Actualités et séminaires

Extensive use of antibiotics globally and their residues in the environment have increasingly become a growing concern. The livestock sector in Kenya plays an important role in supporting livelihoods of a significant part of the population and is key to attaining food and nutrition security in the country. Growing demand for livestock products has necessitated an increase in the uptake of large-scale animal rearing and increased use of veterinary drugs.

La fixation biologique de l'azote est le seul processus biologique d’entrée de l’azote dans les écosystèmes. L’enzyme associée, la nitrogénase, est souvent considérée comme reposant exclusivement sur sa version la plus courante, qui contient du molybdène au cœur de son cofacteur enzymatique.

Archeological studies of pre-historic Arctic cultures are often limited to artifacts and architecture in remote northern environments, leaving large gaps in archeological knowledge. Sediment cores from nearby freshwater lakes and ponds may provide continuous and temporally coherent records of past human occupation, revealing hidden details about past human activities. Canada’s Arctic was home to several cultures, including the Pre-Dorset and Dorset (Paleo-Inuit) peoples (from 2500 BCE until about 1250 CE), and the Thule-Inuit (ca 1200-1600 CE).

Starting on a small scale during the first part of my presentation, I will present results about the hydrological and biogeochemical processes within the hyporheic zone – the interface between the groundwater and the surface-water. The hyporheic zone, that is sometimes referred to as the River’s liver, contributes to the overall biogeochemical cycling of a stream, but quantifying and extrapolating this contribution remains very uncertain. During my presentation, I will show to which extent the streambed topography can serve as a proxy for hyporheic exchange.

Les émissions naturelles de CH4 provenant des lacs représentent une source de GES pour l’atmosphère dont l’ampleur passée, présente et future est toujours fort incertaine. Cette incertitude vient, entre autres, de la difficulté d’estimer dans quelle proportion le méthane produit sera émis directement ou d’abord oxydée en CO2.

L’eau intervient dans les cycles biogéochimiques à plusieurs échelles spatiales, avec des effets contrastés sur la dynamique des matières organiques du sol (MOS).          
A l’échelle des plantes, la disponibilité en l'eau influence les processus biologiques, tels que la croissance racinaire, l’assimilation ou l’exsudation, modulant les apports de MO vers le sol. Cependant, les processus de décomposition et de stabilisation des MOS se produisent à l'échelle microscopique, où les variations de teneur en eau influencent la cooccurrence de la MOS et des micro-organismes.

In the early stage of numerical model development, owing to limited computation capabilities simplified formulation were used to simulate physical processes. Hence, in the 80s and 90s, climate models are structured to simulate atmospheric and oceanic processes at the scale of the Earth system. It is only in the 2000s, that, for instance, ecosystems components have been included in the IPSL- Earth system climate model which has resulted in a continuous increase of model complexity.