1,720,974 research outputs found
Spring-summer drought induces extremely low radial growth reactions in North-Tyrrhenian Pinus pinea L.
Full text linkClimate projections predict shifts in environmental conditions, with cascade effects on forest growth dynamics. As such, Pinus pinea L., an ecologically important low-elevation Mediterranean tree, can be threatened by drought events. The occurrence of negative stem growth anomalies ("negative pointer years", or NPY) and its relation to climatic conditions were analyzed, as well as the influence of extreme dry spells upon the species growth. NPY were temporally independent among the analyzed forest stands, likely due to local factors. We observed that NPY depended on dry and hot conditions during the spring-summer period at both sites, while differences in the NPYclimate reflected the species medium term dendroclimatological signal. Extremely dry years directly reduced stem growth rates. Water stress differentially affected growth at each site, likely reflecting local adaptation to droughts. Because of the increasing drought trend expected for the Mediterranean basin, our findings must be considered regarding the conservation and management of these forests.Fil: Piraino, Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Roig Junent, Fidel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Universidad Mayor; Chile. Universidade de Sao Paulo; Brasi
Assessing the sensitivity of riparian algarrobo dulce (Prosopis flexuosa DC) radial growth to hydrological changes
Full text linkEcotones, as for example riparian zones, have long interested ecologists, due to their potential role in generating species biodiversity and evolutionary novelty, as well as their sensitivity to environmental changes. Along riparian areas, vegetation is recognized for its ecological importance in several ecosystemic processes. In the Central Monte Desert (central-west Argentina), Prosopis flexuosa grows in territories characterized by a permanent access to water reservoirs, e.g. along riverbanks, where the species forms the classic gallery forests. Despite the ecosystemic role of the different Prosopis species distributed in arid lands, thus far no analysis has been conducted regarding the relation between their radial growth and hydrological changes, namely streamflow variability, in riparian settings. To fill this gap of knowledge, we performed a dendrochronological analysis considering several riparian P. flexuosa trees differing in their spatial position in relation to the riverbank. Pointer years, correlation function, and regression analyses show differences in the dendrohydrological signal of the studied species, probably function of tree distance from the river. In this sense, radial growth of trees distributed near the riverbank is tightly coupled to spring-summer (September to March) stream-flow variability, whereas for farthest trees the ring development is driven by a combination of winter and spring river discharge and late-summer precipitation amount. The presented results demonstrate the potentiality of P. flexuosa, and in a broader sense of the Prosopis genus, in dendrohydrological studies.Fil: Piraino, Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Roig Junent, Fidel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentin
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
North Atlantic Oscillation influences on radial growth of Pinus pinea on the italian mid-Tyrrhenian coast
Full text linkThe North Atlantic Oscillation (NAO) is the most important source of winter atmospheric variability in the northern hemisphere. NAO inversely reflects the precipitation regime, which plays a fundamental role in Mediterranean regions, e.g., by recharging the water table. As no attempt has been made thus far to analyze the relationship between NAO variability and tree radial growth in coastal Mediterranean conifers, this paper identifies the monthly, winter, annual, and decadal influence of NAO on tree-ring chronologies of six planted Pinus pinea L. populations distributed along the Tyrrhenian coasts of central Italy. Through multidimensional analyses, we identified tree-ring chronology associations in two main groups. The influence of NAO on the regional chronologies was identified with correlation functions for the comparison period between 1949 and 2003 at both annual and decadal timescales. Results indicate that winter NAO influence on radial tree growth at annual and decadal timescales may depend on geographical location, site characteristics, and the age structure of tree-ring chronologies. These results contribute to a better understanding of the P. pinea coastal forest ecology and provide evidence of large-scale climatic forcings that influence forest Mediterranean ecosystems. Fil: Piraino, Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mendoza. Instituto Argentino de Investigaciones de Zonas Aridas; ArgentinaFil: Roig Junent, Fidel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentin
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
Tree growth habit differences as an explanatory variable of the climatic influence upon the radial growth variability of Prosopis flexuosa in the Central Monte Desert (Argentina)
Full text linkLos métodos dendroclimatológicos representan una de las herramientas más valiosas para analizar la influencia del clima sobre la dinámica del incremento radial y la morfología de las plantas leñosas. En el Desierto del Monte Central, Prosopis flexuosa DC (algarrobo dulce), crece como árbol uni-fustal pero también como multi-fustal. Investigaciones anteriores han evidenciado la utilidad del ancho de anillo de esta especie como registro de eventos climáticos. Sin embargo, estas investigaciones han diferido metodológicamente, considerando o descartando los individuos multi-fustales. Este trabajo analizó si la variabilidad en el hábito de crecimiento expresa diferencias en la señal dendroclimática del algarrobo dulce. Dos cronologías de ancho de anillos, una derivada de individuos uni-fustales (UF) y otra de multi-fustales (MF) presentes en un mismo ambiente ecológico fueron desarrolladas. Se observó que hay una mayor sensibilidad de la cronología MF respecto de la UF en relación a la incidencia en el crecimiento de eventos climáticos extremos y del clima en general en el largo plazo. Esto sugiere que los individuos multi-fustales constituyen una buena representación de la variabilidad del clima local. Debido a la gran extensión territorial de especie, otros estudios que abarquen la extensión geográfica de P. flexuosa son deseables para profundizar los resultados logrados.Dendroclimatological methods represent one of the most useful tools in analyzing the influence of climate upon the radial growth dynamics and morphology of woody species. In the Central Monte Desert, Prosopis flexuosa DC (algarrobo dulce), grows as one-stemmed as well as multi-stemmed tree. Previous researches showed the utility of the species ring widths as a proxy of climate variability. Nevertheless, these researches differed methodologically, by considering or rejecting the multi-stemmed trees. This work analyzed if the variability in the tree growth habit express differences in the algarrobo dulce dendroclimatological signal. Two tree-ring chronologies, one derived from the one-stemmed (UF) and the other from the multi-stemmed trees (MF) growing under the same ecological environment, were developed. The MF chronology showed higher sensibility than the UF to climate extremes and oscillation. This suggested that multi-stemmed trees represent a good proxy for explaining local climatic variability. Due to the widespread spatial distribution of this species, further works are needed to a deeper understanding of the presented results.Fil: Piraino, Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Roig Junent, Fidel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentin
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