Impact Of Climate Fluctuations Research Articles

Intraspecific genetic variation and biogeographic history of the arid relict shrub Amygdalus pedunculata (Rosaceae) in northwest China

We studied the arid shrub Amygdalus pedunculata to better understand biogeographic histories and the impact of climate fluctuations during the Quaternary in shaping genetic variation and in northwest China. Three chloroplast DNA intergenic spacers (psbK‐psbI, trnL‐trnF and trnV) were sequenced in 129 individuals from 10 populations across the range of A. pedunculata, and 17 haplotypes were identified, with one haplotype that was distributed across all sampled populations. High levels of total gene diversity (HT = 0.965) and within‐population diversity (HS = 0.669) were identified. Analysis of molecular variance (AMOVA) indicated that most genetic variation occurred within populations. Neutrality tests and mismatch distribution analysis suggested past range expansions of A. pedunculata. As such, A. pedunculata has likely undergone a substantial postglacial range expansion northward and southward along the margins of the northern Yin Mountains and Mu Us Desert, respectively. Principal coordinate analyses, median‐joining network analysis and Beast analysis revealed that 17 haplotypes mainly formed three clusters, corresponding to the Northern (Damao Banner) and Central (Wula Mountains and Guyang County) regions of Inner Mongolia and the Southern region (Bulang Township) in northern Shannxi. The local adaptative differentiation is speculated to have occurred among the three regions mainly resulting from geographical isolation caused by the uplift and extension of the Yinshan Mountains during the Quaternary.

Phylogeography of the Rice Spittle Bug (Callitettix versicolor) Implies Two Long-Term Mountain Barriers in South China.

South China is a region of remarkable topographic complexity. However, the impact of climate fluctuations in the Pleistocene on the local fauna and especially insects has not been extensively studied. We integrated mitochondrial DNA (mtDNA) and microsatellite data of the rice spittle bug, Callitettix versicolor, to determine the genetic structure, potential biogeographic barriers, and historical demography of this species. The mtDNA data revealed two distinct lineages (Western and Eastern) congruent with the geographically separated western and eastern sub-regions of the Hengduan Mountains. The Eastern lineage was subdivided into two sub-lineages, E1 and E2, congruent with the geographically separated northern and southern sub-regions of the Dabie Mountains. E2 was further subdivided into two sub-groups, E2-1 and E2-2, with a hybrid zone (Guizhou and Hunan Provinces) in which their areas were contiguous. The genetic structures constructed using mtDNA were corroborated by four clusters (G1-G4) of microsatellite data. The populations of each cluster were nearly consistent with a sub-lineage of the mtDNA gene tree (G1-G4 corresponded to the Western, E1, E2-2 and E2-1 lineages, respectively). The divergence time estimated between the Western and Eastern lineages was 1.17 (0.50-2.37) to 0.89 (0.39-1.78) Mya, indicating that the lineages diversified on both geographic and temporal scales. The historical demography of the Eastern lineage showed continuous population growth after the Last Interglacial (LIG) and a stable population during the Last Glacial Maximum (LGM) period. However, the Western lineage remained largely unchanged during the LIG and LGM periods. This suggests that the historical demography of C. versicolor is probably related not only to the paleoclimate of South China, but also to the geological restriction and specific habitat preferences of species.

Impact of climate fluctuations on the spring runoff regime with regard to rivers in Lithuania

AbstractThe article describes the impact of fluctuations in climatic factors on hydrological processes. The analysis of climate and hydrology covers two periods, the first up to 1996 and the second from 1981 to 2012. Study object includes 22 river basins situated on the eastern coast of the Baltic Sea: 1000 km2, up to 10 000 km2and bigger. The study involved Mann–Kendall, Spearman's and linear regression tests. Causal relationships, as criteria that may fundamentally change the runoff regime set up by climatic factors, were established by evaluating the size of the river basin and assessing the spread of sediments, lakes, swamps and forests in the river basin. The analysis of data from the last thirty years disclosed that, with reference to the previously obtained information, floods in lakes became substantially reduced. Nevertheless, within the winter period of recent years, temperatures prevented lakes from acting as water reservoirs. The paper examined and defined the impact of sediments on variations in the runoff regime. For the period of the last thirty years, cut-off dates, i.e. flood start, crest and end, have advanced.

When environmental changes do not cause geographic separation of fauna: differential responses of Baikalian invertebrates

BackgroundWhile the impact of climate fluctuations on the demographic histories of species caused by changes in habitat availability is well studied, populations of species from systems without geographic isolation have received comparatively little attention. Using CO1 mitochondrial sequences, we analysed phylogeographic patterns and demographic histories of populations of five species (four gastropod and one amphipod species) co-occurring in the southwestern shore of Lake Baikal, an area where environmental oscillations have not resulted in geographical isolation of habitats.ResultsSpecies with stronger habitat preferences (gastropods B. turriformis, B. carinata and B. carinatocostata) exhibit rather stable population sizes through their evolutionary history, and their phylogeographic pattern indicates moderate habitat fragmentation. Conversely, species without strong habitat preference (gastropod M. herderiana and amphipod G. fasciatus) exhibit haplotype networks with a very abundant and widespread central haplotype and a big number of singleton haplotypes, while their reconstructed demographic histories show a population expansion starting about 25-50 thousand years ago, a period marked by climate warming and increase in diatom abundance as inferred from bottom-lake sedimentary cores.ConclusionsIn agreement with previous studies, we found that species reacted differently to the same environmental changes. Our results highlight the important role of dispersal ability and degree of ecological specialization in defining a species' response to environmental changes.

Impact of climate fluctuations on deposition of DDT and hexachlorocyclohexane in mountain glaciers: Evidence from ice core records

How do climate fluctuations affect DDT and hexachlorocyclohexane (HCH) distribution in the global scale? In this study, the interactions between climate variations and depositions of DDT and HCH in ice cores from Mt. Everest (the Tibetan Plateau), Mt. Muztagata (the eastern Pamirs) and the Rocky Mountains were investigated. All data regarding DDT/HCH deposition were obtained from the published results. Concentrations of DDT and HCH in an ice core from Mt. Everest were associated with the El Nino-Southern Oscillation. Concentrations of DDT in an ice core from Mt. Muztagata were significantly correlated with the Siberia High pattern. Concentrations of HCH in an ice core from Snow Dome of the Rocky Mountains responded to the North Atlantic Oscillation. These associations suggested that there are some linkages between climate variations and the global distribution of persistent organic pollutants.

How did an annual plant react to Pleistocene glaciations? Postglacial history of Rhinanthus angustifolius in Europe

The impact of climate fluctuations during the Pleistocene on the geographic structure of genetic variation in plant populations is well documented, but there is a lack of studies of annual species at the European scale. The present study aimed to infer the history of the widespread European annual Rhinanthus angustifolius C. C. Gmelin (Orobanchaceae). We explored variation in chloroplast DNA (cpDNA) sequences and amplified fragment length polymorphism (AFLP) in twenty-nine populations covering the entire distribution area of the species. Five AFLP groups were identified, suggesting at least two glacial refugial areas: one area in southwestern Europe and one large eastern area in the Balkan/Caucasus. Recolonization of previously glaciated areas mainly took place from the east of Europe. Despite the difference in life-history traits, the patterns found for the annual R. angustifolius show similarities with those of perennial species in terms of genetic diversity and geographic organization of genetic variation. Although organelle markers have typically been preferred in phylogeographic studies, the cpDNA variation in R. angustifolius did not show any clear geographic structure. The absence of geographic structure in the cpDNA variation may reflect persistence of ancestral polymorphisms or hybridization and introgression with closely-related species.

Impact of Climate Fluctuations on Mountain Environments in the Canadian Rockies

Impact of Climate Fluctuations on Mountain Environments in the Canadian Rockies

Preferential states of seasonal soil moisture: The impact of climate fluctuations

The impact of climate fluctuations on the dynamics of soil moisture is studied through a stochastic model of soil water balance. The analysis focuses on the changes of soil water content induced by the interannual variability of rainfall observed at the decade‐to‐century timescale. Extensive data analyses have been performed to characterize the statistical properties of such a variability. Particular attention is paid to the year‐to‐year variability of the average value of soil moisture during the growing season because of its relevance to the mechanisms affecting the physiology of plants and the dynamics of ecosystems. It is found that the probability distribution of the average seasonal soil moisture may be either unimodal or bimodal depending on the different combinations of climate, soil, and vegetation parameters. The possible occurrence of a double mode has both hydrologic and ecologic implications that are analyzed here.

Impact of Climate Fluctuations on Mountain Environments in the Canadian Rockies

Abstract This paper presents examples of environmental changes in the Canadian Rockies in the context of a 1.5°C increase in mean annual temperatures over the last 100 years. During this period increases in winter temperatures have been more than twice as large as those during spring and summer. Glacier cover has decreased by at least 25% during the 20th century and glacier fronts have receded to positions last occupied ca. 3000 years ago. These two lines of evidence suggest that the climate of the late 20th century is exceptional in the context of the last 1000 to 3000 years. Detailed studies in three closely located upper treeline sites document variable responses of vegetation to climate change that reflect species differences as well as local differences in microclimate and site conditions. Treeline has advanced upslope in response to climate warming, but site and species differences control the rate and nature of the advance. Human impacts on the environment compound the changes due to climate warmin...

On the spatial and temporal links between vegetation, climate, and soil moisture

The impact of climate fluctuations can be observed in the dynamics of vegetation and most particularly in the sensitive environment of savannas. In this paper we present a model for the local competition for soil moisture among neighboring vegetation. The initial condition for the model is a random field where at each point the soil moisture is the mean water content when there are no spatial interactions between sites. The mean soil moisture values account for stochasticity of climate and losses from evapotranspiration and leakage which depend on the existing water content. A spatial dynamics is then implemented based on the explicit minimization of the global water stress over the region. This approach explains the coexistence of herbaceous and woody plants in savannas as well as the changes in canopy density that have been documented in the southwest of the United States as a function of regional climatic fluctuations.

Impact of Present Century Climate Fluctuations in the Northern Hemisphere

This study begins with a short review of the climato-logical evidence which has been presented of a warming of the Northern Hemisphere climate during the period 1880 to 1950. It is shown that winter temperatures in general increased continously from 1880 to 1940 over most of the hemisphere and particularly in high latitudes. There was however a period of slow or no increase in temperatures from 1910 to 1920. Summer temperatures showed a slight increase from 1880 to 1910, a decrease from 1910 to 1920 and then a continous increase until 1950. Key areas of strong temperature increase in winter have proved to be the Arctic, northern Scandinavia and USSR, southern Canada and most of the USA. Similar areas of strong warming in summer have proved to exist in Scandinavia, USSR, northern USA and southern Canada. Hence in many areas there was considerable warming both in winter and summer.For the whole Northern Hemisphere, the annual mean temperature increase from 1880 to 1950 was about 0.6°C while mean temperature in January rose from the coldest to the warmest decade by as much as 6°C in the Arctic and in parts of southern Canada and northern USA. July temperatures similarly rose 3°C in northern Scandinavia and in the Great Plains of the USA and Canada.In the subsequent part, it is demonstrated that after 1950 temperatures have shown much less of consistent trends. The 1950's were still reasonably warm both in summer and winter but the 1960's showed a definite cooling in both seasons. The 1970's again were in general warmer than the 1960's but the temperature level of the first half of the century was not reached.The general circulation conditions which lead to the warming of the Northern Hemisphere in the period 1880–1950 are also summarized. It is shown that from 1880 to 1920 the main cause was an increase in the temperature latitude zonal westerlies while from 1920 to 1940 the general circulation was more meridional with dominating southwesterly to south-easterly wind components, whereby the carrying of warm air into high latitudes was further enhanced.In the second main part of the study the impact of the Northern Hemisphere warming is discussed with particular reference to three key areas, the Arctic, northern Scandinavia and the Great Plains in northern America. It is shown that the warming had considerable consequences for sea temperatures in the northern Atlantic and Arctic waters which in turn led to impact on deep-sea fishing and sea transport in northern latitude areas. Cod catching and industry spred from Iceland waters all the way to Spitsbergen, along the east coast of Greenland and to Jakobs- havn on the Greenland west coast. Sea transport, north of Siberia, was normal throughout the winter in the late 1930's.The warming had a considerable impact on agriculture in northern Finland and in Canada due to the lengthening of the vegetation season. In the 1930's and 1940's settlers in both countries moved northwards into areas not hitherto used for agriculture. In Finland, these settlers experienced a catastrophic setback in the cold 1960's and had to abandon their homes. In Canada, the gains from the move towards the north in the 1930's were more than counterbalanced by the droughts that hit agricultural production in the more central parts of the Great Plains in the same period. Various socio-economic efforts to mitigate such adverse consequences of climate impact on agriculture have been undertaken in many areas situated on the climatic margin in the Northern Hemisphere during the last decades. It is concluded that many areas in the developing countries, where such efforts are not yet undertaken are still suffering from impact of climate fluctuations in a similar way that areas on the margin in the Northern Hemisphere suffered earlier in this century.