of High-Performance Fibre-Reinforced Concrete (HPFRC), and helps to reduce cement consumption, adopt digital fabrication processes, and increase design flexibility. In practice, however, this production employs suboptimal methods of mould-making, using petrochemical or engineered wood products for single-use moulds, entailing excessive amounts of non-recyclable waste. The current work builds on the research and development of a novel production method Ice Formwork facilitated through single-use moulds made of artificially frozen water. Previously published work on the subject has covered topics such as cement hydration at subfreezing temperature, subtractive digital processing of ice and a case of practical application illustrated with the production of a prototype of a lightweight façade rain screen. Yet, since artificial refrigeration and processing of large amounts of water is essential for Ice Formwork production, the environmental performance of this method requires a thorough examination. Thus, the current piece of work attempts to address two major issues, namely: (1) Energy consumption of industrial refrigeration in production of Ice Formwork. (2) Changes in water mineral content after a cycle of Ice Formwork concrete production. For both topics, the research work required development of an original experimental methodology. This aspect has been given the great attention and required development of new technical solutions on many levels. Further research and development is needed to come to a comprehensive environmental assessment, and the results of the current study merely provide a preparatory overview that can help to orient and properly set the objectives for the following research stages.

Narrow-waveband spectral indices for prediction of yield loss in frost-damaged winter wheat during stem elongation

Frost during stem elongation is one of the most destructive disasters in China, which has a significant impact on the production of winter wheat. Automatic monitoring of frost injury to canopy is of vital importance to the early prediction of yield loss. This study investigated the potential of hyperspectral techniques in predicting the Percent Yield Difference (PYD) of frost-damaged winter wheat. Three artificial frost experiments were conducted to obtain hyperspectral reflectance and grain yield for winter wheat subjected to sub-freezing temperature treatments. The PYD was used to evaluate the level of frost damage. Nine new indices based on the best combination of wavelengths were selected through the contour mapping approach. All new and published indices were used to establish the linear regression models with PYD. The results showed that as the value of PYD increased, the NIR reflectance within 760–1140 nm decreased, whereas the red and SWIR reflectance increased. The most significant change was found in the NIR region, where the water absorption bands within 930–970 nm almost disappeared. The cross-validation results indicated that the three water-sensitive spectral indices NWI-2, RDSI ((R958-R545)/(R826-R545)), and NDSI ((R962-R829)/(R962+R829)) demonstrated the best prediction accuracy and outperformed the partial least square regression (PLSR) and support vector regression (SVR) models. NWI-2 and NDSI represented a relatively simple waveband combination similar to NDVI, which could be referenced for developing satellite multispectral products to predict PYD at a large spatial scale. GS and PYD range had a significant impact on the spectral indices. The prediction accuracy of PYD for a single GS improved as development advanced before heading. When the PYD value was above 10 %, no significant differences between the subfreezing treatments and the unfrosted controls was detected until the PYD value exceeded 30–40%. It was difficult to predict the relatively low PYD level due to the hybrid response of the spectral reflectance to frost damage.

Effect of subfreezing storage on the quality and shelf life of frozen fermented dough

The purpose of this study is to explore a new storage method for frozen fermented dough. About −9°C and −12°C are selected as subfreezing storage temperatures according to the results of low-field nuclear magnetic resonance. The effects of subfreezing storage on the properties of dough were investigated and compared with that storage at 4°C and −18°C. The results showed the density of hydrogen protons in fermented dough under subfreezing temperatures was similar to that of the sample at −18°C. Slow increase in titratable acidity and slow decrease in pH of dough were found at subfreezing temperatures and −18°C. The hardness could effectively be reduced and the texture of dough were maintained under subfreezing temperatures. There was no significant difference in the gluten network and sensory quality of the dough between subfreezing temperature storage and −18°C storage. Novelty Impact Statement There are some disadvantages such as mechanical damage, energy consumption, and nutrient loss in the conventional frozen storage. According to the conclusion of LF-NMR, −9°C and −12°C was designated as subfreezing temperatures. The results suggest that the quality of the dough remained stable at subfreezing storage, similar to that at −18°C, so subfreezing storage provides a new energy-saving storage technology for frozen flour products enterprises and catering industries.

Expeditionary Immersion Circulating Heating Device: A Promising Technique for Treating Frostbite Injuries and Warming Intravenous Fluids in a Forward Deployed Cold Weather Environment

Cold weather injuries require prompt warm water immersion therapy, which proves to be a difficult task in the cold austere environment. Current guidelines recommend 104°F water immersion, but producing and maintaining large volumes of warm water is challenging in sub-freezing temperatures. We describe a novel process of utilizing a sous vide immersion circulator to maintain warm fluids for immersion therapy and efficient fluid rewarming in a cold forward-deployed setting for the treatment of cold weather injuries in an effort to bridge the gap between current medical guidelines and practices. Large water cans were warmed to 104°F with the immersion circulator. A thermometer was inserted into a 1-inch steak, frozen to 30°F, and placed in a basin with only the warmed water while the internal temperature was monitored until physiologic temperature was achieved. The time to this endpoint was recorded. A 1-L bag of normal saline and a 450-mL bag of whole blood were also separately warmed by the same technique. The temperature of the normal saline was monitored at 0-, 5-, 7-, 8-, 9-, and 10-minute intervals. The process was similarly repeated, measuring the whole blood temperature at 0-, 5-, 7-, and 10-minute intervals. Ambient internal tent temperatures averaged 54°F; outdoor temperatures were consistently sub-freezing. The 5-gallon cans of water at ambient temperature heated to 104°F in 15minutes. The water temperature remained constant for 3weeks with the circulator running. The frozen steak started at 30°F and reached 98°F in 52minutes and 45seconds. The bag of normal saline and whole blood, refrigerated to 39°F, achieved temperatures of 102°F and 94°F respectively after 10minutes. A heating immersion circulator device is a lightweight, flameless, and inexpensive way to consistently heat large volumes of water for treatment of cold weather injuries, hypothermia, and whole blood rewarming in a cold austere environment.

Numerical study of subfreezing temperature cold start of proton exchange membrane fuel cells with zigzag-channeled flow field

An automotive proton exchange membrane fuel cell (PEMFC) engine needs to be capable of surviving from sub-freezing temperatures. Cold starting up a PEMFC engine presents great technical challenge due mainly to the intra-electrode ice formation that is closely related to the involved multi-physical transport. The flow field configuration to some extent dictates the reactants and product transport and is thus of important influence on PEMFC cold start performance. The present work carefully analyzes the cold start process of PEMFCs with zigzag-channeled flow field (ZZFF). A transient three-dimensional numerical model is established and experimentally validated first, and then we make comparisons of cold-start performance between zigzag and straight channel flow-field PEMFCs to reveal the effects of ZZFF. It is found that the ZZFF better distributes the reactants/product and current density in the PEMFC as it enhances the transport along the flow direction in-between the under-land and under-channel regions inside the cell. The process of cold starting the ZZFF PEMFC is found to generate slightly less heat, which is not good to cold start. Therefore, the ZZFF enhances the survivability of PEMFC engine cold starting from subfreezing temperatures, whereas it slightly degrades the quick self-startup ability of PEMFC engine. Case study with PEMFCs of more zigzagged flow fields further corroborates the effects of ZZFF configuration on PEMFC cold start performance.

Effect of subfreezing testing temperature on tensile mechanical behavior of fine-grained magnesium

The effect of testing temperature on mechanical properties and deformation mechanisms was investigated by tensile testing of fine-grained magnesium samples under a range of temperatures (i.e. room temperature 20 °C, subfreezing temperatures 0 °C, −30 °C, and −60 °C) and microstructural observations of both untested and tested samples using electron backscatter diffraction. The results suggest that mechanical properties and deformation mechanisms were significantly affected by the variation of testing temperature. Strength increased linearly and ductility decreased linearly with the decrease of testing temperature. Although twinning is generally known to be athermal, this experimental study shows that tensile twinning is the dominating deformation mechanism at room temperature, and that twinning is negligible and dislocation operation is the primary deformation mechanism at 0 °C, −30 °C, and −60 °C.

Distribution, coalescence, and freezing characteristics of water droplets on surfaces with different wettabilities under subfreezing convective flow

This paper investigates the effects of surface wettability and surface initial conditions on early frost formation for hydrophobic, hydrophilic, and bare aluminum flat surfaces. The new data revealed that the average droplet sizes were larger and droplet size distributions were wider for the hydrophilic surface than for the hydrophobic and bare aluminum surfaces. This was due to a coalescence phenomenon occurring before the droplets froze into ice beads. Because of the relative high sub-freezing plate temperatures used in this work, the surface wettability of the plates had a smaller impact on the freezing time. Supersaturation degree and temperature difference between the air stream and the surface controlled freezing times for all different surface wettability types. When testing was conducted without cleaning the surfaces in between individual test runs, a film deposited on the surfaces which smoothed surface imperfections, inhibited surface wettability effects on droplet size and shape, and delayed freezing. A large variation in the frost nucleation behavior was measured in the present work due to intentionally different generated initial surface cleanness conditions. This finding could explain some of the significant deviations observed in data from literature studies when comparing freezing times and droplet diameters for similar coatings and similar tests conditions.

Formation, structure and climatic significance of blue rings and frost rings in high elevation bristlecone pine (Pinus longaeva D.K. Bailey)

The study of anatomical irregularities in tree rings has recently gained momentum as a complement to traditional tree-ring measurements as they may provide information on extreme climatic events. Two anomalies, blue rings (BR) and frost rings (FR), were analyzed in bristlecone pine (Pinus longaeva D.K. Bailey) trees located along an elevation gradient in northeastern Nevada. These two subannual ring anomalies were systematically compiled for two periods; one centered on 536 CE (well-known for a volcanically-induced period of climatic cooling) and the other on 1965 CE (useful due to the availability of instrumental climate data). During the period 523–545 CE (n ≥ 10 trees), both BR and latewood FR (LWFR) were recorded abundantly in 532 and 536, as well as a BR cluster from 539 to 542 CE. Years when trees solely recorded a BR (without an accompanying LWFR) were more frequent in the earlier period than in the modern period (1954–2006 CE; n ≥ 10 trees) when both anomalies tended to co-occur. These results suggest a shorter growing season in the 536 period than in the 20th century. Modern BR/LWFR were most abundant in 1965 and 1978 CE. Both anomalies were mainly observed in the highest elevation trees and both were produced in years characterized by cooler than average temperatures throughout the growing season. Anatomically, BR and LWFR did not differ significantly in tracheid dimensions except that LWFR clearly showed damages associated with sub-freezing temperatures. The main feature distinguishing BR and LWFR from “normal” tree rings was a significant reduction in latewood secondary wall thickness. In P. longaeva, BR like pale latewood (light) rings, result from short and cool growing seasons which leads to reduced (or interrupted) lignification of tracheids. In species producing extremely narrow latewood like P. longaeva it may be difficult to macroscopically identify pale latewood years, thus rendering microscopic investigation of BR as a climate proxy useful in paleoclimatic research.

Comparison of Cold Hardiness Evaluation of Woody Species by ELLT and TTCLT

Cold hardiness evaluation is important for screening woody species in cold areas. We compared cold hardiness by estimating the 50% lethal temperature (LT50) using electrolyte leakage test (ELLT50) and triphenyltetrazolium chloride test (TTCLT50) for 26 woody species in the Bashang region of China. One-year-old shoots were collected in January and exposed to five subfreezing temperatures in a programmable temperature and humidity chamber. LT50 was estimated by fitting relative electrolyte leakage and percentage of dead tissue against test temperature. For all tested species, triphenyltetrazolium chloride (TTC) staining of the pith was weak and the cambium TTCLT50 was lower than the extreme minimum temperature (−37 °C) recorded in the region. The cambium TTCLT50 and the sd were lower than that for the phloem and xylem. The phloem TTCLT50 was lower than the xylem TTCLT50, and the two sds were similar. The ELLT50 showed no significant correlation with any TTCLT50. For most species, the ELLT50 was higher than the cambium and phloem TTCLT50 and was not significant different with the xylem TTCLT50. The ELLT50 showed higher sd than any tissue TTCLT50. Based on results obtained in this study, when choosing cold hardiness of single stem tissue as an indicator for screening woody species, the xylem should be considered first, followed by the phloem; the cambium and pith were unsuitable. The cold hardiness estimated by ELLT50 was more suitable as indicator for screening woody species than that of stem tissue in winter estimated by TTCLT50.