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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Modeling spatial dynamic ecological processes with DEVS-Scheme and geographic information systems.

Vasconcelos, Maria Jose. January 1993 (has links)
The objective of this work is to introduce and illustrate the potential of discrete event, hierarchical modular models for simulating spatial dynamic ecological processes in geographic information systems (GIS). The knowledge based discrete-event simulation environment (DEVS-Scheme) associates stand-alone discrete event models with spatial locations represented in a GIS data base, and couples those models in a coherent manner. The dynamic models can then process spatially distributed information available in a GIS data base, and update it through time. The models also can receive external updated information at any moment, due to the continuous time nature of discrete event specifications. The proposed approach facilitates the representation of reality at several levels of resolution, with model components organized in a hierarchical structure and information flow implemented in the form of message passing. These capabilities are illustrated with two applications. The first is a multi-scale spatial succession model of a wet sclerophyllous forest subject to recurrent fires, and the second is a fire growth model.

Changement institutionnel, utilisation des produits phytosanitaires et gestion de la qualité de l'eau : le cas de trois zones d'agriculture intensive au Burkina Faso / Institutional change, use of pesticides and management of water resources quality : the case of three areas of intensive agriculture in Burkina Faso

Diendéré, Achille 29 October 2012 (has links)
L’objectif principal de ce travail de recherche est d’étudier les mécanismes contribuant à accompagner le processus du changement institutionnel pour lutter contre la dégradation de la qualité de l’eau par l’agriculture au Burkina Faso (BF). La première partie retrace l’évolution de la politique agricole et de celle de l’eau au BF. Elle justifie, également, l’intérêt que nous avons à développer la problématique liée à la dégradation de la qualité de l’eau. La deuxième partie examine les motivations des pratiques des agriculteurs en matière d'utilisation des produits phytosanitaires et offre une réflexion sur les conditions et facteurs d’évolution de ces pratiques. Dans cette partie, en nous appuyant sur les concepts et outils de l’économie institutionnelle (école historique), nous faisons l’hypothèse d’un lien de causalité entre le comportement des agriculteurs et le statut de la ressource en eau et, plus précisément, le statut de la qualité de l’eau. La troisième partie de ce travail cherche à vérifier cette proposition théorique par la collecte et le traitement statistique et économétrique de données obtenues auprès d’un échantillon de 389 agriculteurs appartenant à trois zones agricoles présentant des problématiques de développement agricole différentes. Il ressort qu’une gestion collective de l’eau, appelant à la responsabilisation croissante des agriculteurs dans la protection accrue des ressources en eau est d’autant plus difficile en absence des croyances sur la dégradabilité de la qualité de l’eau. Le changement institutionnel permettant de conduire à l’évolution du statut de la qualité de l’eau n’est ainsi pas réductible à une modification du système légal d’incitations et de sanctions mais dépend, également, des croyances partagées d’agriculteurs membres d’un même collectif. Dès lors, le changement institutionnel étudié dépend de la manière dont les apprentissages sont organisés et impulsés par l’action publique. / The principal objective of this research is to study the mechanisms, which contribute to lead the process of institutional change to avoid water pollution by agriculture in Burkina Faso (BF). Part first of the thesis provides an overview of the evolution of agricultural and water policies in BF. We also discuss the interest of addressing the issue regarding the degradation of water quality from an academic and policy points of view. The second part examines the motivations of farmers' practices in the use of pesticides and the conditions for changes. In this section, based on concepts and tools drawn from institutional economics (the historical school), we make the hypothesis of a causal relationship between the behavior of farmers and the property status of water resources and, more precisely, the property status of water quality. The third part of our thesis attempts to test this theoretical proposition by collecting and analyzing, using statistical and econometric methods, data obtained from 389 farmers located in three different agricultural areas of BF. In this last part, we also draw conclusions on policy implications to lead institutional change. One major result of our research is that the degree of farmers’ involvement in collective management of water quality depends on their beliefs about the degradability of quality water. Therefore, a change in the legal system of incentives and penalties is not sufficient for an effective institutional change. To make the status of water quality evolve, the shared beliefs of farmers, who are members of the same collective, have also to evolve. In other words, the process of institutional change sought relies on how collective learning processes are organized and launched by public policy.

Influence of Vineyard Floor Management Practices on Soil Aggregate Stability, Total Soil Carbon and Grapevine Yield

Adams, Kimberly Ellen 01 August 2011 (has links)
Soil aggregates provide pore spaces of various sizes supplying water, gases and nutrients to plant roots and microorganisms, and facilitate moisture retention and availability. Soil aggregate stability is indicative of soil biological and structural health, and is increased by soil carbon derived from plant roots and the soil microbial biomass. Aggregate stability and soil carbon can be enhanced by increasing organic matter through compost additions or by planting cover crops. Additionally, aggregate stability is enhanced by arbuscular mycorrhizal fungi (AMF) that form a symbiotic association with plant roots, and consolidate soil particles into aggregates through hyphal networks and through the production of glomalin, binding soil particles together. The use of herbicides decreases soil carbon as it removes vegetation and the microorganisms associated with it. Soils having poor aggregate stability slake and disperse into primary soil particles becoming dense and subject to erosion when exposed to heavy rains. The use of herbicides amplifies this risk as it removes vegetation, leaving the soil bare, with nothing to absorb rainfall impact. The effect of vineyard floor management practices on aggregate stability, soil carbon and grapevine fruit yield was studied at two vineyard sites located within the Estrella district of Paso Robles, CA. In late fall of 2008, treatments were applied to the vine line including an herbicide, an herbicide plus compost, a cover crop, a cover crop plus compost and a cover crop plus a fungal inoculant treatment. The control had no herbicides, compost, cover crop, or fungal inoculant applied to it. The cover crop treatments were applied at 30 lbs/ac consisting of a mixture of 20 % blando brome (Bromus hordeaceus), 20 % Zorro fescue (Vulpia myuros), 30 % crimson clover (Trifolium incarnatum) and 30 % subterranean clover (Trifolium subterraneum). Commercially available compost was applied at a rate of five tons per acre. The fungal inoculant was applied at eight pounds per acre, consisting of the AMF: Glomus intraradices, G. mosseae, G. aggregatum and G. etunicatum each at 32 propagules/ cc. Samples were collected in the spring of 2009 and the winter of 2010. Percent carbon was significantly higher in the areas where compost applications were received (P=0.014). Cover crops did not significantly increase the level of carbon in the soil (P=0.253). Compost and cover crops significantly increased the amount of > 4.0 mm soil aggregates (P=0.004 for compost and P=0.027 for cover crops). Herbicide treatments significantly reduced the amount of > 4.0 mm aggregates (P=0.028). Fungal inoculants had no effect on > 4.0 mm aggregate stability (P=0.361). Compost significantly increased mean fruit weight (P=0.041). These results suggest that the addition of compost and cover crops are an effective way of increasing > 4.0 mm aggregates and compost alone is an effective way to increase soil carbon and fruit yield.

Combining Conventional Tests and Terminal Restriction Fragment Analysis to Evaluate Microbial Quality of Raw Milk

Guo, Haibin 01 March 2011 (has links)
p.p1 {margin: 12.0px 0.0px 3.0px 0.0px; text-align: center; font: 16.0px 'Times New Roman'} p.p2 {margin: 0.0px 0.0px 10.0px 0.0px; text-align: center; font: 12.0px 'Times New Roman'} p.p3 {margin: 0.0px 0.0px 10.0px 0.0px; font: 12.0px 'Times New Roman'} Abstract Combining Conventional Tests and Terminal Restriction Fragment Analysis to Evaluate Microbial Quality of Raw Milk Haibin Guo The dairy industry is an important part in the domestic economy in the U.S. and the quality of dairy products hinges on raw milk quality. Microorganisms play a critical role in raw milk quality and they are currently tested and monitored by conventional microbiological tests. Some of the most common conventional tests include somatic cell count (SCC), standard plate count (SPC), coliform count (CC), lab pasteurized count (LPC) and proteolytic strain count (PSC). However, these methods do not correlate with each other or with the quality of milk and milk products. One factor that contributes to this lack of correlation is the insufficient knowledge of microbial communities in raw milk. In this work we aimed to evaluate modern molecular methods to complement traditional quality procedures that may eventually complement conventional tests and improve milk quality evaluation. Therefore, a molecular method, Terminal Restriction Fragment (TRF) analysis was introduced. TRF analysis has been widely used as a tool to investigate the microbial communities in environmental samples. In this study, it was applied to investigate the microbial communities in raw milk and evaluate raw milk quality. Milk samples were collected for over six months in the Cal Poly dairy farm and evaluated by conventional tests and TRF analysis. Samples were defined as “high quality” milk and “low quality” milk according to each conventional test first. The cutoffs applied were: 50,000 cfu/ml for SPC, 70,000 cells/ml for SCC, 100 cfu/ml for CC and 250 cfu/ml for LPC. TRF analysis was conducted on raw milk samples subsequently. DNA extraction was optimized. Non-Parametric Multivariate Analysis of Variance (NPMANOVA) was applied to TRF profiles from low and high quality milk. The analysis of Similarity of Percentage (SIMPER) was used to determine each TRF peak’s contribution to the dissimilarity between the profiles of high and low quality milk. The genus/species represented by TRF peaks were estimated via database matching. In addition, conventional tests and TRF analysis were also used to analyze the factors causing low quality milk. Rain event and cow’s apparent health were the two factors investigated since raw milk samples were collected from cows in different apparent health status on wet days and dry days. Conventional tests revealed strong correlations between the results of SPC and PSC, and SPC and CC (coefficients of correlation > 0.8). It implied that the results of conventional tests might not be independent, so the statistics based on the assumption of independence of variables were not suitable to analyze the data. SCC showed no strong correlation with any other conventional tests. Raw milk samples were grouped as high quality and low quality according to SPC, CC, SCC and LPC. Using TRF analysis, it was found that there was a significant difference between TRF profiles from low and high quality milk when the quality was defined by SPC or LPC. A TRF peak at 268 bp generated by DpnII was predominant in the TRF profiles and had high abundance in the profiles of low quality milk. Hence, Pseudomonas spp. represented by TRF peak at 268 bp was likely the predominant bacteria in the microbial community associated with raw milk. TRF peaks at 61 bp, 81 bp, 104 bp, 104 bp, 201 bp, 242 bp, 268 bp, and 270 bp contributed the most to the dissimilarity between TRF profiles from different groups of samples. In addition, the presence of DNA derived from viable but non-culturable species that were associated with raw milk quality was detected. Rain event was the most important factor affecting the microbial quality of raw milk in this study. Both the conventional tests and TRF analysis showed that there was a significant difference between raw milk samples collected on wet days versus dry days. Samples collected on wet days harbored high bacterial counts and had high abundance of the predominant TRF peaks. In addition, the same TRF peaks contributing the most to the dissimilarity between groups separated by rain event were found to be among those contributing the most to the dissimilarity between groups of high and low quality milk defined by conventional tests. During wet days, the low quality milk was likely caused by the increased dirtiness of cow’s teats. Soil microbes are often associated with microorganisms in raw milk such as psychrotrophic bacteria, coliform groups and spore-formers. Cow’s apparent health status showed no significant influence on the microbial quality of raw milk. Overall, the combination of conventional tests and TRF analysis can yield a comprehensive understanding of microbial community in raw milk and improve the evaluation of raw milk quality. TRF analysis was demonstrated as a useful tool and a complement to conventional tests for milk quality evaluation by providing more information on the microbial community associated with raw milk. Findings in this study can offer a basis for further study and may help the dairy industry improve raw milk quality evaluation system.

A Genetic Study of Linkage and Inheritance in Barley

Oldham, Jerald 01 May 1962 (has links)
With the exception of corn, barley has probably been used more than any other cultivated plant in gene tic studies. It was one of several plants with which Erich von Tschermak-Seysenegg was working when he discovered Mendel's paper.

The Effects of Various Nitrogen and Moisture Levels on the Production of Silage Corn, Grain Corn, and Sweet Corn

May, Donald M. 01 May 1958 (has links)
Many experiments have been conducted measuring the effects of nitrogen rates, moisture, or time of application but few combined all three in one experiment. The object of this investigation is to study the effects and interactions of nitrogen fertilizer, moisture, and time of application on silage corn, grain corn, and sweet com. The effects of these factors should be shown by changes in yield and quality of the crop.

Establishing a Fall Harvest Window for Switchgrass Biomass Based on Optimum Decline of Phosphorus and Potassium Levels in Shoots

Lane, Jennifer Kay 01 August 2011 (has links)
Switchgrass (Panicum virgatum) is a perennial grass that remobilizes nutrients during senescence and is being used as biomass for cellulosic ethanol production. Phosphorus (P) and potassium (K) are removed in harvested biomass and replenished through additions of fertilizer. Identifying the appropriate harvest window in a one-cut system based on the remobilization of nutrients can be economically beneficial for biomass producers. The primary objective of this research was to determine if a one-cut harvest can be executed earlier in the fall based on the remobilization of P and K from stems and leaves to crown and roots of plants. Better harvesting conditions and reduced nutrient removal rates are potential benefits of earlier harvest. This project consisted of three parts, evaluating: (1) P and K levels in shoots and whole plants of Alamo and Kanlow cultivars, (2) P and K levels in shoots of upland and lowland switchgrass varieties, and (3) Effects of earlier harvest on yield. Twelve varieties, including ‘Alamo’ and ‘Kanlow’ cultivars, were planted in Knoxville, TN in 2007. Eight of these varieties were planted in Springfield, TN. Above and belowground samples were collected throughout the fall and analyzed for P and K concentrations. No significant declines of P and K were observed in stems and leaves from early October through November. Levels of P and K in leaves, stems, and panicles fluctuated during the fall season; however, final levels were similar in all tissues. Based on these changes in aboveground biomass, the harvest window could begin as early as mid-September. Data suggested that P and K in Alamo and Kanlow followed similar patterns through the fall, without significant declines in shoots. This is confirmed by data from whole plants, which showed no significant increases in P and K in crowns and roots. Levels of P and K in varieties of upland and lowland switchgrass did not differ and followed patterns observed in Alamo and Kanlow. Yields observed in different varieties did not decline when harvested as early as mid-September. Based solely on this study, it is not necessary to delay harvest and could take place as early as September.

The evolution of agricultural resource use strategies in the Willamette Valley /

Blok, Jack H., January 1974 (has links)
Thesis (Ph. D.)--Oregon State University, 1974. / Typescript (photocopy). Includes bibliographical references. Also available online.

Die Zukunft der Argrarpolitik angesichts der EU-Erweiterung

Westerhoff, Horst-Dieter January 2002 (has links)
No description available.

Long-lead forecasting of precipitation and wheat yields in Saskatchewan using teleconnection indices

Garnett, Edmund Ray 14 November 2008
Teleconnections among the central, east equatorial Pacific, the Pacific/North American (PNA) pattern, and Southern Oscillation (SO) and monthly precipitation, monthly temperature, and spring wheat yields in Saskatchewan are examined. When sea surface temperatures in the central equatorial Pacific are warmer than the air temperatures (strong El Niño) there is an upward flux of water vapour into the atmosphere, convection, heat released by condensation, a strengthening of the westerlies and a vitalization of the Hadley circulation. When sea surface temperatures are colder than the air temperatures (strong La Niña) in the central equatorial Pacific it produces the opposite influence on atmospheric processes. Composite analysis reveals that El Niño and La Niña are the primary modulators of the Pacific/North American pattern and movement of surface cyclones across the western continent. Correlation and composite analyses indicate that between 1950 and 1998 warmer than normal sea surface temperatures in the central and east equatorial Pacific during the winter and early spring (El Niño) are associated with cooler and wetter conditions during the May through July period in Saskatchewan and higher wheat yields. Conversely cooler than normal sea surface temperatures in the central and east equatorial Pacific during the winter and early spring (La Niña) are associated with hotter and drier conditions during the May through July period in Saskatchewan and lower wheat yields. The relationship appears to be strongest for the Brown soil zone and weakest for the Black soil zone in Saskatchewan.

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