Дисертації з теми "Aridità"
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Burgess, Tony L. "Agave Adaptation to Aridity." University of Arizona (Tucson, AZ), 1985. http://hdl.handle.net/10150/554187.
Повний текст джерелаFouet, Caroline. "Caractérisation de quelques phénotypes liés à l'aridité et à la température chez Anopheles gambiae sensu stricto (Giles, 1902)." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20155/document.
Повний текст джерелаThanks to progress in sequencing, the genomes of many organisms are known and available. Thus, functional genomics, the elucidation of gene function in sequenced genome, is currently booming. However, there is a gap between our growing knowledge in genetic and the current sparse information on phentoypic data ( "phenotype gap"). All organisms whose genome has been sequenced are facing this problem, including Anopheles gambiae.Anopheles gambiae sensu lato is a complex of sibling species, indistinguishable from a morphological point of view, present on almost the entire African continent. A. gambiae demonstrates an extreme environmental ubiquity and the characterization of phenotypes associated with adaptation to varying environments as well as the identification of genes involved in this adaptation is one of the main research axes in the post-genome area of this major malaria vector.We have studied some phenotypes associated with aridity and temperature in the nominal species of the A. gambiae complex. These two parameters are discriminent in the distribution of molecular forms and chromosomal inversions that characterize this species and may be involved in ecological divergence and speciation. We first measured desiccation resistance of adult mosquitoes of A. gambiae s.s. and we then studied the preferred temperatures of larvae in a choice device set-up (the shuttlebox). We compared the thermoregulation behavior and thermal preferences of a laboratory strain with field larvae of A. gambiae s.s. We also presented preliminary data on the preferred temperatures measured in field larvae of the S and M molecular forms.From a technical point of view, we improved an existing device for testing the survival of mosquitoes in highly desiccated conditions by coupling it with a video surveillance system, which help to increase the accuracy in determining the survival time, to avoid disturbing the system during the experiment and allow to test relatively large numbers of individuals. This study revealed a significant association between the 2La chromosomal inversion and resistance to desiccation in A. gambiae and highlighted the role of body size in the survival of this mosquito in dry environments.We also adapted a new device to study experimentally the thermopreference of A. gambiae s.s. larvae. The results showed that laboratory larvae and field M molecular form larvae had similar thermal preferences, consistent with the values of temperature usually found in natural breeding sites. In addition, the S molecular form larvae from southern Cameroon had preferences similar to those of northern Cameroon, regardless of karyotypes related to chromosomal inversions. In addition, the comparison of data for the M and S molecular forms larvae revealed that there was no significant difference in thermal preferences or in thermoregulatory behavior.Our results have contributed to the development of two experimental devices to study two phenotypes that are of major interest in understanding the adaptation of A. gambiae s.s. to its environment. The differences in desiccation resistance between the different karyotypes associated with the 2La chromosomal inversion and between the M and S molecular forms offer interesting new possibilities for the identification of genetic factors involved in their ecological divergence
Gortan, Emmanuelle. "Misura dello stato idrico di fraxinus ornus L. quale biomonitor dell'aridità ambientale in siti diversi del carso triestino." Doctoral thesis, Università degli studi di Trieste, 2008. http://hdl.handle.net/10077/2658.
Повний текст джерелаL'aridità è una condizione ambientale che comporta una ridotta disponibilità d'acqua per le piante all'interno del suolo. La disponibilità d'acqua rappresenta, unitamente alla temperatura, il fattore ambientale che più di ogni altro condiziona la distribuzione e la produttività primaria della vegetazione. Poiché una prolungata aridità ambientale ha serie conseguenze sulla produttività degli ecosistemi forestali e sulla sopravvivenza di alcune specie vegetali meno competitive di altre in tali condizioni, è di fondamentale importanza quantificare il livello di aridità ambientale per poterne prevedere l'impatto attuale e le tendenze in atto. Il progetto di ricerca si poneva quindi l’obiettivo di individuare e definire un indice di aridità ambientale, che consentisse di rappresentare le relazioni che la pianta contrae con l’acqua presente nell’ambiente in funzione della risposta fisiologica della pianta al variare del contenuto idrico del suolo, attraverso un valore unico a significato ecofisiologico. L'individuazione di un parametro ecofisiologico in grado di stimare in modo affidabile l'impatto dello stress idrico poneva le basi per valutare possibili correlazioni con parametri ottenibili con il telerilevamento. Un'altra finalità del lavoro era, infatti, l'individuazione di un parametro di riferimento mediante l'utilizzo di tecniche di telerilevamento da satellite da applicare nello “scaling up” ecologico, che a partire dallo studio dell'impatto dello stress idrico su singole specie potesse indagare sistemi di vegetazione sempre più grandi nell'ottica di sviluppare una visione olistica di grandi aree in relazione all'aridità ambientale. La specie vegetale che è stata scelta come potenziale biomonitor è Fraxinus ornus L. ossia l'orniello, che è stato selezionato in quanto trattasi di una specie vegetale che si distingue per la notevole capacità di resistenza a condizioni di stress idrico e proprio per questa sua capacità, è una specie diffusa in una grande varietà di ambienti. L'area di studio scelta è stata la provincia di Trieste ed in particolare l'area carsica. Questa zona, infatti, offre l'opportunità di eseguire significativi biomonitoraggi per valutazioni quantitative e qualitative sull'ambiente, in quanto presenta una elevata variabilità di substrati litologici, costituiti da rocce soggette a fenomeni di dissoluzione da parte delle acque meteoriche chimicamente aggressive (rocce carsificabili), a cui sono associati diversi tipi di circolazione idrica. La presenza di una fitta rete di fessure e fratture nei substrati geologici a tratti determina un forte drenaggio dell'acqua all'interno del suolo dovuto a percolamento della stessa verso gli strati più profondi. Nella zona del Carso triestino, sono state selezionate 21 stazioni in base ad un criterio geomorfologico noto come carsificabilità, che misura in modo indiretto e qualitativo la capacità di campo di un suolo, e in modo tale da ricoprire tutto il territorio dell'area carsica all'interno della provincia di Trieste. Al fine di identificare quale fosse il parametro fisiologico o morfologico che meglio si addicesse allo scopo della ricerca, sono stati misurati nel periodo da Maggio a Settembre i parametri relativi alle relazioni pianta-acqua generalmente correlati allo stress idrico e cioè la conduttanza fogliare al vapore d'acqua (gL), il potenziale dell'acqua della foglia (Ψfoglia) e la conduttanza idraulica della foglia (Kfoglia). Contestualmente, sono stati misurati anche i diametri dei vasi xilematici. Grazie all'analisi di questi parametri è stato possibile eseguire uno studio biofisico accurato del comportamento idraulico dell'orniello in condizioni di limitazione della disponibilità d'acqua. Da questi dati emerge che la conduttanza fogliare al vapore d'acqua (gL) è il parametro più affidabile a rappresentare l'indice di aridità ambientale, in quanto è risultato essere il più sensibile alle variazioni nella disponibilità d'acqua. Il tentativo di integrare i dati di campo relativi a gL con quelli ottenuti mediante elaborazione di immagini satellitari non ha portato ai risultati sperati. L'indice ottenuto da dati telerilevati è risultato poco promettente come indice di riferimento per la realizzazione di uno “scaling-up”, in quanto non è risultato essere in grado di rilevare condizioni di stress idrico in aree caratterizzate da forte drenaggio dell'acqua (aree ad alta carsificabilità). L'applicabilità delle tecniche di telerilevamento da satellite nel monitoraggio dell'aridità ambientale risulta quindi fortemente limitata dalla struttura geomorfologica del territorio oggetto di studio.
XX Ciclo
1973
Touzeau, Alexandra. "L'Egypte ancienne, une civilisation face à un changement climatique : le message isotopique (C, N, O, S) des tissus vivants momifiés." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10104.
Повний текст джерелаEgypt is an arid territory, which essentially depends on the Nile river for the irrigation of its agricultural lands. The temporal variability of the river flood thus may have affected directly the dynamics of the Egyptian population. Here, this hypothesis is tested by studying the variation of the climate during Ancient Egypt concurrently to indicators of the life habits of the Egyptians. The variation with time of the δ18Ow of the Nile water is reconstructed from the δ18Op of the apatite phosphate of Egyptian mummies. The increase of +3 ‰ in the Nile water δ18Ow between the predynastic period (5500BP) and the Greco-Roman Period (2000BP) is caused by a change in the conditions of precipitation above the Nile sources. This increase can be the result of an increase in temperature of about +2 °C or of a decrease in the monthly amount of precipitation of about 140 mm. Here, the hypothesis of aridification is preferred: in effect, δ18Op measures on Nile fishes permit to infer a Nile water temperature at the Greco-Roman Period similar to the present-day one. The climatic change seems to have had little impact on the Egyptian civilization. In effect the Egyptian population increases considerably during the selected period and its diet remains funded on C3- plants, feebly adapted to arid environments, with a rare consumption of fishes or other animal protein. The decrease of the flood was admittedly compensated by the technological advances of the Egyptian civilization (shaduf, drainage) which allowed the cultivation of newly reclaimed lands
Reyes, Serrano Héctor Fabian. "La tierra se mueve : les transformations de la propriété agricole dans une zone aride : la province du Limarí (Région de Coquimbo, Chili)." Phd thesis, Université d'Orléans, 2009. http://tel.archives-ouvertes.fr/tel-00455240.
Повний текст джерелаNeilson, Julia W., Katy Califf, Cesar Cardona, Audrey Copeland, Treuren Will van, Karen L. Josephson, Rob Knight, et al. "Significant Impacts of Increasing Aridity on the Arid Soil Microbiome." AMER SOC MICROBIOLOGY, 2017. http://hdl.handle.net/10150/625716.
Повний текст джерелаRey, Carine. "Détection de l’évolution convergente à l’échelle génomique : développement de méthodes et étude des adaptations indépendantes à la vie en milieu aride chez les rongeurs." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEN060.
Повний текст джерелаPhenotypic convergence, the independent acquisition of similar characters by different species,is widespread in nature and has been extensively studied. But this evolutionary process is not well understood. For example, many researchers seek to understand whether there are convergent genetic bases underlying these phenotypic convergences.Some convergent substitutions correlated with a convergent phenotype have been described in the literature, but there are few studies at the genome scale. This can be explained by two methodological problems : 1 / On the one hand, the difficulty of creating multi-species datasets for comparative analyses. 2 / On the other hand, the lack of dedicated methods to detect convergence at the genomic scale.During my thesis, I proposed solutions to these two challenges. As a first step, I created a program (CAARS) to automate the assembly of datasets composed of orthologous families from RNA-Seq data. Then I created a tool (PCOC) to study convergent substitutions within coding sequences, based on the identification of amino acid profile changes rather than strict amino acid changes. These tools have been developed for the sake of reproducibility and ease of use. I then studied the ability of different methods, including PCOC, to detect convergent substitutions in the presence of confounding factors. Finally, I applied these methods to a biological case where I sought to characterize the genomic bases of adaptation to arid environments in rodents
Spinks, Andrew Charles. "Sociality in the common mole-rat, Cryptomys hottentotus hottentotus : the effects of aridity." Doctoral thesis, University of Cape Town, 1998. http://hdl.handle.net/11427/23681.
Повний текст джерелаMpofu, Khulekani. "Evaluation of the performance of community-based natural resources management (CBNRM) projects along an aridity gradient in Botswana." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1006063.
Повний текст джерелаBen, Brahim Mohamed. "Le sillon de Boudenib (SE-Maroc) : structuration morphotectonique, hamadas tertiaires et paléoaltérations associées, morphogenèse quaternaire et aridité actuelle." Paris 1, 1994. http://www.theses.fr/1994PA010597.
Повний текст джерелаThe purpose of this research is to study the role of tectonic and climat in the elaboration of reliefs of high and middle scale. The pluridisciplinary approch constitues the methodologic frame. It is shown that boudenib grooc is situated in the intersection of three major geotectonic units : panafrican, hercynian and atlasic. The dissymetry of topographical features reflects this structure. The sedimentation recorded the total phenomenon which succeeded inside the basin as well as on the borders. Therefore, dissymetry between eastern and western parts of the boudenib groov has been constant in the evolution. The preturonian evolution was caracterized by the control of tectonic factors, climat and eustatic ones. However, from the upper cretaceous only tectonic and climatic factors predominated. The study of hamadas deposits on the piedmont of boudenib brings new factors about the atlasic tectonic, the kind of deposits and associeted paleoweathering in which silicification makes the originaly. Two types of silicification were difined : pedogenetic silicification in the lower part of "hamada de boudenib" (lower eocene) and ground water silicification in the "hamada de guir" (neogene). Eventually, the tertiary morphogenisis is caracterized by the juxtaposition of two piedmonts : accumulation and erosion. .
Frenette-Dussault, Cédric. "L'assemblage des communautés en milieu aride : une approche fonctionnelle." Thèse, Université de Sherbrooke, 2012. http://hdl.handle.net/11143/6546.
Повний текст джерелаvan, Dijk Jeroen. "Size and Abundance of Late Pleistocene Reticulofenestrid Coccoliths from the Eastern Indian Ocean in Relation to Temperature and Aridity." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-325273.
Повний текст джерелаMätningar av abundans och massa hos coccoliter kan användas som en signal för primärproduktion och pelagisk förkalkning som resultat av miljöförändringar. Leeuwin Current (LC) är känd för att transportera varmt vatten och vatten med låg salthalt från Indo-Pacific Warm Pool (IPWP) söderut längs kusten i västra Australien. Tillsammans med början av kontinental torka under sen Neogen kan ökad styrka hos LC ha spelat en roll i expansionen av rev på nordvästsockeln. I denna studie bedömdes den morfologiska variationen i storlek och massa hos coccoliter i material från IODP plats U1461 i östra Indiska oceanen från de senaste 500 000 åren. Både den absoluta abundansen av alla reticulofenstridcoccoliter (Emiliania huxleyi, Reticulofenestra spp., Gephyrocapsa spp. och Pseudoemiliania spp.) bestämdes, liksom den relativa abundansen av stora jämfört med små coccoliter. Storlek och massa av coccoliter mättes kvantitativt under cirkulärt polariserat ljus. Uppgifterna jämfördes med variationer i havsytans temperatur (SST) hos LC, och med kontinental torrhet i Australien. SST-fluktuationer kan påverka produktiviteten hos coccolitoforider genom att påverka deras metabolism, medan kontinental torrhet kan påverka inflödet av markmaterial med vind. Det undersökta intervallet domineras av små arter av Gephyrocapsa. Toppvärden av absolut abundans och massa observerades under marinisotopsteget (MIS) 11, en interglacial period med förlängd värme och fuktighet. Dessa resultat kombinerat med hög densitet av aragonitnålar i samma prover indikerar att sedimenten späddes ut med material som svämmade över från den intilliggande grunda karbonatplattformen, vilket är jämförligt med de vitningshändelser som har observerats i dagens Bahamas. En minskning i abundans av Gephyrocapsa caribbeanica vid 240 ka kan kopplas till tidpunkten för deras senaste gemensamma förekomst (LCO) inom MIS 7. Den efterföljande övergången till Gephyrocapsa oceanica som den dominerande stora arten kan indikera en ekologisk ersättning av G. caribbeanica, eller indikera varmt vatten med låg salthalt.
Kheir, Maya. "Fonctionnement des sols méditerranéens sous changement climatique : effet de la préexposition au stress, de la mixité des litières et de l'identité de l'espèce végétale." Thesis, Aix-Marseille, 2020. http://theses.univ-amu.fr.lama.univ-amu.fr/200710_KHEIR_495pzb687n410mxugdf923oaivtm_TH.pdf.
Повний текст джерелаThis work takes place in the context of climate change. We aimed to explore plant litter microbial communities' functioning depending on climate contrasts Northern/Southern Mediterranean but also according to inland/coastal context, and to assess their response to aridification stresses, considering the effect i) of the type of litter (plant species identity and mixture) and ii) of the preexposure to stress intrinsic of coastal environments. Aridity stress was applied in the laboratory (drying /rewetting cycles) and in natura via "litter bags" transfer from France to Algeria. Results show that microbial biomass and basal respiration depend on litter chemical traits (C/N and lignin/N): when these ratios increase, microbial biomass decreases, while the effect on respiration depends on the climate contrasts. The effect of binary litter mixtures on microbes depends on the climate context and the mixture composition: some mixtures seem to limit carbon release through heterotrophic respiration in Algerian arid context. In addition, a particular microbial functioning of coastal environments was highlighted: i) preexposure to coastal constraints limited the effect of stress applied in the laboratory on microbial catabolic structures ii) the in natura experiment showed that microbial responses to stress depend on the context (coastal/inland) but also on litter type, highlighting litter influence even at large spatial scales
O'Connor, Peter W. "Aeolian activity and environmental change in the Central Mega Kalahari : implications for the timing, nature and causes of late Quaternary aridity." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284355.
Повний текст джерелаTatsumi, Chikae. "Nitrogen cycling driven by soil microbial communities in exotic black locust plantations and native oak forests in the drylands of East Asia." Kyoto University, 2020. http://hdl.handle.net/2433/253313.
Повний текст джерела0048
新制・課程博士
博士(農学)
甲第22477号
農博第2381号
新制||農||1074(附属図書館)
学位論文||R2||N5257(農学部図書室)
京都大学大学院農学研究科森林科学専攻
(主査)准教授 舘野 隆之輔, 教授 北島 薫, 教授 德地 直子
学位規則第4条第1項該当
Rueff, Henri. "Optimizing dryland afforestation : prospects and limitations : minimum carbon payment for non-annex I dryland countries on an aridity gradient with stochastic weather and prices." Aix-Marseille 3, 2009. http://www.theses.fr/2009AIX32045.
Повний текст джерелаRecent findings demonstrate that dryland trees are efficient carbon sinks. The price of carbon at which a farmer would be indifferent between his customary activity and the plantation of trees for the trade of carbon credits remains however unknown. Carbon yields were simulated by means of the CO2FIX v3. 1 model for Pinus halepensis. Wheat yields and pasture yields were predicted on somewhat similar nitrogen-based quadratic models, using 30 years of weather data for the simulation of moisture stress. Both models were developed for dryland conditions, while calibration and validation were done with data collected in Israel on 8 stations (from 200mm to 900mm of annual precipitation). No-till wheat and pasture yield values were then fitted to a gamma probability distribution function, to enable iterative stochastic production simulation. Input and output prices were, however, fitted to a normal distribution. Stochastic production, input and output prices were afterwards simulated on a Monte Carlo matrix with 10,000 iterations on a 30 years cash flow. Results show that, despite the high levels of carbon uptake by dryland trees, carbon trading by afforesting is unprofitable anywhere along the aridity gradient. Indeed, the price of carbon will have to raise unrealistically high, and the certification costs will have to drop significantly, to make afforestation under the clean development mechanism a worthwhile activity for non annex I dryland countries
Tran, Hoa Thi. "Integration of Geospatial Technologies in Monitoring Drought Events in a Coastal Area of Vietnam (Case study: Binh Thuan Province)." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/95471.
Повний текст джерелаDoctor of Philosophy
Drought is a temporal climatic event with "drier than normal" conditions. While drought can occur in any climates, it can be more extreme in arid and semi-arid areas where annual rainfall and water resources are limited. Depending on types of drought, its presences and impacts may differ: (1) meteorological drought relates to a decrease of average rainfall/snowfall may resulting in moisture stress, (2) hydrological drought leads to a reduction of streamflow and groundwater, and (3) agricultural drought influences soil-water-crop balance or vegetation health. Prolonged drought – abnormally long duration of dry conditions, coupled with unsustainable management in water and land practice may cause losses of land productivity, promote soil erosion, and result in sand dominance in coastal areas. These land degradation processes can lead to "a desert-like condition" in impacted areas. This research concerns drought and its impacts in a coastal province in South central Vietnam, Binh Thuan. The study area is distinctive because its climate is characterized as one of the driest provinces in Vietnam. Annual rainfall in the North and near the coast is less than 800 mm per year, and during the 6 months of the dry season, there is almost no rain, or less than 50 mm. Due to precipitation deficits and high surface temperatures in recent years, meteorological droughts have occurred more frequently and lasted longer, stressing water resources for vegetation, wildlife, households, and industry. Additionally, unsustainable land management, such as overgrazing, coupled with movements of sand and barren lands from the coast inland, have accelerated the risks of land degradation. This research applies an integration of geospatial technologies for monitoring drought severity and impacts on land management and illustrates how local people have adapted to droughts.
Fabris, Beatrice <1990>. "Evoluzione della rete di impollinazione lungo il gradiente di successione dei prati aridi." Master's Degree Thesis, Università Ca' Foscari Venezia, 2017. http://hdl.handle.net/10579/11713.
Повний текст джерелаALVES, Telma Lúcia Bezerra. "Avaliação do nível de degradação das terras (desertificação) no alto curso da bacia hidrográfica do rio Paraíba." Universidade Federal de Campina Grande, 2016. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/978.
Повний текст джерелаMade available in DSpace on 2018-06-14T11:32:02Z (GMT). No. of bitstreams: 1 TELMA LÚCIA BEZERRA ALVES - TESE (PPGRN) 2016.pdf: 11238465 bytes, checksum: 7f1bc917d37a959d86daf700437c86cd (MD5) Previous issue date: 2016-02-25
CNPq
A desertificação é um problema ambiental que atinge várias regiões no mundo, sendo definida como a degradação das terras nas zonas áridas, semiáridas e subúmidas resultante de vários fatores, incluindo variações climáticas e atividades humanas. O objetivo desse estudo foi avaliar o nível de degradação das terras (desertificação) no alto curso da bacia hidrográfica do Rio Paraíba, através da dinâmica temporal e espacial de aspectos climáticos, biofísicos e socioeconômicos. O alto curso da bacia hidrográfica engloba total ou parcialmente, a área de 18 municípios, distribuídos entre as microrregiões do Cariri Ocidental e Oriental do estado da Paraíba. Foram utilizados dados climáticos do período de 1950 a 2013 para as variáveis: precipitação pluvial e índice de aridez (Ia), dados de sensores orbitais - Moderate Resolution Imaging Spectro radiometer (MODIS), período de 2000 a 2013, visando à obtenção do albedo da superfície e do índice de vegetação ajustado ao solo (IVAS) e dados censitários (demográficos e agropecuários) para quantificação do índice socioeconômico e do nível de degradação na região. O teste de Mann-Kendall (MK) foi utilizado para identificação da tendência temporal das variáveis, ao nível de significância de α = 0,05, o método de Sen para quantificação da tendência e a krigagem para análise da dinâmica espacial das variáveis. Os principais resultados evidenciam que há uma tendência crescente da precipitação pluvial e decréscimo da aridez no alto curso da bacia como um todo, durante o período estudado. Pode-se inferir que estas condições não contribuem para desencadear o processo de degradação das terras (desertificação), sugerindo que as causas desse problema ambiental não são climáticas. A precipitação média anual aumenta na direção nordeste-noroeste da bacia, com mínimo (320 mm) em Cabaceiras e máximo (680 mm) nas localidades de Ouro Velho e Prata; o albedo da superfície e o índice de vegetação têm seus valores influenciados pela sazonalidade climática da região. A precipitação pluvial é o elemento que condiciona o aumento do índice de vegetação e diminuição do albedo da superfície, considerando-se que estas duas variáveis têm comportamento inverso. A região central do alto curso da bacia hidrográfica (municípios de Congo, Camalaú e Caraúbas) apresentou baixo índice de vegetação e elevado albedo da superfície, caracterizando possivelmente um processo de degradação das terras. Ao longo do período analisado (2000-2013), estas variáveis apresentaram tendência decrescente, mas não significativa, evidenciando um aumento pouco significativo da degradação das terras. Em relação ao índice socioeconômico geral de cada município – Isem observa-se que sete apresentaram “Moderada” degradação, dez “Baixa” degradação e apenas o município de Boqueirão apresentou situação de “Acentuada” degradação das terras. Os valores médios do Isem por município revelam que está havendo degradação das terras em todo o alto curso da bacia, porém em níveis Moderados e Baixos, sendo a região noroeste a área com maior pressão antrópica. Há uma tendência de aumento do índice socioeconômico - Iseb no alto curso da bacia hidrográfica com valor médio que indica uma situação de degradação “Moderada” das terras. Esse aumento é resultante do crescimento econômico, de programas sociais implantados e das melhorias nas condições de vida da população ao longo dos anos.
Desertification is an environmental problem that affects several regions in the world, defined as the land degradation of arid, semi-arid and sub-humid areas resulting from various factors, including climatic variations and human activities. The aim of this study was to evaluate the level of land degradation (desertification) in the upper course of the watershed of Paraíba River, through the temporal and spatial dynamics of climatic, biophysical and socio-economic aspects. The upper reaches of the watershed encompasses all or part of the area of 18 municipalities, distributed among the micro-regions of Western and Eastern Cariri state of Paraiba. Period of climatic data were used in 1950 the 2013 for the variables: rainfall and aridity index (Ia), orbital data from sensors - MODIS (Moderate Resolution Imaging Spectro radiometer), from 2000 to 2013, to obtain the surface albedo and Vegetation Index adjusted to the ground (SA VI) and census data (population and agricultural) to quantify the socio economic index and the level of degradation in the region. The Mann-Kendall test (MK) was used to identify the time trend variable, the level of significance o f α = 0.05, the Sen method to quantify the trend and Kriging for analyzing spatial dynamics of the variables. The main results show that there is an increasing trend of rainfall and decrease dryness on the upper course of the watershed as a whole, during the period studied. You can infer that these conditions do not contribute to trigger land degradation process (desertification), suggesting that the causes of this environmental problem is not climate. The average annual precipitation increases in the north-northwest direction of the watershed, with minimum (320 mm) in Cabaceiras and maximum (680 mm) in Ouro Velho and Prata localities; the surface albedo and vegetation index have their values influenced by the seasonality of the region. Rainfall is the element that determines the increase in vegetation index and decrease in surface albedo, considering that these two variables have opposite behavior. The central region of the upper course of the watershed (municipalities of Congo, Camalaú and Caraúbas) showe d a low rate of vegetation and high albedo surface, possibly featuring a land degradation process. Throughout the period analyzed (2000-2013), these variables showed a downward trend, but not significant, showing a slight increase of land degradation. Rega rding the general socioeconomic index of each municipality – Isem it is observed that seven had "moderate" degradation ten "Low" degradation and only the municipality of Boqueirão presented situation of "Severe" land degradation. The municipality by Isem average values reveal what's going on land degradation across the upper course of the watershed, but in Moderate and Low levels, and northwest region of the area with increased human pressure. There is a tendency to increase the socioeconomic index - Iseb in the upper course of the watershed with an average value indicating the degradation of situation "moderate" land. This increase is the result of economic growth, implemented social programs and improvements in the living conditions of the population over the years.
Scarpace, Michelle Rose. "The effects of tillage and long-term irrigation on dynamic soil properties and genesis of Aridic Argiustolls in western Kansas." Thesis, Kansas State University, 2016. http://hdl.handle.net/2097/32834.
Повний текст джерелаDepartment of Agronomy
Michel D. Ransom
Soil is a dynamic resource that can undergo many changes due to altering conditions (Tugel et al., 2005). With that, humans can have a great effect on the conditions of a landscape and contribute to soil change. As soils change, the function of soils can be altered which would affect the ability of soils to support ecosystem services. The objective of this thesis is to access how management affects dynamic and inherent soil properties in western Kansas soils. Eight sites in Sheridan County, KS mapped as Keith 1-3% slopes (fine-silty, mixed, superactive, mesic Aridic Argiustolls) were described and sampled. Of the eight sites, four are in ST (ST) management and four are in no-till (NT) management. All sites have been irrigated under center pivot irrigation systems since the 1970s. Soil samples of the A horizon were taken at each site to analyze total carbon, aggregate stability, bulk density, pH and microbial respiration to assess the impacts of tillage management on dynamic soil properties. Additionally, pedons were described from the ST sites in the irrigated areas as well as outside the pivot track to represent dryland conditions. Particle size data, field descriptions, and the micromorphology of thin sections were analyzed to determine if the classification of Keith soils are affected by irrigation. Significant differences between NT and ST management were seen in microbial respiration, select water stable aggregate sizes, and pH and bulk density at certain depths. It was also found that irrigation did not affect clay illuviation nor carbonate leaching. Overall, it was concluded that inherent soil properties such as soil map unit composition and parent material can have a greater impact on soil change and prevent the recognition of changes in soil properties over a human time scale.
Carvalho, Vitor Celso de. "Structure et dynamique de la végétation en milieu tropical semi-aride : la Caatinga de Quixaba (Pernambouc, Brésil) du terrain à l'analyse des données MSS/LANDSAT." Toulouse 2, 1986. http://www.theses.fr/1986TOU20031.
Повний текст джерелаSatellite remote sensing is more used as a tool for monitoring the tropical semiarid ecosystems. In this work we propose to do an estimation of practicability and limits of mss landsat datas, from a test region of brazilian nordeste, north of Petrolina (pe) the first part deals with the finalization of a structural classification of the steppe (Caatinga) vegetation and its application to the test region. Then, a 1 100 000 scale structural mapping, drawn from the 1955,1965 and 1983 aerial photographs, allows to discuss the signification of aerial photographic structure perception, and to analyse the 1955-1983 caatinga evolution. At last, the results of four mss landsat scenes (1973,1974 and 1983) numerical processing, are estimated, by comparison to vegetation structure maps : while in these maps, 15 thematic classes are distinguished, only 7 are available on the classified picture. In practice, the whole analysis show that the main characteristics of 1955-1983 landcape evolution are : a clear expansion of agricultural area (mainly after 1974) and, in all probability, a notable stability of Caatinga
Toureiro, António José Pequito. "Estudo da desertificação no Alentejo: causas, consequências e estratégias atenuadoras (caso do Concelho de Arraiolos)." Master's thesis, Universidade de Évora, 2006. http://hdl.handle.net/10174/15854.
Повний текст джерелаWu, Liuliu. "Similarity of Climate Control on Base Flow and Perennial Stream Density in the Budyko Framework." Master's thesis, University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5727.
Повний текст джерелаM.S.
Masters
Civil, Environmental, and Construction Engineering
Engineering and Computer Science
Civil Engineering; Water Resources Engineering
Puig-Gironès, Roger. "Estudi dels patrons de colonització postincendi en vertebrats al llarg de gradients ambientals i espacials." Doctoral thesis, Universitat de Girona, 2016. http://hdl.handle.net/10803/416576.
Повний текст джерелаEls incendis forestals són alteracions naturals que afecten l'estructura del paisatge i la biodiversitat. A la conca mediterrània, els incendis forestals es donen especialment en les estacions caloroses. Tanmateix, en els darrers anys tant el nombre d’incendis con la mida dels mateixos ha anat en augment, associat amb la intervenció humana. En aquesta tesi s’analitza com el gradient d'aridesa regional de Catalunya afecta a la recuperació de la vegetació, la riquesa d'espècies d'aus i l’abundància de tallarols de matollar. S’avalua el paper relatiu de dues hipòtesis sobre l'abundància de rosegadors en els primers moments després d'un incendi forestal. Aquestes hipòtesis contraposades fan referència a la capacitat dels rosegadors a resistir el pas del foc en refugis o, per altre banda, a la colonitzar des de l'àrea no cremada. Finalment, s’avalua com la tala postincendi i la gestió de la fusta cremada poden afectar la recolonització de rosegadors
Konaté, Nianguiri Moussa. "Diversité interspécifique de l'efficience d'utilisation de l'eau des acacias sahéliens et australiens." Thesis, Nancy 1, 2010. http://www.theses.fr/2010NAN10044/document.
Повний текст джерелаThe main objective of this work was to compare water use efficiency (WUE) among various Australian and Sahelian acacia species using isotope discrimination at leaf level (Δ13Cf) and various methods of measurement. Acacia species exhibited a large inter-specific variability of Δ13Cf. This variability was confirmed by direct leaf gas exchange measurements (intrinsic water use efficiency, Wi) and by measurement at the whole plant level (transpiration efficiency, TE). A large interspecific variability of leaf traits (stomatal density DS, leaf nitrogen concentration %N, specific leaf area SLA, net CO2 assimilation of the saturation Asat, stomatal conductance for water vapor of the saturation gssat) and growth characteristics (root shoot biomass ratio R/S) has also been reported. WUE was controlled for gssat. The hypothesis that the species from arid areas exhibit higher WUE was not confirmed. In contrast, the species from semi-wet area exhibited a higher WUE than those from semi-arid and arid zones
Gigliotti, Alessandro. "Groundwater recharge estimation in a data sparse arid catchment of westbank. Stima della ricarica delle falde acquifere in bacini aridi e carenti di osservazioni idrometriche: il Darga in Cisgiordania." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5959/.
Повний текст джерелаBell, Benjamin. "Advancing the application of analytical techniques in the biological chemistry of sporopollenin : towards novel plant physiological tracers in Quaternary palynology." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/advancing-the-application-of-analytical-techniques-in-the-biological-chemistry-of-sporopollenin-towards-novel-plant-physiological-tracers-in-quaternary-palynology(59605f2b-642a-4ea9-8921-4c926217e6f2).html.
Повний текст джерелаDeblauwe, Vincent. "Modulation des structures de végétation auto-organisées en milieu aride." Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210121.
Повний текст джерелаL’auto-organisation de la végétation fut particulièrement bien étudiée dans le cas des structures périodiques connues dès les années '50 sous le nom de brousses tigrées. Depuis les années '90, un pas en avant dans la compréhension de ce phénomène fut accompli grâce au développement de modèles mécanistes de la dynamique de la phytomasse et des ressources, émanant du cadre théorique de l'auto-organisation des structures dissipatives. Ces modèles se rejoignent sur un ensemble de prédictions robustes et vérifiables concernant la formation, le maintien et la modulation par l'environnement des structures macroscopiques. Durant le même laps de temps, notre niveau d’analyse a connu une expansion sans précédent, à la fois dans le temps et dans l’espace, grâce au développement de l’imagerie satellitaire et des outils d’analyse spatiale. Nous nous trouvons dès lors à un moment charnière pour la validation macroscopique des théories d’auto-organisation des végétations en milieu aride.
Le présent travail s'articule en quatre études, chacune traitant d'une prédiction différente. Nous avons mis en évidence les principales variables responsables de la formation des structures et de leur modulation en termes d’échelle et de géométrie. Enfin avons démontré la mobilité des structures sous l’effet d’une pente de terrain.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
Fazel, Modares N. (Nasim). "The role of climate and land use change in Lake Urmia desiccation." Doctoral thesis, Oulun yliopisto, 2018. http://urn.fi/urn:isbn:9789526221021.
Повний текст джерелаTiivistelmä Kuivilla aridisilla ja semiaridisilla alueilla sijaitsevat kosteikot ovat hauraita ekosysteemejä. Ne ovat myös tavallista tärkeämpiä, koska ne ylläpitävät ja säätelevät ympäristön laatua sekä luonnon monimuotoisuutta. Nämä kosteikot, kuten valtaosa muistakin kosteikoista, ovat riippuvaisia vesistöalueen ylemmillä osilla tehdyistä toimista kuten vesistöjen säännöstelystä. Jopa pienet muutokset jokien virtauksissa voivat aiheuttaa merkittäviä muutoksia järvien vedenpinnan korkeuteen, suolapitoisuuteen ja tuottavuuteen. Viimeaikaiset ilmastonmuutoksen ja maankäytön muutosten aiheuttamat voimakkaat muutokset jokien virtaamiin ovat johtaneet ekosysteemien rappeutumiseen sekä monien suolajärvien kuivumiseen kuivilla ja puolikuivilla alueilla. Kuivilla alueilla sijaitsevien suolajärvien hydrologiaa ei ole tarkkailtu riittävästi niiden alhaisemman taloudellisen arvon vuoksi. Se hankaloittaa vesitaseen määrittämistä. Tarkkojen tietojen puuttuessa on vaikea arvioida myös sitä, miten vedenkäyttö ja ilmasto ovat vaikuttaneet järvien kuivumiseen. Lisäksi saatavilla olevat tiedot ovat yleensä sekä ajallisesti että alueellisesti epätarkkoja. Analysointiin tarvittavien tietojen ja välineiden puute saattaa pahimmillaan johtaa ristiriitaisiin oletuksiin. Väitöstyön päätavoite on tarjota puitteet, joilla parannetaan ymmärrystä vesivarojen alueellisista eroista, ihmisen toiminnan vaikutuksista jokien virtausten muutoksiin ja maatalouden maankäytön muutoksista käyttäen kaikkea saatavilla olevaa dataa sekä täsmentäen samalla vesistöistä jo olemassa olevaa tietoa. Väitöskirja tutkii yhden suuren järven kuivumisen syitä ja seurauksia. Urmiajärvi on yksi maapallon suurimmista suolajärvistä sekä erittäin uhanalainen ekosysteemi. Järvi on samankaltaisen ympäristökatastrofin partaalla, joka aiheutti Araljärven kuivumisen. Väitöskirja antaa tietoa veden saatavuuden alueellisista eroista tutkimalla sademäärien alueellista jakautumista Urmiajärven valuma-alueella. Tutkielmassa arvioidaan sadannan ajallista ja paikallista vaihtelua erilaisten tilastollisten menetelmien avulla. Tutkielman toinen tärkeä osa keskittyy vesialtaan latvavesistön ja tasankoalueiden valumatietoihin. Tämän osuuden päätavoite on määritellä johtuvatko havaitut muutokset järvessä pääasiassa ilmastonmuutoksesta vai ihmisen toiminnasta kuten kastelusta. Sadantatietojen pääkomponentti- ja ryhmittelyanalyysien tulokset osoittavat, että Urmiajärven allas on sadannaltaan heterogeeninen alue. Analyysi johti seudun jakamiseen kolmeen homogeeniseen sadanta-alueeseen. Analyysi osoitti, että sademäärien kausittainen vaihtelu on merkittävin järvialtaan alueellisiin sademääriin vaikuttava tekijä. Tulokset osoittavat, että ilmastonmuutoksen vaikutukset latvavesistöön eivät olleet merkittäviä ja keinokastelu on ylivoimaisesti merkittävin järvialtaan jokien virtausten muutoksiin vaikuttava tekijä. Tätä johtopäätöstä tukee se tosiseikka, että maanviljelys ei ole juurikaan vaikuttanut latvavesistöihin eikä niissä näy historiallisten lähteiden perusteella merkittäviä muutoksia. Tutkimuksen hyöty on siinä, että se tulkitsee saatavilla olevan tiedon selkeästi, joka on avuksi, kun maankäyttöön ja ilmastonmuutokseen liittyviä tietoja välitetään päättäjille ja järven kunnostusta suunnitteleville tahoille
Ag, Atteynine Solimane. "Changement climatique et rongeurs ravageurs des cultures : effet attractif des cultures de saison sèche sur les espèces du genre Arvicanthis au Mali." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0130.
Повний текст джерелаIn Mali, during the dry season, there is the issue of the attractive effect of dry season crops on rodent pests, which would be all the more marked in the latitudinal gradient of Sudan-Sahel aridity GECS (1100 mm to 200 mm). These hypotheses are tested in the genus Arvicanthis (A.ansorgei, A. niloticus). The results of the previous cytogenetic survey 1994-1999 and an expanded survey 2009-2014 reveal recent changes in the distribution areas of both species; suggesting a strong role of their chronobiological adaptation in the determinism of their distribution. This horizontal approach followed by a vertical approach (2009-2016) compares four indicators of the attractiveness of the CSS vs. the MNC in the five climatic regions of GECS (Sikasso, Koulikoro, Ségou, Mopti, Gao). The population densities of both species are higher in the CSS vs. the MNC; and this attractiveness of the CSS increases with aridity in the area of A. niloticus. The ratio of "migratory strategists" within populations demonstrates the buffering effect of the CSS and confirms the frequency of these episodes. The diet study confirms their phytophagous diet. In a natural environment, aridity induces a decrease in the consumption of plants compensated by that of non-orthopterous Arthropods; and the diversity of plants consumed decreases with aridity in A.ansorgei vs increases with aridity in A. niloticus. The buffering effect of CSS "neutralizes" inter-specific differences, and in both species, in the CSS, the diversity of weeds consumed decreases to the detriment of crops, especially rice and the consumption in the Orthoptera increases
Myslíková, Tereza. "Ztráty vody výparem u gekonů rodu Paroedura." Master's thesis, 2020. http://www.nusl.cz/ntk/nusl-410608.
Повний текст джерелаTaylor, D. "Tree leaf-and branch-trait coordination along an aridity gradient." Thesis, 2008. http://hdl.handle.net/10453/36066.
Повний текст джерелаNO FULL TEXT AVAILABLE. Access is restricted indefinitely. The hardcopy may be available for consultation at the UTS Library.
NO FULL TEXT AVAILABLE. Access is restricted indefinitely. ----- Functional attributes of leaves and branches have a significant influence on a plant’s establishment, survival and fitness to particular environments. A major environmental variable to which plants must adapt is annual rainfall, or soil water availability. This thesis presents an analysis of variation in leaf- and branch-traits of trees across a rainfall gradient within NSW, Australia. In particular, it quantifies relationships amongst five leaf-traits: C0₂ assimilation rate, stomatal conductance to water vapour (gs), foliar nitrogen (N) concentration, specific leaf area, and foliar carbon isotope ratio (δ¹³C) (a measure of leaf water-use-efficiency and intercellular C0₂ concentration; Cᵢ), and three branch-traits: branch hydraulic conductivity, wood density and the ratio of leaf area to sapwood area (LA:SA), across a total of 16 perennial tree species across 13 native woodland sites spanning a mean annual rainfall gradient of 455 to 1310 mm. The generality of the trends found within tree species of NSW are then compared with the ‘global’ leaf-trait relationships of data obtained through Wright et al. (2004a) (referred to as the GLOPNET dataset), including comparisons among phenological and plant functional groups. Increased gs and foliar N concentration were associated with increased C0₂ assimilation rate. Higher foliar N concentrations were also associated with reduced Cᵢ and higher δ¹³C, suggesting that increased N concentration increases water-use-efficiency. Trees growing at low rainfall sites had lower mean gs, allocated more N to leaves, and consequently had higher foliar δ¹³C, suggesting a water conservation strategy at low rainfall sites. Similarly, reduced sapwood-specific hydraulic conductivity (ks) was correlated with reduced gs, higher foliar N concentration, a lower Cᵢ, but, most importantly, a statistically similar average rate of C0₂ assimilation as branches with higher ks. Overall, these results suggest that trees or species subject to water limitation, either by reduced rainfall or through a lower water transport capacity (a lower ks) ‘substitute’ water for N to achieve a given rate of leaf-level carbon gain. This mechanism represents an optimisation strategy for the use of limited supplies of water and N. Consequently, trees growing at low rainfalls sites, with low ks, maximise water-use-efficiency and minimise any decrease in C0₂ assimilation rate. This is achieved by these low rainfall trees operating at low Cᵢ which increases the diffusional gradient of C0₂ into the leaf. Branch wood density was inversely correlated with leaf area per branch, per unit branch length and per unit sapwood area, consistent with a reduced hydraulic capacity of denser wood. However, leaves of branches with high wood density and low LA:SA exhibited higher rates of C0₂ assimilation per unit leaf area and had a lower average Cᵢ. Thus, whilst branches with low ks invested more carbon in sapwood (higher density wood and more sapwood area per unit leaf area), this investment was supported by maximising C0₂ assimilation per unit leaf area. The patterns of correlation amongst gs, foliar N concentration and C0₂ assimilation observed in NSW were replicated in an analyses of the global data contained in the GLOPNET dataset. Thus, species with low gs had higher foliar N concentration for any given C0₂ assimilation rate, demonstrating the broad generality of water and N substitution. More importantly this pattern was observed only within certain functional groups. Evergreen species, trees, shrubs and N-fixing species exhibited this pattern but functional groups with short leaf lifespan, including deciduous species and grasses, did not display resource substitution. These differences suggest that species which utilise limited quantities of water and N over a long leaf lifespan use water and N sparingly and optimise resource use. In contrast, species with short leaf-lifespan use water and N in a more profligate manner and do not optimise resource use. In addition, N-fixing species were capable of substituting water for N to a greater degree than non-N-fixers, by allocating more N to foliage at low gs. The greater plasticity of N-fixers (such as Acacias) to substitute the two resources to achieve a given rate of carbon assimilation might explain their relative success in low rainfall environments.
Wang, Lixin. "Soil biogeochemistry, aridity and plant adaptation responses in southern Africa savannas." 2008. http://wwwlib.umi.com/dissertations/fullcit/3362902.
Повний текст джерелаColeman, Joy Carol. "Integrated physiology and behaviour of Thallomys nigricauda along an aridity gradient." Thesis, 2008. http://hdl.handle.net/10413/10795.
Повний текст джерелаThesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.
Rose, Cassaundra Ashley. "Late Cenozoic Evolution of Aridity and C4 Vegetation in North Africa." Thesis, 2015. https://doi.org/10.7916/D8NK3DS6.
Повний текст джерелаPaquette, Jesseca. "Tendances environnementales en Afrique de l’Est au Plio-Pléistocène : étude des isotopes stables de carbone et d’oxygène de l’émail des herbivores." Thèse, 2018. http://hdl.handle.net/1866/21909.
Повний текст джерелаBoyers, Melinda Frances. "A comparative study of behavioural and thermoregulatory responses of blue wildebeest and gemsbok to aridity." Thesis, 2018. https://hdl.handle.net/10539/25834.
Повний текст джерелаFuture climate change scenarios predict that many arid and semi-arid ecosystems within southern Africa, will get warmer and drier with increased frequency of droughts. Although the effects of climate change may only be apparent over a few decades, understanding the physiological and behavioural flexibility of individuals currently inhabiting hot and dry climates provides an analogue for conditions likely to become prevalent in the future. To enhance our understanding of how a species may respond to future hotter and drier environments, I set out to investigate seasonal variation in behaviour and thermoregulation of two ungulate species with differing water dependency in a semi-arid savanna. I focused on thermoregulatory (body temperature) and behavioural responses (activity and microclimate selection) of the water-dependent blue wildebeest (Connochaetes taurinus), and the arid-adapted gemsbok (Oryx gazella gazella) free-living in the Kalahari. Both species prioritised behavioural thermoregulation in the form of cool microclimate selection during the heat of the day and reduced both diurnal and 24 h activity, particularly when conditions were hot and dry. Both species experienced high maximum 24 h body temperature when conditions were hot and low minimum 24 h body temperatures when conditions were dry, resulting in a large amplitude of 24 h body temperature rhythm during the hot dry period. Yet, wildebeest appeared to be more sensitive to changes in aridity with a larger amplitude of 24 h body temperature rhythm compared to gemsbok (3.1 ± 0.2 °C vs. 2.1 ± 0.5 °C), during the drought. These seasonal analyses imply that the species behavioural and thermoregulatory responses were influenced by seasonal changes in water and forage availability. Low minimum 24 h body temperatures may result from an energy deficit during the dry season, but no study to date has explicitly linked changes in body temperature of free-living ungulates, to forage quality within the environment. I therefore investigated the influence of vegetation greenness on body temperature and activity of blue wildebeest and gemsbok inhabiting the same environment. I then investigated if the responses of gemsbok were heightened in a more arid environment. I used Normalized Difference Vegetation Index (NDVI) as a standardized index of vegetation greenness, which can be considered a proxy for vegetation productivity and quality. Both species reduced total 24 h activity and became hypothermic when exposed to brown vegetation but when exposed to brown vegetation minimum 24 h body temperatures were lower for blue wildebeest compared to gemsbok. When exposed to more extreme aridity, gemsbok showed an exaggerated lowering of minimum 24 h body temperatures. Under conditions of low food availability, the cost of thermoregulation may become too demanding. Therefore, when food resources are limited in quality, wildebeest and gemsbok in arid regions appear to prioritize the conservation of energy over the maintenance of a high body temperature. Within seasonal environments, access to water is often the limiting factor for plants and animals. I therefore investigated how distance to water (i.e., how frequently animals were likely to have accessed drinking water) during the hot season influenced microclimate selection, activity and body temperature of blue wildebeest and gemsbok. Both species selected similarly cool microclimates during the heat of the day, with slight enhancement in the quality of microclimates selected when they were further from water. Both species decreased activity during the heat of the day when they were further from water. Gemsbok were able to compensate for their reduced activity during the heat of the day and showed little change in total 24 h activity, but wildebeest showed a more exaggerated decline in activity during the heat of the day for which they were unable to compensate, i.e. total 24h activity of wildebeest declines when they were further away from water sources. Both species displayed higher maximum 24 h body temperatures when they were further away from water, with the hyperthermia being exaggerated for the wildebeest compared to gemsbok. Hyperthermia in both species resolved following the first rains and likely access to drinking water. Access to water appears to be the primary driver towards hyperthermia in the wildebeest, potentially resulting from dehydration during thermal stress. In summary, I have investigated behavioural and thermoregulatory flexibility that large African ungulates currently inhabiting hot and dry climates currently employ. I have shown that ungulates in the Kalahari may differ in their use of microclimate selection and activity patterns to buffer thermal, energetic and water stressors. My study is unique in that I have looked at where the animal was in space and time and linked it to their physiological and behavioural responses. I have, therefore, quantified microclimate selection, activity and body temperature responses in relation to NDVI and distance to water and have shown that the driving mechanisms behind the seasonal changes of body temperature and activity patterns is access to energy and water. I have further enhanced our existing knowledge and created the link between body temperature, vegetation quality and distance to surface water for antelope of the Kalahari and effectively assessed a functional trait. With climate change predicted to increase ambient temperatures and have less predictable rainfall in the semi-arid Kalahari, wildebeest will be forced to remain within the Kalahari, because historical migratory paths have been blocked by fences, and they may not have the behavioural and physiological flexibility to survive a hotter and drier future.
LG2018
Fitzsimmons, Kathryn Elizabert. "The late Quaternary history of aridity in the Strzelecki and Tirari Desert dunefields, South Australia." Phd thesis, 2007. http://hdl.handle.net/1885/151056.
Повний текст джерелаKoloadin, Leah S. "Intraspecific and interspecific variation in the xylem functional traits of Callitris species growing along an aridity gradient." Thesis, 2020. http://hdl.handle.net/1959.7/uws:67022.
Повний текст джерелаPotgieter, Henriette Cornelia. "Avian ecology of arid habitats in Namibia / Henriette Cornelia Potgieter." Thesis, 2015. http://hdl.handle.net/10394/15505.
Повний текст джерелаMSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015
Loehr, Victor J. T. "The ecology of the world's smallest tortoise, Homopus signatus signatus: effects of rainfall." Thesis, 2008. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_3016_1259833196.
Повний текст джерелаTortoises appear to be successful in arid ecosystems, where they depend on primary production for their predominantly herbivorous diets. The low primary production of arid regions is exacerbated by priodic droughts, so that iteroparous species such as chelonians require mechanisms to overcome resource shortages. The smallest of all tortoises, Homopus signatus signatus, occurs in a dry winter rainfall area in northwestern South Africa that is threatened with aridification due to regional climate change. The overall aim of this study is to understand the ecology of H. s. signatus, particularly in reference to the importance of rainfall.
Saladino, Saverio Salvatore. "INCREMENTO DELLA FERTILITA’ DEI SUOLI COME CONSEGUENZA DI PRATICHE COLTURALI PER LA GESTIONE SOSTENIBILE DEI VIGNETI IN CLIMI SEMI-ARIDI." Doctoral thesis, 2012. http://hdl.handle.net/10447/94585.
Повний текст джерелаTurton, Anthony Richard. "The hydropolitics of Southern Africa: the case of the Zambezi river basin as an area of potential co-operation based on Allan's concept of virtual water." Diss., 1998. http://hdl.handle.net/10500/16231.
Повний текст джерелаPolitical Sciences
M.A. (International Politics)