Dissertationen zum Thema „Conditions de sécheresse“
Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an
Machen Sie sich mit Top-28 Dissertationen für die Forschung zum Thema "Conditions de sécheresse" bekannt.
Neben jedem Werk im Literaturverzeichnis ist die Option "Zur Bibliographie hinzufügen" verfügbar. Nutzen Sie sie, wird Ihre bibliographische Angabe des gewählten Werkes nach der nötigen Zitierweise (APA, MLA, Harvard, Chicago, Vancouver usw.) automatisch gestaltet.
Sie können auch den vollen Text der wissenschaftlichen Publikation im PDF-Format herunterladen und eine Online-Annotation der Arbeit lesen, wenn die relevanten Parameter in den Metadaten verfügbar sind.
Sehen Sie die Dissertationen für verschiedene Spezialgebieten durch und erstellen Sie Ihre Bibliographie auf korrekte Weise.
Roquet, Dominique. „D'une sécheresse à l'autre : la paysannerie sénégalaise entre permanence et mobilité“. Paris 1, 2003. http://www.theses.fr/2003PA010580.
Der volle Inhalt der QuelleLe, Roux Nadia. „Réponse de la photosynthèse du ricin (Ricinus communis L. ) à différentes conditions environnementales“. Toulouse, INPT, 1999. http://www.theses.fr/1999INPT002A.
Der volle Inhalt der QuelleJambes, Jean-Pierre. „L'or vert du Sertão : combustibles ligneux, économie et sécheresse dans le Nordeste brésilien“. Pau, 1988. http://www.theses.fr/1988PAUU1002.
Der volle Inhalt der QuelleProfessions connected with the exploitation of firewood and vegetable coal went through a period of intense development in brazil's nordeste at the beginning of the nineteen eightles. This phenomenon can be explained through the conjunction of that period : on the one hand, a drought which, from 1979 to 1983, imperiled the agro-pastoral economy of the semi-arid hinterland (the sertao); on the other hand, the increase of the price of hydrocarbons brought about by the second oil crisis. Lack of water almost completely destroyed local agriculture, making it thus necessary for the sertanejos to exploit the ultimate resources of the natural environment : the wood of the sparsely wooded forests of the hinterland. The production, first of firewood, then of vegetable coal, thus increased markedly, all the more so as the soaring prices of hydorcarbons compelled almost all the cement works and the mining concerns in the nordeste to replace oil by-products by ligneous fuel. This twofold exploitation of the work force and of the ecosystem), which is at the origin of the development of the professions linked with the exploitation of firewood, gradually lost its impetus with the return of rain in 1984-85. From 1986 onwards there began a period of shortage, particularly of coal, which hit the concerns which used it. Besides the resuming of traditional agro-pastoral activities, it illustrates the disengagement of the leaders of the sertao economy who, confronted with the disruption of the conditions of production, gradually gave up trading ligneous fuel. Beyond the strictly contingent aspect of this phenomenon, part of the working of the sertao society, its cumbersome structures and its relation-ship with the dominant areas of the brazilian coast are also revealed
Beaudin, Isabelle. „Potentiel de la télédétection pour le suivi et la caractérisation des conditions de sécheresse en milieu méditerranéen“. Thesis, Université Laval, 2007. http://www.theses.ulaval.ca/2007/24216/24216.pdf.
Der volle Inhalt der QuelleCurrent techniques for the detection and monitoring of droughts are based on meteorological networks. The small number of stations, often badly located makes these networks poorly representatives of the area they cover. The aim of this study is to evaluate the potential of satellite imagery for the detection, characterization and monitoring of drought conditions in Andalusia, in southern Spain. The satellite imagery used in this study comes from the NOAA 11 AVHRR sensor. Two indices (VCI and TCI) were calculated over 11 km2 areas centered over 11 meteorological stations. These were compared to the SPI, a widely used meteorological index. Correlation analysis between VCI, TCI and SPI show a good relation during drought periods and seem to support the use of satellite imagery for monitoring drought in the Mediterranean region.
Yamba, Boubacar. „Ressources ligneuses et problèmes d'aménagement forestier dans la zone agricole du Niger“. Bordeaux 3, 1993. http://www.theses.fr/1993BOR30029.
Der volle Inhalt der QuelleCollet, Catherine. „Effet compétitif de deux graminées forestières sur des jeunes chênes sessiles en conditions contrôlées : interaction avec une sécheresse édaphique“. Nancy 1, 1994. http://www.theses.fr/1994NAN10029.
Der volle Inhalt der QuelleMahamat, Moussa Djibrine. „Les Oualad Rachid de l'Ouadi-Rimé (Djédâa-Batha) : une chefferie agro-pastorale du Sahel tchadien face à la sécheresse des années 80“. Bordeaux 3, 1995. http://www.theses.fr/1995BOR30013.
Der volle Inhalt der QuelleThe oualad rachid who number about twenty thousand people form a canton of djedaa, in chad. In fact, it is a sahelian agro-pastoral tribe which is constituted around bedwins. Separated from waves of arab immigrants who had accompanied the islam expansion in nubia, these nomads arrived in chad basin in the fourteenth century. Later. Autochtonal clans were aggregated with the ruling lineages. This was the case for bacara artisans who retained the power in this region before the arab's arrival. Consequently, at the beginning of the seventeenth century a true socio-political entity was born. Grouped in fractions, all its members finished by indentifying themselves, in their speech, with the eponyme ancestor rachid to whom each individual is linked by his genealogy. Faced with events which punctuate a man's life like, birth, marriage and death, they have taken up common attitudes, refering to the habits bequeathed by the ancestors. However, to survive in the context of insecurity which preceded the modern state's emergence, the group affronted foreing aggressions. It defended also its vital space, a sort of tribal territory or a country where rearing and agriculture became possible. This concept applies especially to the fields of cultivation. By another way, this notion is hardly deep-rooted in the ethnic groups of the chad centre which form sedentary stones between wich the oualad rachid pastoral people move. So, the pastoral mobility area of the chiefdom covers a region of more than 180,000 square kilometers from the 11th to the 16th parallels. But the borders of this space change from one year to another. The drought whitch began in 1968 has negative effects on the hydraulic and fodder resources, forcing the herds to move further and further south
Diarra, Alassane. „Utilisation des ressources naturelles et occupation de l'espace par les agriculteurs et les pasteurs en zone aride au Mali“. Montpellier 2, 1993. http://www.theses.fr/1993MON30019.
Der volle Inhalt der QuelleThis thesis aims at contributing to the description as just as possible of sedentary and nomadic populations'behaviour regarding land occupation and natural resources utilization in burem subdivision in mali. It describes the evolution of recent droughts, balances and imbalances between social systems and ecological ones. The methodology suitable to this study is based on : a bibliographic research, investigations near persons-resources ans civil service agents, and investigations near populations. The first part, dealing with an important bibliography presents the characteristics and the evolution of burem subdivision as regards natural milieus, land occupation, production and exchanges and local populations. The second and third parts describe the entire process related to investigations near sedentary population on one hand and near nomadic population on the other hand, sampling, questionnaires, investigations, data processing. The fourth part deepens six themes which are considered as important keys for development are for interatctions between man and natural resources
Gareyane, Mohamed. „La sédentarisation des nomades dans la région de Gao : révélateur et déterminant d'une crise multidimensionnelle au Nord-Mali“. Lyon 3, 2008. https://scd-resnum.univ-lyon3.fr/out/theses/2008_out_gareyane_m.pdf.
Der volle Inhalt der QuelleThe nomads of north Mali a long time refused the policy of the colonial state then of the Malian state that considers the settling process as the basis of their integration and development. The current process results from two major facts that strongly affected the functioning and the structuration of social and economical life of nomads. It acts on the one hand, of the harmful effects of the dryness of 1984 and on the other hand, on the realization, following the intervention of NGO and the development projects, of many socio-economic infrastructures to accompany peace in an area weakened by the rebellion by the nineties. If settling process is justified by a socio-economic requirement, environmental reality constrains to the mobility maintenance, guarantees development of the breeding which remains still the system of production dominating and most viable. But, the priority of the socio-economic development compared to the environmental question puts doubtlessly risks for the future of the nomads. This future also will have to do facing the uncertainties of the recurring insecurity and the large building sites of development, in fact the dam of Taoussa as well as exploration and the possible oil exploitation
Epron, Daniel. „Effets des déficits hydriques et des forts éclairements sur la photosynthèse de jeunes semis de chênes en conditions contrôlées et de chênes adultes en conditions naturelles“. Nancy 1, 1993. http://www.theses.fr/1993NAN10010.
Der volle Inhalt der QuelleStéfanon, Marc Alexandre. „Canicules et sécheresses en Méditerranée : contributions des processus couplés surface-atmosphère à méso-échelle“. Palaiseau, Ecole polytechnique, 2012. https://pastel.hal.science/docs/00/74/71/24/PDF/TheseStefanon.pdf.
Der volle Inhalt der QuelleIn a context defined as that of global warming, with fears that one summer out of two could be very similar to the 2003 European heat wave, the significant role played by droughts and land-atmosphere coupling in the enhanced and persistent high temperatures during heat-wave events has been highlighted by various studies. I have developed an original classification based on the spatial structures of the heat waves ocurring in the Euro-Mediterranean area. Classification are generally designed to classify numerous events, so we have had to adapt to classifying rare events, by introducing three criteria grounded on temperature and the spatio-temporal extension of the phenomena to be described. The classification has enabled us to sort out six different categories of heat wave. In course of the investigation, I then proceeded to focus on one of the categories, id est on Westen Europe heat wave. I carried out numerical sensitivity tests in order to analyse how the hydric deficit of soils contributes to amplifying heat waves and was able to bring out different behaviours. In the continental plains, the atmospheric boundary layer temperatures are largely controlled by local dry convection processes. In the mountainous and coastal areas, mesoscale circulations such as slope winds and sea breezes contribute to mitigating heat waves by allowing fresh and moist air to advect and precipitations to form. The effect of vegetation on heat waves was also examined. To do so, I have developed modelling tools which couple atmospheric dynamics with vegetative dynamics and thus present an innovative view on heatwave and drought conditioning processes in Western Europe. This modelling development is part of a larger project that aims at developing a model for regional climatic system and which has been undertaken at the Institut Pierre Simon Laplace (IPSL) as part of the MORCE-MED project. This question has so far been little addressed in the scientific literature. I have shown that the inclusion of an interactive vegetation into modelling enable to simulate the modifications of the phenological cycle that control plant growth and development as well as evapotranspiration. Used to analyse the heat waves of June and August 2003, I have been able to demonstrate that the interaction of vegetation had a mitigating effect on the June 2003 heat wave, while it had a reversed effect in August, id est that of reinforcing. Lastly, we have measured the effects of land cover change that would allow to mitigate the consequences of heat waves on humans. In a preliminary study, I replaced anthropized surfaces (mainly agricultural land) by forests and meadows. There again, the effects noted were more contrasted than expected and presented a mitigation of the heat in June and an increase in the temperatures in August, with a high spatial variability on a mesoscale
Vion, Bourgeois Emmanuelle. „Caractérisation et expression de gènes de blé dur induits en conditions de stress abiotiques“. Montpellier 2, 1998. http://www.theses.fr/1998MON20223.
Der volle Inhalt der QuelleOuarzane, Aïcha. „Étude comparée des propriétés de la phosphoénolpyruvate carboxylase foliaire de deux cultivars de sorgho (Sorghum bicolor (L. ) Moench) pendant la sénescence et en réponse à des contraintes hydriques en conditions contrôlées“. Paris 12, 1993. http://www.theses.fr/1993PA120009.
Der volle Inhalt der QuelleCanale, Nathalie. „Étude des propriétés enzymatiques de la phosphoénolpyruvate carboxylase de Mil (Pennisetum glaucum (L. ) R. BR. ) soumis à diverses contraintes hydriques en conditions contrôlées“. Paris 12, 1992. http://www.theses.fr/1992PA120035.
Der volle Inhalt der QuelleBernatchez, Antoine. „Conditions de culture propices à l'ail des bois (Allium Tricoccum)“. Master's thesis, Université Laval, 2012. http://hdl.handle.net/20.500.11794/23730.
Der volle Inhalt der QuelleFakiri, Malika. „Obtention chez l'orge (Hordeum vulgare) de régénération par androgenèse et gynogenèse in vitro en conditions de stress salin : application à trois génotypes marocains“. Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL020N.
Der volle Inhalt der QuelleStieber, Pascale. „Approche d'une caractérisation simple de la pollution en hydrologie urbaine, à partir du couple temps sec/pluie“. Vandoeuvre-les-Nancy, INPL, 1996. http://docnum.univ-lorraine.fr/public/INPL_T_1996_STIEBER_P.pdf.
Der volle Inhalt der QuelleRaymond, Florian. „Longs épisodes secs hivernaux dans le bassin méditerranéen et conditions atmosphériques associées : variabilité contemporaine et future (1957-2100)“. Electronic Thesis or Diss., Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCK017.
Der volle Inhalt der QuelleIn the context of climate change, as reflected by a dryer Mediterraneanbasin, this thesis focused on the study of the contemporary and future variability(1957-2100) of the wintertime (September to April) very long dryspells events (called VLDSe) in the Mediterranean basin. An original methodologywas developed in this thesis in order to define VLDSe as singularclimatic events, characterized by location, duration and spatial extent criteria.76 VLDSe were detected in the Mediterranean basin on the contemporaryperiod (1957-2013). These events are divided into 4 main geographicalpatterns: North-East, West, Scattered Localized and South-East. North-East and West configurations are associated with anticyclonic conditionslocated approximately 1 000 km northwestern to the areas affected by theVLDSe, favoring a clear sky and no precipitations. The Scattered Localizedand South-East configurations are special: the first one is characterized asa residual class grouping VLDSe with small spatial extent and distributedthroughout the entire basin, and the second one is characterized by seasonalVLDSe which are the continuation of the dry summer observed in the eastof the Mediterranean basin.Euro-Atlantic weather regimes have some control on the VLDSe. Thepositive phase of the north-atlantic oscillation regime (NAO+) is the onlyone that is clearly favorable to the development of VLDSe on almost the entirebasin. The east-atlantic regime (EA) does not show any control on theVLDSe, and the atlantic ridge (AR) and the negative phase of the northatlanticoscillation (NAO-) regimes are generally detrimental to VLDSe. However,some VLDSe can sometimes be associated with AR, EA and NAOregimes.This requires these three weather regimes to be associated withslightly higher atmospheric pressure northwest of the areas impacted bythe VLDSe, compared to their respective climatology. Long duration of theAR, EA and NAO+ regimes, which are coupled with sustained atmosphericstability, are preferentially associated with VLDSe, in contrast to the shortduration. Conversely, the long duration of the NAO- regime, reinforcingthe low atmospheric pressure on Europe and the Mediterranean basin, areweakly associated with VLDSe.Although the two climate models ALADIN52 and LMDZ4-NEMOMED8 differ in several respects, they agree in that VLDSe should be longer by 2100,especially in the RCP8.5 trajectory. A multi-model analysis with 12 CMIP5simulations shows that wintertime sea-level pressure tends to increase in theAtlantic Ocean, off the French coast and in the central the Mediterraneanbasin for the RCP8.5 trajectory. Conversely, the frequency and duration ofthe 4 weather regimes do not show significant trends until the end of the21st century.Finally, a study is carried out to assess the impact of VLDSe on agriculturalproduction in Spain. The number of VLDSe days has a larger impactson the yields of barley, wheat and oats (winter species and cultivatedthrough rainfed agriculture) than the simple ratio of dry days or seasonalrainfall amounts in Spain. A two-season case study, based on seasons withcomparable rainfall amounts, shows that in addition to yields, a VLDSecauses a significant decrease in soil moisture and in the Ebro River flow
Bekmirzaev, Gulom. „Relations eau et cultures de légumes : effet des sols salins et conditions de sècheresse sur la croissance, composition minérale et photosynthèse“. Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10010/document.
Der volle Inhalt der QuelleConventional techniques used to control the soil salinization process - soil leaching or fertilization enhancing - contribute highly to soil and aquifers contamination; on the other hand, the use of salt tolerant species will be very useful to the plants, but does not solve the problem of soil or groundwater contamination. Hence, the only way to control the salinization process to maintain the sustainability of landscapes and agricultural fields is to combat the salinization problems with environmentally safe and clean techniques. One of these new techniques is the use of salt removing species. In order to study the potential capacity to remove soil salts, two horticultural species Portulaca oleracea and Tetragonia tetragonioides, and the salt sensitive crop lettuce (Lactuca Sativa L) were evaluated for their efficiency to remove salts from sandy soil. Plants were analysed relatively to total growth and mineral composition of the leaves and soil. According to the results, it was seen that T. tetragonioides is the best salt removing species and complementary, it has other benefits, which are as follows: 1) high biomass production; 2) several harvests; 3) high content of minerals; 4) horticultural importance; 5) easy multiplication; 6) easy crop management; 7) tolerance to drought conditions; 8) soil erosion control. P. oleracea is a high drought tolerant species, followed by T. tetragonioides. As concluding remarks, it was shown that this new technique to control salinity is a powerful and environmental clean tool to maintain the sustainability of the landscape and of the irrigated areas
Raymond, Florian. „Longs épisodes secs hivernaux dans le bassin méditerranéen et conditions atmosphériques associées : variabilité contemporaine et future (1957-2100)“. Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCK017/document.
Der volle Inhalt der QuelleIn the context of climate change, as reflected by a dryer Mediterraneanbasin, this thesis focused on the study of the contemporary and future variability(1957-2100) of the wintertime (September to April) very long dryspells events (called VLDSe) in the Mediterranean basin. An original methodologywas developed in this thesis in order to define VLDSe as singularclimatic events, characterized by location, duration and spatial extent criteria.76 VLDSe were detected in the Mediterranean basin on the contemporaryperiod (1957-2013). These events are divided into 4 main geographicalpatterns: North-East, West, Scattered Localized and South-East. North-East and West configurations are associated with anticyclonic conditionslocated approximately 1 000 km northwestern to the areas affected by theVLDSe, favoring a clear sky and no precipitations. The Scattered Localizedand South-East configurations are special: the first one is characterized asa residual class grouping VLDSe with small spatial extent and distributedthroughout the entire basin, and the second one is characterized by seasonalVLDSe which are the continuation of the dry summer observed in the eastof the Mediterranean basin.Euro-Atlantic weather regimes have some control on the VLDSe. Thepositive phase of the north-atlantic oscillation regime (NAO+) is the onlyone that is clearly favorable to the development of VLDSe on almost the entirebasin. The east-atlantic regime (EA) does not show any control on theVLDSe, and the atlantic ridge (AR) and the negative phase of the northatlanticoscillation (NAO-) regimes are generally detrimental to VLDSe. However,some VLDSe can sometimes be associated with AR, EA and NAOregimes.This requires these three weather regimes to be associated withslightly higher atmospheric pressure northwest of the areas impacted bythe VLDSe, compared to their respective climatology. Long duration of theAR, EA and NAO+ regimes, which are coupled with sustained atmosphericstability, are preferentially associated with VLDSe, in contrast to the shortduration. Conversely, the long duration of the NAO- regime, reinforcingthe low atmospheric pressure on Europe and the Mediterranean basin, areweakly associated with VLDSe.Although the two climate models ALADIN52 and LMDZ4-NEMOMED8 differ in several respects, they agree in that VLDSe should be longer by 2100,especially in the RCP8.5 trajectory. A multi-model analysis with 12 CMIP5simulations shows that wintertime sea-level pressure tends to increase in theAtlantic Ocean, off the French coast and in the central the Mediterraneanbasin for the RCP8.5 trajectory. Conversely, the frequency and duration ofthe 4 weather regimes do not show significant trends until the end of the21st century.Finally, a study is carried out to assess the impact of VLDSe on agriculturalproduction in Spain. The number of VLDSe days has a larger impactson the yields of barley, wheat and oats (winter species and cultivatedthrough rainfed agriculture) than the simple ratio of dry days or seasonalrainfall amounts in Spain. A two-season case study, based on seasons withcomparable rainfall amounts, shows that in addition to yields, a VLDSecauses a significant decrease in soil moisture and in the Ebro River flow
Rabarijaona, Arivoara. „L'efficience intrinsèque d'utilisation de l'eau (WUEi) du chêne sessile conditionne-t-elle sa résilience à la sécheresse ?“ Electronic Thesis or Diss., Paris, AgroParisTech, 2023. http://www.theses.fr/2023AGPT0016.
Der volle Inhalt der QuelleAssisted migration constitute a possibility to adapt forest ecosystems face to the increase in drought intensity and frequency. However, this strategy requires identification of drought-resistant populations and characterization of the diversity within them. Water use efficiency (WUE) is a key trait to assess for this choice, as it reflects a trade-off between carbon assimilation and water loss through transpiration. By combining dendrochronology and stable isotope analysis, this thesis investigates the effect of WUE on the growth performance and resilience to drought of sessile oak (Quercus petraea).Firstly, WUE was compared among 16 populations whose individuals, from seeds originating from sites along a wide range of pedoclimate gradient, had grown in the common garden Sillegny. Significant differences in WUE were found among these populations, but these differences were not correlated with the pedoclimatic conditions of the sites of origin. However, populations from provenances with sandy soils showed a larger increase in WUE in response to the drought of 2003 (compared to the wet year of 2000) than populations from provenances with silty soils. In addition, trees with higher WUE showed larger radial growth only in wet years. Although these results suggest an adaptation of the sessile oak, reflected by the plasticity of WUE to drought, the variability of WUE within populations was higher compared to the differences among populations.Then, the phenotypic variability of WUE was studied within two populations with contrasting soil and climate conditions, at the Blois (wet) and the Harth (dry) sites. All the trees within each plot were sampled, with a particular focus on the relationship between WUE and radial growth. While stomatal control appeared to be the key factor in inter-annual variations in WUE, the inter-individual (intra-annual) variability in WUE was driven more by net CO2 assimilation, which is strongly affected by tree social status. The intra-annual relationships between WUE and growth appeared more significant as the competition among trees within the stand intensified (particularly when trees become mature), and when light availability became a limiting factor rather than water (in a humid site, at Blois).Finally, the effect of WUE expressed by trees at a young age on growth trajectory was assessed within the Blois and the Harth stands. At the Harth site, trees with higher WUE during their young age were the most dominant in 2021, suggesting selection for higher WUE in dry environment. In contrast, at the Blois site, the effect of WUE at the young age on the social status of the trees ceased after 60 years. The response of trees to drought was not significantly affected by WUE at the young age at the Blois site and only during the first decades at the Harth site. Moreover, the plasticity of WUE to drought might play a diminishing role in the selection process as trees age and were exposed to changing environmental conditions.WUE is a complex trait influenced by multiple factors, including genetics, microenvironmental conditions, and tree age. Given that intra-population variations were more pronounced than differences among populations, and that the relationship between WUE and resilience to drought was tenuous, the selection of drought-adapted sessile oak populations cannot be only based on WUE
Caiserman, Arnaud. „Adapter les stratégies agricoles aux évolutions socio-économiques et climatiques en milieu méditerranéen : comparaison de l'usage de l'eau et des choix de plantes des agriculteurs dans la plaine de la Békaa (Liban) et de Marvdasht (Iran)“. Thesis, Lyon, 2020. http://www.theses.fr/2020LYSE3009.
Der volle Inhalt der QuelleAccording to Köppen’s climate map, the semi-arid Mediterranean climate covers several countries in this region, including Lebanon and Iran. In order to regionalize the understanding of the water challenge of this region, two agricultural plains with similar characteristics were selected as study areas: the Bekaa plain in Lebanon and the Marvdahst plain in Iran. The Marvdasht plain is slightly drier and through climate change, the Bekaa plain will look like the present climate conditions of Marvdasht before 2100. It is therefore necessary to grasp the agricultural practices in the Marvdasht plain in order to imagine how Bekaa agriculture will look like in the future. Farmers must adapt their strategies to the local climate that is characterized by strong uncertainties (interannual variability of rainfall or frequent droughts) but also to economic uncertainties (prices’ variability). Despite (geo)political differences, some farmers in the Bekaa and Marvdasht have chosen strong water demanding crops, compared to the local renewable water resources. However, these crops are profitable on the market. In total, the water balances for the years under consideration are negative: in Marvdasht, farmers pumped 0,25 km3 of groundwater to meet the total irrigation needs, but the groundwater recharge was only 0,09 km3 in that year. In the Bekaa, this balance is also negative, but to a lesser extent: 0,15 km3 were pumped for a recharge of 0,1 km3. In both cases, irrigation needs are therefore higher than renewable water. They have therefore promoted market adaptation rather than sustainable resource management. Thus, the reasons for crop choices were closely analysed through field surveys and certain remote sensing methods to generate crop maps. The net irrigation requirements of crops are also estimated through remote sensing. Indeed, water needs determine whether or not farmers promote climate change adaptation strategies with relevant crop choices. This regional imbalance at the expense of resources stems from the productivism in the early 1950s. This paradigm is rooted on farm’s profitability and a more ambitious political objective, food self-sufficiency, especially in Iran. This causes an overexploitation of groundwater for irrigation and thus a lowering of groundwater by several tens of meters since the 1980s. Some alternatives consist of growing plants with high added value and modest water requirements: saffron, canola, quinoa and cannabis (in Lebanon). We have highlighted these alternative crops since their cultivation on large areas could save millions of water cubic meters each year. Still not widely cultivated, these plants need incentive markets to attract the interest of agricultural stakeholders. This operational part thus analyses the reasons for this lukewarm success in order to find incentive markets. Such local markets would strengthen a more sustainable agricultural policy than restrictive measures on water management that farmers always manage to circumvent
Gutierrez, Cori Omar. „Relationship and feedback between LULC changes and hydroclimatic variability in Amazonia“. Electronic Thesis or Diss., Sorbonne université, 2024. http://www.theses.fr/2024SORUS123.
Der volle Inhalt der QuelleThe Amazon rainforest plays a vital role by functioning as a regulator of the climate system and as the main terrestrial carbon sink. It drives hydroclimatic processes and mitigates the effects of droughts through vegetation-atmosphere coupling. Indeed, Amazon forests have the potential to impact rainfall patterns through biophysical processes like water recycling. However, these capacities have been reduced during the last decades due to disturbances in the climate-vegetation system together with the intensification of droughts. All this has accentuated a process of biophysical transition from a predominantly forested ecosystem to a Savanna. Therefore, given these complexities, understanding the direction of changes is of vital importance.Using multiple datasets and the coupled ORCHIDEE and LMDZ models, this thesis delves into the study of the interactions between Amazon hydroclimatology and vegetation. In addition, it seeks to expand our understanding of modifications in the vegetation-atmosphere system and its links with climate and LULC changes. Likewise, taking into account the increasing rates of deforestation, it investigates the effects and feedback resulting from a large-scale forest loss scenario on hydrological processes.The results show that, over the southwestern Amazon, forests undergo a transition from being influenced by energy availability to depending on water availability throughout the year. During the rainy season, vegetation growth is primarily influenced by energy availability rather than water availability. Nevertheless, outside of this period, forests respond positively to precipitation and terrestrial water storage, suggesting that vegetation is primarily dependent on water supply. However, a spatial analysis reveals that recent deforestation modifies these transitions and destabilizes the natural balance in the climate-vegetation system.The nature of these imbalances in the Amazon is not entirely clarified. Through an approach based on the relationships of water/energy fluxes and vegetation conditions over the last four decades, it is explored whether these changes are intrinsic to climate variability or are driven by anthropogenic processes. 67% of the southwestern Amazon has experienced a transition towards a predominantly dry state due to climatic factors (external forcing), while 21% has transitioned towards a state dominated by deforestation (internal forcing). However, external and internal forcings are not independent processes, as both mechanisms drive changes simultaneously. By weighing the magnitudes of these forcings, we show that the synergies have led 74% of the southwestern Amazon toward a state of greater water stress. Nevertheless, during recent years, although combined external-internal processes continue to exert significant control over changes, 30% of these are strictly dominated by internal forcing. This suggests that internal processes are playing an increasingly relevant role in the transition towards a state characterized by high forest water stress, especially in areas where deforestation and anthropogenic pressure are increasing.Using the coupled ORCHIDEE and LMDZ models, the effects of projected Amazon deforestation by 2050 on the hydrological cycle and dryness are examined. Deforestation decreases precipitation, reduces evapotranspiration and increases runoff. Furthermore, deforestation accentuates water stress especially in the southwestern Amazon (positive feedback). Water demands in the atmosphere, on the land surface and even in the soil root zone intensify during the dry season. During the wet season, the deficit of specific atmospheric humidity becomes even more acute towards the tropical Andes over the Altiplano region. These findings provide a more thorough understanding of the possible effects of massive forest removal on the water availability and resilience of the Amazon in a context where changes are occurring at an accelerated rate
Van, Rooij Mahaut. „Etude du rougissement hivernal du Douglas : entre températures douces & formation de glace“. Electronic Thesis or Diss., Université Clermont Auvergne (2021-...), 2023. http://www.theses.fr/2023UCFA0154.
Der volle Inhalt der QuelleThe Douglas fir is the first reforestation species in the Auvergne-Rhône-Alpes region and the second in France as a whole, and is of considerable economic importance in France, where 13 million trees are produced each year. Winter reddening affects young Douglas-fir (< 15 years old), affecting up to 80% of the plantation. A reddening tree has no silvicultural future and typically dies within a year after reddening. The objectives of my PhD thesis were to have a better understanding of winter reddening by identifying the climatic parameters that trigger reddening and, more importantly, the physiological mechanism(s) that cause needle reddening.A thorough literature review and bioclimatic analysis were undertaken to identify critical climatic factors. The literature synthesis identified certain climatic conditions characteristic of 'reddening' years, including anticyclonic periods after winter and/or alternating cold and warm periods. Both the literature synthesis and the bioclimatic analysis identified a combination of climatic variables: warm daily temperatures, high daily temperature amplitude, at least moderate wind speeds and relative humidity. However, the freeze-thaw cycles with cold night temperatures did not emerge from the climate analysis, although they are mentioned in the literature.In order to understand how Douglas fir reddens, we first identified gaps in our knowledge of winter reddening and proposed potential mechanisms, either single or interacting, that cause this physiological disorder: 1) winter drought leading to hydraulic failure, 2) photo-oxidative stress, and 3) premature deacclimation. Under controlled conditions, young Douglas fir trees were exposed to winter drought through a temperature differential between roots and canopy (TSOIL < 5°C; TMOY_AIR ~ 14°C). Some of these trees were exposed to light intensities that could induce photooxydative stress (> 1800 PPFD). Cold soil temperatures induced moderate water stress by limiting root water uptake, while warm air temperatures caused water loss at the needle level. However, Douglas fir was able to acclimate to this new environment and even resumed growth. Exposure to high light intensity did not cause irreversible damage to PSII or photooxydative stress. No reddening of the Douglas fir was observed, thus refuting hypothesis 2, but partially supporting hypothesis 1, as the canopy was not exposed to freezing stress. In the field, continuous measurements of young Douglas fir diameter variation were coupled with temperature/humidity measurements from four plots in the Massif Central from December 2020 to June 2023. Spring frosts in April 2021 on deacclimated Douglas fir did not result in needle reddening or cambial damages, thus failing to validate hypothesis 3. Nevertheless, comparison of a asymptomatic winter (2021) with a asymptomatic winter i.e. with winter reddening (2022) revealed significant hydraulic stress generated from the apex, associated with an anticyclone period in January 2022. Hydraulic failure could be exacerbated by daily transpiration, combined with freeze-thaw cycles that increase hydraulic stress, leading to canopy hydraulic failure that could explain needle desiccation and reddening. We therefore favour hypothesis 1, which should be tested under controlled conditions
Ndiaye, Mbaye. „Systèmes de production et mutations des paysages ruraux dans la basse vallée du Ferlo au Sénégal“. Phd thesis, Université Michel de Montaigne - Bordeaux III, 2007. http://tel.archives-ouvertes.fr/tel-00519417.
Der volle Inhalt der QuelleTallieu, Clara. „État sanitaire et croissance radiale des arbres : Analyse spatiale et temporelle des données du réseau systématique de suivi des dommages forestiers“. Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0185.
Der volle Inhalt der QuelleFor the past 30 years, annual visual assessments of crown condition, on the French part of the transnational monitoring network (ICP Forests, level 1), was essential for monitoring forest health. However, the use of crown condition as an indicator of tree health is regularly questioned for methodological reasons but also because of the lack of knowledge on the determinism of crown condition and its functional impact on the tree. In this context, and through the records of 9 tree species’ crown condition (deciduous and coniferous) spread over more than 300 plots in France, we have 1) described and interpreted the spatial and inter-annual variations of leaf loss, in addition to 2) discussing the use of crown condition as an indicator of tree health status based on the joint analysis of inter-annual variations of leaf loss and radial growth. The analysis of spatial variations in crown condition between plots showed multiple relationships with edaphic and climatic factors, but with relatively moderate explanatory power. The study of inter-annual variations in crown condition confirmed that the climatic factors of the previous year control crown condition of the current year. However, compared to radial growth, crown condition presents a less dynamic and inconsistent response to climate between trees in the same plot. The joint analysis of the two signals showed the existence of a weak link between growth and crown condition. We only observed a decrease in tree growth in the case of important leaf loss during years of extreme climatic hazards (dry or cold). However, the introduction of leaf loss as a predictor of radial growth had little or no significant effect for beech and fir. Finally, the evidence of the major influence of age on leaf loss precludes the interpretation of raw crown condition as an indicator of tree health
Wagner, Pierre-André. „Écophysiologie comparée de plants de chêne pédonculé (Quercus robur L. ) et de chêne sessile (Quercus petraea (Matt. ) Liebl. ) soumis à deux contraintes racinaires successives : hypoxie et sécheresse : application à la mise en valeur forestière des pélosol-pseudogleys“. Nancy 1, 1996. http://docnum.univ-lorraine.fr/public/SCD_T_1996_0354_WAGNER.pdf.
Der volle Inhalt der Quelle„Potentiel de la télédétection pour le suivi et la caractérisation des conditions de sécheresse en milieu méditerranéen“. Thesis, Université Laval, 2007. http://www.theses.ulaval.ca/2007/24216/24216.pdf.
Der volle Inhalt der Quelle