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| Registros recuperados: 152 | |
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| Perruche, Coralie; Riviere, Pascal; Pondaven, Philippe; Carton, Xavier. |
| This paper aims at studying analytically the functioning of a very simple ecosystem model with two phytoplankton species. First, using the dynamical system theory, we determine its nonlinear equilibria, their stability and characteristic timescales with a focus on phytoplankton competition. Particular attention is paid to the model sensitivity to parameter change. Then, the influence of vertical mixing and sinking of detritus on the vertically-distributed ecosystem model is investigated. The analytical results reveal a high diversity of ecosystem structures with fixed points and limit cycles that are mainly sensitive to variations of light intensity and total amount of nitrogen matter. The sensitivity to other parameters such as remineralisation, growth... |
| Tipo: Text |
Palavras-chave: Water mixing; Dynamical system; Phytoplankton; Competition; Ecosystem; Modelling. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/2009/publication-7334.pdf |
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| Witzke, Heinz Peter; Britz, Wolfgang. |
| In the context of a long run agricultural outlook on behalf of the European Environmental Agency a new methodology has been developed to systematically integrate external forecasts into a quite detailed agricultural sector model. External forecasts usually provide estimates for the exogenous variables in modelling work and frequently they are also used for comparisons and potential reassessment of empirical specifications. The innovative characteristic of this study is that expert forecasts have been used to specify parameter changes expressing structural change affecting behavioural functions. The outlook was therefore set up as a simultaneous estimation and forecasting effort which permitted to integrate various, usually contradictory expert forecasts... |
| Tipo: Conference Paper or Presentation |
Palavras-chave: Agricultural outlook; Forecasting; Modelling; Expert information; Agricultural and Food Policy; C15; C53; Q11; Q19; Q21. |
| Ano: 2005 |
URL: http://purl.umn.edu/24666 |
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| Peters,Jan; Wieme,Vanessa; Boeckx,Pascal; Samson,Roeland; Godoy,Roberto; Oyarzún,Carlos; Verhoest,Niko. |
| Ecohydrology investigates how hydrological processes affect plant growth and vice versa. As these mutual interactions are important in many ecosystems, ecohydrology has wide applicability. An important aspect of ecohydrological research is the assessment and prediction of the occurrence of plant species or vegetation types in relation to hydrological or hydrogeochemical habitat conditions. Several models have been developed (e.g. DEMNAT, ICHORS, ITORS, ITORS-VL). All of these models are data driven. Consequently a monitoring network has to be installed, possibly in addition to existing databases. These networks are ecosystem specific but the most widely monitored variables are: water table depth, electric conductivity of groundwater, soil moisture content... |
| Tipo: Journal article |
Palavras-chave: Ecohydrology; Modelling; Vegetation; Hydrology; Decision support systems. |
| Ano: 2005 |
URL: http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-66432005000200007 |
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| Pereira,André Belmont; Villa Nova,Nilson Augusto; Ramos,Valdir Josué; Pereira,Antonio Roberto. |
| There is currently a great deal of interest in estimating crop productivity as a function of climatic elements by means of different crop weather models. An agrometeorological model is presented based on carbon dioxide assimilation maximum rates for C3 plants, fraction of photosynthetically active radiation, air temperature, photoperiod duration, and crop parameters under tropical climate conditions. Such crop parameters include leaf area and harvest indexes, dry matter content of potato tubers, and crop cycles to estimate potato potential yields. Field data from observed productivity obtained with the cultivar Itararé (IAC-5986), grown under adequate soil water supply conditions at four different regions in the State of São Paulo (Itararé, Piracicaba,... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Modelling; Solanum tuberosum L.; Climatic elements; Crop indexes; Yield. |
| Ano: 2008 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052008000200008 |
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| Sultan, Nabil; Voisset, Michel; Marsset, Bruno; Marsset, Tania; Cauquil, E; Colliat, J. |
| The study area, offshore Nigeria, is located in one of the compressional zones within the Niger Delta, which is characterized by imbricate thrust structures. Although the low mean slope angle (around 2°), bathymetry data from the study area have shown the existence of several submarine landslides which coincide with known subsurface faulted compressive features. In this paper, we have focused on a submarine slide occurring in water depths ranging between 1690 and 1750 m. Headwall scars, internal architecture and associated deposits have been characterized using a combination of 3D seismic data, near-bottom echosounder seismic profiles, Kullenberg cores and in-situ geotechnical measurements. The slide shows horseshoe shaped headwall scars and depositional... |
| Tipo: Text |
Palavras-chave: Slope stability; Piezometer; Penetrometer; Niger Delta; Modelling; Compressional structures. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2408.pdf |
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| Nkakini, Silas Ovua; Douglas, I. E.. |
| In this study, a comparative evaluation of tractive force models for disc harrowing, at different tillage speeds was carried out in order to determine optimal tillage speeds. The predictive models were developed using dimensional analysis. The tillage operation in a loamy sand soil, at tillage speeds of 1.94 m s-1, 2.22 m s-1 and 2.5 m s-1 respectively was conducted, using trace tractor techniques. Parameters such as drawbar pull, rolling resistance, wheel slip, moisture content, cone index, wheel numeric, contact pressure, speed, width of harrow, depth of harrow, and tractive force were measured. The developed mathematical models describing the tractors tyre-soil interactions parameters were evaluated using sensitivity analysis of the measured... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Predictive; Tractive force; Disc harrowing; Tillage; Loamy; Sand; Soil; Modelling; Sensitivity measurement; Soil moisture.. |
| Ano: 2013 |
URL: http://www.cigrjournal.org/index.php/Ejounral/article/view/2374 |
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| Evans, Matthew R.; Bithell, Mike; Cornell, Stephen J.; Dall, Sasha R. X.; Diaz, Sandra; Emmott, Stephen; Ernande, Bruno; Grimm, Volker; Hodgson, David J.; Lewis, Simon L.; Mace, Georgina M.; Morecroft, Michael; Moustakas, Aristides; Murphy, Eugene; Newbold, Tim; Norris, K. J.; Petchey, Owen; Smith, Matthew; Travis, Justin M. J.; Benton, Tim G.. |
| Human societies, and their well-being, depend to a significant extent on the state of the ecosystems that surround them. These ecosystems are changing rapidly usually in response to anthropogenic changes in the environment. To determine the likely impact of environmental change on ecosystems and the best ways to manage them, it would be desirable to be able to predict their future states. We present a proposal to develop the paradigm of predictive systems ecology, explicitly to understand and predict the properties and behaviour of ecological systems. We discuss the necessary and desirable features of predictive systems ecology models. There are places where predictive systems ecology is already being practised and we summarize a range of terrestrial and... |
| Tipo: Text |
Palavras-chave: Modelling; Systems ecology; Climate change; Ecosystem assessment. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00177/28816/27291.pdf |
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| Lasserre, Pierre. |
| Coordinated ECOTRON Program on the Arcachon Basin (Aquitaine, France) : Control of marine biological production in a man-modified lagoon ecosystem (fish ponds). Results, synthesis and prospects. The "fish reservoirs" of the Arcachon Basin consist of eutrophic lagoon ecosystems, empirically exploited for extensive amphihaline fish culture (grey mullets, sea bass, eels, sea breams). The 1000 hectares of exploited farms, well integrated in a traditional socio-economic context, are presently not adapted for various reasons.The coordinate researches, which have been developed at Arcachon since 1974, within the ECOTRON (CNEXO) Program, show that these highly productive man modified ecosystems are well adapted for the development of semi-intensive aquaculture.... |
| Tipo: Text |
Palavras-chave: Lagunes côtières exploitées; Réservoirs à poissons; Bassin d'Arcachon; Fonctionnement écosystème; Contrôle productivité; Modélisation; Développement potentiel; Exploited coastal lagoons; Fish ponds; Arcachon Bay; Ecosystem functioning; Productivity control; Modelling; Potential development. |
| Ano: 1979 |
URL: http://archimer.ifremer.fr/doc/00306/41676/40885.pdf |
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| Peck, Myron A.; Arvanitidis, Christos; Butenschon, Momme; Canu, Donata Melaku; Chatzinikolaou, Eva; Cucco, Andrea; Domenici, Paolo; Fernandes, Jose A.; Gasche, Loic; Huebert, Klaus B.; Hufnagl, Marc; Jones, Miranda C.; Kempf, Alexander; Keyl, Friedemann; Maar, Marie; Mahevas, Stephanie; Marchal, Paul; Nicolas, Delphine; Pinnegar, John K.; Rivot, Etienne; Rochette, Sebastien; Sell, Anne F.; Sinerchia, Matteo; Solidoro, Cosimo; Somerfield, Paul J.; Teal, Lorna R.; Travers-trolet, Morgane; Van De Wolfshaar, Karen E.. |
| We review and compare four broad categories of spatially-explicit modelling approaches currently used to understand and project changes in the distribution and productivity of living marine resources including: 1) statistical species distribution models, 2) physiology-based, biophysical models of single life stages or the whole life cycle of species, 3) food web models, and 4) end-to-end models. Single pressures are rare and, in the future, models must be able to examine multiple factors affecting living marine resources such as interactions between: i) climate-driven changes in temperature regimes and acidification, ii) reductions in water quality due to eutrophication, iii) the introduction of alien invasive species, and/or iv) (over-)exploitation by... |
| Tipo: Text |
Palavras-chave: Distribution; Modelling; Habitat; Resources; Man-induced effects. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00337/44845/44436.pdf |
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| Bergmann, Holger; Thomson, Kenneth J.. |
| A modified version of a system dynamics model constructed for an EU-wide case-study project (TOP-MARD) using STELLA software was used to simulate the effects of a number of development scenarios for a remote rural area in Northern Scotland, i.e. Caithness & Sutherland, which is characterised by a high regional importance of agriculture for the local economy. In this paper, the context of the modelling work in policy and socio-economic terms is first described. This is followed by the specification of the model and of the several modelling scenarios, which relate to the reconfiguration of Pillar 2 spending within the area and an reversal of recent Structural Funds spending for 2007 onwards. The modelling results are discussed, in terms of regional... |
| Tipo: Conference Paper or Presentation |
Palavras-chave: Modelling; Input-output; Systems dynamics; Rural viability; Marketing. |
| Ano: 2008 |
URL: http://purl.umn.edu/52645 |
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| OLIVEIRA,LAIO Z.; KLITZKE,ALINE R.; FANTINI,ALFREDO C.; ULLER,HEITOR F.; CORREIA,JEAN; VIBRANS,ALEXANDER C.. |
| Abstract The majority of Atlantic Forest fragments in Southern Brazil are second-growth forests dominated by fast-growing species with considerable market-value timber. Nevertheless, volume prediction models are scarce, especially to estimate tree total volume (i.e., stem plus branches). This study approached the issue through the following aims: to fit and select stem and total volume models (generic and species-specific) using data from 288 harvested trees in a management operation, and to fit generic and species-specific bark factors. The power model embedding diameter at breast height (D) and tree stem or total height (H) presented the greatest prediction strength for both stem and total tree volume. Models including only D to predict total tree volume... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Forest inventory; Mata Atlântica; Modelling; Regression. |
| Ano: 2018 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652018000703729 |
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| Graham, Phil; White, A.. |
| Difficult seasonal conditions during the last six years have placed many farms under significant financial pressure. Producers have been looking for enterprise changes which will quickly improve their profits. New breeds have increased the options available, but there is rarely any local production data for them. Information in the media has done little more than create confusion about the true differences between sheep enterprises. Modelling allows this complex question to be looked at in a logical fashion and combines production and financial factors in the comparison. GrassGro® was used at two locations in southern NSW, Yass and Cowra, for the period 1960 to 2007. The results indicated that no enterprise performed consistently better based on profit per... |
| Tipo: Article |
Palavras-chave: Sheep enterprises; Modelling; GrassGro®; Profitability; Farm Management. |
| Ano: 2010 |
URL: http://purl.umn.edu/120870 |
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| Pallas Sanz, Enric. |
| The "Pertuis Breton" is a macrotidal estuary with an important mollusc exploitation of the inter-tidal zones. The main cultivated specie is M.edulis. In 1991, 250 long lines have been immersed in the centre of the bay. It will be able to extend the concession on the basis of the studies results about the trophy capacity of the "Pertuis Breton". Two deterministic models have been developed for to determining the geographical origin of the matter organic sources for the long line mussels culture, and the destine of this matter in the culture park: a) a model of trajectories of the organic matter particles, b) a coupled model of the hydrodynamic conditions and a ecophysiological model of the mussel growth. The result's simulations of the trajectories model... |
| Tipo: Text |
Palavras-chave: M. edulis; Potentialité mytilicole; Déplétion; Trajectoires; Modélisation; M. edulis; Trophy capacity; Depletion; Trajectories; Modelling. |
| Ano: 2001 |
URL: http://archimer.ifremer.fr/doc/00449/56098/57634.pdf |
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| Priour, Daniel. |
| Measurements at sea during fishing trials on bottom trawl, have revealed that the geometry of the trawl is affected by the catch. A series of 27 hauls of around 3h have been carried out during the EFFICHALUT project. This project aimed to find out improvements on the fishing gear in order to reduce the energy consumption. For this project numerous sensors have been used, for bridles tension, doors spread, vertical opening, doors attitude. The measurements show quite clearly that the doors spread decreases and the bridles tension increases along most of the hauls. The doors spread decreases by 1.35m per hour, with a standard deviation of 1.98m/h when the top bridle tension increases of 47kg/h, with a standard deviation of 59kg/h. The mean catch per haul is... |
| Tipo: Text |
Palavras-chave: Trawl; Data; Modelling; Doors spread; Bridle tension; Catch weight. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00186/29761/28208.pdf |
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| Registros recuperados: 152 | |
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