1,721,105 research outputs found
Garrigue plant communities of ultramafic outcrops of Tuscany (central Italy)
No full textGarrigue plant communities of the ultramafic outcrops in Tuscany are here analyzed from a phytosociological point of view on the basis of original and published data. All the investigated vegetation types belong to the association Armerio-Alyssetum bertolonii, already described from Monte Ferrato. Two subassociations, typicum and Euphorbietosum spinosae subass. nova, are recognized, their distribution evidenced and their structural and chorological differences pointed out. The syntaxonomical problems of the Tuscan ultramafic communities are discussed. -Author
Echium anchusoides (Boraginaceae), a new species from Sardinia (Italy)
No full textThe new species Echium anchusoides, endemic to the main siliceous massifs of
Sardinia, is described and illustrated. It was formerly confused with E. pustulatum, a
Mediterranean form of E. vulgare, but differs in characters regarding habit, leaves,
inflorescence, corolla, stamens and mericarps. Contrary to the taxa of the E. vulgare
group, E. anchusoides is also characterized by a higher ecological specificity, being
linked to natural habitats with siliceous growth substratum. Micromorphological
analyses provide additional information on the indumentum and reproductive
structures, such as pollen, stigmatic papillae, nectar ducts and mericarp coat surface
Variation in nectar sugar profile of Anchusa and allied genera (Boraginaceae)
No full textThe nectar-sugar profile (fructose, glucose and sucrose) of 14 species of Anchusa and five members of the allied genera Anchusella, Cynoglottis, Hormuzakia and Lycopsis (Boraginaceae: tribe Boragineae) was determined. Most of the species examined (c. 74%) produce sucrose-dominant nectar, whereas the remaining taxa produce sucrose-rich nectars. Little variation in nectar-sugar composition was found in some species, even when sampling was repeated in different years and/or localities. Average sucrose concentration was 57.75% (coefficient of variation 19.1%). The only floral morphological character that was correlated with the nectar-sugar profile is the length of the corolla tube, as taxa with relatively long floral tubes produce nectar with lower glucose concentrations. The flowering period is also related to sugar composition, as nectar of late-flowering species contains lower sucrose concentrations. However, small differences in sugar profiles do not reflect phylogenetic relationships based on molecular studies. It would appear that dry habitats and time of flowering are the main determinants of nectar-sugar composition in the genus Anchusa sensu lato. (C) 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 162, 616-627
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
Floristic richness and phytogeography of the “Torrente Trasubbie” nature reserve in southern Tuscany (Italy)
No full textSystematics, phylogenetic relationships and conservation of the taxa of Anchusa (Boraginaceae) endemic to Sardinia (Italy)
No full textSardinia is a major centre of diversity of Anchusa, but the systematics,
phylogenetic relationships and conservation status of the taxa endemic to the island
are still poorly known mainly because of their remarkable rarity. We present a
study on these endemics based on the results of field research focusing on the
distribution, the number and size of the populations, the characteristics of the habitat
and the factors of threat. Combined with observations on aspects of reproductive
biology, on wild populations and cultivated plants, we evaluate the conservation
status of the taxa and propose Red List IUCN categories of vulnerability. Original
descriptions, nomenclatural types and karyological data are added. The following
Anchusa taxa are endemic to Sardinia: A. capellii, A. crispa ssp. crispa, A. crispa
ssp. maritima, A. formosa, A. littorea, A. sardoa and A. montelinasana sp. nov. The
latter is described, based on the discovery of a morphologically distinct entity on
a mountain in southwest Sardinia. Anchusa littorea was found at a single site after
c. 25 years fromthe last record and 7 years ofunsuccessfulfield research; this species
is at the brink of extinction due to the extremely reduced size of the only remaining
population. Our complete collection of taxa allowed an analysis of phylogenetic
relationships based on DNA sequences from the ITS1 ribosomal genome. In spite of
the low variation, this marker produced Maximum Parsimony and Neighbour-Joining
phylograms suggesting that the group is monophyletic and that the split between
the two clades of the mountain and coastal endemics has been a key evolutionary
event. We assume the three mountain species to be relict schizoendemics ancestral
to the coastal taxa, and the Paleozoic siliceous massifs of central and south Sardinia
as the centre of origin of the group
Seismic performance of an existing RC structure retrofitted with buckling restrained braces
Full text linkThe use of buckling restrained braces (BRBs) represents one of the best solutions for retrofitting or upgrading the numerous existing reinforced concrete framed buildings in areas with a high seismic hazard. This study investigates the effectiveness of BRBs for the seismic retrofit of reinforced concrete (RC) buildings with masonry infills. For this purpose, an advanced non-linear three-dimensional model of an existing building in L'Aquila is developed in OpenSees, by accounting for the effect of infill walls through an equivalent strut approach, and by using a recently developed hysteretic model for the BRBs. The seismic performance of the building before and after the retrofit with BRBs is evaluated by performing both non-linear static analyses and incremental dynamic analyses under a set of real ground motion records along the weak direction of the frame. Seismic demand hazard curves are built for different response parameters before and after the retrofit, by accounting for and by disregarding the contribution of the infill walls. The study results shed light on the effect of the BRBs and of the infill walls on the seismic performance of the various components of the system, and on the effectiveness of the retrofit with BRBs for a real case study
Vascular flora of natural reserve Poggio all'Olmo (Cinigiano, Grosseto) [Flora vascolare della Riserva Naturale di Poggio all'Olmo (Cinigiano, Grosseto)]
No full textVengono riportati i risultati dell’indagine floristica effettuata durante gli anni 1998-2000 nella riserva naturale di Poggio al’Olmo (Cinigiano, Grosseto). L’area indagata si estende per 431 ha alla periferia dei borghi di Monticello Amiata e Castiglioncello Bandini. La flora consiste di 511 entità appartenenti a 75 famiglie. La ricchezza floristica del biotopo risulta piuttosto elevata ed è associata alla presenza di un fine mosaico di tipologie vegetazionali ecologicamente e strutturalmente distinte, determinato dall’interazione di fattori antropici e naturali. Dal punto di vista qualitativo, la flora di Poggio all’Olmo presenta alcuni elementi di notevole valore biologico e conservazionstico, rappresentati, oltre che dai taxa endemici, dalle specie rare, disgiunte o al limite dell’areale che in tale biotopo trovano rifugio. L’analisi delle componenti corologiche mette in evidenza la preponderanza di specie a gravitazione continentale (44% circa), accanto ad una cospicua componente euri-mediterranea a conferma della posizione di transizione dell’area indagata fra il dominio centroeuropeo, e quello mediterraneo. Dallo spettro biologico emerge che le emicriptofite (41,9%) sono le più rappresentate e largamente prevalenti sulle terofite (31,1%), in linea con quanto riscontrato in generale per la flora della Toscana e per gran parte del territorio italiano. Allo stato attuale i pascoli risultano la tipologia con il maggior numero di specie e il maggior numero di emergenze floristiche ma sono anche gli habitat a maggior rischio di scomparsa, si auspicano pertanto opportuni interventi per evitare l’evoluzione di queste cenosi verso formazioni boschive
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