Subzero Air Temperatures Research Articles

Seasonal trends in the biomass and structure of bryophyte‐associated fungal communities explored by 454 pyrosequencing

Bryophytes are a dominant vegetation component of the boreal forest, but little is known about their associated fungal communities, including seasonal variation within them. Seasonal variation in the fungal biomass and composition of fungal communities associated with three widespread boreal bryophytes was investigated using HPLC assays of ergosterol and amplicon pyrosequencing of the internal transcribed spacer 2 (ITS2) region of rDNA. The bryophyte phyllosphere community was dominated by Ascomycota. Fungal biomass did not decline appreciably in winter (P=0.272). Significant host-specific patterns in seasonal variation of biomass were detected (P=0.003). Although seasonal effects were not the primary factors structuring community composition, collection date significantly explained (P=0.001) variation not attributed to locality, host, and tissue. Community homogenization and a reduction in turnover occurred with the onset of frost events and subzero air and soil temperatures. Fluctuations in the relative abundance of particular fungal groups seem to reflect the nature of their association with mosses, although conclusions are drawn with caution because of potential methodological bias. The moss-associated fungal community is dynamic, exhibiting seasonal turnover in composition and relative abundance of different fungal groups, and significant fungal biomass is present year-round, suggesting a winter-active fungal community.

Effects of freezing on soil temperature, freezing front propagation and moisture redistribution in peat: laboratory investigations

Abstract. There are not many studies that report water movement in freezing peat. Soil column studies under controlled laboratory settings can help isolate and understand the effects of different factors controlling freezing of the active layer in organic covered permafrost terrain. In this study, four peat Mesocosms were subjected to temperature gradients by bringing the Mesocosm tops in contact with sub-zero air temperature while maintaining a continuously frozen layer at the bottom (proxy permafrost). Soil water movement towards the freezing front (from warmer to colder regions) was inferred from soil freezing curves, liquid water content time series and from the total water content of frozen core samples collected at the end of freezing cycle. A substantial amount of water, enough to raise the upper surface of frozen saturated soil within 15 cm of the soil surface at the end of freezing period appeared to have moved upwards during freezing. Diffusion under moisture gradients and effects of temperature on soil matric potential, at least in the initial period, appear to drive such movement as seen from analysis of freezing curves. Freezing front (separation front between soil zones containing and free of ice) propagation is controlled by latent heat for a long time during freezing. A simple conceptual model describing freezing of an organic active layer initially resembling a variable moisture landscape is proposed based upon the results of this study. The results of this study will help in understanding, and ultimately forecasting, the hydrologic response of wetland-dominated terrain underlain by discontinuous permafrost.

Monitoring rapid head scarp movement in an alpine rockslide

The Aresawa rockslide in the Japanese Alps, which partially collapsed in May 2004, produced a number of new tension cracks in the head area. This paper discusses the dynamics of the rock slope and controls on the surface velocity, based on the results of on-site monitoring of the surface movement and meteorological parameters (air and ground surface temperatures, precipitation and snow depth). The rock mass deformation progressed at ca. 60 cm yr − 1 mainly along a slip plane dipping downslope at ca. 50°. The surface velocity of the slipping rock mass showed a significant seasonal variation in response to the water infiltration. The velocity was small (≤ 1 mm day − 1 ) in winter. Subzero air temperatures and a heat-insulating snow cover, and resulting growth of seasonal frost, prevent water infiltration into the bedrock and contribute to the rock slope stability. Most of the movement in this period is attributed to gravitational deformation originating from the overburden pressure. In contrast, the surface velocity increased (up to 10 mm day − 1 ) during snow-melting and snow-free periods. Snowmelt and rainfalls promote water infiltration into the bedrock, destabilizing the rock slope and accelerating the rock slip. Such a rapid movement is attributed to water-induced sliding superimposed on gravitational deformation.

Rapid degradation of ground ice in a ventilated talus slope: Flüela Pass, Swiss Alps

AbstractThe degradation of ground ice in talus deposits, which are important forms of debris storage in mountain environments, can cause mass movements, subsidence or instability of mountain infrastructure. Two 20 m deep boreholes instrumented with thermistors and located in a talus slope at 2400 m asl above a lake at Flüela Pass in the eastern Swiss Alps allow the analysis of the evolution of ground temperature and permafrost thickness between 2003 and 2008. The occurrence of intra‐talus ventilation can be discerned due to thermal anomalies within a layer of coarse blocks with large voids at around 15 m depth near the base of the slope and at 10 m depth mid‐slope. Intra‐talus ventilation is particularly effective in winter when subzero air temperatures coincide with snow depths less than 50 cm and reverses to a gravity discharge of intra‐talus air when air temperatures become positive. Despite the lack of annual variability in active layer depth, rapid permafrost degradation and thinning of ground ice (from 7 m thickness to 3.5 m in 4 years) is currently occurring. It is attributed to latent heat transfer from the moving air stream, caused by the flux of vapour from the relatively warm lake water table at 20 m depth and its condensation at the base of the permafrost body. Copyright © 2009 John Wiley & Sons, Ltd.

Survival and metabolism of Rana arvalis during freezing

Freeze tolerance and changes in metabolism during freezing were investigated in the moor frog (Rana arvalis) under laboratory conditions. The data show for the first time a well-developed freeze tolerance in juveniles of a European frog capable of surviving a freezing exposure of about 72 h with a final body temperature of -3 degrees C. A biochemical analysis showed an increase in liver and muscle glucose in response to freezing (respectively, 14-fold and 4-fold between 4 and -1 degrees C). Lactate accumulation was only observed in the liver (4.1+/-0.8 against 16.6+/-2.4 micromol g(-1) fresh weight (FW) between 4 and -1 degrees C). The quantification of the respiratory metabolism of frozen frogs showed that the aerobic metabolism persists under freezing conditions (1.4+/-0.7 microl O(2) g(-1) FW h(-1) at -4 degrees C) and decreases with body temperature. After thawing, the oxygen consumption rose rapidly during the first hour (6-fold to 16-fold) and continued to increase for 24 h, but at a lower rate. In early winter, juvenile R. arvalis held in an outdoor enclosure were observed to emerge from ponds and hibernate in the upper soil and litter layers. Temperature recordings in the substratum of the enclosure suggested that the hibernacula of these juvenile frogs provided sheltering from sub-zero air temperatures and reduced the time spent in a frozen state corresponding well with the observed freeze tolerance of the juveniles. This study strongly suggests that freeze tolerance of R. arvalis is an adaptive trait necessary for winter survival.

In situ photosynthetic freezing tolerance for plants exposed to a global warming manipulation in the Rocky Mountains, Colorado, USA

Summary • This research tested the hypothesis that experimental infrared warming will reduce photosynthesis for the evergreen shrub Artemisia tridentata and the subalpine, herbaceous Erythronium grandiflorum exposed to an in situ experimental freezing event during the spring snowmelt period. • Photosynthetic tolerance of freezing was measured for plants growing under infrared (IR) warming at 3050 m in the Rocky Mountains, Colorado, USA. In situ freezing was imposed using cold nitrogen gas (from a pressurized container of liquid nitrogen) passed through a heat exchanger placed on top of stems and leaves. • Plant water potential, photosynthetic CO2 assimilation, and stomatal conductance to water vapor were higher for both species on IR-warmed compared with control plots. For A. tridentata, IR warming caused enhanced tolerance of in situ freezing temperatures. There was no difference in freezing tolerance for E. grandiflorum on control vs IR plots. • These results suggest that some species will not be negatively affected by freezing, whereas others may exhibit enhanced tolerance of subzero air temperatures, under a future warmer climate in which snowmelt occurs earlier in the year.

Aspects of the Cryobiology of the Intertidal Harpacticoid CopepodTigriopus brevicornis(O. F. Müller)

Cold-resistance studies of marine invertebrates have concentrated on intertidal sedentary organisms, which are often subjected to subzero air temperatures in winter. Mobile rock pool inhabitants have been rarely studied because such habitats are thought to buffer environmental variation. However, it is not uncommon for small upper-shore rock pools (∼2 by 1 cm) to become completely frozen. Such supralittoral habitats are subject to extreme physicochemical fluctuations especially in salinity (0 to 300‰) and temperature (−1 to +32°C) due to evaporation and dilution. The dominant invertebrate in such habitats is the harpacticoid copepodTigriopus brevicornis.Aspects of the cryobiology ofT. brevicorniswere investigated using differential scanning calorimetry (DSC). Thermograms obtained from DSC allowed determinations of freeze-onset (supercooling point, SCP), melt-onset, and melt-peak (melting point, MP) temperatures, together with estimation of the proportion of water freezing in the samples. The effects of acclimation salinity, temperature, starvation, and reproductive state on these cryobiological parameters were investigated. Acclimation to increasing salinity depressed the SCP, with the highest salinity (70‰) producing the lowest SCP, melt-onset, and MP temperatures at −27.5, −15.2, and −9.5°C respectively. The highest acclimation temperature (20°C) produced the lowest SCP (−23.4°C). Starvation significantly increased the SCP, melt-onset, and MP temperatures in comparison to fed individuals acclimated to the same salinity. The presence of eggs or ovaries in individual copepods elevated the SCP compared to nongravid females and males. LT50studies showed that acclimation to high salinity improved the ability ofT. brevicornisto survive in frozen seawater. Seventy parts per thousand acclimated individuals had an LT50of 64.9 h compared with just 1.4 h for 5‰ acclimated individuals in frozen seawater at −5°C. The study shows that the cold-resistance capabilities ofT. brevicorniscan be affected by several different factors, and the link between the osmoconforming nature of this species and its cold resistance is discussed.

Soil Water Pressure Measurements in Subzero Air Temperatures

AbstractAir temperatures below freezing often preclude soil water pressure measurements with tensiometers. The use of antifreeze solutions facilitates tensiometer use in weather when air temperatures are below 0°C yet the soil remains unfrozen. We studied the applicability of methanol concentrations ranging from 100 to 500 cm3 L−1. Soil water pressures were measured with ceramic cup tensiometers installed at 15‐cm depth within 38‐L‐capacity buckets. Experimental temperatures were ‐2, 0, 5, and 15°C. The pressures ranged from 0 to −60 kPa. Readings of the tensiometer with the methanol‐water mixture were within 0.6 kPa of that of the tensiometer with pure water. No statistically significant difference (α = 0.05) in soil water pressure was found between the methanol‐water mixtures and the pure water system using 1:1 lines and the Wilcoxon signed rank test for paired data. The results indicate that field tensiometer data may be collected in unfrozen soils by the use of the appropriate methanol concentration based on the temperature range expected.

Freezing tolerance and avoidance in high‐elevation Hawaiian plants

ABSTRACTFreezing resistance mechanisms were studied in five endemic Hawaiian species growing at high elevations on Haleakala volcano, Hawaii, where nocturnal subzero (°C) air temperatures frequently occur. Extracellular freezing occurred at around ‐5°C in leaves of Argyroxiphium sandwicense and Sophora chrysophylla, but these leaves can tolerate extracellular ice accumulation to ‐15°C and ‐12°C, respectively. Mucilage, which apparently acted as an ice nucleator, comprised 9 to 11% of the dry weight of leaf tissue in these two species. Leaves of Vaccinium reticulatum and Styphelia tameiameiae were also found to tolerate substantial extracellular freezing. Dubautia menziesii, on the other hand, exhibited the characteristics of permanent supercooling; a very rapid decline in liquid water content associated with simultaneous intracellular and extracellular freezing. However, in those species that tolerate extracellular freezing, the decline in liquid water content during freezing is relatively slow. Osmotic potential was lower at pre‐dawn than at midday in four of the species studied. Nocturnal production of osmotically active solutes may have helped to prevent intracellular freeze dehydration as well as to provide non‐colligative protection of cell membranes. Styphelia tameiameiae supercooled to ‐9·3°C and tolerated tissue freezing to below ‐15°C, a unique combination of physiological characteristics related to freezing. Tolerance of extracellular ice formation after considerable supercooling may have resulted from low tissue water content and a high degree of intracellular water binding in this species, as determined by nuclear magnetic resonance studies. The climate at high elevations in Hawaii is relatively unpredictable in terms of the duration of subzero temperatures and the lowest subzero temperature reached during the night. It appears that plants growing in this tropical alpine habitat have been under selective pressures for the evolution of freezing tolerance mechanisms.

Hibernation in the Eastern Box Turtle, Terrapene c. carolina

Hibernation in the Eastern Box Turtle, Terrapene c. carolina

Application of a Temperature Function Integration Technique to Assess the Hygienic Adequacy of a Process for Spray Chilling Beef Carcasses

The hygienic performance of a commercial beef carcass cooling process was assessed by a temperature function integration technique. The process involves the automatic loading of beef sides into two continuous chillers, where the sides are periodically sprayed with water during the early part of the process, and subsequently are exposed to subzero air temperatures. The times required for the beef sides to cool to a deep temperature of 7°C indicated that the process was in accord with currently accepted views of Good Manufacturing Practice. The potential proliferations of Escherichia coli were calculated from 48 temperature histories obtained from the site-on-side surfaces that have been shown to remain at the highest temperatures for the longest periods. The extent of calculated E. coli proliferation did not correlate significantly with the time for deep tissue to cool to a chilled temperature. The range of proliferation values was comparable with the ranges obtained for other, dissimilar meat cooling processes. The spray-chilling process therefore met with a temperature function integration criterion for the hygienic adequacy of meat cooling processes that had been proposed on the basis of the finding from other meat cooling procedures.

Seasonal Growth Studies of Intertidal Gastropods From Shell Micro-Growth Band Measurements, Including A Comparison With Alternative Methods

Tidal micro-growth bands were used to study the annual cycle of shell growth of individuals dated predominantly by the immersion mark technique, in three common intertidal gastropods Nucella lapillus (L.), Littorina littorea (L.) and Patella vulgata L. growing naturally in the Menai Straits. Growth in all three species approximated to the von Bertalanaffy type. All three species grew throughout the year, N. lapillus and L. littorea with early autumn and summer maxima, respectively, and P. vulgata with two maxima, one in late spring and the other in early autumn. P. vulgata alone were observed during exposure to a 6-day period of sub-zero air temperature in January 1982 when shell growth was totally interrupted. In Nucella and Littorina shell growth was found to be closely related to ambient temperature but in Patella there was a summer depression in growth. The file technique when combined with the immersion mark technique in date marking, was found to be inferior to the immersion mark technique on its own, since filing occasionally affected growth adversely.From among the factors determining the seasonal changes in growth rate, temperature was of major importance. Seasonal reproduction may also have an influence, especially in P. vulgata where gametogenesis coincides with the depression in growth rate during summer months.Alternative methods used in gastropod growth studies were compared. In the light of inadequacies associated with other methods of measuring growth, micro-growth band measurements in gastropods offers a new method with high resolution suitable both for short and long-term growth studies. It has potential also for ecological and physiological aspects of growth measurements.

Freeze-induced fluctuations in xylem sap pressure in Acer pseudoplatanus

Xylem sap pressures in response to temperature changes were investigated in Acer pseudoplatanus L., the British sycamore. Mature trees were used for field experiments; excised seedling stem segments were used in the laboratory. A general correlation was observed between changes in pressure potential (ψp) of the xylem sap of mature trees and ambient temperatures above zero (freezing point). More outstanding, however, were the characteristic decreases in pressure potential observed in response to subzero air temperatures. Investigation of this phenomenon under controlled conditions using excised stem segments revealed that rapid decreases in sap pressure occurred simultaneously with freezing. Freezing caused the stem wood to absorb water. This is a surprising response because water expands on freezing. Subsequently exudation of sap was triggered by thawing. Freezing and thawing responses appeared to be similar whether stem segments were collected during summer, when the xylem sap contained no detectable sugars, or during winter, when sugars were present in the sap. Apparently water uptake or replenishment (termed "conditioning") during cooling is of paramount importance in determining the capability of maple wood to exude sap. The freeze-induced uptake of sap under negative pressures described here is considered to be the process fundamental to conditioning.

Mass concrete placement under subzero temperatures

1. The investigations carried out on the testing ground of the Sayano-Shushenskoe hydroelectric station, under conditions most closely approximating working conditions, showed the technical possibility of concrete placement in the open, without tent protection, at subzero air temperatures down to −20° to −30°C. 2. For the open method of placing mass concrete blocks in hydrotechnical structures to be put into practice, special measures will have to be developed, taking into account the climatic and technological conditions for construction.

Transportation of rubber-coated equipment at subzero air temperatures

Transportation of rubber-coated equipment at subzero air temperatures

ASSOCIATION OF SUBZERO TEMPERATURES, SNOW COVER, AND WINTER MORTALITY OF GRASSHOPPER EGGS IN SASKATCHEWAN

AbstractHigh winter mortality of eggs of three species of grasshopper occurred at various locations in Saskatchewan. Climatological factors associated with these mortalities indicated that egg survival during the winter is dependent upon snow cover as well as upon the intensity and duration of periods of subzero air temperatures.