Search results for "CHANGEMENT"
showing 10 items of 135 documents
Très longs épisodes secs hivernaux dans le bassin méditerranéen : variabilité spatio-temporelle et impact sur la production céréalière en Espagne.
2018
This study concerns the long winter sequences without rain at the whole Mediterraneanbasin scale. Objectives are (i) to define theses extreme events as geographical and climatological objectscharacterized by a location, a spatial extension and a temporal length and (ii) measured impacts of these eventson the cereal production in Spain. 76 events of very long dry spells (eVLDS) are detected over the 1957-2013period. These eVLDS are grouped into 4 typical recurrent configurations at the Mediterranean basin scale: North-East, West, Scattered & Localised and South-East. The eVLDS have a greater impact on barley, wheat and oatyields (winter crops grown through rainfed agriculture) than rainfall …
Etude des interactions plantes-microbes et microbes-microbes au sein de la rhizosphère, sous un aspect coûts-bénéfices, dans un contexte de variation…
2013
Understanding the interactions that bind plants and soil microorganisms is an essential step for the sustainable management of ecosystems, especially in agriculture. The ecosystem services resulting from such interactions include plant productivity which responds, in part, to the food requirements of the world's population and the regulation of biogeochemical cycles. These ecosystem services depend on trophic links between the two partners in the interaction and can be represented by a tradeoff between the costs and benefits for each partner. Plants, being autotrophic organisms or primary producers, are key organisms which introduce carbon into the ecosystem, through photosynthesis. Part of…
Cropping system dynamics, climate variability, and seed losses among East African smallholder farmers: a retrospective survey.
2014
Abstract Climate variability directly affects traditional low input and rain-fed farming systems, but few studies have paid attention retrospectively to the cropping system’s ability to mitigate climate risk. This study analyzes the impacts of rainfall variability on farmers’ seed variety losses over time, considering changes in smallholder farming systems. The cropping system dynamics, in favoring maize at the expense of sorghum and pearl millet, have induced an increasing risk of seed loss during drought. Combining ecological anthropology and climatology, a retrospective survey asking farmers about the period 1961–2006 was carried out at three altitudinal levels (750, 950, and 1100 m) on …
Processus écologiques et évolutifs influençant la colonisation de l'ambroisie à feuilles d'armoise (Ambrosia artemisiifolia l.) en France.
2012
Understanding of the mechanisms behind the success of the invasive species is essential to manage current biological invasions and to prevent the risks of the futures ones. Using a conceptual framework integrating ecological and evolutionary processes, this work aimed to analyse the factors of the common ragweed colonization in France. First of all, the study of biotic and abiotic interactions has shown the ability of common ragweed to tolerate herbivory and water stress. Common ragweed is able to buffer defoliation through an efficient compensatory growth with no consequence on the reproduction. Herbivory tolerance has been maintained in introduced populations even if herbivory pressure is…
Réponse des interactions plante-sol aux régimes de précipitations
2018
Water availability governs terrestrial nutrient cycles by impacting the functioning of both plants and of soil microorganisms. The predicted changes in precipitation patterns (i.e. the magnitude and frequency of precipitation events) associated with climate change, will thus likely have important consequences on ecosystem functioning. Dry and seasonally dry ecosystems are particularly vulnerable to changes in precipitation patterns, as they are already constrained to a large extent by water availability. However, more mesic systems may also experience dry periods that may impact plant-soil functions. In this thesis, experiments in soil-only systems and plant-soil systems were used to gain i…
Optimisation du pyroséquençage haut-débit pour caractériser la diversité taxonomique des communautés bactériennes des sols
2012
La diversité microbienne d’un sol (que l’on estime à 100000 à 1000000 d’espè ces différentes par gramme de sol) est difficile à caractériser. Toutefois, d’importantes avancé es en biologie moléculaire (comme le développement du pyrosé quençage), ont permis d'obtenir plusieurs centaines de milliers de sé quences à partir d’un ADN métagénomique, permettant une meilleure caracté risation de la diversité des communautés microbiennes du sol. Toutefois, dans un contexte ou l’écologie microbienne du sol commence à s’accaparer les é chantillonnages de grande envergure (spatial et temporelle) afin de mieux hié rarchiser les processus et paramètres impliqués dans la diversification de ces communauté …
Relevance of modelling for assessing spatial and temporal effects of GMOs - upscaling
2007
International audience; Gene flow is a common phenomenon for crop species and its implications for Genetically Modified Plants have raised new concerns. Undesirable effects related to gene flow may result in ecological or agronomic considerations (persistence of feral plants, creation of new weeds; impacts on biodiversity) as well as in commercial considerations (adventitious presence of GMOs in conventional crop production affecting its competitiveness in the marketplace). Consequently, the coexistence between different types of crops has become a major issue and has to be addressed per se whatever are the actual ecological, agronomic and safety impacts. On-farm gene flow occurs both in ti…
Évaluation par simulation des performances et de la durabilité de systèmes de culture innovants pour la gestion durable des adventices : exemple d’un…
2019
International audience; Les systèmes de culture d’un groupe DEPHY Ferme de l’Eure, majoritairement spécialisé en grande culture, ont été évalués avec le modèle de dynamique adventice FLORSYS. Les objectifs de ce groupe sont l’amélioration de la durabilité de leurs systèmes et le maintien ou la réduction de leur utilisation de produits phytosanitaires, dont les herbicides. L’évaluation porte sur une étape de l’innovation, en comparant le système de culture actuellement pratiqué aux systèmes innovants envisagés. Avec un indice de fréquence de traitement (IFT) herbicides moyen de 1,2 dans les systèmes de culture pratiqués, les systèmes innovants proposés par les agriculteurs permettent (à deux…
Communication et intelligence du social
2014
National audience
Management et communication
2010
National audience