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Modelling biogeochemical cycles in forest ecosystems: a Bayesian approachBagnara, Maurizio <1985> 18 May 2015 (has links)
Forest models are tools for explaining and predicting the dynamics of forest ecosystems. They simulate forest behavior by integrating information on the underlying processes in trees, soil and atmosphere.
Bayesian calibration is the application of probability theory to parameter estimation. It is a method, applicable to all models, that quantifies output uncertainty and identifies key parameters and variables. This study aims at testing the Bayesian procedure for calibration to different types of forest models, to evaluate their performances and the uncertainties associated with them. In particular,we aimed at 1) applying a Bayesian framework to calibrate forest models and test their performances in different biomes and different environmental conditions, 2) identifying and solve structure-related issues in simple models, and 3) identifying the advantages of additional information made available when calibrating forest models with a Bayesian approach.
We applied the Bayesian framework to calibrate the Prelued model on eight Italian eddy-covariance sites in Chapter 2. The ability of Prelued to reproduce the estimated Gross Primary Productivity (GPP) was tested over contrasting natural vegetation types that represented a wide range of climatic and environmental conditions.
The issues related to Prelued's multiplicative structure were the main topic of Chapter 3: several different MCMC-based procedures were applied within a Bayesian framework to calibrate the model, and their performances were compared.
A more complex model was applied in Chapter 4, focusing on the application of the physiology-based model HYDRALL to the forest ecosystem of Lavarone (IT) to evaluate the importance of additional information in the calibration procedure and their impact on model performances, model uncertainties, and parameter estimation.
Overall, the Bayesian technique proved to be an excellent and versatile tool to successfully calibrate forest models of different structure and complexity, on different kind and number of variables and with a different number of parameters involved.
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Role of xanthophyll and water-water cycles in the protection of photosynthetic apparatus in Arbutus unedo and Arabidopsis thalianaZamboni, Alessandro <1978> 21 May 2007 (has links)
Photosynthetic organisms have sought out the delicate balance between
efficient light harvesting under limited irradiance and regulated energy
dissipation under excess irradiance. One of the protective mechanisms is the
thermal energy dissipation through the xanthophyll cycle that may
transform harmlessly the excitation energy into heat and thereby prevent the
formation of damaging active oxygen species (AOS). Violaxanthin deepoxidase
(VDE) converts violaxanthin (V) to antheraxanthin (A) and
zeaxanthin (Z) defending the photosynthetic apparatus from excess of light.
Another important biological pathway is the chloroplast water-water cycle,
which is referred to the electrons from water generated in PSII reducing
atmospheric O2 to water in PSI. This mechanism is active in the scavenging
of AOS, when electron transport is slowed down by the over-reduction of
NADPH pool.
The control of the VDE gene and the variations of a set of physiological
parameters, such as chlorophyll florescence and AOS content, have been
investigated in response to excess of light and drought condition using
Arabidopsis thaliana and Arbutus unedo.. Pigment analysis showed an
unambiguous relationship between xanthophyll de-epoxidation state
((A+Z)/(V+A+Z)) and VDE mRNA amount in not-irrigated plants.
Unexpectedly, gene expression is higher during the night when
xanthophylls are mostly epoxidated and VDE activity is supposed to be
very low than during the day.
The importance of the water-water cycle in protecting the chloroplasts from
light stress has been examined through Arabidopsis plant with a suppressed
expression of the key enzyme of the cycle: the thylakoid-attached
copper/zinc superoxide dismutase. The analysis revealed changes in
transcript expression during leaf development consistent with a signalling
role of AOS in plant defence responses but no difference was found any in photosynthesis efficiency or in AOS concentration after short-term
exposure to excess of light.
Environmental stresses such as drought may render previously optimal light
levels excessive. In these circumstances the intrinsic regulations of
photosynthetic electron transport like xanthophyll and water-water cycles
might modify metabolism and gene expression in order to deal with
increasing AOS.
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Novel techniques for the remote sensing of photosynthetic processesDayyoub, Ammar <1973> 12 April 2011 (has links)
Remote sensing (RS) techniques have evolved into an important instrument to investigate forest function. New methods based on the remote detection of leaf biochemistry and photosynthesis are being developed and applied in pilot studies from airborne and satellite platforms (PRI, solar-induced fluorescence; N and chlorophyll content).
Non-destructive monitoring methods, a direct application of RS studies, are also proving increasingly attractive for the determination of stress conditions or nutrient deficiencies not only in research but also in agronomy, horticulture and urban forestry (proximal RS).
In this work I will focus on some novel techniques recently developed for the estimation of photochemistry and photosynthetic rates based (i) on the proximal measurement of steady-state chlorophyll fluorescence yield, or (ii) the remote sensing of changes in hyperspectral leaf reflectance, associated to xanthophyll de-epoxydation and energy partitioning, which is closely coupled to leaf photochemistry and photosynthesis. I will also present and describe a mathematical model of leaf steady-state fluorescence and photosynthesis recently developed in our group. Two different species were used in the experiments: Arbutus unedo, a schlerophyllous Mediterranean species, and Populus euroamericana, a broad leaf deciduous tree widely used in plantation forestry.
Results show that ambient fluorescence could provide a useful tool for testing photosynthetic processes from a distance. These results confirm also the photosynthetic reflectance index (PRI) as an efficient remote sensing reflectance index estimating short-term changes in photochemical efficiency as well as long-term changes in leaf biochemistry.
The study also demonstrated that RS techniques could provide a fast and reliable method to estimate photosynthetic pigment content and total nitrogen, beside assessing the state of photochemical process in our plants’ leaves in the field. This could have important practical applications for the management of plant cultivation systems, for the estimation of the nutrient requirements of our plants for optimal growth.
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Evaluation of Microbial Contamination in Bivalve Mollusks: Epidemiology and DiagnosisGrodzki, Marco <1980> 20 April 2012 (has links)
Shellfish are filter-feeding organisms that can accumulate many bacteria and viruses. Considering that depuration procedures are not effective in removal of certain microorganisms, shellfish-borne diseases are frequent in many parts of the world, and their control must rely primarily on investigation of prevalence of human pathogens in shellfish and water environment. However, the diffusion of enteric viruses and Vibrio bacteria is not known in many geographical areas, for example in Sardinia, Italy.
A survey aimed at investigating the prevalence of Norovirus (NoV), hepatitis A virus (HAV), V. parahaemolyticus, V. cholerae and V. vulnificus was carried out, analyzing both local and imported purified, non-purified and retail shellfish from North Italy and Sardinia. Shellfish from both areas were found contaminated by NoVs, HAV and Vibrio, including retail and purified animals. Molecular analysis evidenced different NoV genogroups and genotypes, including bovine NoVs, as well as pathogenic Vibrio strains, underlining the risk for shellfish consumers.
However, also other approaches are needed to control the diffusion of shellfish-borne diseases.
It was originally thought that enteric viruses are passively accumulated by shellfish. Recently, it was proven that NoVs bind to specific carbohydrate ligands in oysters, and various NoV strains are characterized by a different bioaccumulation pattern. To deepen the knowledge on this argument, a study was carried out, analyzing bioaccumulation of up to 8 different NoV strains in four different species of shellfish. Different bioaccumulation patterns were observed for each shellfish species and NoV strain used, potentially important in setting up effective shellfish purification protocols.
Finally, a novel study of evaluation of viral contamination in shellfish from the French Atlantic coast was carried out following the passage of Xynthia tempest over Western Europe which caused massive destruction. Different enteric viruses were found over a one month period, evidencing the potential of these events of contaminating shellfish.
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New techniques for the remote sensing of foliar nitrogen concentration in forest ecosystems.Mezzini, Elena <1984> 09 April 2013 (has links)
During my Doctoral study I researched about the remote detection of canopy N concentration in forest stands, its potentials and problems, under many overlapping perspectives. The study consisted of three parts.
In S. Rossore 2000 dataset analysis, I tested regressions between N concentration and NIR reflectances derived from different sources (field samples, airborne and satellite sensors). The analysis was further expanded using a larger dataset acquired in year 2009 as part of a new campaign funded by the ESA.
In both cases, a good correlation was observed between Landsat NIR, using both TM (2009) and ETM+ (2000) imagery, and N concentration measured by a CHN elemental analyzer.
Concerning airborne sensors I did not obtain the same good results, mainly because of the large FOV of the two instruments, and to the anisotropy of vegetation reflectance. We also tested the relation between ground based ASD measures and nitrogen concentration, obtaining really good results. Thus, I decided to expand my study to the regional level, focusing only on field and satellite measures.
I analyzed a large dataset for the whole of Catalonia, Spain; MODIS imagery was used, in consideration of its spectral characteristics and despite its rather poor spatial resolution. Also in this case a regression between nitrogen concentration and reflectances was found, but not so good as in previous experiences. Moreover, vegetation type was found to play an important role in the observed relationship.
We concluded that MODIS is not the most suitable satellite sensor in realities like Italy and Catalonia, which present a patchy and inhomogeneous vegetation cover; so it could be utilized for the parameterization of eco-physiological and biogeochemical models, but not for really local nitrogen estimate. Thus multispectral sensors similar to Landsat Thematic Mapper, with better spatial resolution, could be the most appropriate sensors to estimate N concentration.
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Effects of N fertilization on forest trees and ecosystems: water use, WUE, growthZhang, Qiran <1982> 08 May 2014 (has links)
During my three academic years, I focused on the effects of N fertilization on growth and function
of plants and forest stands. The study had the dual objective of estimating the effects of atmospheric
N deposition and evaluating the potential management value of N fertilization itself. In particular,
the analysis took into account the changes induced in water use and intrinsic transpiration efficiency
(ITE), an aspect often overlooked in world literature but of great importance especially in
Mediterranean environment, where the positive effects of N fertilization may be denied by the
parallel increased transpiration and exacerbated water stress.
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Analisi degli effetti degli interventi agronomici all’impianto in un intervento di recupero ambientale di una cava di sabbie ed argille della collina bolognese: parametrizzazione e quantificazione dell’azoto. / Analysis of the effects of the initial agronomic management in an intervention of environmental restoration of a sandy-claily quarry located on the Bologna hills: Parametrization and nitrogen assesment.Almeida De Mendonca, Maria De Jesus <1977> 16 April 2012 (has links)
In questo lavoro sono state analizzate diverse strategie di recupero di una cava dismessa situata presso la località Colombara (Monte San Pietro, Bologna).
Su questi terreni sono state condotte tre prove, costituite da diverse parcelle nelle quali sono stati adottati differenti trattamenti. Sono state svolte analisi di tipo quantitativo del suolo e della parte epigea delle specie arbustive e arboree, focalizzandosi sull'azoto (N totale, ammoniacale, nitrico, e firma isotopica) e sulla sostanza organica del suolo. Inoltre è stata effettuata un'indagine qualitativa della composizione floristica. Scopo della tesi è quello di individuare le strategie più efficaci per un recupero di suoli degradati. Non sempre a trattamenti iniziali migliori corrispondono i migliori risultati portando a conclusioni apparentemente controintuitive a cui si è cercato di dare risposta. / In this work we have analyzed different restoration strategies of an abandoned quarry located at Colombara (Monte San Pietro, Bologna, Italy). On these surfaces we carried out three experiments,
based on manifold land parcels on which different agronomic treatments were applied.
On was conducted analyses of soil and of the aboveground plant biomass of shrub and tree species.
We focused on soil and leaf Nitrogen content and on the soil organic Carbon in order to evaluate the soil fertility. Moreover we carried out a qualitative analysis about the botany species composition. The main scope of this thesis was to find out the most suitable strategies to restore degraded soils. Just few times the best results correspond to better initial treatments. The latter brought to apparently counter intuitive conclusions to which we tried to find the causes.
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Flussi di carbonio in due sistemi arborei della pianura padanaPanzacchi, Pietro <1972> 29 April 2008 (has links)
No description available.
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Cost-Benefit Analysis Using GIS: an Application to the Forest Bioenergy sectorGrilli, Gianluca January 2017 (has links)
This doctoral thesis introduces a novel methodology to optimize the use of forest biomass for energy purposes at regional scale, by means of GIS applications and economic tools. The procedure calculates, at first, the energy potential of a given forested area, as well as a reasonable location and dimension of a district heating power plant, based on local energy availability and energy demand. In a second step, it runs a cost-benefit analysis (CBA) to assess the economic feasibility of the plant. The CBA considers financial costs and benefit, social benefits and environmental costs, estimated by means of market and non-market valuation techniques. Financial, social and environmental flows are combined to produce four different scenarios, for which the net present value is calculated. Afterwards, a probabilistic sensitivity analysis is carried out, to assess the stability of the results when different assumptions of input values are included. Such procedure have been tested in an Italian case study, the valleys of Gesso and Vermenagna in the Piedmont region. These alpine valleys are interesting, because forests are at present under-utilized. At the same time, the presence of the Alpi Maritime Natural Park provides constraints to the use of natural resources; for these reasons, a carefull planning of the activities is fundamental to assure sustainability. The GIS methodology has been developed in GRASS GIS and automatized in python, while econometric computations were carried out in R. This procedure may facilitate energy planning and increase the efficiency of the forest-timber-energy chain.
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Fine spatial scale modelling of Trentino past forest landscape and future change scenarios to study ecosystem services through the yearsGobbi, Stefano 09 December 2021 (has links)
Over recent decades, forest land cover is dramatically changing in European mountains and in the Alps in particular. Since the 1950s the progressive urbanization of the valleys and the abandonment of mountain and rural dwellers has intensified. More than 60% of the Trentino land, is covered by forest and mainly by high forest. This human migration have brought to a progressive shrinking of meadows and pastures due to the natural forest expansion causing a dramatic change in the landscape, the consequences of which affect biodiversity, social and cultural dynamics and landscape perception as well as ecosystem services. The objective of this research focused on the application and experimentation of advanced GIS and modeling techniques to compare aerial imagery, historical maps and data and remote sensed images to understand the past landscape changes and their dynamics in Trentino and to build future scenarios based on long-term set ofobservations. The research produced a fine scale dataset representing past forest landscape for the Trentino territory. The analysis of these output data revealed a progressive afforestation process which interested homogeneously all the Trentino territory. A future forest landscape scenarios at a detailed scale (10 m) was as well produced, to simulate the future of the forest in a protected area of Trentino, to outline if the afforestation process will continue. Along with these main output of the research, new tools for image processing and evaluation of forest changes were developed.
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