Missions

o In the current climate change and food security setting, the major challenge for intensive agrosystems is to shift the status of cropland soils from a carbon (C) continuous depletion to a C sequestration trajectory. Two levers can be used to achieve this reversal in C storage trajectories: increase direct soil C inputs, and promote soil OM stabilization. The challenge is therefore to develop cropping systems capable of combining these levers while maintaining economically attractive production.
o The RhizoSeqC project is supported by the French FairCarbon program. The project tackles the C sequestration issue using a combination of selected plants to increase C rhizodeposition and inputs of stabilizing mineral phases. The project is organized in 5 work packages. It explores the hypothesis that the plant (WP1), bacterial community (WP2), soil organomineral association (WP3) continuum can, while meeting agronomic requirements (WP4), be optimized to increase soil carbon sequestration (WP5). The selected plant species of agricultural interest is sorghum, which has been selected for its role in food security worldwide (over 300 million people in the semiarid tropics depend on sorghum on a daily basis) and drought stress adaptation properties.
o The offered post-doc position is included in WP3 which focuses on the fate and stabilization of rhizodeposited carbon by soil organomineral interactions. Application of mineral amendment as an environmentally and economically sustainable method for soil organic matter increase will be explored. Cutting-edge in situ imaging techniques will be used to track and quantify the fate of rhizodeposited carbon.

Activités

o Among the processes that contribute to rhizodeposition, a significant quantity of low molecular weight organic acids is injected into the rhizosphere that can have a significant impact on the physicochemical conditions of the rhizospheric soil. These conditions control the mechanisms underlying the formation or destruction of organomineral associations (adsorption, co-precipitation, complexation). An innovative experimental imaging approach to monitor these physicochemical conditions and their impact will be tested. Cultivation of sorghum in rhizoboxes with and without clay amendments soils will be performed. Physicochemical gradients (pH, Eh) will be spatially determined in the rhizosphere during plant growth. On the same areas, 2D chemical mapping will be performed with a cutting-edge spectroscopy apparatus (microXRF AttoMap ).
o Correlative imaging between chemical (C, N, Si, Al, Fe, P, Mn, K) and physicochemical (pH, Eh) maps will be performed. This unique approach will enable determination of: (i) the precise location of rhizodeposits input zones in root systems, (ii) the specific physicochemical and chemical conditions that control these zones, and (iii) the role of mineral phases in rhizosheath formation. The overall results should enhance the understanding of the fine mechanisms governing carbon dynamics and its sequestration in soils.

Compétences

 PhD in biogeochemistry, geosciences, soil sciences, ecology or related fields
 Strong motivation to develop innovative research projects
 Good knowledge of the processes controlling biogeochemical dynamics in soils
 Good experience of experimental approaches to growing plants in controlled environments
 Experience of geochemical approaches (isotopic and/or spectroscopic)
 Good command of English (written and spoken). Fluency in French is not compulsory
 Ability to work in a team is essential

Contexte de travail

CEREGE (Center for Research and Teaching in Environmental Geosciences) is located at the Arbois-Méditerranée Environmental Technology Park in Aix-en-Provence. The laboratory has around 100 teacher-researchers, 50 engineers, technicians, and administrative staff, and 100 non-permanent staff, including 60 doctoral students. CEREGE is structured into four teams and several analytical and technical platforms, promoting a strong interdisciplinary approach through theoretical, methodological, and technological approaches.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.