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141.
Giuseppina Pardi Luigi Piazzi David Balata Ilaria Papi Francesco Cinelli & Lisandro Benedetti-Cecchi 《Marine Ecology》2006,27(4):397-403
This paper investigates patterns of variability in epiphytes of Posidonia oceanica leaves at various spatial scales around Sicily, including geographical differences among the Mediterranean basins, differences between the small islands and mainland, and the variability among and within replicated meadows in each of the previous conditions. Data on percentage cover of the most common epiphytic organisms were analysed by univariate techniques. Encrusting red algae, encrusting brown algae, filamentous algae, encrusting bryozoans, erect bryozoans, hydroids and Foraminifera were the most abundant taxa. Significant differences in the abundance of taxa were detected among geographical regions, while no significant differences were found between the islands and mainland. At smaller scales, variability was concentrated mostly among leaves 100s of centimetres apart and among meadows a few kilometres apart. These results suggest that both geographical and local processes are important in structuring the epiphytes of P. oceanica leaves in this area of the Mediterranean. 相似文献
142.
Comparison of wind and wave measurements and models in the Western Mediterranean Sea 总被引:2,自引:0,他引:2
Fabrice Ardhuin Luciana Bertotti Jean-Raymond Bidlot Luigi Cavaleri Valentina Filipetto Jean-Michel Lefevre Paul Wittmann 《Ocean Engineering》2007,34(3-4):526-541
We have hindcast the wind and wave conditions in the Mediterranean Sea for two one month periods. Four different meteorological models and three different wave models have been used. The results have been compared with satellite and buoy wind and wave observations.Several conclusions concerning both the instruments and the models have been derived. The quality of both wind and wave results has been assessed. Close to the coasts high resolution, nested wave models are required for sufficient reliability.A wave threshold analysis suggests a sufficient reliability only off the coast, with a substantial decrease for low wave heights. 相似文献
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Dr. Luigi Accardi 《Pure and Applied Geophysics》1952,22(1-2):84-88
Riassunto Viene fatta la descrizione di un nuovo sensibile apparecchio registratore per la misura del campo elettrico atmosferico che offre la possibilità di una registrazione differenziata dei campi positivi e negativi. Vengono presentate inoltre alcune registrazioni di campo elettrico atmosferico nelle più varie condizioni, ottenute col discritto apparecchio nell'Istituto di Fisica Terrestre dell'Università di Napoli.
Summary The Author describes a new highly sensitive recording instrument for the measurement of the atmospheric electric field, which enables a separated registration of the plus and minus fields. Furthermore the author presents some registrations of the atmospheric electric field obtained in the most various conditions at the Institute for terrestrial physics of the University of Naples.相似文献
145.
Remnants of a fossil continent–ocean transition similar to that of the modern non-volcanic continental margins are preserved in the Jurassic External Liguride units. They consist of fertile lherzolites of subcontinental origin, MOR-type basalts and rare gabbroic intrusives, together with continental crust bodies exhumed during the rifting phases preceding the oceanization. The gabbroic rocks include troctolites, (olivine) gabbros, Fe–Ti oxide-bearing gabbros and diorites. Trace element and Nd isotope compositions indicate that these rocks were derived from N-MORB melts variably evolved through fractional crystallisation. In the gabbroic rocks, high-temperature ( 900 °C) shearing along ductile shear zones is locally overprinted by amphibolite-facies recrystallization (T 650 °C), which was most likely assisted by seawater-derived fluids. Basalts crop out as lava flows and as dykes crosscutting mantle lherzolites and gabbroic rocks. They display nearly flat REE patterns and high Y/Nb values (5–14), similar to modern N-MORB. Basalts are also characterised by weak Zr enrichment relative to neighbouring REE (Zr/Zr = 1.1–1.7) and high (Sm/Yb)DM ratios (1.5–1.8). Their Nd isotope compositions are close to typical depleted mantle (initial Nd = +7.6 to + 9.4). The geochemical features of parental melts of basaltic and gabbroic rocks may be attributed to melting of a MORB-type asthenospheric source. Trace element modelling shows that low-degree (≤ 6%) fractional melting of a depleted spinel peridotite cannot account for the elevated Sm/Yb ratios of basalts. Low-degree melting of a mixed source of spinel peridotite with small amounts of garnet pyroxenite has been proposed to explain the trace element signature of basalts. 相似文献
146.
This paper reviews the main studies dealing with epiphytes of both leaves and rhizomes of Posidonia oceanica, the main seagrass found in the Mediterranean Sea. A total of 660 epiphyte species has been recorded, including 430 on leaves and 437 on rhizomes. Of these, 205 are Rhodophyta, 59 Ochrophyta, 43 Chlorophyta, 78 Porifera, 82 Cnidaria, 19 Annelida, 155 Bryozoa and 19 Tunicata. The epiphyte assemblages demonstrate a gradient of dissimilarity from west to east, with the eastern area being the most unlike the others. The differences can be attributed mostly to rare species that differ amongst the Mediterranean regions. Many of the dominant taxa have been found in all meadows studied. Data concerning species composition, abundance, and patterns of spatial and temporal variability are summarized, and biotic and abiotic factors controlling the structure of assemblages are discussed. Responses of epiphyte assemblages to anthropogenic stressors, such as nutrient enrichment and biological invasions, are discussed in relation to the use of epiphytes as ecological indicators. 相似文献
147.
Rainfall thresholds for the possible landslide occurrence in Sicily (Southern Italy) based on the automatic reconstruction of rainfall events 总被引:1,自引:1,他引:0
Massimo Melillo Maria Teresa Brunetti Silvia Peruccacci Stefano Luigi Gariano Fausto Guzzetti 《Landslides》2016,13(1):165-172
Review of the literature on the reconstruction of the rainfall responsible for slope failures reveals that criteria for the identification of rainfall events are lacking or somewhat subjective. To overcome this problem, we developed an algorithm for the objective and reproducible reconstruction of rainfall events and of rainfall conditions responsible for landslides. The algorithm consists of three distinct modules for (i) the reconstruction of distinct rainfall events, in terms of duration (D, in h) and cumulated event rainfall (E, in mm), (ii) the identification of multiple ED rainfall conditions responsible for the documented landslides, and (iii) the definition of critical rainfall thresholds for possible landslide occurrences. The algorithm uses pre-defined parameters to account for different seasonal and climatic settings. We applied the algorithm in Sicily, southern Italy, using rainfall measurements obtained from a network of 169 rain gauges, and information on 229 rainfall-induced landslides occurred between July 2002 and December 2012. The algorithm identified 29,270 rainfall events and reconstructed 472 ED rainfall conditions as possible triggers of the observed landslides. The algorithm exploited the multiple rainfall conditions to define objective and reproducible empirical rainfall thresholds for the possible initiation of landslide in Sicily. The calculated thresholds may be implemented in an operational early warning system for shallow landslide forecasting. 相似文献
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