This thesis describes the growth of European olive (Olea europaea L.) at three different trial sites located near Laverton, in the north-eastern Goldfields region of Western Australia. The local region comprises part ofthe rangelands area of Australia and has a semi-arid climate. The initial reason for planting olives was indirectly related to the rapid decrease in the local population and the economic downturn that resulted within that community during the late 1990's. This prompted an investigation into other possibilities for economic diversity for remote communities such as Laverton, which are located in the rangelands area of Australia. In Australia, much of the southern and eastern areas of the country have similar climate to traditional olive growing areas in Europe. [n the rangelands however, the environment is different to most other areas in the world where olive trees are grown and there is a notable absence of a commercial olive industry. Whilst locally, individual trees were also observed to be growing well and fruiting abundantly, it is not known whether it is possible to grow olive trees successfully on a commercial scale. Two preliminary trials were established in an ad-hoc manner, to examine whether olive trees could be grown successfully in the rangelands environment. Eighty-eight trees of 5 different cultivars were planted on a shallow, clay soil profile at the first trial site. Ninety-eight trees of 11 different cultivar were planted on a deep sand soil profile at the second site. Higher mortality rate occurred at the first site, with most tree deaths being recorded in the first two years. Peak growth of branch tips occurred during the spring-summer seasons at both sites. Differences in trial design and timing of planting prevented statistical comparison of growth performance between sites however. / A third olive trial, consisting of 3 olive groves was established according to randomised design. In the north and middle groves, 54 trees of 3 different cultivar were planted on a deep alluvial soil profile. In the south grove, 53 trees of 3 different cultivar were planted on a shallow clay soil profile. High mortality rates were recorded at all 3 groves during the first year, as a result of high salinity levels in irrigation water during the establishment period. Overall, most tree mortality was recorded at the south grove. Significantly higher growth performance occurred within the deeper alluvial soil profile at the north and middle groves, compared to the shallow clay soil profile in the south grove. Negligible olive fruit production occurred at the first site. At the second site, small quantities of olive fruit were produced during some seasons only. No olive fruit production occurred at any grove at the randomized site. Successful fruit formation appears directly related to tree health, as a function of water supply. Ripening of olive fruit occurred earlier than at other more temperate olive growing areas of Australia. Similar major and trace element deficiencies occurred at all sites, interpreted to be a function of universal alkaline ground-water conditions. / This study failed to confirm conclusively, whether European olive could be grown successfully in the semi-arid climate, typical of much of the rangelands area of Australia. As a result of the study however, successful growth in this environment is confirmed to be highly dependent on three factors. Firstly, availability of reliable irrigation waters of sufficient quality. Secondly, choice of suitable soil types. Thirdly, selection of suitable cultivars. Quality of olive oil produced from fruit appears to be influenced by local climatic factors The study also highlighted the issues of land tenure, current management attitudes and level of support within the local community as having a direct and significant impact on the trial.

Water is the most important resource on Earth. Climate and land cover changes are two important factors that directly influenced water resources. This research provides important information for water resources management and contributes on understanding of the responses of water resources to climate and land cover changes in two different climates. The Neches River watershed located in a humid subtropical climate had a 0.7 °C increase in temperature and a 16.3 % increase in precipitation. Developed and crop land covers increased whereas vegetation cover decreased, as a result of human activities. Hydrologic responses to climate and land cover changes resulted in the increases of surface runoff (15.0 %), soil water content (2.7 %), evapotranspiration (20.1 %), and a decrease of groundwater discharge (9.2 %). Surface runoff had an increasing trend with precipitation whereas soil water content was sensitive to changes in land cover, especially human intervention. The Canadian River watershed, a semi-arid watershed, experienced a 0.9 °C increase in temperature and a 10.9 % decrease in precipitation. Land cover was converted from developed and crop lands into barren land and grass covers, as a result of the decrease in human activity. The change of grass and forest covers into bush/shrub cover is thought to be linked to climate change. Surface runoff, groundwater discharge, soil water content, and evapotranspiration were all decreased by 10.2 %, 10.0 %, 7.7 %, and 9.4%, respectively. Hydrologic parameters generally follow similar patterns to that of precipitation. The trend in water resources followed a similar trend of precipitation for the two watersheds with different climates; a humid watershed and a semi-arid watershed. The humid climate watershed, the Neches River watershed, experienced increasing trends in temperature and precipitation. Groundwater discharge was sensitive to changes in land cover caused by human activities. The semi-arid watershed, the Canadian River watershed, had an increase in precipitation and a decrease in precipitation. Conversion of developed and crop land covers into barren and grass land covers was thought to be the result of the decrease in human activity. The volume of soil water was relatively offset by a combination of precipitation changes and land-cover changes.

This thesis aims to discuss the archaeological concerns about how surveys can provide data tht is meaningful to construct spatial patterning and its intricacies for inferences through altering processes diversified as cultural and natural processes. Along with that there is also a second concern dealing with the application of these theoretical issues to practical basis. It consists both methodological limits and also limits governed by the legislation of the particular area according to the aim of the study. A particular space, semi-arid climate is selected for comparing the amount of attrition and accretion caused by natural factors, to be able to apply the studies to Anatolian geography. However applications from around the world are frequently discussed here, these are mainly the case studies bringing methodological scheme for the appropriate data collection.

Made available in DSpace on 2014-12-17T15:49:14Z (GMT). No. of bitstreams: 1 IsabeMSR_DISSERT.pdf: 3941458 bytes, checksum: 4b09d98a0eb4509332c88708ef85f1de (MD5) Previous issue date: 2013-08-30 / Edaphic ecosystems are the basis for the production of terrestrial biological resources and their dynamics affect not only the natural environment but also society and their economic activities. In Caatinga biome, the semi-arid climate associated with an inadequate soil management has increased the degradation and loss of productive potential of the soil. In this context, the study of soil fauna, including springtails, becomes an important indicator of soil quality. This study aimed to evaluate the fauna of Collembola in an area of Caatinga of Rio Grande do Norte State and the influence of biotic and abiotic factors, such as soil, vegetation and climate characteristics, on the structure of the taxocenosis. The environmental variables which were used were the following ones: granulometry (represented by the proportion of sand), quantity of organic matter and soil pH, richness, density and aerial biomass of the vegetal structure, and necromass. We used pitfall traps intending to collect specimens of the epiedaphic fauna of Collembola in 30 points located on Caua?u Farm, Jo?o C?mara, RN, in July (rainy season) and November (dry season) 2011. We collected 5513 individuals of 15 species distributed in 13 genera and 9 families of Collembola. Five of the recorded species are new to science, confirming the expected high degree of endemism for Caatinga biome, and the highest abundance was recorded in the rainy season, which suggests Collembola sensitivity to low humidity. Four species were more abundant in the dry season, all of them belonged to the Order Entomobryomorpha. Results of statistical analyzes suggest that plant species richness, aerial biomass of vegetal structure, proportion of sand in the soil, pH and humidity are the main influences to the abundance of Collembola in the region studied / Os ecossistemas ed?ficos s?o base para toda produ??o de recursos biol?gicos terrestres e sua din?mica afeta n?o apenas os ambientes naturais, mas tamb?m a sociedade e suas atividades econ?micas. Na Caatinga, o clima semi?rido associado ao uso inadequado do solo t?m potencializado a degrada??o e a perda do potencial produtivo das terras. Considerando que a fauna ed?fica, incluindo os col?mbolos, ? um importante indicador da qualidade do solo, este trabalho objetivou avaliar a fauna de Collembola numa ?rea de Caatinga do Rio Grande do Norte, verificando a influ?ncia de fatores bi?ticos e abi?ticos, tais como caracter?sticas do solo, da vegeta??o e do clima, sobre a estrutura da taxocenose. As vari?veis ambientais utilizadas foram: granulometria (representada pela propor??o de areia), quantidade de mat?ria org?nica e pH do solo; riqueza, densidade e biomassa a?rea vegetal; e necromassa. Foram utilizadas armadilhas de queda (pitfall) para coletar esp?cimes da fauna epied?fica de Collembola em 30 pontos localizados na Fazenda Caua?u, Jo?o C?mara, RN, nos meses de julho (per?odo chuvoso) e novembro (per?odo seco) de 2011. Foram coletados 5.513 indiv?duos de 15 esp?cies, distribu?das em 13 g?neros e 9 fam?lias de Collembola. Cinco das esp?cies registradas s?o novas para a ci?ncia, confirmando a expectativa de alto grau de endemismo para o bioma, e a maior abund?ncia de indiv?duos foi registrada na esta??o chuvosa, o que sugere sensibilidade dos col?mbolos ? baixa umidade. Quatro esp?cies foram mais abundantes na esta??o seca, todas da Ordem Entomobryomorpha, e os resultados das an?lises estat?sticas sugerem que a riqueza de plantas, a biomassa vegetal a?rea, a propor??o de areia no solo, o pH e a umidade devida ?s chuvas sejam os principais influenciadores da abund?ncia de Collembola na regi?o estudada

Thesis (MScAgric)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Soils of semi-arid regions generally have low organic matter contents, primarily attributed to prevailing climatic conditions. Yet, the spekboom thicket, located in the semi-arid region of the Eastern Cape (South Africa) has been distinguished to accumulate large amounts of soil carbon. To further understand this remarkable accumulation, a detailed investigation was carried out to evaluate the distribution, speciation and stability of the soil carbon from directly beneath spekboom (Portulacaria afra) and other “nonspekboom” vegetation within the intact thicket, and from adjacent, degraded (overgrazed), open thicket sites. In the first experimental chapter, the distribution of organic and inorganic C, as well as general soil properties (pH, EC, exchangeable and water soluble cations, hydrophobicity, water stable aggregates) were investigated in the intact (spekboom and nonspekboom) and degraded (open) thicket soils. There were no significant differences in the C content (organic or inorganic) between the spekboom and nonspekboom sites in the intact thicket. Soil organic carbon (SOC) content however was greatly influenced by thicket degradation, whereas, inorganic C remained unaffected. Mean organic C (0-50 cm) ranged from 19-34, 22-62, and 19-58 g C kg-1 for open, spekboom, and nonspekboom sites, respectively. Whereas, mean inorganic C ranged from 2-9 g C kg-1 irrespective of sites, representing 4-22 % of total soil C. However, no significant differences were detected between degraded and intact sites for all (total, organic and inorganic) C stocks, attributed to variation in bulk density. Spekboom soils contained significantly higher concentrations of exchangeable and water soluble Mg, Na, and K, and consequently had higher pH and EC compared to the other sites. Soils tended to be hydrophobic especially at shallower depths in the intact thicket irrespective of vegetation type, whereas soils from the adjacent open sites were not significantly hydrophobic. Macro-aggregates were considerably more stable under intact sites compared to open sites. The second experimental chapter investigated the effects of degradation and vegetation type on the stability and structural chemistry of SOC. This involved partitioning the soil organic matter into particulate and mineral-bound (stable) fractions, and then examining the relationships between the stable organic C fraction and various soil properties as an attempt to elucidate the stabilization mechanism(s). Particulate organic C ranged from 7.0, 9.3, and 14.4 g C kg-1 for open, spekboom, and nonspekboom respectively; representing 22-34 % of total SOC. Stable (mineral-bound) organic C accounted for the largest fraction ca. 60-66 % of total SOC; 28.0 and 26.2 g C kg-1 for spekboom and non-spekboom respectively, versus 17.2 g C kg-1 for open sites. It was concluded that SOC stability was influenced by the inherent residue quality (recalcitrance) rather than soil properties, attributed to the aliphatic (lipids and waxes) and highly aromatic nature of the spekboom litter substrate and particulate OM. These research findings are of fundamental significance in understanding soil organic matter stabilization in semi-arid environments. / AFRIKAANSE OPSOMMING: Gronde van semi–ariede streke het oor die algemeen 'n lae organiese materiaalinhoud, wat hoofsaaklik aan die heersende klimaatstoestande toegeskryf kan word. Tog, het die spekboomruigtes, geleë in die semi-ariede streek van die Oos-Kaap (Suid Afrika), onderskeidelik groot hoeveelhede grondkoolstof geakkumuleer. Om hierdie merkwaardige akkumulasie verder te verstaan, was 'n gedetailleerde ondersoek uitgevoer om die verspreiding, spesiasie en stabiliteit van die grondkoolstof direk onder spekboom (Portulacaria afra) en ander “nie-spekboom” plantegroei binne die intakte ruigte en van die aangrensende gedegradeer (oorbeweide), oop gras areas te evalueer. In die eerste eksperimentele hoofstuk, is die verspreiding van organiese en anorganiese C, sowel as algemene grondeienskappe (pH, uitruilbare en wateroplosbare katione, hidrofobisiteit, water-stabiele aggregate) was in die intakte (spekboom en nie-spekboom) en degradeerde (oop) ruigtes ondersoek. Daar was geen betekenisvolle verskille in die C-inhoud (organies of anorganies) tussen die spekboom en nie-spekboom gronde in die intakte ruigtes gevind nie. Grond organiese koolstof (GOK) inhoud is grootliks deur die ruigte se agteruitgang beïnvloed, maar anorganiese C-voorrade was egter nie beïnvloed nie. Die gemiddelde organiese C-inhoud (0-50 cm) het van 19-34, 22-62 en 19-58 g C kg-1 onderskeidelik vir 'n oop, spekboom, en nie-spekboom areas gewissel. Die anorganiese C-inhoude het vanaf 2-9 g C kg-1 gewissel, ongeag van ligging, wat 4-22 % van die totale grond C uit maak. Daar is egter geen beduidende verskille tussen vervalle en heel terreine vir almal (totaal, organiese en anorganiese) C aandele opgespoor, toegeskryf word aan die variasie in die massadigtheid. Spekboom gronde het beduidende hoër konsentrasies van uitruilbare en wateroplosbare Mg, Na, en K waardes bevat. Dit het ook hoër pH en EC, in vergelyking met die ander areas gehad. Gronde was geneig om hidrofobies te wees, veral op vlakker dieptes in die intakte ruigte, ongeag van die plantegroei, terwyl die gronde van die aangrensende oop areas nie beduidend hidrofobies was nie. Makro grond aggregate was aansienlik meer stabiel onder intakte ruigtes as in die oop areas. Die tweede eksperimentele hoofstuk het die gevolge van die weiding-geïnduseerde degradasie en tipe plantegroei op die stabiliteit en strukturele chemie van GOK ondersoek. Dit het die skeiding van die grond organiese materiaal in die vrye en mineraalgebonde (stabiele) fraksies behels. Daarna is die verhoudings tussen die stabiele organiese C fraksie en verskeie grondeienskappe ondersoek om die stabiliseringmeganisme(s) uit te lig. Die chemiese aard van die blare, plante oorblyfsels, fyn en minerale gebinde organiese C is met behulp van spektroskopie ondersoek. Vrye organiese C voorraad het van 7.0, 9.3, en 14.4 g C kg-1 vir oop, spekboom, en nie-spekboom onderskeidelik gewissel, wat ongeveer 23-34% van die totale GOK verteenwoordig. Stabiele (minerale gebind) organiese C-voorrade is vir die grootste fraksie ca. 60-66% van die totale GOK verantwoordelik. Dit was 28.0 en 26.2 g C kg-1 onderskeidelik vir spekboom en nie-spekboom, teenoor 17.2 g C kg-1 vir 'n oop area. Die mineraalgebonde GOK het geen noemenswaardige korrelasies met die ondersoekte grondeienskappe getoon nie. Dus is tot die gevolgtrekking gekom dat GOK stabilisering eerder deur die plante oorblyfsel se chemiese kwaliteit beïnvloed word. Strukturele chemiese karakterisering (13C CP-MAS KMR) van die spekboom afval en vrye C fraksie het gewys dat weerspannigheid die mees prominente meganisme van koolstof stabilisering van organiese koolstof in die gronde is. Dit word aan die alifatiese (lipiede en wasse) en sterk aromatiese aard van die spekboom substrate toegeskryf. Hierdie ondersoek het tot die fundamentele kennis van grond organiese materiaalstabilisering in 'n semi-ariede omgewings bygedra.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The aim of this work was to evaluate the influence of different seasons on the ingestive behavior, on the botanical composition of the diet of goats grazing in the caatinga and on the availability and quality of forage of the caatinga. Four castrated male goats were used, with a mean weight of 30.2 kg and mean age of 20 months. The experiment had a duration of 12 months, comprising two rainy seasons and one dry season, and the treatments consisted of the three seasons (the two rainy seasons were treated separately) with 3 repetitions per season. Each animal was always accompanied by the same observer. The observed behaviors were feeding, idleness, rumination, displacement, social interaction and water intake. Forage collections were performed at 30 points in the area, considering a maximum collection height of 1.5m. All the forage collected and classified in the different strata (herbaceous, woody and litter), after the analysis was performed to know the bromatological composition of these. Non-parametric tests of Kruskal-Wallis (5%) and Nemenyi (5%) were performed in order to identify differences in the occurrence of behaviors between each season of the year. There was no significant difference (P≥0.05) between rumination, displacement and others (sum of social interaction and water intake) in the different seasons. However, a significant difference was observed in the occurrence of feeding and idleness (P = 0.0015 and P = 0.0001, respectively). In the dry season, a higher feeding occurrence and less occurrence of idleness occurred, contrary to what occurred in the rainy season/18 where there was greater occurrence of idleness and less feeding. The woody stratum presented the best bromatological composition, however the stratum was less present, and the herbaceous stratum was more available during the experimental period. The species whose consumption was recorded were: pinhão (jatropha molissima), velande (Croton heliotropiifolius), catingueira (Poincianella pyramidalis), marmeleiro (Croton blanchetianus), pereiro (Aspidosperma pyrifolium), macambira (Bromelia laciniosa), umburana (Commiphora leptophloeos) maniçoba (Manihot glaziovii), besides the herbaceous stratum, litter and cactaceae, the latter consisting of clusters of species of the same habit of growth. Most of the food in the rainy season/17 consisted of the herbaceous stratum (67.47%), in the dry season consisted of litter (56.12%) and in the rainy season/18 consisted of macambira (61.13%). The seasons influenced the pattern of behavior, the choice of food and the availability and quality of forage found in the caatinga. / O objetivo deste trabalho foi avaliar a influência de diferentes estações no comportamento ingestivo, na composição botânica da dieta de caprinos pastejando na caatinga e na disponibilidade e qualidade de forragem da caatinga. Foram utilizados 4 caprinos machos castrados sem raça definida, com peso médio de 30,2 Kg e idade média de 20 meses. O experimento teve um período de duração de 12 meses, englobando duas estações chuvosas e uma seca, sendo que os tratamentos consistiram nas 3 estações (as duas estações chuvosas foram tratadas de forma separada) com 3 repetições por estação. Cada animal foi sempre acompanhado pelo mesmo observador. Os comportamentos observados foram alimentação, ócio, ruminação, deslocamento, interação social e ingestão de água. Coletas de forragem foram realizadas em 30 pontos na área, considerando uma altura máxima de coleta de 1,5m. Toda a forragem coletada e classificada nos diferentes estratos (herbáceo, lenhoso e liteira), após foi realizada a análise para se conhecer a composição bromatológica destes. Foram realizados os testes não paramétricos de Kruskal-Wallis (5%) e Nemenyi (5%) com o intuito de identificar diferenças na ocorrência dos comportamentos entre cada estação do ano. Não foi observada diferença significativa (P≥0,05) entre a ruminação, deslocamento e outros (soma da interação social e ingestão de água) nas diferentes estações. Contudo, observou-se diferença significativa na ocorrência de alimentação e ócio (P=0,0015 e P=0,0001, respectivamente) sendo que na estação seca se observou maior ocorrência de alimentação e menor ocorrência de ócio, ao contrário do que ocorreu na estação chuvosa/18 onde houve maior ocorrência de ócio e menor alimentação. O estrato lenhoso apresentou a melhor composição bromatológica, contudo foi o estrato menos presente, estando o estrato herbáceo em maior disponibilidade durante o período experimental. As espécies cujo consumo foi registrado foram: pinhão (jatropha molissima), velande (Croton heliotropiifolius), catingueira (Poincianella pyramidalis), marmeleiro (Croton blanchetianus), pereiro (Aspidosperma pyrifolium), macambira (Bromelia laciniosa), umburana (Commiphora leptophloeos), maniçoba (Manihot glaziovii), além do estrato herbáceo, liteira e cactáceas, consistindo estas últimas em conjuntos de espécies de mesmo hábito de crescimento. A maior parte do alimento na estação chuvosa/17 consistiu no estrato herbáceo (67,47%), na estação seca consistiu na liteira (56,12%) e na estação chuvosa/18 consistiu na macambira (61,13%). As estações influenciaram o padrão de comportamento, na escolha dos alimentos e na disponibilidade e qualidade da forragem encontrada na caatinga. / São Cristóvão, SE

La plaine du Souss est délimitée au nord par le Haut-Atlas, au sud par l’Anti-Atlas et à l’estpar le massif cristallin de Siroua. Les principales formations géologiques sont des marnocalcaireset conglomérats assez perméables, les calcaires du Turonien qui leur sont sousjacentset le lit fossile de l’oued Souss composé d’alluvions sablo-graveleuses trèsperméables.La nappe du Souss est la plus importante du sud du Maroc, elle est très exploitée par unsecteur agricole exportateur, la surexploitation de la nappe s’est traduite par une baissecontinue des niveaux. Depuis 1970, les prélèvements dépassent de loin les ressourcesrenouvelables de la nappe (déficit : 185 Mm3 en 1976, 358 Mm3 en 1998, 228 Mm3 en 2003).Le barrage d’Aoulouz est principalement destiné à la recharge artificielle de la nappe par deslâchers d’eaux stockées pendant les périodes pluvieuses. En zone semi-aride, une estimationprécise de la recharge est souvent délicate, la variabilité spatio-temporelle de la recharge étantgénéralement forte et les processus variés.Ce travail a permis de mieux caractériser l’impact de la recharge sur la nappe et d’évaluer letemps de séjour et le renouvellement des eaux souterraines.L’évolution de la piézométrie à la suite des lâchers d’eau à partir du barrage Aoulouz montredes remontées locales du niveau piézométrique sur la haute plaine, environ 85% des eauxlâchées à partir du barrage d’Aoulouz s’infiltrent 80 km entre Aoulouz et Taroudant.Toutefois, le niveau général de la nappe continue de baisser.Le faciès géochimique est principalement bicarbonaté calcique (dissolution des carbonates), etpar endroits sulfaté calcique (évaporites au pied du Haut-Atlas). Les eaux de surface ont unfaciès bicarbonaté calcique et magnésien acquis lors de leur circulation sur des calcaires et desdolomies.[...] / The Souss valley is bounded to the North by the High Atlas, to the South by the Anti-Atlasand to the East by the Siroua crystalline massif. The main geological formations arecalcareous marls of the Plio-Quaternary, the Turonian limestones that underlie them, and thefossil bed of River Souss formed by sands, sandstones and gravels from high permeabilityalluvium.The Souss aquifer is the most significant aquifer in southern Morocco, highly exploited by anagricultural exporting activity. Groundwater overexploitation induced a decreases ofpiezometric heads. Since 1970, water demand far exceeds renewable groundwater resources(balance defecit: 185 Mm3 in 1976, 358 Mm3 in 1998, and 228 Mm3 in 2003).The mean role of the Aoulouz dam is the artificial recharge of the Souss plain by release ofwater stored during rainy periods in the plain.In semi-arid areas, estimating recharge is often difficult, the spatial and temporal variabilitiesof recharge are generally high, and processes are varied.This work has enabled to characterize the impact of artificial recharge and to estimate therenewal of water in the aquifer.Water releases from Aoulouz dam has permitted an increase of the piezometric level on thehigh plain, about 85% of the water released are unfiltered in the first 80 Km between Aoulouzand Taroudant cities. However, the general water level decline goes on.The geochemical facies is mainly calcium bicarbonate type (dissolution of limestone), andlocally calcium sulphate type (evaporites of the High Atlas). Surface waters are a calcium andmagnesium bicarbonate types, acquired during their flow through limestones and dolomitesoutcrops.[...]

Vertisols cover a hydrologically very significant area of semi-arid regions, and thus understanding of water flow and solute accumulation is very relevant to agricultural activity and water resources management. Previous works suggest a conceptual model of desiccation-crack-induced salinization where salinization of sediment in deep section of the vadose zone (up to 4 m) is induced by subsurface evaporation due to convective air flow in desiccation cracks. This thesis presents a conceptual model of water flow and solute transport in vertisols, and its numerical implementation. The model uses a single-porosity material but unconventionally prescribes a boundary condition representing a deep crack in soil and uses the unsaturated hydraulic conductivity as one of the fitting parameters. The numerical model is bound to one location close to a dairy farm waste pond, but the application of the suggested conceptual model could be possibly extended to all semi-arid regions with vertisols. Simulations were conducted using several modelling approaches with an ultimate goal of fitting the simulation results to the controlling variables measured in the field: water content, and chloride salinity of pore water. The development of the model was engineered in numerous steps; all computed as forward solutions by...

Le Norte-Chico constitue une zone tampon ayant enregistrée les fluctuations climatiques quaternaires. La fraîcheur des modelés et des formes présents dans la haute cordillère de l’Elqui, va nous permettre de tenter d’expliquer le calendrier de mise en place des éléments du relief. Les indices de terrain nous permettent de mettre en évidence un enchaînement de processus faisant intervenir la notion de relais et de zones tampons dans le transit sédimentaire. Les crises morphogéniques à l’origine des formations de versant et de fond de vallée actuellement visibles résultent d’une réponse plus ou moins directe de l’orogène Andin aux épisodes climatiques ; par conséquent, les résultats obtenus sont confrontés aux résultats d’autres études et dans des sites proches ou non de notre lieu d’étude afin d’apporter des exemples et des arguments aux hypothèses actuelles sur l’évolution des conditions climatiques quaternaires du Norte-Chico. La complexité de la mise en place des éléments du relief nécessite en premier lieu une explication des différentes phases orogéniques ainsi que des évolutions morphoclimatiques ayant abouti à la mise en place des conditions actuelles. Ensuite, la méthodologie nécessaire au travail de terrain et à l’obtention de résultats cohérents est définie et expliquée. Une dernière partie est consacrée à la synthèse de l’enchaînement de mise en place des formations de fond de vallée ; les résultats de cette étude sont également replacés dans un débat scientifique plus large permettant d’appréhender les potentialités apportées par la géomorphologie dans l’étude des paléoenvironnements quaternaires dans le Norte-Chico comme à l’échelle planétaire. / Norte Chico is a buffer zone having registered Quaternary climatic fluctuations. The preservation of landforms and relief present in the Elqui cordillera, make it a rich geomorphological study area, which may provide answers to many of the assumptions Quaternary calendar climate of the region. Freshness and modeled forms present in the high Andes of Elqui, coupled with the presence of datable organic matter, will allow us to to explain the timing of implementation of the elements of relief. Field indices surveys allow us to highlight a series of processes involving the notion of relay and buffer zones in the sediment transport. Morphogenic crises originally training slope and valley floor currently visible result of a more or less direct answer of the Andean orogen to climatic events, so the results are compared with the results of other studies and in sites close or not our place of study to provide examples and arguments to current hypotheses on the evolution of the Quaternary climatic Norte Chico and multiscale way. The complexity of the implementation of the relief units, requires firstly an explanation of the different orogenic phases and developments morphoclimatic leading to the gradual development of current conditions. Second, the methodology necessary fieldwork and consistent results is defined and explained. A final section presents the synthesis of the series of training implementation valley bottom; the results of this study are also viewed in a broader scientific debate to apprehend the potential provided by the geomorphology in the Quaternary paleoenvironmental study of the Norte Chico as globally.

Le nord du Chili est soumis à un contexte climatique aride à semi-aride présentant une variabilité saisonnière et inter-annuelle forte. Dans cette région les zones de haute altitude soutiennent les parties plus basses des bassins versants, mais la ressource en eau reste malgré tout limitée. Afin d'améliorer les méthodes de gestion de l'eau dans ces bassins versants, il est important de préciser le rôle des zones de haute altitude dans le soutien des parties basses, mais aussi de caractériser les modalités de transfert et d'interaction entre les compartiments constitutifs de l'hydrosystème. Ce travail porte sur la caractérisation du fonctionnement hydrologique du bassin versant de l'Elqui depuis la tête de bassin, située au cœur de la cordillère des Andes, jusqu'aux vallées de la zone inférieure situées entre 500 et 2000 mètres d'altitude. En tête de bassin, les processus d'interaction entre les compartiments cryosphériques, hydrologiques et hydrogéologiques, et leurs impacts sur le transfert des masses d'eau vers l'aval de la zone d'étude sont caractérisés. Le comportement hydrologique des sous bassins versant partiellement ou non‑englacés est également étudié. Dans la zone inférieure du bassin, l'étude porte principalement sur les processus d'interactions surface-souterrain en contexte semi‑aride et sur les impacts des forçages climatiques et anthropiques sur ces derniers. Cette étude s'appuie sur plus de 40 ans de données hydro-météorologiques disponibles sur la zone inférieure du bassin, complétés par des mesures hydrologiques sur la zone supérieure (> 2000 mètres d'altitude) et des prélèvements chimiques (majeurs et traces) et isotopiques (²D, 18O) sur la totalité de la zone d'étude, réalisés entre 2011 et 2013.Ces travaux ont montré que le modèle conceptuel de fonctionnement du bassin versant de l'Elqui généralement accepté était incomplet. Dans la zone supérieure, l'étude d'un bassin versant englacé a permis de montrer que le rôle de la cryosphère dépasse la fonction de production d'eau, avec certains compartiments stockant temporairement de l'eau en période humide et la libérant en période sèche. Ce processus permet d'amortir la variabilité temporelle des précipitations et du taux de fonte en altitude. Les analyses physico-chimiques réalisées dans le bassin versant ont également permis d'identifier des compartiments aquifères ignorés jusqu'à maintenant, comme les compartiments volcanique et plutonique. En améliorant les connaissances sur les processus d'interactions entre compartiments cryosphériques, hydrologiques et hydrogéologiques, les résultats de ce travail ont apporté des précisions sur le fonctionnement hydrologique de la zone de haute altitude. Cela a permis l'estimation des impacts potentiels de la variabilité climatique sur ces processus d'interactions et leurs conséquences sur la disponibilité et la qualité de la ressource. Dans la zone inférieure, la caractérisation des interactions surface-souterrain a montré qu'il existe un fort potentiel d'interaction entre le compartiment hydrologique et le compartiment alluvial, mais également entre le compartiment alluvial et le socle plutonique. L'étude des données hydrologiques et physico-chimiques a permis de caractériser le type d'échanges se déroulant entre les compartiments. Dans certains secteurs le processus dominant est la recharge du compartiment alluvial par le compartiment hydrologique, tandis que pour d'autres il existe une alternance entre période de drainage du compartiment alluvial par le compartiment hydrologique et période de recharge du compartiment alluvial. La réponse de ces processus face aux impacts des forçages climatiques et anthropiques contraindra la disponibilité et la qualité de la ressource dans les années à venir. Ainsi, les résultats apportés par ce travail permettront certainement de mieux anticiper les modifications futures du fonctionnement hydrologique des bassins versant montagneux en contexte semi-arides. / The north Chile is affected by an arid to semi-arid climate, associated with a strong seasonal to inter-annual variability. In this region, while mountainous areas are supporting low areas, the availability of water resources remains limited. In order to improve the water management in these basins, it is necessary to precise how the high areas support the low areas, and to characterize water transfers and interaction processes between the constitutive compartments of the hydrosystem. This work concern the characterization of the hydrodynamic behavior of the Elqui watershed from the headwaters, in the Andes, to the valleys, ranging between 500 and 2000 m.a.s.l.In the headwaters, the interactions processes between cryospheric and hydrologic compartments and their impact on water transfers to the low areas are characterized. The behavior of unglacierized or partially glacierized watershed is also studied. In the low area of the watershed, the study mainly considers groundwater-surface water interactions under semi-arid context and the impact of the climatic variability on these processes. This study is based on more than 40 years of hydro-meteorological data available in the lower zone of the basin, completed by hydrological measurements in the upper zone (> 2000 m.a.s.l.) and chemical (majors and traces elements) and isotopic samples (²D, 18O) over the whole study area realized between 2011 and 2013.This work demonstrated that the conceptual model of the Elqui basin hydrological behavior, generally accepted, was incomplete. In the high area (> 2000 m.a.s.l.), the study of a glacierized watershed show that the function of the cryosphere overpass the water production with some compartments storing water during humid periods and draining their water content during dry periods. This process buffers the temporal variability of precipitations and melting rates in the high area. Physico-chemical analysis, allows to identify some ignored aquifer compartments, as the volcanic and plutonic compartments. The results of this study improve the knowledge about interactions processes between cryospheric, hydrologic and hydrogeologic compartments, which precise the hydrological functioning of the high area. The interpretation of the hydrological behavior of the high altitude area allows to better understand the way that it support the low area, and the way that climate variability may affects it.In the low area, results show that the groundwater-surface water interaction potential is good between alluvial and hydrological compartments, but also between the plutonic and the alluvial compartments. The study of hydro-meteorological and physico-chemical data allowed to characterize the type of exchanges that take place between groundwater and surface water. In some sectors the main process is the recharge of the alluvial compartment by the hydrological compartment, while in other sectors the processes show a seasonal variability with periods of alluvial compartment recharge and periods of hydrological compartment support. The answer of these processes face to climatic and anthropic forcing will constrain the evolution of the availability and quality of the water resources in the Elqui basin. Finally, the results of this study will certainly allow to better anticipate the future modifications of the semi-arid mountainous watershed hydrological functioning.