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Winter Conditions (winter + condition)
Selected AbstractsRegional variability of climate,growth relationships in Pinus cembra high elevation forests in the AlpsJOURNAL OF ECOLOGY, Issue 5 2007MARCO CARRER Summary 1The tree-ring growth response of stone pine (Pinus cembra L.) to climatic variability was studied in the Alps. The aims were (i) to assess tree-ring growth patterns at different spatial-temporal scales; (ii) to identify the climate parameters that explain most of the variability in radial growth at different time domains; and (iii) to study past and current trends in radial growth and climate,growth relationships at different locations. 2High- and low-frequency stone pine chronologies were compiled for 30 treeline sites on the French and Italian Alps. We used gridded climate data computed from 200 years of instrumental records from an extensive Alpine network. Climate,growth relationships were computed with bootstrap correlation functions and their stationarity and consistency over time assessed with moving correlation. 3No spatial patterns were detected in stone pine chronology statistics despite the regional clustering observed in tree-ring series and climate responses. This can be attributed to (i) local weather variability; (ii) different biophysical conditions caused by soil moisture, solar radiation, snowmelt dynamics and growing season length; and (iii) forest stand history and age structure, the expression of long-term land use and disturbances. 4The exceptionally long-term climate records allowed significant stone pine growth response changes to be assessed at both annual and decadal time scales. Winter conditions and spring,summer temperatures mainly affected the growing season length, in addition to site carbon and water balance. Most of these limiting factors varied spatially and temporally along the latitudinal and longitudinal gradients in response to the corresponding changes in local conditions. 5Our results show evidence of a clear response variability of Pinus cembra to climate limiting factors, at both spatial and temporal scale. Such knowledge extended to other species and regions will provide better estimates of the effect of climate variability on species distribution and dynamics within global change scenarios and more accurate past climate reconstruction and forest ecosystem modelling. [source] Effect of ENSO on the Hong Kong winter seasonATMOSPHERIC SCIENCE LETTERS, Issue 2 2009M. C. Wu Abstract The relationship between the ENSO condition and the winter condition in Hong Kong is investigated in this study. The winter monsoon over southern China tends to be weaker (stronger) during El Niño (La Niña) winters and Hong Kong tends to have higher (lower) mean winter temperatures against the background of the warming trend. On the other hand, there are more (fewer) surge events, which represents the southeastward advance of the Siberian cold air across the East Asian coast, affecting Hong Kong. Analyses showed that Hong Kong tends to be warmer with a shorter duration for the longest cold spell during the winter without blocking event over the Eurasian continent. Furthermore, blocking events are also less common during El Niño winters. Copyright © 2009 Royal Meteorological Society [source] FC02.4 Meteorological factors and standard series patch test reactionsCONTACT DERMATITIS, Issue 3 2004Janice Hegewald The existence of seasonal patterns to patch test reactions has been described, but with conflicting causal interpretations. The potential seasonality of patch tests may be due to irritation, changes to skin barrier or changes to immunological functions caused by meteorological fluctuations. For example, increased skin irritability due to cold winter weather and low humidity may cause an increase in irritative/doubtful and weak positive (false positive) reactions. To investigate the extent of the association between weather and patch test results, consecutive patients (N = 73691) patch tested with the standard series of the German Contact Dermatitis Research Group (DKG) at German or Austrian IVDK (http://www.ivdk.de) centres were matched with weather data collected at a nearby (30 km radius) weather station. Temperature and absolute humidity (AH) on the day of patch test application and the two preceding days were averaged to represent the environment most likely to have influenced the skin condition at the time of testing. The results of 24 standard series substances were analyzed with multivariate logistic regression. Half of the standard series substances examined, including fragrance mix, nickel sulphate, and formaldehyde, exhibited evidence of a relationship with meteorological conditions. Fragrance mix and p-Phenylene diamine exhibited the strongest evidence of an association to weather, with the odds of the reactions in all three reaction categories (ir/?, +, ++/+++) increasing during winter conditions. Due to the association between weather and patch test reactivity, the potential effect of meteorological conditions should be considered in the interpretation of patch test reactions. [source] An experimental evaluation of ice cover effects on the dynamic behaviour of a concrete gravity damEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 12 2002Patrick Paultre Abstract An extensive forced-vibration testing programme has been carried out on an 84-m concrete gravity dam located in northeastern Québec, Canada. The dam was subjected to a harmonic load on the crest in summer and severe winter conditions with temperatures ranging from ,10°C to ,15°C and a 1.0,1.5m ice cover. Acceleration and hydrodynamic frequency responses were obtained in different locations on the dam and in the reservoir. The main objective of the repeated tests was to investigate the effects of the ice cover on the dynamic behaviour of the dam,reservoir,foundation system, by comparing summer and winter results. Modifications in damping and resonance frequencies were observed, as well as an additional resonance that was attributed to an interaction of the dam with the ice cover. These findings provided a reliable and unique database for the investigations of dam,reservoir,foundation interaction and, in particular, the ice-cover effects for dams located in northern regions. Copyright © 2002 John Wiley & Sons, Ltd. [source] Contrasting responses of migration strategies in two European thrushes to climate changeGLOBAL CHANGE BIOLOGY, Issue 1 2007PHILIPPE RIVALAN Abstract Migration is a widespread strategy that enables animals to escape harsh winter conditions. It has been well documented that migration phenology in birds is changing in response to recent climate warming in the northern hemisphere. Despite the existence of large temporal and geographical scale ringing data on birds in Europe, changes in migration strategies in relation to climate warming have not been well studied, mainly because of a lack of appropriate statistical methods. In this paper, we develop a method that enables us to investigate temporal changes in migration strategies from recoveries of dead ringed birds. We estimated migration probability as the ratio between recovery probabilities of conspecific birds originating from different countries but potentially wintering in the same country. We applied this method to two European thrushes: the entirely migrant redwing Turdus iliacus, and the partially migrant blackbird T. merula. We tested for an immediate and a 1-year lagged relationship between our migration probability and climatic covariates (i.e. mean winter temperature in France and the North Atlantic Oscillation). Using ringing-recovery data collected in Finland, Germany, Switzerland and France from 1970 to 1999, we detected contrasting responses in these two species, likely related to their different migratory behaviours. Both species showed a decline in the probability for northern and eastern birds to winter in France. The entirely migratory redwing exhibited a year-to-year plastic response to climate, whereas the decline in the partially migrant blackbird was smooth, suggesting underlying genetic processes. The proposed method, thus, allows us to identify useful indicators of climatic impacts on migration strategies, as well as highlighting differences between closely related species. [source] The effect of truck traffic and road water content on sediment delivery from unpaved forest roadsHYDROLOGICAL PROCESSES, Issue 8 2006Gary J. Sheridan Abstract A study investigated the effect of truck-traffic intensity and road water-content on the quality of runoff water from unsealed forest roads. Three sections of a gravel-surfaced forest road were instrumented and exposed to low and high levels of truck traffic during wet winter conditions and dry summer conditions between July 2001 and December 2002. Rainfall, runoff, road moisture, and traffic were measured continuously, and suspended and bedload sediments were integrated measurements over 2-week site-service intervals. The median suspended sediment concentration from the three road segments under low truck-traffic conditions (less than nine return truck passes prior to a storm) was 269 mg l,1, increasing 2·7-fold to a median of 725 mg l,1 under high truck-traffic conditions (greater than or equal to nine return truck passes prior to a storm). These concentrations, and increases due to traffic, are substantially less than most previously reported values. When these data are expressed as modified universal soil loss equation (MUSLE) erodibility values K, accounting for differences in rainfall energy, site characteristics and runoff, high traffic resulted in a road surface that was four times more erodible than the same road under low traffic conditions. Using multiple regression, traffic explained 36% of the variation in MUSLE erodibility, whereas road water content was not significant in the model. There was little difference in the erodibility of the road when trafficked in low water-content compared with high water-content conditions (MUSLE K values of 0·0084 versus 0·0080 respectively). This study shows that, for a good quality well-maintained gravel forest road, the level of truck traffic affects the sediment concentration of water discharging from the road, whereas the water content of the road at the time of that traffic does not (note that traffic is not allowed during runoff events in Victoria). These conclusions are conditional upon the road being adequately maintained so that trafficking does not compromise the lateral drainage of the road profile. Copyright © 2005 John Wiley & Sons, Ltd. [source] Quantifying contributions to storm runoff through end-member mixing analysis and hydrologic measurements at the Panola Mountain Research Watershed (Georgia, USA)HYDROLOGICAL PROCESSES, Issue 10 2001Douglas A. Burns Abstract The geographic sources and hydrologic flow paths of stormflow in small catchments are not well understood because of limitations in sampling methods and insufficient resolution of potential end members. To address these limitations, an extensive hydrologic dataset was collected at a 10 ha catchment at Panola Mountain Research Watershed near Atlanta, GA, to quantify the contribution of three geographic sources of stormflow. Samples of stream water, runoff from an outcrop, and hillslope subsurface stormflow were collected during two rainstorms in the winter of 1996, and an end-member mixing analysis model that included five solutes was developed. Runoff from the outcrop, which occupies about one-third of the catchment area, contributed 50,55% of the peak streamflow during the 2 February rainstorm, and 80,85% of the peak streamflow during the 6,7 March rainstorm; it also contributed about 50% to total streamflow during the dry winter conditions that preceded the 6,7 March storm. Riparian groundwater runoff was the largest component of stream runoff (80,100%) early during rising streamflow and throughout stream recession, and contributed about 50% to total stream runoff during the 2 February storm, which was preceded by wet winter conditions. Hillslope runoff contributed 25,30% to peak stream runoff and 15,18% to total stream runoff during both storms. The temporal response of the three runoff components showed general agreement with hydrologic measurements from the catchment during each storm. Estimates of recharge from the outcrop to the riparian aquifer that were independent of model calculations indicated that storage in the riparian aquifer could account for the volume of rain that fell on the outcrop but did not contribute to stream runoff. The results of this study generally indicate that improvements in the ability of mixing models to describe the hydrologic response accurately in forested catchments may depend on better identification, and detailed spatial and temporal characterization of the mobile waters from the principal hydrologic source areas that contribute to stream runoff. Copyright © 2001 John Wiley & Sons, Ltd. [source] A simplified method for modelling the effect of blinds on window thermal performanceINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 7 2006D. Naylor Abstract An approximate method is presented for predicting the effect of a louvered blind on the centre-glass thermal performance of a fenestration. The method combines a one-dimensional heat transfer model with data from a numerical simulation of the window and blind. Sample results for a blind mounted on the indoor surface of a window show the effect of blind slat angle on heat transmission. Both summer and winter conditions are considered. The results show that a louvered blind can improve the U -value of a standard double-glazed window by up to 37%. Also, the radiation heat exchange with the room can be dramatically reduced (by up to 60%), which will improve the level of occupant comfort. However, there was found to be a trade-off between U -value and occupant comfort; placing the blind closer to the window improves the U -value, but increases the radiation heat exchange with the room. The predictions from the present simplified method compare well with results from a full two-dimensional computational fluid dynamics solution of the conjugate blind/window interaction. Copyright © 2005 John Wiley & Sons, Ltd. [source] Overwinter mass loss of snowshoe hares in the Yukon: starvation, stress, adaptation or artefact?JOURNAL OF ANIMAL ECOLOGY, Issue 1 2006KAREN E. HODGES Summary 1Overwinter mass loss can reduce energetic requirements in mammals (Dehnel's phenomenon). Alternatively, mass loss can result from food limitation or high predation risk. 2We use data from fertilizer, food-supplementation and predator-exclusion experiments in the Yukon during a population cycle from 1986 to 1996 to test the causes of overwinter mass loss by snowshoe hares (Lepus americanus). In all years, some hares on control sites gained mass overwinter. During the increase phase the majority gained mass, but in all other phases the majority lost mass. 3Snowshoe hares weighing < 1000 g in autumn always gained mass overwinter, as did the majority that weighed 1000,1400 g. Hares weighing > 1800 g in autumn usually lost mass. 4Snowshoe hares on the predator-exclosure + food site gained mass overwinter in all years. Hares on the food-supplementation sites lost mass during the decline but gained mass in all other phases. Fertilization had little effect on mass dynamics. 5Snowshoe hares were more likely to lose mass during winters with low survival rates. Snowshoe hares on the predator-exclosure treatments were more likely to gain mass than were hares on control sites. 6Overwinter mass loss was correlated with maximum snow depth. At equivalent snow depths, hares on food-supplemented areas lost 98 g (± 14·6 SE) less on average than hares on the controls and predator-exclosure treatment. 7Bone-marrow fat was related to body mass and cause of death. Small hares had the lowest marrow fat. Hares killed by humans had higher marrow fat than those killed by predators; hares that simply died had the lowest marrow fat. Hares on food-supplemented sites had the highest kidney and marrow fat. 8Overwinter-mass loss for snowshoe hares is explained interactively by winter conditions, food supply, predation risk and autumn mass. Some snowshoe hares lost mass overwinter in all years and on all treatments, suggesting that reducing body mass may facilitate survival, especially in cases where foraging costs are high energetically or increase predation risk. [source] Phenotypic compromise in the face of conflicting ecological demands: an example in red knots Calidris canutusJOURNAL OF AVIAN BIOLOGY, Issue 1 2010François Vézina Phenotypic flexibility is a phenomenon where physiological functions in animals are reversibly adjusted in response to ecological constraints. Research usually focuses on effects of single constraints, but under natural conditions animals face a multitude of restrictions acting simultaneously, and potentially generating conflicting demands on the phenotype. We investigated the conflicting demands of low temperatures and a low quality diet on the phenotype of a shorebird, the red knot Calidris canutus. We tested the effects of switching diet from a high quality trout food to low quality hard-shelled bivalves in captive birds acclimated to temperatures reflecting natural winter conditions. Feeding on bivalves generated a digestive constraint forcing the birds to increase the height and width of their gizzard by 66% and 71%, respectively, over 30 days. The change in gizzard size was associated with an initial 15% loss of body mass and a reduction in size of the pectoral muscles by 11%. Because pectoral muscle size determines summit metabolic rate (Msum, an indicator of cold endurance), measured Msum declined by 9%. Therefore, although the birds were acclimated to cold, gizzard growth led to a loss of cold endurance. We propose that cold-acclimated knots facing a digestive constraint made a phenotypic compromise by giving-up cold hardiness for digestive capacity. Field studies suggest that phenotypic compromises occur in free-living red knots as well and help improve survival. [source] Progress Toward Year-round Spawning of Southern Flounder Broodstock by Manipulation of Photoperiod and TemperatureJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 3 2006Wade O. Watanabe Reliable methods have been developed for controlled spawning of captive southern flounder, Paralichthys lethostigma, broodstock during their natural winter (December,February) spawning season. From 1999 to 2004, we evaluated the effects of manipulation of photoperiod and temperature on both advance and delay spawning to produce viable embryos throughout the year. Wild-caught adult broodstock were held in 4.8- to 7.0-m3 controlled-environment tanks at a sex ratio of approximately 12 females to 4 males. Broodstock were subjected to different artificial photothermal conditioning regimes: extended winter (EW), accelerated (A-10-, A-6-, A-4.5-, and A-3.8-mo regimes), and delayed (D-16- and D-14-mo regimes), with gradual and abrupt transitions, respectively, from long to short daylengths. Under an EW cycle, fish were exposed to constant short daylengths (10 L: 14 D) after the winter solstice in January. Eighty-seven natural spawnings from December to April produced 18.3 × 106 eggs, with 20.9% hatching successfully (i.e., overall egg viability). Under an A-10-mo cycle, rate of decrease in daylength was accelerated after the summer solstice in July, to reach winter conditions in October. Seven induced spawning trials from October to November produced 897 × 103 eggs, with 40.4% viability. Under an A-6-mo cycle, rate of change of photoperiod was accelerated after the winter solstice in January, to reach winter conditions in July. Three induced spawning trials in July produced 550 × 103 eggs, with 14.7% viability. Under an A-4.5-mo cycle, broodstock exposed to EW from January through April were exposed to an accelerated cycle to reach winter conditions by October. Four induced spawning trials from September to November produced 729 × 103 eggs, with 28.7% viability. Under an A-3.8-mo cycle, broodstock exposed to EW conditions from January through April were exposed to an accelerated cycle to reach winter conditions by September. Five induced spawning trials from September to November produced 510 × 103 eggs, with 45.9% viability. Under a D-16-mo cycle, fish were exposed to a decelerated decline in photoperiod after the summer solstice in July, to reach winter conditions in May, when atretic females were observed. Under a D-14-mo cycle, fish were exposed to constant summer conditions from December through mid-June and then to an abrupt decline in photoperiod to winter conditions in late June. Six induced spawning trials from September to November produced 763 × 103 eggs, with 13.0% viability. Production of viable embryos was greatest during the extended winter because of abundant natural spawnings. While successful natural spawnings were rare during the fall or summer, viable embryos were produced through induced spawnings during all seasons of the year, with no significant (P > 0.05) differences in egg viability. Extended winter conditions prolonged spawning from 3 to 5 mo. Accelerated (3.8,10 mo) regimes were effective in producing viable embryos from summer through fall, but a minimum of 5 mo was required to complete gonadal recrudescence. While constant long daylengths after the summer solstice delayed gonadal recrudescence, with spawning obtained 2.5 mo after an abrupt reduction to short daylengths, a decelerated decline in photoperiod did not. Artificial control of daylength enabled precise control of gonadal recrudescence and year-round spawning in southern flounder without adverse effects on the quality of eggs and larvae and will improve availability of seedstock for commercial aquaculturists. [source] Palaeoclimate signals as inferred from stable-isotope composition of ground ice in the Verkhoyansk foreland, Central YakutiaPERMAFROST AND PERIGLACIAL PROCESSES, Issue 2 2006Steffen Popp Abstract Ice-rich permafrost deposits and their isotopic composition were studied at four sites in the western foreland of the Verkhoyansk Mountains, Central Yakutia. The isotopic composition of ice wedges formed in alluvial and loess-like sediments generally reflects the palaeoclimate of winter conditions. The middle Weichselian Ice Complex developed around 41,ka,14C BP during a period with colder winters than today. Similarly severe conditions are reflected in the late Weichselian Ice Complex from around 20,ka to 13,ka,14C BP. The transition to the Holocene is characterised by increases of 5, and 35, in ,18O and ,D, respectively. This warming is documented in wedge ice, which grew between 8.5 and 4.5,ka BP. Towards the late Holocene and sub-recent times, a climatic deterioration is recorded, reflected by lighter isotopic composition of ice wedges, which developed between 1.2,ka and 0.7,ka,14C BP. Copyright © 2006 John Wiley & Sons, Ltd. [source] 2-D DIGE and MS/MS analysis of protein serum expression in rats housed in concrete and clay cages in winterPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 17 2008Jong-Choon Kim Abstract In a previous study, we examined the physiological responses of male Sprague,Dawley rats over a 4-week exposure to concrete and clay cages. No general toxicological changes were observed in rats exposed to either of the two cage types in summer. Under winter conditions, however, various general toxicological effects were detected in rats housed in concrete cages, although rats housed in clay cages showed no such effects. The infrared thermographic examination indicated that skin temperature in the concrete-housed rats was abnormally low, but not so in the clay-housed rats. We examined proteomic changes in the serum of rats housed in winter in concrete and clay cages using two-dimensional differential in-gel electrophoresis and mass spectrometry/mass spectrometry. Five proteins were identified and quantitatively validated; all were cold stress-induced, acute phase proteins that were either up-regulated (haptoglobin) or down-regulated (alpha-1-inhibitor III, alpha-2u globulin, complement component 3, and vitamin D-binding protein) in the concrete-housed rats. These results suggest that the 4-week exposure to a concrete cage in winter elicited a typical systemic inflammatory reaction (i.e. acute phase response) in the exposed rats. [source] Infants sleeping outdoors in a northern winter climate: skin temperature and duration of sleepACTA PAEDIATRICA, Issue 9 2010Marjo Tourula Abstract Aim:, The aim of the study is to describe the relationships among thermal environment, skin temperatures and infants' daytime outdoor sleep duration in northern winter conditions. Methods:, This study is a cross-over observational study. Skin temperatures of three-month-old infants were recorded from seven skin sites continuously throughout outdoor (n = 34) and indoor sleep (n = 33) in the families' homes. The duration of the sleep was observed, and temperature and the air velocity of the environment were recorded. Results:, Skin temperatures increased towards the end of indoor sleeping, whereas they decreased during outdoor sleeping. The cooling rate of mean skin temperature (Tsk) increased in lower outdoor temperatures (rs = 0.628, p < 0.001) in spite of increased clothing. On some occasions, cold extremities were observed, suggesting slight deviations from thermoneutrality. Sleep time was 92 min longer in outdoors than in indoors. However, outdoor sleep duration was shortened when the cooling rate of Tsk increased (rs = 0.611, p < 0.001). Conclusion:, The longest sleep was recorded outdoors when the cooling rate of Tsk was minimal. Restriction of movements by clothing probably increases the length of sleep, and a cold environment makes swaddling possible without overheating. A decrease in ambient temperature increased the cooling rate, suggesting that the cold protection of the clothing compensated only partly for the increased heat loss. [source] | |||||||||||||||||||