1,720,972 research outputs found
High ENSO sensitivity in tree rings from a northern population of Polylepis tarapacana in the Peruvian Andes
No full textPolylepis tarapacana is the highest-elevation tree species worldwide growing between 4000 and 5000 m a.s.l. along the South American Altiplano. P. tarapacana is adapted to live in harsh conditions and has been widely used for drought and precipitation tree-ring based reconstructions. Here, we present a 400-year tree-ring width (TRW) chronology located in southern Peru (17ºS; 69ºW) at the northernmost limit of P. tarapacana tree species distribution. The objectives of this study are to assess tree growth sensitivity of a northern P. tarapacana population to (1) precipitation, temperature and El Niño Southern Oscillation (ENSO) variability; (2) to compare its growth variability and ENSO sensitivity with southern P. tarapacana forests. Our results showed that this TRW record is highly sensitive to the prior summer season (Nov-Jan) precipitation (i.e. positive correlation) when the South American Summer Monsoon (SASM) reaches its maximum intensity in this region. We also found a positive relationship with current year temperature that suggests that radial growth may be enhanced by warm, less cloudy, conditions during the year of formation. A strong positive relationship was found between el Niño 3.4 and tree growth variability during the current growing season, but negative during the previous growth period. Growth variability in our northern study site was in agreement with other populations that represent almost the full range of P. tarapacana latitudinal distribution (~ 18ºS to 23ºS). Towards the south of the P. tarapacana TRW network there was a decrease in the strength of the agreement of growth variability with our site,with the exception of higher correlation with the two southeastern sites. Similarly, the TRW chronologies recorded higher sensitivity to ENSO influences in the north and southeastern locations, which are wetter, than the drier southwestern sites. These patterns hold for the entire period, as well as for periods of high and low ENSO activity. Overall, P. tarapacana tree growth at the north of its distribution is mostly influenced by prior year moisture availability and current year temperature that are linked to large-scale climate patterns such as the SASM and ENSO, respectively.Fil: Crispín-DelaCruz, Doris B.. Universidad Continental; PerúFil: Morales, Mariano Santos. 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 Continental; PerúFil: Andreu Hayles, Laia. Columbia University; Estados Unidos. Universitat Autònoma de Barcelona; España. Universidad de Barcelona. Institució Catalana de Recerca i Estudis Avançats; EspañaFil: Duncan, Christopher C.. Universidad Austral de Chile; Chile. Center for Climate and Resilience Research; ChileFil: Guerra, Anthony. Missouri Botanical Garden; PerúFil: Requena Rojas, Edilson Jimmy. Universidad Continental; Per
Dendrocronología de Alnus acuminata en el bosque reservado de San pedro de Saño, Huancayo
Full text linkThe objective is to evaluate the Alnus acuminate potential for its later use in dendroclimatological studies. The research analyses the width tree-ring chronology for an A forest. “acuminate” in San Pedro de Saño and it was related the trees growth with the instrumental records of average, maximum and minimum temperature, precipitation and sunshine hours of the Huayao Weather Stations (12° 02’ 18.1¨ S - 75° 19’ 22.2¨ O) and Santa Ana (12° 00’ 15¨ S - 75° 13’ 15¨ O). The width ring chronology is composed of 33 sets of 22 trees and covered the 1968-2013 period. The trees growth was negatively related to the minimum monthly temperature of April this year. It was observed a positive and significant relationship between the growth timing and the Santa Ana station precipitation for March of the previous year and December of the current growth year. The April monthly sunshine hours of current year are significantly correlated with the radial growth. There is a precipitation influence of the previous summer and spring of the current year favoring the trees growth. The tree enters in dormancy, possibly due to the fall low temperatures. The wide range of distribution and the historic use of its wooden buildings in the past, opens the possibility to temporarily extend the dendrochronological records in the central Andes of Peru.En este trabajo evaluamos el potencial de Alnus acuminata para su uso posterior en estudios dendroclimatológicos. Se analizó una cronología de ancho de anillos para un bosque de A. acuminata en San Pedro de Saño y se relacionó el crecimiento de los árboles con los registros instrumentales de temperatura media, máxima y mínima, precipitación y horas sol de las estaciones meteorológicas de Huayao (12° 02´ 18.1¨ S - 75° 19´22.2¨ O) y Santa Ana (12° 00´ 15¨ S - 75° 13´ 15¨ O). La cronología de ancho de anillos está compuesta por 33 series de 22 árboles y cubre el período 1968-2013. El crecimiento de los árboles estuvo relacionado negativamente con la temperatura mínima mensual del mes de abril del año corriente. Se observó una relación positiva y significativa entre la cronología de crecimiento y la precipitación de la estación de Santa Ana para los meses de marzo del año previo y diciembre del año actual de crecimiento. Las horas sol mensuales de abril del año corriente tienen una correlación significativa con el crecimiento radial. Existe influencia de las precipitaciones del verano previo y primavera del año corriente favoreciendo el crecimiento del árbol. El árbol entra en dormancia, posiblemente por las bajas temperaturas de otoño. El amplio rango de distribución y la utilización histórica de su madera en construcciones en el pasado, abre la posibilidad de extender temporalmente los registros dendrocronológicos, en los Andes centrales de Perú
Temporal Growth Variation in High-Elevation Forests: Case Study of Polylepis Forests in Central Andes
No full textPolylepis species form the dominant high-altitude forests in the tropicalAndes, one of the most vulnerable regions to future climate change scenarios. Thestudy of the growth of these forests provides useful information about their ontogenyand the environmental conditions where they develop. The identification ofgrowth patterns is relevant for understanding the dynamics of the forests in responseto climatic variables. In this chapter, we present a brief review of dendroecologicalstudies on Polylepis species. We also developed for the first time in the centralAndes of Peru three new Polylepis ring-width chronologies together with a diametergrowth modeling for the following species: Polylepis rodolfo-vasquezii, Polylepisrugulosa, and Polylepis tarapacana. Dendrochronological techniques together with a biologically based model help us to obtain information on forestry traits ofPolylepis species. P. rodolfo-vasquezii to growth response to summer temperature ofthe current growth period determined radial growth, whereas spring and summerprecipitation from the previous growth period determined the radial growth in P.rugulosa and P. tarapacana, respectively. The radial growth models indicated differencesin the growth of the three Polylepis species with P. rodolfo-vasquezii reachingthe highest rate (0.11 cm/yr), while P. tarapacana showed the lowest (0.08 cm/yr). Due to the low growth rates of these Polylepis species, long periods (>100 years)are required to establish and provide ecosystem services. As these forests face thechallenge of climate change and anthropogenic pressure, there is a clear need toobtain precise information in order to formulate guidelines for the conservation ofthese forests, and the application of dendroecology is indispensable in this context.Fil: Requena Rojas, Edilson Jimmy. Universidad Continental; PerúFil: Crispín DelaCruz, Doris B.. Universidad Continental; PerúFil: Ticse-Otarola, Ginette. Universidad Continental; PerúFil: Rusbelth Quispe Melgar, Harold. Universidad Continental; PerúFil: Inga Guillen, Janet G.. Universidad Continental; PerúFil: Camel Paucar, Vladimir. Universidad Nacional Agraria La Molina; PerúFil: Guerra, Anthony. Universidad Nacional del Centro del
Perú; PerúFil: Ames Martinez, Fressia Nathalie. Universidad Continental; PerúFil: Morales, Mariano Santos. 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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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