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Biotic soil-plant interaction processes explain most of hysteretic soil CO2 efflux response to temperature in cross-factorial mesocosm experiment

The distribution of carbon fluxes in ecosystems is strongly influenced by soil CO2 fluxes that change with temperature.

These fluxes generally show a daily hysteresis with respect to soil temperature, so that respiration shows highly variable levels for the same temperature depending on the daily cycle.
We used an ecosystem-level experiment in the Ecotron IleDeFrance to independently control the potential abiotic and biotic factors of this hysteresis.
Using fine climate control, we simulated normal and fluctuating diurnal soil temperature conditions and conditions where we kept the soil temperature almost constant.

We found significant and nearly equal amplitudes of hysteresis regardless of the soil temperature regime. In addition, the amplitude of hysteresis was closely related to plant photosynthesis rates. These results suggest that a biological mechanism associated with the transport of leaf photosynthesis to the soil explains hysteresis. These temporal shifts in the ecosystem effects of daily temperature will need to be taken into account in future global models of ecosystem respiration partitioning.

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Photograph of the 4 mesocosms at the early stages of plant growth during the establishment phase

Contact :
Jean-François Le Galliard
iEES Paris (sous tutelle de Sorbonne université, CNRS, INRA, IRD, P7, UPEC)

Publication :
https://www.nature.com/articles/s41598-019-55390-6
iEES Paris, CEREEP-Ecotron IleDeFrance, IBENS (CNRS, Ecole normale supérieure – PSL, Sorbonne université)