1,720,995 research outputs found
Maquis fuel model development to support spatially-explicit fire modeling applications
Full text linkThe availability of accurate data on conditions and spatial distribution of fuels has been shown to be critical in numerous topics of fire studies. In Italy, there is a lack of studies devoted to a systematic analysis of the vegetation characteristics related to fire behaviour, thus involving the use of fuel data and fuel models developed in other countries.
In this perspective, the aim of this work is to propose an integrated approach to fuel model development and assessment based on field data collection, fuel classification, and fuel mapping. The methodology was applied to the Mediterranean maquis ecosystem. The survey of the main fuel variables allowed the analysis and the characterization of fuel complexes, classified in four main fuel types. The relative custom fuel models were developed and compared with other fuel model developed for Mediterranean shrublands, showing values similar to standard fuel models but different fire behaviour and spread. Maximum Likelihood algorithm was applied on IKONOS satellite image to map the Mediterranean maquis, evidencing that the use of remotely sensed data at high spatial and spectral resolution provided valuable maps of fuel models. Thus, the maps of fuel models derived by remotely sensed images were used at different resolution as input data in the FARSITE fire area simulator, showing that the fine resolution of fuel maps affects the simulation accuracy, improving the predictive capabilities of the simulator
Methods for biomass stock estimation in Mediterranean maquis systems
No full textAs a result of Kyoto Protocol agreements, the scientific community increased its efforts to enhance the availability of biomass and organic carbon stock data in forest ecosystems. Nevertheless, a considerable data shortage has been recognized in estimating the stock of above-ground biomass (AGB) in Mediterranean maquis systems. This work aims at contributing in addressing such shortage by testing quick and non-disruptive methods to estimate the AGB stock in maquis species. Two methodologies were tested in three widespread sclerophyllous evergreen species (Pistacia lentiscus, Euphorbia dendroides, and Cystus monspeliensis). Both methodologies were based on the estimation of the apparent volume (AV): the first one assumed the shrub shape (or canopy) to be similar to a regular tridimensional solid, while the second method was based on plant digital images analysis. Results showed some differences in AV values estimated through the two methodologies, although a high correlation was found between them (R2 = 0.92-0.98) and with the AGB weight obtained from plant samples (R2 = 0.89-0.96). As a consequence, the shrubs apparent density values (i.e., weight/AV) vary depending on the method used for AV estimation. This should be taken into account when AV is used for AGB estimation. Besides, measurements of above-ground biomass were carried out to characterize the studied area. Results showed high variability in AGB values, ranging from 7.04 to 48.05 Mg ha-1 of dry matter. © SISEF
The growing link between heatwaves and megafires: evidence from southern Mediterranean countries of Europe
No full textThe increasing trend of extreme wildfire events is concerning national agencies at multiple levels because of their potential impacts on ecosystem services and the capacities of emergency management systems. This concern is exacerbated by the increasing occurrence of heatwaves (HWs) which intensify the impacts of concomitant events. Thus, we wanted to assess recent trends on HWs and megafires and the spatial and temporal co-occurrence of these events. We focused on the most fire prone countries in Europe, i.e., Portugal, Spain, France, Italy and Greece, and considered varying fire size thresholds for defining megafires. Our analysis shows that HWs and megafires have increased during the last 16 years, especially those of greater size. Furthermore, the percentage of events occurring under a HW increases when increasing the threshold used for defining megafires. HW intensity emerges as a more important HW characteristic driving megafires occurrence than HW duration. The research’s temporal scope (2008–2023) provides a contemporary view of these relationships, capturing recent changes in both climate and fire regimes. However, it also raises questions about other important factors not captured in the analysis that might drive extreme wildfire occurrence
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
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