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Growth dynamics of Picea abies Karst and Larix decidua Mill. and climatic factors: first results of a study at the timberline in Italian Eastern Alps
No full textTree water relations and climatic variations at the alpine timberline: seasonal changes of sap flux and xylem water potential in Larix decidua Miller, Picea abies (L.) Karst. and Pinus cembra L.
No full textTrees growing at the alpine timberline very seldom undergo severe water stress because of high precipitation during the vegetative period. Since trees are adapted to moist conditions, moderate water deficit may lead to a strong reduction in transpiration. Transpiration and xylem water potential were measured in two individuals each of Pinus cembra, Larix decidua and Picea abies growing at the timberline (2 080 m a.s.l.) in the north-eastern Italian Alps. From June to October 1996 predawn water potential was between -0.29 and -1.0 MPa with moderate differences among species. Throughout the growing period L. decidua showed a progressive decrease in the minimum water potential (from -0.45 to -1.93 MPa); in P. abies and P. cembra variations were more correlated to weather conditions with minima (-1.2 and -1.49 MPa, respectively) during a mild drought period. L. decidua showed the mean daily maximum sap flux density (about 3.3 dm 3 dm-2 h-1) while mean maximum values in P. abies and P. cembra were about 0.9 and 0.7, respectively. High daily fluctuations of sap flow were observed in relation to rapid variations in weather conditions, particularly in L. decidua. Regardless of species a very high stomatal sensitivity to vapour pressure deficit was recorded. The three species seem to have evolved different drought avoidance strategies. L. decidua maintained a relatively high transpiration even during moderate water deficit periods because of its high water uptake capacity. During the same drought period P. abies and P. cembra showed an evident reduction in sap flux, suggesting a water saving behaviour. These different responses should be taken into account when considering the effects of global change on timberline trees
Long and short term growth dynamics of Picea abies (L.) Karst., Larix decidua Mill., Pinus cembra L. and climatic factors: first results of an integrated study at the timberline in Eastern Italian Alps
No full text
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
Tree water relations and climatic variations at the alpine timberline: seasonal changes of sap flux and xylem water potential in Larix decidua Miller, Picea abies (L.) Karst. and Pinus cembra L
No full textTrees growing at the alpine timberline very seldom undergo severe water stress because of high precipitation during the vegetative period. Since trees are adapted to moist conditions, moderate water deficit may lead to a strong reduction in transpiration. Transpiration and xylem water potential were measured in two individuals each of Pinus cembra, Larix decidua and Picea abies growing at the timberline (2 080 m a.s.l.) in the north-eastern Italian Alps. From June to October 1996 predawn water potential was between -0.29 and -1.0 MPa with moderate differences among species. Throughout the growing period L. decidua showed a progressive decrease in the minimum water potential (from -0.45 to -1.93 MPa); in P. abies and P. cembra variations were more correlated to weather conditions with minima (-1.2 and -1.49 MPa, respectively) during a mild drought period. L. decidua showed the mean daily maximum sap flux density (about 3.3 dm 3 dm-2 h-1) while mean maximum values in P. abies and P. cembra were about 0.9 and 0.7, respectively. High daily fluctuations of sap flow were observed in relation to rapid variations in weather conditions, particularly in L. decidua. Regardless of species a very high stomatal sensitivity to vapour pressure deficit was recorded. The three species seem to have evolved different drought avoidance strategies. L. decidua maintained a relatively high transpiration even during moderate water deficit periods because of its high water uptake capacity. During the same drought period P. abies and P. cembra showed an evident reduction in sap flux, suggesting a water saving behaviour. These different responses should be taken into account when considering the effects of global change on timberline trees. (© Inra/Elsevier, Paris.)Relations hydriques des arbres et facteurs du climat à la limite forestière alpine : variations saisonnières du flux de sève et du potentiel hydrique chez Larix decidua Miller, Picea abies (L.) Karst. et Pinus cembra L. Les arbres situés à la limite forestière dans les Alpes sont rarement soumis à des contraintes hydriques sévères, car les précipitations durant la période de végétation sont élevées. Alors que ces arbres sont adaptés à des conditions de forte humidité, une contrainte hydrique modérée peut conduire à une forte réduction de leur transpiration. La transpiration et le potentiel hydrique ont été mesurés sur deux individus de chacune des espèces : Pinus cembra, Larix decidua et Picea abies dans la zone de la limite forestière (altitude 2 080 m), dans le nord-est des Alpes italiennes. De juin à octobre 1996, le potentiel hydrique de base a varié entre -0,29 et -1,0 MPa, avec peu de différences entre espèces. Au cours de la période de végétation, L. decidua a montré une diminution progressive de son potentiel hydrique minimum (passant de -0,45 Mpa à -1,93 Mpa). Chez P. abies et P. cembra, les variations de ce paramètre étaient plus fortement corrélées aux facteurs climatiques, les valeurs atteintes étant respectivement de -1,2 Mpa et de -1,49 Mpa pour ces deux espèces, lors d'une période de sécheresse modérée. Les valeurs les plus élevées de densité de flux de sève ont été observées chez L. decidua (environ 3,3 dm3 dm-2 h-1), contre 0,9 dm3 dm-2 h-1 chez P. abies et 0,7 dm 3 dm-2 h-1 chez P. cembra. Des fortes variations journalières de flux de sève ont été mises en évidence en relation avec les fluctuations rapides des conditions climatiques, notamment chez L. decidua. Une forte sensibilité des stomates au déficit de saturation de l'air a été observée pour chacune de ces espèces. Ces trois espèces semblent avoir développé différentes stratégies de réponse à la sécheresse : L. deciduca a maintenu un taux de transpiration relativement élevé, même lors d'une sécheresse, en relation avec une forte capacité d'extraction de l'eau dans le sol. Au cours de la même période de dessèchement, P. abies et P. cembra ont montré une nette réduction de leur flux de sève, ce qui indiquerait une stratégie d'évitement. Ces différentes réponses doivent être prises en compte lorsqu'on s'intéresse aux effets des changements climatiques dans cette zone de limite forestière. (© Inra/Elsevier, Paris.
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