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READING THE SIGNATURES OF CHANGING ENVIRONMENTAL FORCINGS IN SALT-MARSH BIOGEOMORPHIC SYSTEMS
Get PDFThe question on whether actual tidal morphologies are in equilibrium with current environmental conditions or retain signatures of past climatic changes or human interventions is a classical and fascinating one, furthermore being of intellectual as well as practical interest. Understanding the dynamic response of tidal landscapes to past conditions is critical to predict their response to future environmental changes, such as rate of relative sea-level rise and sediment supply. This is an open and fundamentally important point, particularly in times of natural and anthropogenic changes, during which tidal environments are most exposed to possibly irreversible transformations with far-reaching socio-economic and ecological implications worldwide.
The proposed work aims at analyzing the signatures of changing environmental forcings imprinted in the landscape and in the sedimentary record of the Venice Lagoon to refine our knowledge of tidal landforms dynamics. The thesis is developed following a biogeomorphic approach to the study of salt-marsh landscapes. Marsh biomorphological evolution, in response to changes in the environmental forcings, is analyzed investigating the relative role and mutual interactions and adjustments between physical and biological processes shaping the salt-marsh landscape.
This thesis was carried out through a series of extensive temporal and spatial high-resolution morphological, sedimentological, geochronological and elemental analyses, aimed at exploring the main features of sub-surface marsh samples and lagoonal sediment cores.
The study of sub-surface marsh samples highlights the mutual role of inorganic and organic accretion on salt marshes, which is mainly driven by the inorganic component near the channels, while the organic component largely contributes in the inner-marsh portion. The analyses carried out on sediment cores refine the knowledge of the latest Holocene sedimentary succession of the Venice Lagoon, and furnish a chronostratigraphical model for the evolution over the last two millennia. In particular, for a salt-marsh succession, the analyses highlight the occurrence of a delayed marsh-dynamic response to changing sediment delivery rates
Changes in the wind‐wave field and related salt‐marsh lateral erosion: inferences from the evolution of the Venice Lagoon in the last four centuries
No full textSalt marshes are crucially important ecosystems at the boundary between the land and the sea, that are experiencing
significant losses worldwide mainly dictated by the erosion of their margins. Improving our understanding of the mechanisms controlling
marsh edge erosion is a key step to address conservation issues and salt-marsh response to changes in the environmental forcing.
Here we have employed a complete, coupledWind-Wave Tidal Model (WWTM) to analyse the temporal evolution of the wave field,
and in particular of the mean wave-power density, in the Venice Lagoon over the past four centuries (from 1611 to 2012). We have
then related wave-field changes to the observed erosion patterns determined by comparing recent aerial photographs (1978–2010)
and historical bathymetric data. The results of our analyses from the Venice Lagoon show that, while wave-fields did not significantly
change from 1611 to 1901, a rapid increase in wave-power densities occurred in the last century. This is suggested to depend on the
positive feedback between relevant morphological evolutions and changes in the wave field, both influenced by natural forcing and
anthropogenic pressures.We also emphasize the existence of a strong positive linear relationship between the volumetric marsh erosion
rate and mean wave-power density. We thus suggest that relating salt-marsh lateral erosion rates to properly computed mean
wave-power densities provides a valuable tool to address long-term tidal morphodynamics
Aggradation and lateral migration shaping geometry of a tidal point bar: an example from salt marshes of the Northern Venice Lagoon (Italy).
No full textOn the mutual role of salt-marsh inorganic and organic deposition in the Venice Lagoon (Italy)
No full textFluvial response to tectonic deformation: the Ambra Plio-Pleistocene incised-valley deposits (Tuscany, Italy)
No full textLatest Holocene depositional history of the southern Venice Lagoon, Italy
No full text Analyzing the signatures of landscape changes in the stratigraphic record is crucial to refine our knowledge of tidal landform dynamics and represents a first step toward the development of predictive morphodynamic models. The southern Venice Lagoon (Italy) is particularly suited to analyze modifications in the depositional environment and, consequently, in the sedimentary record because of the remarkable changes that occurred in the last centuries. We collected 25 cores along a NE–SW linear transect about 5 km long cutting through salt marshes, tidal flats, and subtidal platforms. High-resolution sedimentological analyses defined the spatial arrangement of four deposits along the transect (palustrine, salt marsh, lag, and tidal-flat/subtidal-platform deposits), whose cores were dated through radiocarbon, 210Pb, and 137Cs geochronological analyses. The study succession testifies an evolution from a palustrine freshwater environment to a lagoonal environment over the last 2000 years. The palustrine peat progressively evolved into salt marshes in the 14th century. Salt-marsh aggradation is characterized by different accretion rates over time and occurred in parallel with the decrease in the salt-marsh extent and tidal-flat expansion. Where salt-marsh deposits were locally flooded and impacted by wind waves, a lag deposit developed. As a consequence of the progressive water deepening, organic-rich mud accumulated above the lag. The results, as well as providing the first accretion model for the latest Holocene succession in the southern Venice Lagoon, highlight that the disappearance of salt marshes in this area has to be ascribed to the lateral erosion of their margins, rather than to their progressive drowning. </jats:p
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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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