78 research outputs found
Центральная Азия в интересах Ирана, Китая, России и Турции: взгляд из США
Работа посвящена изучению реакции американских специалистов на внешнюю политику Ирана, Китая, России и Турции в Центральной Азии. В исследовании комплексно рассмотрена политика единственной сверхдержавы относительно отдельного региона в рамках общей стратегии США.Робота присвячена вивченню реакції американських фахівців на зовнішню політику Ірану, Китаю, Росії та Туреччини у Центральній Азії. У дослідженні комплексно розглянута політика єдиної наддержави щодо окремого регіону в рамках її загального стратегічного курсу.The thesis is focused on a study of the american specialists reactions toward foreign policy of China, Iran, Russia and Turkey in Central Asia. The research presents a complex investigation of the policy of the only superpower in the relation to a separate region in the frame of its general strategic course
Looking forward through the past: identification of 50 priority research questions in palaeoecology
1. Priority question exercises are becoming an increasingly common tool to frame future agendas in conservation and ecological science. They are an effective way to identify research foci that advance the field and that also have high policy and conservation relevance. 2. To date, there has been no coherent synthesis of key questions and priority research areas for palaeoecology, which combines biological, geochemical and molecular techniques in order to reconstruct past ecological and environmental systems on time-scales from decades to millions of years. 3. We adapted a well-established methodology to identify 50 priority research questions in palaeoecology. Using a set of criteria designed to identify realistic and achievable research goals, we selected questions from a pool submitted by the international palaeoecology research community and relevant policy practitioners. 4. The integration of online participation, both before and during the workshop, increased international engagement in question selection. 5. The questions selected are structured around six themes: human–environment interactions in the Anthropocene; biodiversity, conservation and novel ecosystems; biodiversity over long time-scales; ecosystem processes and biogeochemical cycling; comparing, combining and synthesizing information from multiple records; and new developments in palaeoecology. 6. Future opportunities in palaeoecology are related to improved incorporation of uncertainty into reconstructions, an enhanced understanding of ecological and evolutionary dynamics and processes and the continued application of long-term data for better-informed landscape management
Climatic significance of the marginalization of Scots pine (Pinus sylvestris L.) c. 2500 BC at White Moss, south Cheshire, UK
Subfossil wood from White Moss, south Cheshire, has become the focus of palaeoenvironmental research employing not only conventional coring, pollen analysis, radiocarbon dating and dendrochronology on pine and oak, but also the exhumation of in situ peat areas and dendroecology of the pine ring-width records. Initial dendrochronological research at the site yielded five pine chronologies dating from 3520 to 2462 cal. BC. These and other data indicate three episodes of pine colonization of the mire in the period between 3643 and 1740 cal. BC. Comparison of the pollen and spore records suggest that pine became marginalized at the site c. 2500 cal. BC after successive episodes of increased wetness, and this may represent a staged response to climatic deterioration. Two oak chronologies were dated by reference to the Belfast and to English oak master chronologies to 3228-2898 BC and 2190-1891 BC, respectively, showing the possible co-existence of pine and oak on the mire for part of the time. Further dendrochronological work on subfossil pine at the site resulted in a chronology (WM4) that was cross-matched with pine from elsewhere in England, and subsequently dated absolutely to 2881-2559 BC. Detailed dendroecological information, such as fire episodes and periods of environmental stress indicated in the tree-ring records, have been assigned, precisely and accurately, to calendar years in prehistory. The detailed data show the potential for both dendroecological and wider palaeoclimatic and palaeoenvironmental information that may become available from prehistoric bog-pine chronologies, which might then permit precise correlation and comparisons of proxy-climate data between sites
Mineral deficiency and the presence of Pinus sylvestris on mires during the mid- to late Holocene: Palaeoecological data from Cadogan's Bog, Mizen Peninsula, Co. Cork, southwest Ireland
Pollen records across parts of Ireland, England and northern Scotland show a dramatic collapse in Pinus pollen percentages at approximately 4000 radiocarbon years BP. This phenomenon has attracted much palaeoecological interest and several hypotheses have been put forward to account for this often synchronous and rapid reduction in pine from mid-Holocene woodland. Explanations for the 'pine decline' include prehistoric human activity, climatic change, in particular a substantial increase in precipitation resulting in increased mire wetness, and airborne pollution associated with the deposition of tephra. Hitherto, one largely untested hypothesis is that mineral deficiency could adversely affect pine growth and regeneration on mire surfaces. The discovery of pine-tree remains (wood pieces, stumps and trunks) within a peat located at Cadogan's Bog on the Mizen Peninsula, southwest Ireland, provided an opportunity to investigate the history of Pinus sylvestris and also to assess the importance of mineral nutrition in maintaining pine growth on mires. Pollen, plant macrofossils, microscopic charcoal and geochemical data are presented from a radiocarbon dated monolith extracted from this peat together with tree ring-width data and radiocarbon dated age estimates from subfossil wood. Analyses of these data suggest that peat accumulation commenced at the site around 6000 years BP when pine was the dominant local tree. Thereafter Pinus pollen percentages diminish in two stages, with the second decline taking place around 4160 ± 50 years BP. Concomitant with this decline in Pinus pollen, there is a noticeable, short-lived increase in wet-loving mire taxa and a decrease in the concentration of phosphorus, potassium, magnesium, calcium, sodium, iron and zinc. These results suggest that increased mire surface wetness, possibly the result of a change in climate, created conditions unsuitable for pine growth c. 4000 years BP. Mire surface wetness, coupled with a period of associated nutrient deficiency, appears to be a possible explanation for a lack of subsequent pine-seedling establishment for most of the later Holocene
Lateglacial and early Holocene vegetation and climate gradients in the Nordfjord–Alesund area, western Norway
Modern climate in western Norway shows a strong west–east gradient in oceanicity–continentality (coast to inner
fjord) and altitudinal temperature gradients that control the regional and altitudinal zonation of vegetation. To
discover if similar gradients existed during the Lateglacial and early Holocene, plant-macrofossil analyses were
made from five lacustrine sediment sequences in the Nordfjord–A˚ lesund region selected to sample the present climatic
gradients. The macrofossil assemblages could be interpreted as analogues of the present vegetation, thus
allowing reconstruction of past vegetation and climates. When the five sites were compared, climatic gradients
could be detected. During the Lateglacial interstadial, mid-alpine assemblages with Salix herbacea and S. polaris
occurred at the lowland coast and upland inland sites, whereas the inland lowland site had low-alpine dwarf-shrub
heath dominated by Betula nana, demonstrating a strong west–east gradient in temperature and precipitation and
an altitudinal gradient inland. During the Younger Dryas stadial, assemblages at the lowland coast and upland
inland sites resembled high-alpine vegetation, whereas the inland lowland site was warmer with mid-alpine vegetation,
demonstrating west–east and altitudinal temperature gradients. Gradients became less pronounced in the
Holocene. The early abundance of Betula nana in the inner fjord sites but its rarity at the coast is striking and
reflects the oceanicity gradient. All sites became forested with Betula pubescens a few centuries into the Holocene.
This forest was probably close to tree line at 370m a.s.l. at the coast. Inland, there was no detectable altitudinal
gradient, with the tree line well above 400m a.s.l. reflecting the present pattern of tree-line elevation
PLANT MACROFOSSIL RECORDS | Late Glacial Multidisciplinary Studies
Amplitudes and rates of climate changes and environmental responses were especially high during the Late Glacial (ca. 16 000–11 500 years BP). By applying several methods on the same material (if possible on the same core to avoid correlation problems), the uncertainties and weaknesses of single disciplines can be reduced. Case studies are summarized to illustrate three types of research questions: What were the qualitative changes in the Late Glacial? How large were the temperature changes quantitatively? and What were the biotic responses to an independently recorded temperature change? Plant macrofossils play an important role in answering these questions. When several biostratigraphies and isotope stratigraphies are combined in a multidisciplinary study, we may disentangle the changes in various ecological factors, such as temperature, effective moisture, salinity, pH, or nutrient availability
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