54 resultados para NORTHEAST

em QUB Research Portal - Research Directory and Institutional Repository for Queen's University Belfast


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A long-synonymized species Benthoctopus normani (Massy 1907) (Cephalopoda: Octopodidae) is redescribed from material collected over 30 years by the National Oceanography Centre, Southampton and the National Museums of Scotland. It can be distinguished from other octopodid specimens found in deep waters of the Northeast Atlantic by its biserial suckers, lack of ink sac, and simple ligula, which lacks transverse ridges. Examination of the collections led to the identification of a new species of Benthoctopus from the Northeast Atlantic, which is described herein.

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Biological activities greatly influence the formation of many soils, especially forest soils under cool humid climates. The objective of this study was to investigate the effects of vegetation and soil biota on the formation of selected soils. Field morphology, micromorphology, and carbon and organic matter analysis were determined on six Podzols (Spodosols) and two Cambisols (Inceptisols) from the eastern United States and north-east Scotland. Humification of plant material by soil fauna and fungi occurs in all organic horizons. Thick organic coatings are observed on soil peds and rock fragments from the E1 to the Bs horizon in a Haplic Podzol from Clingmans Dome Mt., TN. Thin sections reveal large accumulations of root material in different stages of decomposition in the spodic horizons of a Haplic Podzol from Whiteface Mt., NY. Organic carbon ranges from 5.4 to 8.5% in the spodic B horizons of the Whiteface Mt. Podzol. Earthworms and enchytraeids have a great effect on the structure of the surface and subsurface horizons in the Dystric Cambisols from Huntly and Clashindarroch Forests, Scotland and a Cambic Podzol from the Corrie Burn Basin, Scotland. Podzols from Speymouth Forest, Scotland (Gleyic Podzol), Cling-mans Dome Mt., and Whiteface Mt. have thick organic horizons. The Podzols from the Flatwoods in Georgia, the Pine Barrens in New Jersey, the Corrie Burn Basin, and the Cambisol from Huntly Forest have only A horizons at the surface. The Clashindarroch Forest soil has a very thin organic horizon. Warm and humid climates and sandy parent material are responsible for thick E horizons and lack of thick organic horizons in the Flatwoods (Carbic Podzol) and Pine Barrens (Ferric Podzol) soils. Earthworms and enchytraeids thrive in the Corrie Burn Basin and Huntly Forest soils due to the vegetation and the highly weathered basic parent material. The site at Clashindarroch once carried oak, and then birch forest, both of which produce a mild litter and also encourage earthworm and enchytraeids. This fauna is responsible for much mixing of the topsoil. The present conifer vegetation will eventually produce a deep litter and cause podzolization.

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India’s Northeast frontier is at the margins of three study areas: South Asia, Southeast Asia, and East Asia. This paper attempts a history of “mapping” in its broader sense as a cultural universal over a relatively long period. It is not a history of cartography, but focuses on the interface between cartography and cosmography, which were, in turn, shaped by imperial power and geographical knowledge. This approach offers a high-altitude view of this Asian borderland as the imperial frontier of both the Mughals and the British, and the national fringe of Republican India. The authors argue that imperial geographical discourses invested the colonial Northeast (British Assam) with a new kind of territorial identity. Surveyors and mapmakers objectified the “geo-body” of this borderland in a spatial fix and visualized it as a Northeast-on-the-map. Cartographic territoriality naturalized traditional frontiers into colonial borderlands, which, in turn, forged national boundaries.

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The long-term climatic and environmental history of Southeast Asia, and of Thailand in particular, is still fragmentary. Here we present a new 14C-dated, multi-proxy sediment record (TOC, C/N, CNS isotopes, Si, Zr, K, Ti, Rb, Ca elemental data, biogenic silica) for Lake Kumphawapi, the second largest natural lake in northeast Thailand. The data set provides a reconstruction of changes in lake status, groundwater fluctuations, and catchment run-off during the Holocene. A comparison of multiple sediment sequences and their proxies suggests that the summer monsoon was stronger between c. 9800 and 7000 cal yr BP. Lake status and water level changes around 7000 cal yr BP signify a shift to lower effective moisture. By c. 6500 cal yr BP parts of the lake had been transformed into a peatland, while areas of shallow water still occupied the deeper part of the basin until c. 5400–5200 cal yr BP. The driest interval in Kumphawapi's history occurred between c. 5200 and 3200 cal yr BP, when peat extended over large parts of the basin. After 3200 cal yr BP, the deepest part of the lake again turned into a wetland, which existed until c. 1600 cal yr BP. The observed lake-level rise after 1600 cal yr BP could have been caused by higher moisture availability, although increased human influence in the catchment cannot be ruled out. The present study highlights the use of multiple sediment sequences and proxies to study large lakes, such as Lake Kumphawapi in order to correctly assess the time transgressive response to past changes in hydroclimate conditions. Our new data set from northeast Thailand adds important palaeoclimatic information for a region in Southeast Asia and allows discussing Holocene monsoon variability and ITCZ movement in greater detail.

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Geochemical variables (TOC, C/N, TS, delta C-13) and diatom assemblages were analyzed in a lake sediment sequence from Nong (Lake) Han Kumphawapi in northeast Thailand to reconstruct regional climatic and environmental history during the Holocene. By around c. 10,000-9400 cal yr BP, a large shallow freshwater lake had formed in the Kumphawapi basin. Oxygenated bottom waters and a well-mixed water column were characteristic of this early lake stage, which was probably initiated by higher effective moisture and a stronger summer monsoon. Decreased run-off after c. 6700 cal yr BP favored increased aquatic productivity in the shallow lake. Multiple proxies indicate a marked lowering of the lake level around 5900 cal yr BP, the development of an extensive wetland around 5400 cal yr BP, and the subsequent transition to a peatland. The shift from shallow lake to wetland and later to a peatland is interpreted as a response to lower effective moisture. A hiatus at the transition from wetland to peatland suggests very low accumulation rates, which may result from very dry climatic conditions. A rise in groundwater and lake level around 3200 cal yr BP allowed the re-establishment of a wetland in the Kumphawapi basin. However, the sediments deposited between c. 3200 and 1600 cal yr BP provide evidence for at least two hiatuses at c. 2700-2500 cal yr BP, and at c. 1900-1600 cal yr BP, which would suggest surface dryness and consequently periods of low effective moisture. Around 1600 cal yr BP a new shallow lake became re-established in the basin. Although the underlying causes for this new lake phase remain unclear, we hypothesize that higher effective moisture was the main driving force. This shallow lake phase continued up to the present but was interrupted by higher nutrient fluxes to the lake around 1000-600 cal yr BP. Whether this was caused by intensified human impact in the catchment or, whether this signals a lowering of the lake level due to reduced effective moisture, needs to be corroborated by further studies in the region. The multi-proxy study of Kumphawapi's sediment core CP3A clearly shows that Kumphawapi is a sensitive archive for recording past shifts in effective moisture, and as such in the intensity of the Asian summer monsoon. Many more continental paleorecords, however, will be needed to fully understand the spatial and temporal patterns of past changes in Asian monsoon intensity and its ecosystem impacts. (C) 2012 Elsevier B.V. All rights reserved.

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Evidence of 11-year Schwabe solar sunspot cycles, El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) were detected in an annual record of diatomaceous laminated sediments from anoxic Effingham Inlet, Vancouver Island, British Columbia. Radiometric dating and counting of annual varves dates the sediments from AD 1947-1993. Intact sediment slabs were X-rayed for sediment structure (lamina thickness and composition based on gray-scale), and subsamples were examined for diatom abundances and for grain size. Wavelet analysis reveals the presence of ~2-3, ~4.5, ~7 and ~9-12-year cycles in the diatom record and an w11e13 year record in the sedimentary varve thickness record. These cycle lengths suggest that both ENSO and the sunspot cycle had an influence on primary productivity and sedimentation patterns. Sediment grain size could not be correlated to the sunspot cycle although a peak in the grain size data centered around the mid-1970s may be related to the 1976-1977 Pacific climate shift, which occurred when the PDO index shifted from negative (cool conditions) to positive (warm conditions). Additional evidence of the PDO regime shift is found in wavelet and cross-wavelet results for Skeletonema costatum, a weakly silicified variant of S. costatum, annual precipitation and April to June precipitation. Higher spring (April/May) values of the North Pacific High pressure index during sunspot minima suggest that during this time, increased cloud cover and concomitant suppression of the Aleutian Low (AL) pressure system led to strengthened coastal upwelling and enhanced diatom production earlier in the year. These results suggest that the 11-year solar cycle, amplified by cloud cover and upwelling changes, as well as ENSO, exert significant influence on marine primary productivity in the northeast Pacific. The expression of these cyclic phenomena in the sedimentary record were in turn modulated by the phase of PDO, as indicated by the change in period of ENSO and suppression of the solar signal in the record after the 1976-1977 regime shift. © 2013 Elsevier Ltd and INQUA. All rights reserved.

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Kelp forests along temperate and polar coastlines represent some of most diverse and productive habitats on the Earth. Here, we synthesize information from >60 years of research on the structure and functioning of kelp forest habitats in European waters, with particular emphasis on the coasts of UK and Ireland, which represents an important biogeographic transition zone that is subjected to multiple threats and stressors. We collated existing data on kelp distribution and abundance and reanalyzed these data to describe the structure of kelp forests along a spatial gradient spanning more than 10° of latitude. We then examined ecological goods and services provided by kelp forests, including elevated secondary production, nutrient cycling, energy capture and flow, coastal defense, direct applications, and biodiversity repositories, before discussing current and future threats posed to kelp forests and identifying key knowledge gaps. Recent evidence unequivocally demonstrates that the structure of kelp forests in the NE Atlantic is changing in response to climate- and non-climate-related stressors, which will have major implications for the structure and functioning of coastal ecosystems. However, kelp-dominated habitats along much of the NE Atlantic coastline have been chronically understudied over recent decades in comparison with other regions such as Australasia and North America. The paucity of field-based research currently impedes our ability to conserve and manage these important ecosystems. Targeted observational and experimental research conducted over large spatial and temporal scales is urgently needed to address these knowledge gaps.

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The 1950s excavations by Charles McBurney in the Haua Fteah, a large karstic cave on the coast of northeast Libya, revealed a deep sequence of human occupation. Most subsequent research on North African prehistory refers to his discoveries and interpretations, but the chronology of its archaeological and geological sequences has been based on very early age determinations. This paper reports on the initial results of a comprehensive multi-method dating program undertaken as part of new work at the site, involving radiocarbon dating of charcoal, land snails and marine shell, cryptotephra investigations, optically stimulated luminescence (OSL) dating of sediments, and electron spin resonance (ESR) dating of tooth enamel. The dating samples were collected from the newly exposed and cleaned faces of the upper 7.5m of the ~14.0m-deep McBurney trench, which contain six of the seven major cultural phases that he identified. Despite problems of sediment transport and reworking, using a Bayesian statistical model the new dating program establishes a robust framework for the five major lithostratigraphic units identified in the stratigraphic succession, and for the major cultural units. The age of two anatomically modern human mandibles found by McBurney in Layer XXXIII near the base of his Levalloiso-Mousterian phase can now be estimated to between 73 and 65ka (thousands of years ago) at the 95.4% confidence level, within Marine Isotope Stage (MIS) 4. McBurney's Layer XXV, associated with Upper Palaeolithic Dabban blade industries, has a clear stratigraphic relationship with Campanian Ignimbrite tephra. Microlithic Oranian technologies developed following the climax of the Last Glacial Maximum and the more microlithic Capsian in the Younger Dryas. Neolithic pottery and perhaps domestic livestock were used in the cave from the mid Holocene but there is no certain evidence for plant cultivation until the Graeco-Roman period. © 2013 Elsevier Ltd.

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The Southeast Asian mainland is located in the central path of the Asian summer monsoon, a region where paleoclimatic data are still sparse. Here we present a multi-proxy (TOC, C/N, δ13C, biogenic silica, and XRF elemental data) study of a 1.5m sediment/peat sequence from Lake Pa Kho, northeast Thailand, which is supported by 20 AMS 14C ages. Hydroclimatic reconstructions for Pa Kho suggest a strengthened summer monsoon between BC 170-AD 370, AD 800-960, and after AD 1450; and a weakening of the summer monsoon between AD 370-800, and AD 1300-1450. Increased run-off and a higher nutrient supply after AD 1700 can be linked to agricultural intensification and land-use changes in the region. This study fills an important gap in data coverage with respect to summer monsoon variability over Southeast Asia during the past 2000 years and enables the mean position of the Intertropical Convergence Zone (ITCZ) to be inferred based on comparisons with other regional studies. Intervals of strengthened/weaker summer monsoon rainfall suggest that the mean position of the ITCZ was located as far north as 35°N between BC 170-AD 370 and AD 800-960, whereas it likely did not reach above 17°N during the drought intervals of AD 370-800 and AD 1300-1450. The spatial pattern of rainfall variation seems to have changed after AD 1450, when the inferred moisture history for Pa Kho indicates a more southerly location of the mean position of the summer ITCZ.