1,720,970 research outputs found
Do soil features condition seed germination of gypsophiles and gypsovags? An analysis of the effect of natural soils along an alkalinity gradient
No full text© 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Gypseous soils are widespread across drylands worldwide. They present remarkable challenges to plants and host a unique flora. We aimed to assess if the specificity and distribution of species on gypsum might be driven by species-specific germination responses to soil gypsum availability. We analyzed the germination of six gypsum specialists (gypsophiles) and four closely related generalist plant species (gypsovags) from the Iberian Peninsula and the Chihuahuan Desert in different field soils with contrasting concentrations of gypsum, pH and soil texture. Plant restriction to gypsum was unrelated to the germinating ability of seeds on different substrates. Irrespective of their affinity for gypsum, most species germinated better on mixed gypsum-calcareous soil and worse in the acidic soil treatment. Our data suggest soil pH and Ca availability were the main soil features driving seed germination, while the effect of gypsum content was generally not significant. The main exception was the Iberian gypsophile Helianthemum squamatum (L.) Dum. Cours., which showed increased germination on gypseous soils and higher germination in response to increased soil gypsum content. Except for this species, our findings indicate alkaline soils with high Ca availability favor the germination of most of the species analyzed, irrespectively of their gypsum content.Funding was provided by MICINN, Spain, [projects CGL2015-71360-P and PID2019-111159 GB-C31)] and the European Union's Horizon 2020 research and innovation program under grant agreement No [H2020-MSCA-RISE-777803]. NH, AC and SP were funded by a Fulbright Research Grant, a FPI fellowship [MICINN, BES-2016-076455] and a Ramón y Cajal Fellowship [MICINN, RYC-2013-14164], respectively.Peer reviewe
Cover of Ramalina species as an indicator of habitat quality in threatened coastal woodlands
No full textCoastal forests in the Mediterranean area are threatened habitats due to intense human influence. In the context of global change, a rapid tool is needed for the evaluation of habitat quality in woodlands by calculating lichen cover on twigs rather than weight biomass. We selected epiphytic Ramalina species as indicators of habitat quality and evaluated them in threatened woodlands dominated by Olea europea var. sylvestris on the island of Menorca, a UNESCO Biosphere Reserve in the Mediterranean area. We measured species richness, percentage cover and dry weight in nine sites grouped into urban, rural and naturalized areas to evaluate the effect of land uses, and regressed dry weight against percentage cover. Percentage cover, dry weight, species richness of Ramalina and of its species varied depending on land use, reaching higher rates in naturalized and rural areas rather than in urban areas. In addition, we showed for the first time that field estimates of Ramalina cover at the field were related to dry weight by applying a logarithmic transformation to dry weight. Percentage cover of Ramalina was a good indicator of land uses and will be a rapid, easy and non-destructive tool to assess the quality of woodland habitats in the coastal zone.
The woodlands of the hot lowlands and shores of the Mediterranean region are threatened habitats in Europe due to intense human influence (Janssen et al. 2016). These woodlands are dominated by Olea europaea and Ceratonia siliqua (Janssen et al. 2016), and their main threat is habitat fragmentation due to the extension of anthropogenic habitat, mainly agricultural and cattle lands, and urbanization (Rey et al. 2009). Despite the threat, these harbor epiphytic lichens tied to humid areas (Incerti & Nimis 2006). Epiphytic lichens are an important component of forest ecosystems (Brunialti et al. 2012), and can reach a high biomass on tree trunks and especially on branches (Arseneau et al. 1998). Some of these epiphytic lichen species growing on twigs of coastal shrubs and trees are considered aerohygrophylous, as for example those belonging to the genus Ramalina (Roux 2020), which are considered threatened in Italy (Nascimbene et al. 2013) and France (Roux 2020). However, most studies considered only presence or absence, and few data exist on their cover or biomass. We propose to use these to assess the health of these threatened forest ecosystems.
Quantitative studies of epiphytic lichens provide information on population dynamics (Gauslaa et al. 2005), lichen communities (Phinney et al. 2021), the role of lichens in ecosystem functioning (Miranda-González & McCune 2020), and have been used as indicators for sustainable forestry (Boudreault et al. 2015; Longan & Gómez-Bolea 2002), since epiphyte lichens are especially sensitive to forest habitat quality and, consequently, to management (Aragón et al. 2010). These studies have mainly focused on specific species and sometimes to a group of species as indicators of habitat quality and monitoring of forest ecosystems (Martínez et al. 2014; Otálora et al. 2015). Quantitative studies include several approaches to evaluate abundance, such as visual estimation of cover, measurement of maximum length and width of the largest individual of a species, or biomass (McCune 1990). Biomass is the accumulated growth of lichens in a given time, and is the variable that best explains how factors influence lichen growth, and how factors act directly to species distribution or indirectly by altering competitive balance among species (Armstrong 2015). Despite its biological value, measuring biomass is a tedious and can be destructive; however, estimates of lichen cover have been shown to be a good indicators of lichen biomass (Pike 1981). However, the relationship between cover and biomass is often species- or group-specific (McCune 1990), and data are lacking for groups of major ecological and conservation interest, such as the epiphytic fruticose lichens of the Mediterranean region.
Species of Ramalina have been used in several fields of research, as evaluation of climatic changes (Bannister et al. 2004), understanding lichen responses to industrial activities (Garty et al. 2002), and biomonitoring the impacts of these human activities to the environment (Garty 2001; Giralt 1996). Species of Ramalina can grow on rocks, trunks and branches (Spjut et al. 2020). Species growing on branches of Mediterranean woodlands were considered threatened due to the restriction of their habitat (Nascimbene et al. 2013; Roux 2020). Despite this concern, the island of Menorca, a UNESCO Biosphere Reserve in the Mediterranean region, shows a high richness of Ramalina species on trunks and branches (Stolley & Kappen 2002), although we lack high quality data on Ramalina populations.
In the Mediterranean Sea, Menorca Island was declared a Biosphere Reserve in 1993 (Lavola 2019). The Menorca Biosphere Reserve has an action plan to achieve sustainable development in a context of global change, which requires indicators to evaluate the health of terrestrial ecosystems (Lavola 2019). In Menorca, various land uses linked to human activity affect habitats of conservation interest (Fernández et al. 2021), such as the thermo-mediterranean coastal woodlands of Olea europea and Ceratonia siliqua (Janssen et al. 2016). The potential extension of these woodlands have been reduced due to agricultural and grazing practices and urbanization, especially in the Balearic Islands (Rey et al. 2009), including Menorca, when many of them are included in the Natura 2000 Network (IDE Menorca 2022). Lichens are good indicators of atmospheric quality (Garty 2001) and also of habitat quality (Asta et al. 2002; Bergamini et al. 2005). Therefore, the aim of this work was to provide a rapid and easy tool for the evaluation of habitat quality in these threatened woodlands by estimating percentage cover of Ramalina species on twigs instead of measuring biomass directly.Peer reviewe
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
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
