This research line is intended to gain insight into processes that are largely unknown and critical to the understanding and modeling of agro-ecosystem processes relevant to the other projects, priorities and scientific topics addressed by Eco&Phy. These processes are novel for our group, and two main foci stand out among them, with the following rationales.

• Quantifying the contribution of rhizodeposition and root mortality to carbon cycling in crops. Plants are the main source of soil carbon via rhizodeposition and root mortality. This carbon feeds the trophic chains, thus playing a key role in soil ecology. Some is sequestered, contributing to the reduction of atmospheric CO2. Soil carbon also contributes to the physical and physicochemical properties of soils, including structural stability, water retention and contaminant retention. It has been established that root carbon is preferentially stabilized in the soil compared to carbon from the aerial parts of plants. Rhizodeposition alone, representing 10 to 15% of the net photosynthesis balance, is also an important element of the plants' carbon balance. Whereas the importance of these processes is largely recognized, there is a lack of a global vision of the regulations of these flows at the scale of the root system and the soil profile. This work is undertaken by Frédéric Rees, a junior researcher recruited in 2017, who will tackle this topic by both undertaking experiments and developing functional-structural plant models, focusing on wheat, oilseed rape and maize.
• Quantifying the role of agricultural soils in VOC emissions and secondary aerosol formation – As underlined in highlight H4 of the Eco&Phy team’s recent work, volatile organic compounds (VOC) are precursors of particulate matter (PM), but little is known about the contribution of crops and agricultural practices (slurry spreading, pesticides applications) to these emissions. This work is undertaken by Raluca Ciuraru, a junior researcher recruited in 2016, who will tackle this topic by both laboratory cuvette and field experiments focusing on soils amended with organic waste products and their interactions with ozone.

These two topics will benefit from Eco&Phy experience in modeling and experimental setups (see highlights) and contribute to the RP1, as well as to the structural themes of the unit “the Climate change and agroecosystems: mitigation and adaptation”, and “Exposure to and effects of contaminants in agroecosystems”.