Dissertationen zum Thema „Stress hydrique végétal“
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Koch, Garance. „Effet du stress hydrique sur la croissance de la tomate : une étude multi-échelle : de la cellule à la plante entière pour une meilleure compréhension des interactions entre les différentes échelles“. Thesis, Avignon, 2018. http://www.theses.fr/2018AVIG0347.
Der volle Inhalt der QuelleAs for other multicellular organs, growth and development of leaves and fruits arecharacterized by cell division and expansion. Cell division and expansion are two maingrowth processes. Fleshy fruit pericarp cells also include successive endocycles that providean important increase in cell ploidy. There is a clear link between cell growth andendoreduplication. However, this link is still unclear from a functional point of view. Cellularprocesses interact during organ development and are related to plant water and carbon flows.The objective of this thesis is to give insights into the multi-scale control of leaves and fruitsgrowth in tomato (Solanum lycopersicum Mill.) and the plasticity of growth-related traits inresponse to soil water stresses.This study mainly focused on cherry tomato Solanum lycopersicum, cv. West Virginia 106(WVa 106). This genotype was cultivated in different conditions of watering regimes withautomated systems developed for this study. Soil water deficit response was studied atdifferent observation scales (tissue, organ, whole plant) and at different plant growth stagesthanks to protocols that were used until now on plants with determinate growth and simpleleaves that were modified for this study. Two transgenic genotypes modified on a cell cycleregulation gene were also cultivated to create variations on growth related traits for a betterunderstanding of their relationships. Multi-scale growth kinetics of source and sink organs(leaf and fruit) were also analyzed. Results have brought new elements about growth-relatedtraits coordination and have reinforced a few hypotheses already presented in scientificpapers. This work has supplied an original dataset on water stress effects on cellular processes(division, expansion, endoreduplication) related to leaf and fruit growth in tomato in thecontext of the plant as a whole. In perspectives, this dataset may allow to further develop anexisting model of fleshy fruit development which was first developed for fruits of plantsgrowing optimal condition. Genericity of this model will be tested on another organ, the leaf.This work also opens some tracks about how the model could be modified when growth islimited by water stress
Hjeij, Maroun. „Imagerie hyperspectrale active dans l'infrarouge moyen "application agrophotonique“. Electronic Thesis or Diss., Université de Rennes (2023-....), 2024. https://ged.univ-rennes1.fr/nuxeo/site/esupversions/cdff6e07-14e9-46bd-bdb3-3c9196819dc4.
Der volle Inhalt der QuelleThis thesis focuses on the design of the architecture of an active hyperspectral imaging system in the mid-infrared, with an emphasis on the early and accurate measurement of water stress in plants. Despite the high potential of this technology in agriculture, its use remains limited due to the cost of equipment. The study aims to improve the technological and scientific understanding of active hyperspectral imaging by evaluating the impact of speckle on images and proposing digital and optical solutions. The integration of a rotating diffuser has reduced speckle, while lighting enhancements have preserved image resolution. The study revealed that the active laser source induces distortions related to beam displacement during changes in wavelength, with power fluctuations reaching approximately 20%. These challenges were overcome using calibrated motorized mirrors and a reference ring, reducing power fluctuations to 2.8% through a compensation algorithm. In conclusion, the experimental setup characterizes plant samples in terms of water stress, enabling early detection from the fourth day, with potential applications in various fields for material characterization in an observed scene
Lamy, Geneviève. „Etude du rôle des inhibiteurs de kinases-cycline-dépendantes (CKI) de la classe des SIM/SMR en réponse au stress abiotique chez Arabidopsis thaliana“. Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-00919383.
Der volle Inhalt der QuelleChabi, Malika. „Approches transcriptomique et protéomique pour étudier les rôles de l’environnement et du génotype sur le métabolisme pariétal chez le lin“. Thesis, Lille 1, 2015. http://www.theses.fr/2015LIL10206/document.
Der volle Inhalt der QuelleFlax (Linum usitatissimum L.) is grown for its cellulose-rich bast fibers used in the textile industry and for reinforcing composite materials. Fiber “quality” depends partly on the structure of the cell wall and we have therefore tried to obtain a better understanding of the different factors that can influence the structure of flax cell walls. We firstly confirmed the use of a new Nimblegen microarray changing from a system based on short (25-mer) oligonucleotides to a system based on long oligonucleotides (60 mers). A proteomics approach was then used and allowed us to identify 1,242 non-redundant proteins of which 410 could be related to cell wall metabolism. In parallel we demonstrated the presence of xyloglucan hemicelluloses in flax fiber cell walls and identified an important paralogy in the IIIA XTH (xyloglucan endo-transglycosylase/hydrolase) family potentially implicated in the formation/structuration of the flax fiber cell wall. Then a transcriptomic and proteomic comparison between different field-grown flax varieties (spring fiber, winter fiber, winter oil) over 2 consecutive years allowed us to identify 659 differentially-expressed genes (DEGs) at the variety level, and 1,571 genes at the environmental level. A non-negligible number of these genes is involved in cell wall metabolism thereby providing some initial clues allowing a link to be made between variety and quality. This study also underlined the potential importance of the XTH protein in flax cell wall metabolism. The role of the environment on cell wall metabolism was further explored in a study aiming to dissect the impact of drought stress on the transcriptomes of 3 vegetative organs (stem, leaf, root). Preliminary analyses identified an important number of DEGs involved in the biosynthesis and remodeling of several cell wall polymers
Morillon, Raphaël. „Modifications de perméabilité cellulaire à l'eau liées au développement, au stress hydrique, et aux mutations“. Rouen, 1999. http://www.theses.fr/1999ROUES032.
Der volle Inhalt der QuelleTisné, Sébastien. „Bases écophysiologiques et génétiques de la plasticité de la croissance foliaire en réponse à une contrainte hydrique édaphique chez Arabidopsis thaliana“. Montpellier SupAgro, 2009. http://www.theses.fr/2009NSAM0033.
Der volle Inhalt der QuelleAl, Abras Kamal. „La crise de transplantation chez l'épicéa commun : Analyse du comportement des mycorhizes“. Nancy 1, 1988. http://www.theses.fr/1988NAN10325.
Der volle Inhalt der QuelleMentewab, Ayalew. „Androgénèse in vitro chez le blé : utilisation pour la transformation génétique et l'amélioration de la résistance au stress hydrique“. Toulouse, INPT, 1998. http://www.theses.fr/1998INPT001A.
Der volle Inhalt der QuellePerfus-Barbeoch, Laetitia. „Identification et régulation de transporteurs membranaires d'Arabidopsis thaliana impliqués dans la réponse aux stress métallique et hydrique“. Aix-Marseille 2, 2002. http://www.theses.fr/2002AIX22057.
Der volle Inhalt der QuelleQuéro, Anthony. „Approche métabolomique de l'amélioration de la tolérance au stress hydrique chez le lin (Linum usitatissimum) par application de l'acide β-amino butyrique (BABA) ou d'oligosaccharides“. Amiens, 2012. http://www.theses.fr/2012AMIE0118.
Der volle Inhalt der QuelleThe cultivation of linseed (Linum usitatissimum), fell into disuse in the last century, is gaining interest through the abundance in seeds of compounds as α-linolenic acid and lignans. Despite its benefits, linseed is often considered as unprofitable particularly due to its regular exposure to drought which disrupts yield. To assess plant plasticity during osmotic stress, changes in metabolome and in inorganic solutes content were evaluated. Content analysis of these two classes of solutes has highlighted an opposite behavior during osmotic stress. Thus, metabolites accumulation is associated with a decreased in inorganic solutes content. The application of β-amino butyric acid (BABA) has led to an improved linseed drought stress tolerance. This tolerance is associated with a higher water content in leaves of treated plants, with a major solute content reorganization and an osmotic potential decrease. We showed that solute content deviations in response to anionic oligosaccharides application were similar that observed in linseed submitted to oligosaccharides or BABA treatments. These preliminary results suggest a role of oligosaccharides in improving of linseed drought stress tolerance
Loayza, Loza Hildo. „Suivi expérimental du rendement de fluorescence des couverts végétaux par des techniques actives et passives. Application à la détection du stress hydrique“. Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS465.
Der volle Inhalt der QuelleThe chlorophyll fluorescence (ChlF) is directly related to the photosynthetic process. However, at canopy level this physiological link between fluorescence and photosynthesis may be blurred by structural vegetation changes and geometrical effects linked to interactions between sunlight and the three-dimensional structure of the canopy. Furthermore, much of our knowledge about the relationship between fluorescence and the physiological status of plants come from leaf level studies carried out under laboratory conditions. The physiological significance of ChlF at canopy level and under natural conditions is still a major subject of research and a source of uncertainties in the interpretation of SIF. This doctoral project aims were: 1. To study chlorophyll fluorescence yield at canopy level: we describe a new instrument, Ledflex, which is a micro-LIDAR dedicated to perform continuous measurements of vegetation fluorescence yield. Ledflex has been successfully applied under full sunlight conditions to establish the signature of water-stress on a pea (Pisum Sativum) canopy. Under well-watered conditions the Fs diurnal cycle present an M shape with a minimum (Fmin) at noon which is higher than the fluorescence level observed at predawn (Fo). After several days withholding watering, Fs decreases and Fmin
El, Hage Fadi. „Impact du déficit hydrique sur la dégradabilité, la biochimie pariétale et la répartition des tissus lignifiés chez l’entrenoeud de maïs et déterminisme génétique de ces caractères“. Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS609.
Der volle Inhalt der QuelleThis PhD project encompass in a context of global warming and replacement of fossil resources, where both water supply decrease and biomass valorisation optimisation are two major issues for providing sustainable systems of production. Biomass degradability is mainly limited by cell wall degradability and in order to improve it, it is necessary to understand what are the factors involved in the limitation of the degradability. Several studies have shown that cell wall degradability is impacted by the structure and the composition of the cell wall but also by the distribution of the lignified tissues within the organs. To decipher the impact of the biochemistry and from the one of the histology on degradability under different watering conditions, high-throughput quantifications tools for histology and biochemistry have been developed and dedicated to the study of the internode carrying the main ear. The studies were conducted on a maize genetic diversity panel and a recombinant inbred lines population, cultivated during several years under contrasted irrigation conditions in South of France. Our results highlight that water deficit induce an increase of the cell wall degradability, associated to a decrease of the cell wall lignin content and a preferential induction of a cortical lignification, more p-coumaroylated. In original ways, we also detected 90 QTLs for histological traits under the different irrigations scenarios on the maize genome. More particularly, a large region between bin 1.07 and bin 1.11 is involved in the observed variations of the bundle number and the stem section area of the internodes. More generally, numerous QTLs of cell wall composition of the internode co-localised with the ones detected for the whole plant without ear level in the same population. Finally we were able to demonstrate that the choice of the internode carrying the main ear is judicious to represent both histological characteristics from the whole stem and biochemical characteristics from the lignocellulosic biomass of the whole plant. Thus, histological and biochemical traits in maize internode are proposed as particular targets to select lines resilient to water deficit
Meridja, Samir. „Approche biophysique des processus de développement et de croissance des couverts végétaux : Interaction avec le stress hydrique et optimisation des pratiques culturales en climat méditerranéen“. Phd thesis, AgroParisTech, 2011. http://pastel.archives-ouvertes.fr/pastel-00776775.
Der volle Inhalt der QuelleBresson, Justine. „Interaction plante-microorganismes : Implication de la rhizobactérie Phyllobacterium brassicacearum dans les réponses d'Arabidopsis thaliana au stress hydrique“. Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2013. http://tel.archives-ouvertes.fr/tel-01012108.
Der volle Inhalt der QuelleBernard-Verdier, Maud. „Structure et assemblage des communautés végétales de parcours des Grands Causses : approche fonctionnelle, phénologique et phylogénétique“. Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20047/document.
Der volle Inhalt der QuelleUnderstanding how the environment influences plant species distribution is a fundamental question in plant ecology. This work aims at understanding how soil resource availability influences plant community assembly and structure in Mediterranean rangelands of Southern France. To do this, the niche structure of plant communities has been described in terms resource use, regeneration strategy, phenology and evolutionary history along a soil resource gradient. Using a trait-based approach, we show that (1) filtering processes, both abiotic and biotic, may restrain trait ranges within communities and sort species along a gradient of soil resource availability, and (2) patterns of functional convergence and divergence among species within communities may reveal different processes of local species coexistence under different soil conditions. Within productive habitats, we found a strong convergence in resource use strategies, possibly resulting from strong aboveground competition, which was accompanied by a divergence in reproductive and regenerative strategies. By contrast, towards more constrained habitats, and despite a strong abiotic filter, a diversity of resource use strategies coexisted, creating a maximum of functional diversity at intermediate levels of constraints. Moreover, the strong phylogenetic convergence in these rangeland communities, mainly related to the dominance of graminoid species, diminished towards the more constrained soils where a diversity of drought-adapted lineages coexisted. In addition, we were able to relate dominance in these rangelands to a few general characters – namely high leaf dry matter content, large seeds and high reproductive heights – which were modulated at a finer spatial scale by local soil conditions influencing different criteria such as specific leaf area. Finally, we highlight the strong phenological response of communities to soil resource availability and the timing of summer drought. However, results also suggest a role of biotic factors, such as competition, in limiting flowering overlap among coexisting species in productive habitats. Combining functional, phenological and phylogenetic approaches allowed us to provide an integrative understanding of the complex processes driving community assembly in these rangelands
Bizet, François. „Division et élongation cellulaire dans l'apex de la racine : diversité de réponses au déficit hydrique“. Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0258/document.
Der volle Inhalt der QuelleRegulation of root growth is a crucial capacity of plants for acclimatization to environmental stresses. At cell scale, this regulation is controlled through cell division and cell elongation but respective importance of these processes and interactions between them are still poorly known. Notably, the cell production activity of the root apical meristem (RAM) is often excluded. During this thesis, spatial analyses of growth along the root apex were coupled with temporal analyses of cell trajectories in order to decipher the links between cell division and cell elongation. This required the setup of a system for phenotyping root growth at a high spatiotemporal resolution which was applied to study the growth of roots from an euramerican poplar (Populus deltoides × Populus nigra) in response to different environmental stresses (osmotic stress or mechanical impedance). An important variability of root growth rate between individuals as well as individual cyclic variations of growth along time were observed despite tightly controlled environmental conditions. Use of this variability coupled with quantification of the RAM activity led us to a better understanding of the importance of the cell production rate for sustaining root growth. This work analyses a new spatiotemporal scale of growth variability poorly considered. Widely applicable to others scientific questioning, temporal analyses of cell fate once produced in the RAM is also discussed for non-steady growth conditions
Bernard, Amélie. „Étude de cer1, le gène clé de la biosynthèse des alcanes cuticulaires chez arabidopsis thaliana“. Thesis, Bordeaux 2, 2011. http://www.theses.fr/2011BOR21858/document.
Der volle Inhalt der QuelleProtective functions of the cuticle, the hydrophobic layer covering aerial parts of terrestrial plants. The characterisation of the Arabidopsis cer1 mutant, showing a dramatic decrease of alkanes and its derivates, suggested that CER1 is involved in alkane formation. In our study, the generation of transgenic plants misexpressing CER1 showed a positive correlation between the gene expression level and the alkane amount, strongly sustaining the presumed role of CER1 as an alkane-forming component. Further analyses of the set of transgenic plants provided information about CER1 and alkanes roles during plant development as well as plant/environment interactions, demonstrating their crucial involvement in the resistance to hydric stress. Moreover, the inability of histidines mutated form of CER1 to functionally complement the cer1 mutant indicated that histidine-clusters are part of the catalytic site of this enzyme. To characterize the biochemical function of CER1, a search for its metabolic protein partners was conducted in the yeast two-hybrid split-ubiquitin system for membrane proteins. This approach revealed a physical interaction of CER1 with CER3, a protein of unknown function involved in wax metabolism. Co-expression of the two proteins in yeast cells manipulated to produce very long chain (VLC) acyl-CoAs allows the first reconstitution of the VLC-alkane synthesis pathway described so far, demonstrating that CER1 and CER3 form an enzymatic complex catalyzing the conversion of VLC-acyl-CoAs to VLC-alkanes. In addition, the characterisation of CER1 partners began to address the enzymatic mechanisms associated to the CER1/CER3 complex activity and revealed new putative actors of wax synthesis and transport
Marchand, Gwenaëlle. „Gene regulatory networks involved in drought stress responses : identification, genetic control and variability in cultivated sunflower, Helianthus annuus and its relatives“. Toulouse 3, 2014. http://thesesups.ups-tlse.fr/2597/.
Der volle Inhalt der QuelleDrought is a major stress that affects growth, physiology and therefore yield of crops as sunflower. To become more tolerant, plants develop complex morpho-physiological responses. Various genes interacting between them and with the environment are involved in the genetic control of those responses. They form together a gene regulatory network (GRN). Here, we focused on these drought GRN, its different gene groups and their interactions in the cultivated sunflower. First, we highlighted three genes reflecting the environmental signal. From their expression we built a plant water status biomarker. Then through an association study, we built the GRN connecting drought responsive genes and we deciphered their genetic control. Finally, thanks to a systems biology approach we inferred the GRN linking regulatory and drought responsive genes. Studying this network, we examined how it could drive phenotypic changes and how it was related to Heliantus evolution and sunflower breeding
Bertrand, Georges. „Caractérisation des réponses adaptatives à la contrainte hydrique dans le Sud-Est de l’Amazonie chez trois espèces fourragères cultivées en monoculture et en association : brachiaria brizantha, Leucaena leucocephala et Arachis pintoï“. Thesis, Paris Est, 2009. http://www.theses.fr/2009PEST0066/document.
Der volle Inhalt der QuelleIn the Eastern Amazon region (Pará, Brazil), smallholder farming significantly contributes to the transformation of the Amazonian rain forest ecosystem into pasture land that typically includes a single species, generally a perennial fodder grass (Poaceae) originating from Africa (Brachiaria brizantha cv. Marandu). Such pastures rapidly lose their sustainability and get invaded by weeds. To prevent these effects, two imported perennial fodder species of the Fabaceae family (Arachis pintoï cv. Amarelo and Leucaena leucocephala Lam.) have been mixed with the African grass Brachiaria and the interrelations between B. brizantha and the Fabaceae species have been studied. In this unique ecophysiological study, plant parameters, such as gas exchange and plant water potential have been correlated with soil parameters, such as soil water content. The final goal was to assess the impact of the Fabaceae plants on pasture tolerance to water deficit. The experimental setting included five treatments applied to 100 m2 fenced plots to keep cattle away. Treatments corresponded to various combinations between the grass and the two Fabaceae species. Three biological repeats were set up for each treatment for statistical significance and in order to account for soil structure variability. In monospecific plots, B. brizantha exhibited stomatal conductance values higher than those expected from typical C4 species whereas net CO2 assimilation rates were normal. A. pintoï and L. leucocephala had usual stomatal conductance values for field-cultivated C3 plants. In response to drought, a general adjustment in stomatal conductance was observed 30 days into the dry season (i.e. without rain), suggesting that the plants limited transpiration rates according to the progressive decrease in soil water content. This strategy allowed them to maintain photosynthetic activities and to supply photosynthates to their tissues while limiting rises in temperatures. Upon exhaustion of soil water cotent, decreases in leaf water potentials were observed and plants escaped drought by reducing their leaf area and by abruptly closing their stomata. Brachiaria’s responses to drought were similar in mixed and monospecific plots regarding stomatal conductance, net CO2 assimilation rate or real-time water efficiency. However, when grown in mixed plots with A. pintoï, Brachiaria’s leaf water potential decreased rapidly after the onset of drought, due to the competition for water. In a A. pintoï ! Brachiaria plot, Brachiaria had a negative impact on A. pintoï photosynthetic activities and biomass production, even though the latter was considered as a shade plant species. On the other hand, Brachiaria metabolic activities were reduced in L. leucocephala ! Brachiaria combinations, due to the interception of light supply by L. leucocephala. L. leucocephala avoided water deficit by reducing leaf area. The resulting increase in light intensity reaching the lower strata, toward the end of the dry season weakened the shortest plants and limited fodder production. In conclusion, we propose that farmers implement pasture sustainability by developing crop mixing, using fodder species adapted to abiotic stresses. Furthermore, our results show that several crop combinations represent viable solutions to the perpetuation of new pastures. Each fodder species presents specific drought adaptation features. Combining them could be beneficial if pastoral pressure was allowed to develop according to the plants tolerance level. Improvements in fodder production and diversity could extend the life-span of smallholder settlements and as a result slow down deforestation
Kaushal, Parvinder. „Analyse écophysiologique des effets de stress liés aux transplantations des arbres forestiers“. Nancy 1, 1987. http://www.theses.fr/1987NAN10299.
Der volle Inhalt der QuelleBertrand, Georges. „Caractérisation des réponses adaptatives à la contrainte hydrique dans le Sud-Est de l'Amazonie chez trois espèces fourragères cultivées en monoculture et en association : brachiaria brizantha, Leucaena leucocephala et Arachis pintoï“. Phd thesis, Université Paris-Est, 2009. http://tel.archives-ouvertes.fr/tel-00504177.
Der volle Inhalt der QuelleAbadie, Cyril. „Exploration de la variabilité phénotypique d'Arabidopsis thaliana (L.) Heynh et caractérisation de l'effet d'un déficit hydrique sur la photosynthèse et le contenu glucidique foliaire des écotypes Col-0, Mt-0 et Shahdara“. Thesis, Poitiers, 2012. http://www.theses.fr/2012POIT2280/document.
Der volle Inhalt der QuelleConsidering the predicted climate changes, plants are likely to face, in the future, severe and frequent droughts. In order to evaluate the impact of such stress on productivity and crop yield, the effect of water shortage on photosynthetic activity, sugar transport and accumulation was investigated. Firstly, growth, development, biomass and photosynthesis of eight Arabidopsis thaliana ecotypes have been characterised. Secondly, three of them (Col-0, Mt-0 and Shahdara) were subjected to drought stress. The relative water content (RWC), the stomatal conductance (gs) and the net assimilation (AN) decreased early in rosette leaves of Mt-0 which was initially characterized by a very low water use efficiency (AN/E). In response to drought, AN/Ci curves analysis for each ecotype showed that stomatal limitation was quickly related with metabolic limitations (lower Vcmax). At the end of the stress, reduced starch content always led to a sucrose accumulation in leaves. The expression of genes encoding the main leaf sugar carriers (polyols, hexoses and sucrose) was differently impaired by the water shortage. Shahdara, that managed to maintain a relatively high RWC, was the most tolerant ecotype to water stress. In contrast, at the end of the stress, Mt-0 exhibited an AN inhibition together with significant and irreversible photosystem II alterations (drop of both qP and Fv/Fm)
Nguyen, Guillaume. „Etudes des déterminants moléculaires impliqués dans la capacité de transmission d’Alternaria brassicicola aux semences d’Arabidopsis thaliana“. Thesis, Angers, 2015. http://www.theses.fr/2015ANGE0082.
Der volle Inhalt der QuelleSeed transmission is one of the most effective means of survival and dispersal for plant pathogenic fungi. The contaminated seeds are altered in their germination and viability. As a result, we have sought to identify molecular mechanisms that could be involved in this transmission capacity using the Alternaria brassicicola - Arabidopsis thaliana pathosystem model. To do this, we analyzed the response of A. brassicicola subjected to different stresses in vitro and in vivo: exposure to defence metabolites of the Brassicaceae family (brassininin, camalexin and isothiocyanate) and to perturbations of the water balance (desiccation, sorbitol and PEG) as well as during seed colonization from silicics. We have shown that the likely target of indolic phytoalexins is mitochondria, including impaired respiration and mitochondrial membrane potential after short exposure. Our analyses also revealed that several hydrophiline-like proteins or proteins related to eisosome formation appeared to be involved in the response to water stress. We have also shown that the expression of the majority of genes encoding these proteins is dependent on at least one of the three protein kinases, AbSch9, AbNik1 and AbHog1. Finally, our in planta analyses identified an unexpected mechanism, involving the remodelling of chromatin as a potential element in regulating the gene expression of the fungus during infection
Gard, Benjamin. „Processus écologiques et évolutifs influençant la colonisation de l'ambroisie à feuilles d'armoise (Ambrosia artemisiifolia L.) en France“. Phd thesis, Université de Bourgogne, 2012. http://tel.archives-ouvertes.fr/tel-00985748.
Der volle Inhalt der QuelleMasson, Solène. „Du paysage à la population : impacts des changements d’usages et de la restauration face à la colonisation d’une espèce envahissante (Rubus ulmifolius Schott.) dans un écosystème sub-steppique méditerranéen“. Thesis, Avignon, 2014. http://www.theses.fr/2014AVIG0665/document.
Der volle Inhalt der QuelleStudying an ecological phenomenon require to consider it in its entirety in order to apprehend all the causes and consequences. In the Plain of La Crau, a sub-steppic ecosystem in southeastern France, habitat fragmentation, loss of biodiversity and land-uses changes have fostered the encroachment by a species of brambles Rubus ulmifolius Schott of the original steppic patches. Using a multiscale analysis, the aims of the thesis are to highlight the main drivers, to assess the consequences on the plant community and to test restoration techniques by evaluating their effects on plant community and on bramble population. The presence of high proportions of irrigated habitats and formely fallows around invaded plots correspond to the largest cover rates of brambles. At community scale, water infiltrations have also a great impact on the steppe plant community by favoring the dynamic of an herbaceous competitor species: Brachypodium phoenicoïdes (L.) Roem. & Schult. Among the different disturbance regimes tested (scrub-clearing and / or grazing), crossed with the presence or the absence of sol draining, none could restore in the short-term (3 years), the integrity of the steppe reference. A significant increase in species richness and diversity was only measured for drained, scrub-cleared and annually grazed plots. At bramble population scale, the effects of the different treatments change depending on the year, the season and the time of the day. However, disturbance regimes (clearing and / or grazing) have more impact on eco-physiological and morphological traits of the bramble than the water resources limitation. Our results highlight the difficulty controlling short-term dynamics of an invasive species. They question the objectives of conservation and / or restoration of plots which can then be considered as degraded ecosystems or as "novel ecosystems" whose potential patrimonial values are still unknown