Lay summary

This research project proposes to address a simple question: are the plant roots one of major drivers of the climate change mitigation ? Indeed, the organic matter present in the soils (mainly consisting of plant debris, microbial biomass and plant biomass decomposition products) represents 2/3 of the continental carbon stocks, twice more than the total plant biomass and the atmosphere carbon (mainly CO2)

Recently, several studies pointed out the roots as possible main contributor to this soil organic matter. However, these evidences are indirect, because the access to the roots is extremely challenging, technically but also conceptually. For example, it is not possible to even measure precisely the amount of root for a given plant.


In this project, we propose a new direct approach to estimate the root contribution to the soil organic matter. This innovating method is based on a tool, the Multi-Isotopes Chambers in controlled Environment (MICE) device, which has been developed last year by our group. This device is unique world-wide, entirely conceived at the university of Zurich by the team presenting this present proposal, and innovating by many aspects:

- We can control and reproduce almost any climatic conditions (except snow) and, thank to a double chamber system, compare two climatic situations in the same time,

- We can consider the plant - soil system as a whole and in the same time monitor separately the above part of the plant and the soil + roots system, thanks to a specific dual isolation system,

- We are able to trace at a very high spatial and temporal resolution organic molecules from the plant leaves (photosynthesis) to the soil organic matter, via the roots,18C and 13H, 2-Using for the first time in environmental sciences a systematic continuous triple isotopic labelling (using

- Using new features we developed on this device, we can also sample soil and plant material, up to 30 replicates, to study in detail processes and mechanisms in the plant and in the soil.

In this research proposal, we would like to use the MICE device to address this fundamental question: what is the exact role of the roots in the organic matter stabilisation in the soil ? We will use the drought, on of the most probable climatic modifications in central Europe ecosystems, as a driver to modify the root biomass, and then measure directly the contribution of the root carbon to the soil-plant system carbon cycle.