COMPARISON OF DUNE HABITATS OF NORTH MEDITERRANEAN COASTS - TUSCANY (IT) WITH THOSE OF BLACK SEA COASTS -DOBROGEA (RO, BG): SIMILARITIES AND DIFFERENCES

Data related to the floristic and phytocoenotic features of dune areas located in two European coastal areas are reported. These areas are very different by the biogeographical point of view: the coast of Tuscany (Italy, Mediterranean Region, Italo-Thyrrenian province), and the coast of Dobrogea, a cross-border coastal strip between Romania and Bulgaria on the Black Sea (Eurosiberian Region, Escitian province). Both coasts are about 300 km long, and include main habitats (sensu Directive 92/43/EEC) of European coastal dune environments (habitats 1210, 2110, 2120, 2130, 2160, 2210, 2230, 2240, 2250) (Tab. 1). Some habitats have been identified exclusively in a specific geographical area (H2210, H2230, H2240, H2250 only in Tuscan coast (T), H2130, H2160 only in Dobrogea (D), some common to both (H1210, H2110, H2120) (Fig.1) (1, 2). A gradual increase of stenomediterranean species (Tuscany) or eurimediterranean species (Dobrogea) proceeding from north to south was found; as well as a high floristic diversity between the two compared bioregions even within the same habitats. Finally the floristic difference tends to increase from foredune habitats to fixed dunes. This is related mainly to phytoclimatic, phytogeographical, ecological and geomorphological factors. In both study areas a discontinue presence of some foredune habitats (eg. H1210, H2110, H2120) due to anthropic alterations was found

Survival, extinction and approximation of discrete-time branching random walks

We consider a general discrete-time branching random walk on a countable set X. We relate local, strong local and global survival with suitable inequalities involving the first-moment matrix M of the process. In particular we prove that, while the local behavior is characterized by M, the global behavior cannot be completely described in terms of properties involving M alone. Moreover we show that locally surviving branching random walks can be approximated by sequences of spatially confined and stochastically dominated branching random walks which eventually survive locally if the (possibly finite) state space is large enough. An analogous result can be achieved by approximating a branching random walk by a sequence of multitype contact processes and allowing a sufficiently large number of particles per site. We compare these results with the ones obtained in the continuous-time case and we give some examples and counterexamples.Comment: 32 pages, a few misprints have been correcte

VEGETATION LANDSCAPE MANAGEMENT OF “NATURAL RESERVE OF CHIARONE”, MASSACIUCCOLI LAKE BASIN (TUSCANY, IT)

The Massaciuccoli Lake is located in NW of Tuscany (Italy) (43°50’N 10°19’E) and it is integral part of the Regional Park of San Rossore, Migliarino and Massaciuccoli. This endorheic lake and the surrounding marshlands, with over 2,000 hectares of surface, form the largest retrodunal wetland of Tuscany. Over the last century this ecological system has undergone profound changes both because of land drainage, both because of the industrial and agricultural development of the surrounding areas that have heavily polluted lake, whose waters are still affected by serious eutrophication and ecological degradation. In order to preserve the great natural value of the lake in 1979, with the birth of the regional protected area, was established in the marshy area around the village of Massaciuccoli, the "Natural Reserve of Chiarone"(100 ha). Since 1985 the association LIPU (Italian League for Bird Protection) has obtained the management of the reserve, and its activity is directed to purposes of environmental education, environmental restoration, monitoring and conservation of specific habitats. This report shows the results of several years of investigation on the main vegetational types and their diachronic tranformations, the presence and distribution of endemic/rare/protected species, the changes on the structure of floating islands of peats and the main actions of conservation and management of these wetlands. The vegetation landscape is mainly formed by a mosaic of Phragmitetum australis Gams 1927, Cladietum marisci (Allorge 1922) Zobrist 1935, Typhetum angustifoliae Pignatti 1953, Myriophyllo-Nupharetum Koch 1926, and a large spread of microwoods of hygrophilous phanerophytes as Alnus glutinosa, Frangula alnus, Salix sp.pl. A particular aspect of this lake environment are the "aggallati", floating islands of peat incurred by intertwining rhizomes of straws. Above these peatlands often develop communities of Sphagnum sp.pl, Osmunda regalis L. and Thelypteris palustris Schott (Fig.1). The monitoring of these environments has highlighted the importance of ongoing management, in relation to the maintenance of certain habitats, through periodic cuttings, such as Sphagnum bogs, the control of exotic fauna such as Myocastor coypus, particularly damaging for Cladietum meadows and the special maintenance of the islands, whose structural peculiarity has lately been severely damaged catastrophic weather event

Statistical atmospheric downscaling for rainfall estimation in Kyushu Island, Japan

International audienceThe present paper develops linear regression models based on singular value decomposition (SVD) with the aim of downscaling atmospheric variables statistically to estimate average rainfall in the Chikugo River Basin, Kyushu Island, southern Japan, on a 12-hour basis. Models were designed to take only significantly correlated areas into account in the downscaling procedure. By using particularly precipitable water in combination with wind speeds at 850 hPa, correlation coefficients between observed and estimated precipitation exceeding 0.8 were reached. The correlations exhibited a seasonal variation with higher values during autumn and winter than during spring and summer. The SVD analysis preceding the model development highlighted three important features of the rainfall regime in southern Japan: (1) the so-called Bai-u front which is responsible for the majority of summer rainfall, (2) the strong circulation pattern associated with autumn rainfall, and (3) the strong influence of orographic lifting creating a pronounced east-west gradient across Kyushu Island. Results confirm the feasibility of establishing meaningful statistical relationships between atmospheric state and basin rainfall even at time scales of less than one day. Keywords: atmospheric downscaling, precipitation, rainfall, singular value decomposition, southern Japa

Survival of branching random walks in random environment

We study survival of nearest-neighbour branching random walks in random environment (BRWRE) on ${\mathbb Z}$. A priori there are three different regimes of survival: global survival, local survival, and strong local survival. We show that local and strong local survival regimes coincide for BRWRE and that they can be characterized with the spectral radius of the first moment matrix of the process. These results are generalizations of the classification of BRWRE in recurrent and transient regimes. Our main result is a characterization of global survival that is given in terms of Lyapunov exponents of an infinite product of i.i.d. $2\times 2$ random matrices.Comment: 17 pages; to appear in Journal of Theoretical Probabilit

Modelli digitali 3D per documentare, conoscere ed analizzare l’architettura e la costruzione nel mondo antico: l’esempio della Sala Ottagonale delle Piccole Terme di Villa Adriana

For its unique features and size, the Hadrian’s Villa site has always been the object of studies and investigations. Italian and foreign institutions, as well as research organizations, are working together with the common purpose of understanding and protecting the universally recognized ensemble of buildings and works of art, belonging to the World Heritage List since 1999. Within this interdisciplinary framework, over the past decade, new technologies for digital documentation in the field of cultural heritage have gained more importance with respect to the traditional field of architectural/archaeological surveying. Through expeditious surveying (with no physical contact with the object and different measurement resolutions) several 3D reality-based models were created in the last years, with special regards to the Villa’s pavilions characterized by more complex and daring shapes. The aim was a better understanding of specific problems in those cases where archaeological investigation methods may take advantage of a correct and complete digital surveying of elevations in general and in particular of vaulted spaces, intrados and extrados surfaces. 3D digital models of complex roofing, as shown in the case study of the Small Baths, provide additional advantages concerning the use of finite elements analysis (FEA). Both the digital models (current state of conservation and reconstruction hypothesis) underwent to an accurate stress analysis that enables further achievements for site conservation and management and for ancient constructive and designing techniques

Random walks on combs

We develop techniques to obtain rigorous bounds on the behaviour of random walks on combs. Using these bounds we calculate exactly the spectral dimension of random combs with infinite teeth at random positions or teeth with random but finite length. We also calculate exactly the spectral dimension of some fixed non-translationally invariant combs. We relate the spectral dimension to the critical exponent of the mass of the two-point function for random walks on random combs, and compute mean displacements as a function of walk duration. We prove that the mean first passage time is generally infinite for combs with anomalous spectral dimension.Comment: 42 pages, 4 figure

Random walks on graphs: ideas, techniques and results

Random walks on graphs are widely used in all sciences to describe a great variety of phenomena where dynamical random processes are affected by topology. In recent years, relevant mathematical results have been obtained in this field, and new ideas have been introduced, which can be fruitfully extended to different areas and disciplines. Here we aim at giving a brief but comprehensive perspective of these progresses, with a particular emphasis on physical aspects.Comment: LateX file, 34 pages, 13 jpeg figures, Topical Revie

The Relationships between Tropical Pacific and Atlantic SST and Northeast Brazil Monthly Precipitation

ABSTRACT The monthly patterns of northeast Brazil (NEB) precipitation are analyzed in relation to sea surface temperature (SST) in the tropical Pacific and Atlantic Oceans, using singular value decomposition. It is found that the relationships between precipitation and SST in both basins vary considerably throughout the rainy season (February-May). In January, equatorial Pacific SST is weakly correlated with precipitation in small areas of southern NEB, but Atlantic SST shows no significant correlation with regional precipitation. In February, Pacific SST is not well related to precipitation, but south equatorial Atlantic SST is positively correlated with precipitation over the northern Nordeste, the latter most likely reflecting an anomalously early (or late) southward migration of the ITCZ precipitation zone. During March, equatorial Pacific SST is negatively correlated with Nordeste precipitation, but no consistent relationship between precipitation and Atlantic SST is found. Time-lagged analyses show the potential for forecasting either seasonal mean or monthly precipitation patterns with some degree of skill. In some instances, individual monthly mean SST versus seasonal mean (FebruaryMay) precipitation relationships differ considerably from the corresponding monthly SST versus monthly precipitation relationships. It is argued that the seasonal mean relationships result from the relatively strong monthly relationships toward the end of the season, combined with the considerable persistence of SST in both oceans