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561.
A Comparison Among Assemblages in Areas Invaded by Caulerpa taxifolia and C. racemosa on a Subtidal Mediterranean Rocky Bottom 总被引:1,自引:0,他引:1
Abstract. This study compares the structure of Mediterranean macroalgal assemblages invaded by Caulerpa taxifolia and C. racemosa . Assemblages in areas colonized by the two algae and in reference areas were sampled and analyzed for 2 years. Significant differences were recorded both between reference and invaded areas and between areas invaded by different Caulerpa species. Macroalgal assemblages colonized by C. racemosa were more separated from references than those colonized by C. taxifolia . Differences between assemblages colonized by C. racemosa and the others decreased during the alga's period of vegetative rest and increased at the last sampling date. While erect and turf species showed similar patterns in invaded areas, covers of encrusting algae were lower in C. racemosa areas than in C. taxifolia areas. 相似文献
562.
Fish Assemblages in Shallow Marine Caves of the Salento Peninsula (Southern Apulia, SE Italy) 总被引:1,自引:0,他引:1
Simona Bussotti Francesco Denitto Paolo Guidetti Genuario Belmonte 《Marine Ecology》2002,23(S1):11-20
Abstract. Fish assemblages of three shallow marine caves from the Salento Peninsula (Apulia, SE Italy) were investigated in July 2000. Data were collected in situ by using visual census. A total of nineteen fish species were recorded inside the caves. The species richness generally displayed a similar pattern in all three caves, decreasing from the entrance towards the innermost sections, whereas the patterns of total fish abundance differed among caves. Apogon imberbis (mainly represented by juveniles) was the most important species in terms of number of individuals (accounting for more than 85% of the censused fish) and showed a fairly even distribution inside the investigated caves. Without the numerical contribution of A. imberbis , fish abundance decreased from the entrance to the inner sections and this pattern was common to all three caves. Juvenile fishes of economic interest ( e. g., Diplodus vulgaris and Epinephelus marginatus ) were also recorded inside. The present study suggests that: (1) environmental constraints could affect distribution patterns in fish species richness and in the abundance of several fish along the axis of "blind caves" (with a single entrance), as already observed for sessile benthos and plankton assemblages; (2) shallow marine caves of the Salento Peninsula could exert the role of refuge and/or nursery for some littoral fish species during the adult and/or juvenile stages of their life histories. 相似文献
563.
David Balata Stefano Acunto Francesco Cinelli 《Estuarine, Coastal and Shelf Science》2006,67(4):553-561
Natural assemblages show large variability at multiple scales in space and time as a consequence of several abiotic and biological factors. This study was conducted in conditions of high turbidity of the water and examined the spatio-temporal variability and the vertical distribution at two different depths of a low rocky subtidal assemblage. Algal and invertebrate organisms were sampled at a range of spatial scales extending from meters to a few kilometers, over a period of 21 months. Results indicated that patterns of distribution and abundance of organisms differed between the two depths and at the smallest spatial scales examined. These differences were due to differences in relative abundance rather than differences in composition of taxa. Results showed that assemblages varied largely among dates of sampling, suggesting that temporal variability of these organisms may be more important than previously stated. The patchy distribution and the peculiar life traits of most taxa of these assemblages allowed the concept of metapopulation and metacommunity to be applied to this system. This might have implications for predictions of the responses of subtidal assemblages to environmental changes due to anthropogenic activities. 相似文献
564.
P. Prof. Francesco Saverio Zanon 《Pure and Applied Geophysics》1952,23(1):174-184
Riassunto L'anno 1951, climatologicamente, fu un anno straordinario. Ebbe temperatura moderatamente più elevata della normale, specialmente in Gennaio e Febbraio. Notevole in alcuni mesi l'abbondanza di pioggia. Le condizioni meteorologiche sono rispecchiate dalle date di fioritura, che anticipano o ritardano in corrispondenza non solo con le variazioni della temperatura, ma anche con le variazioni di piovosità e di intensità della radiazione solare.
Summary The year 1951 was climatologically an extraordinary year. It had a little higher temperature than normally, especially in January and February. In some months there was abundance of rainfall. The meteorological conditions are shown by the dates of flowering which are in advance or delayed in conformity not only with the variations of the temperature, but also with the variations of rainfall and of the intensity of the sun's radiation.相似文献
565.
Prof. Francesco Saverio Zanon 《Pure and Applied Geophysics》1948,12(5-6):200-209
Riassunto Ricordata la legge delle registrazioni a Venezia dei microsismi generati dai cicloni dell'Atlantico NE, e riportati fatti nuovi e nuovi studi che la confermano, trovate insufficienti altre spiegazioni del fenomeno, e introdotto il confronto con lePulsazioni della pressione atmosferica di periodo inferiore cd un'ora, ultimamente studiato dall'Autore, si propone per la spiegazione una nuovaipotesi da lavoro.
Summary After having remembered the law of registration at Venice of the microseisms produced by the cyclones of the Atlantic NE and related the new facts and new studies which confirm it, after having found insufficient other explanations of the phenomenon and introduced the comparison withthe pulsation of the atmospheric pressure of period inferior to one hour, studied by the author lately, as explanation, a new hypothesis of work is proposed.相似文献
566.
567.
568.
Impact of different regression frameworks on the estimation of the scaling properties of radar rainfall 总被引:1,自引:0,他引:1
Gabriele Villarini Joseph B. Lang Federico Lombardo Francesco Napolitano Fabio Russo Witold F. Krajewski 《Atmospheric Research》2007,86(3-4):340-349
Rainfall is characterized by high variability both in space and time. Despite continuous technological progress, the available instruments that are used to measure rainfall across several spatio-temporal scales remain inaccurate. To remedy this situation, scaling relationships of spatial rainfall offer the potential to link the observed or predicted precipitation quantities at one scale to those of interest at other scales. This paper focuses on the estimation of the spatial rainfall scaling functions. Standard scaling analysis constructed by means of the ordinary least squares method often violates such basic assumptions implicit in its use and interpretation as homoschedasticity, independence, and normality of the errors. Consequently, the authors consider alternative regression frameworks i.e. bootstrapping regression, semi parametric linear model, and multilevel normal linear model to show how these different approaches exert a significant impact on the multifractal analysis of radar rainfall. In addition, the uncertainties associated with the construction of the scaling function due solely to the regression procedure are quantified. The radar data come from the polarimetric C-band weather radar located in Rome, Italy, and the scaling properties are computed for a square domain centred on the radar site with a side length of 128 km and a finest resolution of 1 km2. 相似文献
569.
A fairly detailed structural model of the lithosphere-asthenosphere system (thickness, S- and P-wave velocities of the crust
and of the uppermost mantle layers) has been defined in the Calabrian Arc region (Southern Tyrrhenian Sea, Calabria and the
northwestern part of the Ionian Sea) in Southern Italy using seismic data from literature as a priori constraints of the nonlinear
inversion of surface-wave data.
The main features identified by this study are: (1) A very shallow (less then 10 km deep) crust-mantle transition in the Southern
Tyrrhenian Sea and a very low vs just below a very thin lid, in correspondence of the submarine volcanic bodies Magnaghi, Marsili and Vavilov, while the vs in the lid is quite high in the area that separates Marsili from Magnaghi-Vavilov; (2) a shallow and very low vs layer in the uppermost mantle in the areas of the Aeolian Islands, Vesuvius, Phlegraean Fields and Ischia, which represents
their shallow-mantle magma source; (3) a thickened continental crust and lithospheric doubling in Calabria; (4) a crust about
25-km thick and a mantle velocity profile versus depth consistent with the presence of a continental rifted lithosphere, now
thermally relaxed, in the investigated part of the Ionian Sea; (5) the subduction towards northwest of the Ionian lithosphere
below the Southern Tyrrhenian Sea; (6) the subduction of the Adriatic/Ionian lithosphere underneath the Vesuvius and Phlegraean
Fields. 相似文献
570.
Francesco Dramis Mohammed Umer Gilberto Calderoni Mitiku Haile 《Quaternary Research》2003,60(3):274-283
Stratigraphic analysis of alluvial/colluvial sequences and 14C dating have been used as proxies for Holocene climate changes in the highlands of Tigray (northern Ethiopia). The studied records show alternations of buried soils and peaty–clayey sediments, pointing to wet, stabilization phases, and organic-free colluvium layers resulting from the abrupt occurrence of dry-climate episodes. The 14C dates, mostly unpublished, cluster in the 11,090–9915, 9465–9135, 8450–7330, 6720–3635, 2710–2345, and 1265–790 cal yr B.P. time spans. Evidence of subsequent pedogenesis is lacking in the area, apart from a buried humified horizon dated at 300 ± 60 14C yr B.P. (460–295 cal yr B.P.). Both the timing and the pattern of Tigray paleoclimatic events fit the corresponding framework, based on lake level changes, previously implemented for the Main Rift Valley. These findings give further support for arguing that the forcing mechanisms of the wet/dry fluctuations during the Holocene were effective over a large scale. 相似文献