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Continental Climate (continental + climate)
Selected AbstractsIDENTIFICATION OF CLIMATE CONTROLS ON THE DYNAMIC BEHAVIOUR OF THE SUBARCTIC GLACIER SALAJEKNA, NORTHERN SCANDINAVIAGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 1 2005PER KLINGBJER ABSTRACT. In this paper we describe the dynamic behaviour of Salajekna, a valley glacier, over the last 200 years using terrestrial observations, in situ measurements, remote sensing observations and glacier reconstructions. The response time of the glacier was calculated using analytical models and field measurements. We were subsequently able to attribute specific dynamic responses to climate trends in the available climate record. The glacier's historical maximum extension was reached around 1880,1910 and was the result of a more continental climate with multi-modal airflows in the late 18th and early 19th centuries. A transition to more maritime conditions in the mid-19th century resulted in a near-continuous 20th century retreat before the glacier adjusted to a near-steady state. [source] Evidence for a combination of pre-adapted traits and rapid adaptive change in the invasive plant Centaurea stoebeJOURNAL OF ECOLOGY, Issue 4 2010Martin L. Henery Summary 1. Introduced plants have the potential to rapidly evolve traits of ecological importance that may add to their innate potential to become invasive. During invasions, selection may favour genotypes that are already pre-adapted to conditions in the new habitat and, over time, alter the characteristics of subsequent generations. 2. Spotted knapweed (Centaurea stoebe) occurs in two predominantly spatially separated cytotypes in its native range (Europe,Western Asia), but currently only the tetraploid form has been confirmed in the introduced range (North America), where it is invasive. We used several common garden experiments to examine, across multiple populations, whether tetraploids and diploids from the native range differ in life cycle, leaf traits and reproductive capacity and if such differences would explain the predominance of tetraploids and their advance into new habitats in the introduced range. We also compared the same traits in tetraploids from the native and introduced range to determine whether any rapid adaptive changes had occurred since introduction that may have enhanced invasive potential of the species in North America. 3. We found tetraploids had lower specific leaf area, less lamina dissection and fewer, narrower leaves than diploids. Diploids exhibited a monocarpic life cycle and produced few if any accessory rosettes. Diploids produced significantly more seeds per capitulum and had more capitula per plant than tetraploids. In contrast, the vast majority of European tetraploids continued to flower in both seasons by regenerating from multiple secondary rosettes, demonstrating a predominantly polycarpic life cycle. 4. During early growth tetraploids from North America achieved greater biomass than both tetraploids and diploids from the native range but this did not manifest as larger above-ground biomass at maturity. In North American tetraploids there was also evidence of a shift towards a more strictly polycarpic life cycle, less leaf dissection, greater carbon investment per leaf, and greater seed production per capitulum. 5.,Synthesis. Our results suggest that the characteristics of tetraploid C. stoebe pre-adapted them (compared to diploid conspecifics) for spread and persistence of the species into habitats in North America characterized by a more continental climate. After the species' introduction, small but potentially important shifts in tetraploid biology have occurred that may have contributed significantly to successful invasion. [source] Using farmers' knowledge for defining criteria for land qualities in biophysical land evaluationLAND DEGRADATION AND DEVELOPMENT, Issue 6 2001I. Messing Abstract The objective of this paper is to present a way of complementing empirical results with farmers' perceptions in defining limiting biophysical land properties in a land suitability evaluation using the FAO framework methodology. The farmers' perceptions were identified using rapid and participatory rural appraisal (RRA/PRA) tools. The study catchment, having a semiarid continental climate and located on the Loess Plateau in northern China, covered an area of 3.5 km2. Most of the land users were dependent on subsistence agriculture. There were important topographic variations in the catchment and arable cropping on steep slopes brought about degradation of land due to water erosion. The biophysical monitoring, soil survey and RRA/PRA survey, carried out one year prior to the present investigation, supplied the data needed for identification of preliminary limiting land properties and land evaluation units. The land properties that needed further investigation in the present study were slope aspect, soil workability, flooding hazard and farmers' criteria on choice of land-use type. The farmers were able to give a comprehensive picture of the spatial and temporal variation and the importance for land-use options of the land properties concerned, and thereby complement the information gained from empirical results (measurements). In order to guarantee good production for dry as well as wet years, both south- and north-facing sites were chosen for most crops, and the slope aspect did not need to be differentiated in the final land suitability evaluation for arable crops. Grassland, however, was considered to be more suitable than woodland on south-facing sites. Hard soil layers were found to be important, since they affected soil workability and erosion negatively, giving slightly reduced suitability for the land units in which they occurred. Flooding events affecting crops on alluvial soils negatively were considered to occur once every 5 to 10 years, which is considered to be a low rate, so this property was therefore not included in the final suitability evaluation. Copyright © 2001 John Wiley & Sons, Ltd. [source] Influence of Temperature on the Liver Circadian Clock in the Ruin Lizard Podarcis siculaMICROSCOPY RESEARCH AND TECHNIQUE, Issue 7 2007Manuela Malatesta Abstract Reptiles represent an interesting animal model to investigate the influence of temperature on molecular circadian clocks. The ruin lizard Podarcis sicula lives in a continental climate and it is subjected to wide range of environmental temperatures during the course of the year. As consequence, ruin lizard daily activity pattern includes either the hibernation or periods of inactivity determined by hypothermia. Here we showed the rhythmic expression of two clock genes, lPer2 and lClock, in the liver of active lizards exposed to summer photo-thermoperiodic conditions. Interestingly, the exposition of lizards to hypothermic conditions, typical of winter season, induced a strong dampening of clock genes mRNA rhythmicity with a coincident decrease of levels. We also examined the qualitative and quantitative distribution of lPER2 and lCLOCK protein in different cellular compartments during the 24-h cycle. In the liver of active lizards both proteins showed a rhythmic expression profile in all cellular compartments. After 3 days at 6°C, some temporal fluctuations of the lCLOCK and lPER2 are still detectable, although, with some marked modifications in respect to the values detected in the liver of active lizards. Besides demonstrating the influence of low temperature on the lizard liver circadian oscillators, present results could provide new essential information for comparative studies on the influence of temperature on the circadian system across vertebrate classes. Microsc. Res. Tech., 2007. © 2007 Wiley-Liss, Inc. [source] Migration and diversity in Roman Britain: A multidisciplinary approach to the identification of immigrants in Roman York, EnglandAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2009Stephany Leach Abstract Previous anthropological investigations at Trentholme Drive, in Roman York identified an unusual amount of cranial variation amongst the inhabitants, with some individuals suggested as having originated from the Middle East or North Africa. The current study investigates the validity of this assessment using modern anthropological methods to assess cranial variation in two groups: The Railway and Trentholme Drive. Strontium and oxygen isotope evidence derived from the dentition of 43 of these individuals was combined with the craniometric data to provide information on possible levels of migration and the range of homelands that may be represented. The results of the craniometric analysis indicated that the majority of the York population had European origins, but that 11% of the Trentholme Drive and 12% of The Railway study samples were likely of African decent. Oxygen analysis identified four incomers, three from areas warmer than the UK and one from a cooler or more continental climate. Although based on a relatively small sample of the overall population at York, this multidisciplinary approach made it possible to identify incomers, both men and women, from across the Empire. Evidence for possible second generation migrants was also suggested. The results confirm the presence of a heterogeneous population resident in York and highlight the diversity, rather than the uniformity, of the population in Roman Britain. Am J Phys Anthropol 2009. © 2009 Wiley-Liss, Inc. [source] Peat multi-proxy data from Männikjärve bog as indicators of late Holocene climate changes in EstoniaBOREAS, Issue 1 2007UULLE SILLASOO Sillasoo, Ü., Mauquoy, D., Blundell, A., Charman, D., Blaauw, M., Daniell, J. R. G., Toms, P., Newberry, J., Chambers, F M. & Karofeld, E. 2007 (January): Peat multi-proxy data from Männikjärve bog as indicators of late Holocene climate changes in Estonia. Boreas, Vol. 36, pp. 20,37. Oslo. ISSN 0300,9483. As part of a wider project on European climate change over the past 4500 years, a 4.5-m peat core was taken from a lawn microform on Männikjärve bog, Estonia. Several methods were used to yield proxy-climate data: (i) a quadrat and leaf-count method for plant macrofossil data, (ii) testate amoebae analysis, and (iii) colorimetric determination of peat humification. These data are provided with an exceptionally high resolution and precise chronology. Changes in bog surface wetness were inferred using Detrended Correspondence Analysis (DCA) and zonation of macrofossil data, particularly concerning the occurrence of Sphagnum balticum, and a transfer function for water-table depth for testate amoebae data. Based on the results, periods of high bog surface wetness appear to have occurred at c. 3100,3010,2990,2300, 1750,1610, 1510, 1410, 1110, 540 and 310 cal. yr BP, during four longer periods between c. 3170 and 2850 cal. yr BP, 2450 and 2000 cal. yr BP, 1770 and 1530 cal. yr BP and in the period from 880 cal. yr BP until the present. In the period between 1770 and 1530 cal. yr BP, the extension or initiation of a hollow microtope occurred, which corresponds with other research results from Mannikjarve bog. This and other changes towards increasing bog surface wetness may be the responses to colder temperatures and the predominance of a more continental climate in the region, which favoured the development of bog micro-depressions and a complex bog microtopography. Located in the border zone of oceanic and continental climatic sectors, in an area almost without land uplift, this study site may provide valuable information about changes in palaeohydrological and palaeoclimatological conditions in the northern parts of the eastern Baltic Sea region. [source] Evidence for an ice-free Wrangel Island, northeast Siberia during the Last Glacial MaximumBOREAS, Issue 3 2005LYN GUALTIERI 10Be and 26Al surface exposure ages from 22 tors and bedrock samples from Wrangel Island, northeast Siberia, indicate that the East Siberian and Chukchi shelves were ice-free during the Last Glacial Maximum (LGM). The paucity of glacial landforms and deposits, the absence of erratics and the presence of radiocarbon dates on plant and mammal fossils that span the LGM suggest that Wrangel Island also remained free of extensive glacial ice during the LGM. The lack of moisture due to the continental climate on the emergent Bering Land Bridge is the most likely reason for limited ice in this part of the Arctic. Alternative interpretations regarding the age and origin of ,glaciogenic' bedforms on the Chukchi shelf should be considered. [source] Climate change and cattle nutritional stressGLOBAL CHANGE BIOLOGY, Issue 10 2010JOSEPH M. CRAINE Abstract Owing to the complex interactions among climate, plants, cattle grazing, and land management practices, the impacts of climate change on cattle have been hard to predict. Predicting future grassland ecosystem functioning relies on understanding how changes in climate alter the quantity of forage produced, but also forage quality. Plant protein, which is a function of plant nitrogen concentrations, and digestible energy limit the performance of herbivores when in short supply; moreover, deficiencies can be expensive to mitigate. To better understand how changes in temperature and precipitation would affect forage protein and energy availability, we analyzed over 21 000 measurements of cattle fecal chemistry acquired over 14 years in the continental US. Our analysis of patterns in forage quality among ecologically defined regions revealed that increasing temperature and declining precipitation decreased dietary crude protein and digestible organic matter for regions with continental climates. Within regions, quality also declined with increased temperature; however, the effects of precipitation were mixed. Any future increases in precipitation would be unlikely to compensate for the declines in forage quality that accompany projected temperature increases. As a result, cattle are likely to experience greater nutritional stress in the future. If these geographic patterns hold as a proxy for future climates, agriculture will require increased supplemental feeds or the consequence will be a decrease in livestock growth. [source] | |||||||||||||