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Warmer Periods (warmer + period)
Selected AbstractsAround or across the Carpathians: colonization model of the Danube basin inferred from genetic diversification of stone loach (Barbatula barbatula) populationsMOLECULAR ECOLOGY, Issue 5 2008ALENA, EDIVÁ Abstract Despite increasing information about postglacial recolonization of European freshwater systems, very little is known about pre-Pleistocene history. We used data on the recent distribution and phylogenetic relationships of stone loach mitochondrial lineages to reconstruct the initial colonization pattern of the Danube river system, one of the most important refuges for European freshwater ichthyofauna. Fine-scale phylogeography of the Danubian populations revealed five highly divergent lineages of pre-Pleistocene age and suggested the multiple origin of the Danubian stone loach. The mean sequence divergence among lineages extended from 7.0% to 13.4%, which is the highest intraspecific divergence observed so far within this river system. Based on the phylogeographical patterns, we propose the following hypothesis to relate the evolution and dispersal of the studied species with the evolution of the Danube river system and the Carpathian Mountains: (i) during the warmer period in the Miocene, the areas surrounding the uplifting Alps and Carpathians served as mountainous refuges for cold-water adapted fish and promoted the diversification of its populations, and (ii) from these refuges, colonization of the emerging Danube river system may have taken place following the retreat of the Central Paratethys. Co-existence of highly divergent mtDNA lineages in a single river system shows that range shifts in response to climatic changes during the Quaternary did not cause extensive genetic homogenization in the stone loach populations. However, the wide distribution of some mtDNA lineages indicates that the Pleistocene glaciations promoted the dispersal and mixing of populations through the lowlands. [source] Temperature and soil moisture effects on dissolved organic matter release from a moorland Podzol O horizon under field and controlled laboratory conditionsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 5 2007M. I. Stutter Summary Organic upland soils store large amounts of humified organic matter. The mechanisms controlling the leaching of this C pool are not completely understood. To examine the effects of temperature and microbial cycling on C leaching, we incubated five unvegetated soil cores from a Podzol O horizon (from NE Scotland), over a simulated natural temperature cycle for 1 year, whilst maintaining a constant soil moisture content. Soil cores were leached with artificial rain (177 mm each, monthly) and the leachates analysed for dissolved organic carbon (DOC) and their specific C-normalized UV absorbance determined (SUVA, 285 nm). Monthly values of respiration of the incubated soils were determined as CO2 efflux. To examine the effects of vegetation C inputs and soil moisture, in addition to temperature, we sampled O horizon pore waters in situ and collected five additional field soil cores every month. The field cores were leached under controlled laboratory conditions. Hysteresis in the monthly amount of DOC leached from field cores resulted in greater DOC on the rising, than falling temperature phases. This hysteresis suggested that photosynthetic C stimulated greater DOC losses in early summer, whereas limitations in the availability of soil moisture in late summer suppressed microbial decomposition and DOC loss. Greater DOC concentrations of in-situ pore waters than for any core leachates were attributed to the effects of soil drying and physico-chemical processes in the field. Variation in the respiration rates for the incubated soils was related to temperature, and respiration provided a greater pathway of C loss (44 g C m,2 year,1) than DOC (7.2 g C m,2 year,1). Changes in SUVA over spring and summer observed in all experimental systems were related to the period of increased temperature. During this time, DOC became less aromatic, which suggests that lower molecular weight labile compounds were not completely mineralized. The ultimate DOC source appears to be the incomplete microbial decomposition of recalcitrant humified C. In warmer periods, any labile C that is not respired is leached, but in autumn either labile C production ceases, or it is sequestered in soil biomass. [source] Variability of total and solid precipitation in the Canadian Arctic from 1950 to 1995INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2002Rajmund Przybylak Abstract Trends in solid and total precipitation, as well as in the ratio of solid to total precipitation (hereinafter S/T ratio), in the Canadian Arctic in recent decades have been investigated. In addition, the influence of air temperature and circulation factors (atmospheric and oceanic) on the above-mentioned precipitation characteristics have been examined. Recently updated and adjusted data by the Canadian Climate Centre from 16 stations located in the Canadian Arctic and two stations from the sub-Arctic were used for the investigation. The southern boundary of the study area was taken after Atlas Arktiki (Tresjinkov, A. 1985. Glavnoye Upravlenye Geodeziy i Kartografiy: Moscow; 204 pp). The majority of the data cover the period from 1950 to 1995. A statistically significant increase in all kinds of areally averaged seasonal and annual precipitation for the Canadian Arctic over the period 1950,95 has been found. On the other hand, the S/T ratio did not change significantly, except for summer values, and its behaviour was also in accord with small variations noted in air temperature. An increase in air temperature in the Canadian Arctic most often led to a rise in all kinds of annual precipitation sums, but only when the warmest and coldest years were chosen based on individual stations. The pattern of the relationship is significantly more complicated, and can even be opposite to that presented above, when the sets of the warmest and coldest years are chosen based on the areally averaged annual temperature for the Canadian Arctic. Significantly more stable results of changes were found for the S/T ratio, which in warmer periods was usually lower. However, more detailed and reliable investigations of temperature,precipitation relationships conducted for individual stations showed that though the S/T ratio in warmer periods may well be lower, this only applies to the southern (warmer) part of the Canadian Arctic (<70 °N). During periods with high positive values of the North Atlantic Oscillation Index (NAOI), a decrease in precipitation is observed in the south-eastern part of the Canadian Arctic, i.e. in the area where strong cooling was also observed. During El Niño events most of the Canadian Arctic had both greater precipitation and a higher S/T ratio than during La Niña events. The most unequivocal results of precipitation and S/T ratio changes were found for changes in the Arctic Ocean circulation regimes. In almost the whole study area, a lower precipitation and S/T ratio were noted during the anticyclonic circulation regime in the Arctic Ocean. Copyright © 2002 Royal Meteorological Society [source] Positive association between ambient temperature and salmonellosis notifications in New Zealand, 1965,2006AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH, Issue 2 2010Emma Britton Abstract Objective: To investigate the temporal relationship between the monthly count of salmonellosis notifications and the monthly average temperature in New Zealand during the period 1965,2006. Methods: A negative binomial regression model was used to analyse monthly average ambient temperature and salmonellosis notifications in New Zealand between 1965 and 2006. Results: A 1°C increase in monthly average ambient temperature was associated with a 15% increase in salmonellosis notifications within the same month (IRR 1.15; 95% CI 1.07 , 1.24). Conclusion: The positive association found in this study between temperature and salmonellosis notifications in New Zealand is consistent with the results of studies conducted in other countries. New Zealand is projected to experience an increase in temperature due to climate change. Therefore, all other things being equal, climate change could increase salmonellosis notifications in New Zealand. Implications: This association between temperature and salmonellosis should be considered when developing public health plans and climate change adaptation policies. Strategically, existing food safety programs to prevent salmonellosis could be intensified during warmer periods. As the association was strongest within the same month, focusing on improving food handling and storage during this time period may assist in climate change adaptation in New Zealand. [source] | ||||||||||