1,720,960 research outputs found
Modelling vegetation cover and wetland expansion in the Lower Thames Valley, UK: Multi-proxy records from Littlebrook Power Station, Kent
No full textThe interaction of ‘natural’ environmental processes and human activity in shaping landscapes is vividly illustrated in the Lower Thames Valley, UK. Through development-led (geo)archaeological investigations, intensifying redevelopment of this (currently) industrial landscape presents opportunities to gain long-term perspectives on these processes and to investigate the timing and extent of human impact on the environment in the past. This paper describes a novel multi-method approach undertaken at the former Littlebrook Power Station, Kent, comprising landscape-scale deposit modelling, multi-proxy palaeo-environmental analysis and vegetation cover reconstruction using REVEALS to produce schematic landscape reconstruction maps. Micropaleontological data reveal variable estuarine/freshwater influence, which alongside longer-term trends towards rising relative sea level drove lateral expansion of wetlands through the Holocene. Pollen-derived vegetation models show Early Holocene dense forest cover reduced to ∼55 per cent by 7–8 kyr BP followed by a step-change to grassland dominance in the early Bronze Age. Since grassland expansion was not proportionate to modelled expansion of wetlands but was associated with increased pastoral indicators, an anthropogenic cause of the deforestation in the Bronze Age is probable. This paper highlights the value of combining geoarchaeological data with novel modelling approaches to visualise ancient landscapes and thereby offer long-term perspectives on landscape-scale human-environment interactions
Modelling prehistoric topography and vegetation in the lower Thames Valley, UK: Palaeoenvironmental context for wetland archaeology and evidence for Neolithic Landnám from north Woolwich
No full textMulti-proxy investigations at 2 Pier Road, North Woolwich, London, UK, have revealed deposits spanning the Middle-Late Holocene from the late Mesolithic (c. 4360 cal BC) onwards. Pollen data show an Elm Decline at c. 4210–3950 cal BC followed by landnám clearances at c. 4210–3910 cal BC and c. 3710–3030 cal BC and the first appearance of cereal at c. 3540–3030 cal BC. These events are potentially contemporary with the construction of nearby Neolithic trackways, providing indirect evidence for agriculture and settlement. REVEALS modelling shows the first significant reduction in woodland cover is coincident with the Neolithic Elm decline, but the main step-change to open conditions occurred in the Early Bronze Age, following a decline in lime at c. 2110–1630 cal BC. Palaeo-topographic modelling of the region shows that although the trend towards increasing openness coincides with gradual wetland expansion, the shift to open vegetation cover cannot be explained by this and is probably the result of human activity. This study highlights the value of combining deposit and vegetation cover modelling to contextualise wetland archaeology and shows that together these provide useful proxies for landscape-scale human activity that can identify ephemeral signals of prehistoric activity.</p
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The late prehistoric ‘Dark Age’ in Ireland and climate fluctuation: buffering strategies and the agency of the environment
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Examining the relationships between Holocene climate change, hydrology, and human society in Ireland
No full textThis thesis explores human-environment interactions during the Mid-Late Holocene in raised bogs in central Ireland. The raised bogs of central Ireland are widely-recognised for their considerable palaeoenvironmental and archaeological resources: research over the past few
decades has established the potential for such sites to preserve sensitive records of Holocene climatic variability expressed as changes in bog surface wetness (BSW); meanwhile archaeological investigations over the past century have uncovered hundreds of peatland archaeological features dating from the Neolithic through to the Post-Medieval period including wooden trackways, platforms, and deposits of high-status metalwork. Previous studies have attempted to explore the relationship between records of past environmental change and the occurrence of peatland archaeological sites reaching varying conclusions. More recently, environmentally-deterministic models of human-environment
interaction in Irish raised bogs at the regional scale have been explicitly tested leading to the conclusion that there is no relationship between BSW and past human activity. These relationships are examined in more detail on a site-by-site basis in this thesis. To that end, testate amoebae-derived BSW records from nine milled former raised bogs in central Ireland were produced from sites with known and dated archaeological records.
Relationships between BSW records and environmental conditions within the study area were explored through both the development of a new central Ireland testate amoebae transfer function and through comparisons between recent BSW records and instrumental weather data.
Compilation of BSW records from the nine fossil study sites show evidence both for climate forcing, particularly during 3200-2400 cal BP, as well as considerable inter-site variability. Considerable inter-site variability was also evident in the archaeological records of the same sites. Whilst comparisons between BSW and archaeological records do not show a consistent linear relationship, examination of records on a site-by-site basis were shown to reveal interpretatively important contingent relationships. It is concluded therefore, that future research on human-environment interactions should focus on individual sites and should utilise theoretical approaches from the humanities in order to avoid the twin pitfalls of masking important local patterns of change, and of environmental determinism
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Bog microtopography and the climatic sensitivity of testate amoeba communities: implications for transfer function-based paleo-water table reconstructions
Full text linkAlthough the use of sub-fossil testate amoebae as a proxy for raised bog hydrology in Holocene paleoecological studies is well-established, some detailed aspects of species-environment relationships remain under-researched. One such issue is the effect of bog surface microtopography on the climatic sensitivity of testate amoeba communities. Although it has been suggested that some microforms—especially hummocks—may be less sensitive to climatic forcing than others, this has rarely been objectively tested. To investigate this, subfossil testate amoebae assemblages have been examined in a series of shallow cores collected along a hummock-lawn-hollow transect from a bog in central Ireland and the resulting reconstructed water table records, dated using 210Pb, have been compared with instrumental weather data. Testate amoebae communities in the hollow microform were found to be significantly less diverse than those in the hummock and lawn, and both the hummock and lawn showed statistically significant correlations with instrumental temperature and precipitation data. Therefore, whilst the suggestion that paleoecological investigations should target intermediate bog microforms remains sound, the notion that hummock-based testate amoebae hydrological data are climatically-insensitive is challenged
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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