1,720,998 research outputs found
Climate and human influence on the vegetation of Tyrrhenian Italy during the last 2000 years. New insights from microcharcoal and non-pollen palynomorphs
No full textLa storia della vegetazione degli ultimi 2000 anni nella penisola italiana è stata determinata da una complessa interazione di diversi fattori, tra i quali spiccano la storia delle società umane, i cambiamenti nell'uso del suolo e la successione di eventi climatici. Al fine di distinguere l’effetto di questi fattori, abbiamo svolto uno studio multidisciplinare di una carota di sedimenti marini campionata nel Golfo di Gaeta e interpretata alla luce di altre ricerche paleoambientali dell'Italia tirrenica. I dati pollinici, integrati da palinomorfi non pollinici e da concentrazioni di microcarbone, sono stati usati per ricostruire i cambiamenti nel paesaggio
vegetale, attività di allevamento, incendi e uso del suolo. I dati degli isotopi dell'ossigeno e dei foraminiferi forniscono informazioni indipendenti sui cambiamenti climatici. Le curve dell'indice NAO e delle macchie solari sostengono l'interpretazione dei cambiamenti nella circolazione atmosferica. In questo articolo, esaminando l'effetto del clima e dell'attività umana sul paesaggio in una serie di periodi storici degli ultimi 2000 anni, che rappresentano fasi culturali o climatiche (Periodo Romano, Medio Evo, Anomalia climatica medievale, Piccola Età Glaciale e Periodo moderno), abbiamo documentato un declino generale e progressivo della vegetazione forestale prodotto dall’attività antropica. Tuttavia, indipendentemente dalla fase storica, si sono registrate riduzioni
delle foreste anche quando oscillazioni NAO negative hanno indotto siccità del clima, specialmente durante i minimi dell’attività solare.The history of vegetation in the Italian peninsula during the last 2000 years was shaped by a complex interplay of several factors, including the history of human societies, changes in land use, and the succession of climate events. In order to disentangle these factors, we present a multidisciplinary record from a marine core collected in the Gulf of Gaeta, interpreted in the light of other palaeoenvironmental records from Tyrrhenian Italy. Pollen records, complemented by new data on Non-Pollen Palynomorphs (NPPs) and microcharcoal, are used to reconstruct changes in the vegetational landscape, stock-breeding activities, fire, and land use. Foraminiferal and oxygen isotope data provide independent information on climate changes. NAO-index and sunspot data support the interpretation of changes in atmospheric circulation. In this paper, by examining the effect of climate and human activity on the landscape during a series of periods of the last 2000 years, representing cultural or climate phases (Roman Period, Dark Ages, Medieval Climate Anomaly, Little Ice Age, and
Modern Period), we found that human impact produced a general and progressive decline of forest vegetation. However, irrespective of the societal
cultural phase, forest declines occurred when negative NAO oscillations induced dry climate, especially during sunspot minima
Vegetation history of SE Sicily from feudal land management to post-war agricultural industrialization
No full textA new marine pollen record from SE Sicily is presented. The pollen study was done at a sub-decadal resolution to assess the role and extent of human impact in driving regional environmental and land cover changes over the last four hundred years. The combination of palaeoecological evidence and historical documents provides a detailed report of the main ecological dynamics in relation to socio-economic events, past land use, and land management regulations in Sicily. Our palaeovegetational reconstruction reveals a remarkably stable landscape, preserved by traditional land use practices that have persisted through the long-lasting feudal history of Sicily. After centuries of human-induced environmental stability, an abrupt change in vegetation structure occurred around 1950 AD, reflecting the modern land use policies and agricultural reforms following the Second World War. This vegetational breakpoint in SE Sicily corresponds to a suggested date for the onset of the Anthropocene
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Holocene forest dynamics in central and western Mediterranean: periodicity, spatio-temporal patterns and climate influence
Get PDFIt is well-known that the Holocene exhibits a millennial-scale climate variability. However, its periodicity, spatio-temporal patterns and underlying processes are not fully deciphered yet. Here we focus on the central and western Mediterranean. We show that recurrent forest declines from the Gulf of Gaeta (central Tyrrhenian Sea) reveal a 1860-yr periodicity, consistent with a ca. 1800-yr climate fluctuation induced by large-scale changes in climate modes, linked to solar activity and/or AMOC intensity. We show that recurrent forest declines and dry events are also recorded in several pollen and palaeohydrological proxy-records in the south-central Mediterranean. We found coeval events also in several palaeohydrological records from the south-western Mediterranean, which however show generally wet climate conditions, indicating a spatio-temporal hydrological pattern opposite to the south-central Mediterranean and suggesting that different expressions of climate modes occurred in the two regions at the same time. We propose that these opposite hydroclimate regimes point to a complex interplay of the prevailing or predominant phases of NAO-like circulation, East Atlantic pattern, and extension and location of the North African anticyclone. At a larger geographical scale, displacements of the ITCZ, modulated by solar activity and/or AMOC intensity, may have also indirectly influenced the observed pattern
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Get PDFWe 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
Warm signature of the Roman period in Mediterranean sea surface temperatures
No full textSea surface temperature reconstruction (SST) over the last millennia in the Mediterranean area represent an important challenge to document the possible link of past climate variability on the rise and fall of ancient civilizations. In addition, the last report of the Intergovernmental Panel on Climate Change (IPCC 2018) underlines the requirement to assess climate feedbacks during past episodes of moderately warmer (1.5ºC-2°C) conditions.Within this framework, we present the reconstruction of the SST anomaly over the last five millennia based on the Mg/Ca ratios measured in the planktonic foraminifer /Globigerinoides ruber/ from the sediment core SW104-ND11 extracted in the western part of Sicily Channel (water depth 475 m, central Mediterranean Sea) during the oceanographic creuise NEXTDATA 2014 on board the Urania Vessel (CNR-Italy) wit the the SW104 corer. This new generated SST record is compared with previous published SST records reconstructed from Alboran Sea, Minorca Basin, Aegean Sea and from a north Hemisphere temperature reconstruction. This exercise provides the basis to discuss the regional impact of the most recent episode of apparently warmer conditions than present in the social-economical development of the Mediterranean region
- …
