1,720,985 research outputs found
Syndinamic, synecology and syntaxonomy of eastern white oak woods (Habitat 91AA*) along tyrrhenian sector of central italy
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Classificazione ecologica territoriale e serie di vegetazione: i querceti termofili del settore Tirrenico dell’Appennino centrale.
Full text linkObiettivo di questo lavoro è proporre e testare una metodologia per la delimitazione, il campionamento e la definizione delle serie di vegetazione. La metodologia viene applicata nel settore appenninico dell’Italia centrale per definire le serie di vegetazione dei querceti a Quercus virgiliana e Q. pubescens. La delimitazione degli ambiti territoriali di pertinenza di queste serie (unità ambientali) è stata effettuata tramite la classificazione ecologica territoriale, il cui obiettivo è l’individuazione di aree ecologicamente omogenee. Le unità ambientali, individuate tramite l’integrazione in ambiente GIS delle informazioni climatiche, litologiche e morfologiche, sono state utilizzate come base per la stratificazione del campionamento fitosociologico della vegetazione. Per testare la validità del campionamento, l’insieme dei rilievi effettuati è stato sottoposto a “Permutation multivariate Analysis of Variance”, effettuata sui dati delle specie di tutti i rilievi, raggruppati in base all’unità ambientale di appartenenza. Per definire le serie in termini sinecologici, sindinamici e sintassonomici i rilievi delle comunità forestali, arbustive ed erbacee, sono stati sottoposti a tecniche di analisi multivariata. Nonostante la tappa matura delle serie analizzate sia rappresentata da foreste fisionomicamente simili e con distribuzione ridotta, l’integrazione dell’approccio fitosociologico e della classificazione ecologica ha permesso di individuare 5 serie di vegetazione, ciascuna con una combinazione unica di stadi dinamici, la cui composizione specifica riflette la diversità ecologica delle unità ambientali individuate. Si sottolinea, dunque, l’importanza della stratificazione del campionamento fitosociologico tramite le unità ambientali, in quanto strumento efficace sia per la classificazione e caratterizzazione ecologica delle comunità vegetali, che per la ricostruzione delle serie di vegetazione
Phytosociological analysis of white oak (Quercus pubescens s.l.) woodlands and related successional stages. Spatial patterns and their drivers
No full textThe woodlands dominated by white oak (Q. pubescens s.l.) in south and south-eastern Europe are a habitat of high conservation concern that is undergoing intense fragmentation as a result of human settlements and agriculture. Owing to this high degree of fragmentation and the taxonomic complexity of the subgenus Quercus, an in-depth analysis of white oak woodland communities is still lacking. The aims of this study were i) to identify and describe the spatial patterns of white oak woodlands and related successional stages in central Italy, and ii) to explore the drivers of compositional variation within these plant communities. We collected in central Italy 337 original phytosociological relevés of Quercus virgiliana and Q. pubescens s. str. woodlands and of the communities representing their successional stages. Samples were distributed within ecologically homogeneous areas (i.e. land units), which were specifically defined and mapped for this study on the basis of climate, lithology and land morphology. Vegetation data were analysed through cluster and constrained ordination analyses using a set of natural and anthropogenic explanatory variables. We identified five land units (consisting of numerous polygons), characterized by a specific set of abiotic constraints, and with a specific series of successional stages resulting in 8 vegetation classes, 9 orders, 10 alliances and 17 community types. The diverse
types of white oak woodland and of the related stages are differentiated mainly along a steep climatic gradient derived from the combined effect of altitude and continentality. Indeed, the most striking compositional differences were observed between the Mediterranean and Submediterranean communities of the subcoastal area, and the communities in the temperate inner Apennines
Changes in plant diversity and carbon stocks along a succession from semi-natural grassland to submediterranean Quercus cerris L. woodland in Central Italy
No full textAims: The majority of research on the diversity-productivity relationship has utilized aboveground plant biomass as a measure of overall ecosystem productivity and investigated successions with species-poor early stages. During this study we modelled patterns of plant diversity and carbon pools along a succession from pasture abandonment to submediterranean Quercus cerris woodland and investigated ecosystem productivity using biomass and soil carbon. Study area: The hilly-mountainous area of Tolfa in Central Italy. Methods: We used chronosequences to analyse changes in vascular plant species richness and composition across successional stages and along a gradient of productivity (i.e. of increasing carbon stocks). To test possible differences across successional stages species richness and carbon pool data were analysed through analysis of variance. Mixed model regression analyses were used to test the effect of the amount of the carbon stocks on the variation in plant species richness and composition. Results: We found a high variation in plant species richness along the succession, with grasslands and newly formed woods showing the highest values. The amount of carbon in biomass and soil increased along the succession, even if soil carbon did not differ significantly among successional stages. Plant species richness was not dependent on the variation in the carbon pools (i.e. biomass and soil carbon) along the succession, while plant species composition significantly responded to this variation. Conclusions: Our results strongly support the need to manage semi-natural ecosystems through a multi-functional perspective that values both carbon sequestration and biodiversity
Submediterranean dry grasslands along the Tyrrhenian sector of central Italy: Synecology, syndynamics and syntaxonomy
No full textSemi-natural dry grasslands are habitats of high conservation concern. These ecosystems have not been extensively explored in the Tyrrhenian sector of the Italian peninsula, particularly in the Submediterranean climatic region. In order to address this issue and to define the synecology, syndynamics and syntaxonomy of calcareous grasslands in this area, we considered 127 phytosociological relevés. Our sampling was performed in the Lazio region according to a stratified sampling scheme based on homogeneous land units, defined by means of an ecological land classification process. We analyzed the vegetation data using multivariate methods. Two new associations, whose typical aspects occur in the mesotemperate phytoclimatic belt, were identified:Erysimo pseudorhaetici-Dasypyretum villosi (Taenianthero-Aegilopion) and Scorpiuro muricati-Brometum erecti (Phleo-Bromion). Phytoclimatic belts within the Submediterranean region cause a significant degree of differentiation within Scorpiuro-Brometum, which was described at the subassociation and variant levels. The overall relevance of therophytes represents the most important feature distinguishing Scorpiuro-Brometum from the published Bromus erectus associations. At a finer scale, the presence of the two physiognomically different grassland communities is related to different soil types. All these communities are dynamically linked to Quercus virgiliana and Q. pubescens woods, and contribute to the coenological differentiation of the vegetation series related to such woodlands. © 2012 Copyright Taylor and Francis Group, LLC
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
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