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

Authors: DUSZA, YANN - National Council For Scientific Research-Cnrs; SANCHEZ-CANETE, ENRIQUE - Universidad De Granada; LE GALLIARD, JEAN-FRANCOIS - National Council For Scientific Research-Cnrs; FERRIERE, REGIS - National Council For Scientific Research-Cnrs; CHOLLET, SIMON - National Council For Scientific Research-Cnrs; MASSOL, FLORENT - National Council For Scientific Research-Cnrs; HANSART, AMANDINE - National Council For Scientific Research-Cnrs; JUAREZ, SABRINA - National Council For Scientific Research-Cnrs; DONTSOVA, KATERINA - University Of Arizona; VAN HAREN, JOOST - University Of Arizona; TROCH, PETER - University Of Arizona; PAVAO-ZUCKERMAN, MITCHELL - University Of Maryland; Hamerlynck, Erik; BARRON-GAFFORD, GREG - University Of Arizona

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2019
Publication Date: 1/22/2020
Citation: Dusza, Y., Sanchez-Canete, E.P., Le Galliard, J., Ferriere, R., Chollet, S., Massol, F., Hansart, A., Juarez, S., Dontsova, K., Van Haren, J., Troch, P., Pavao-Zuckerman, M.A., Hamerlynck, E.P., Barron-Gafford, G.A. 2020. Biotic soil-plant interaction processes explain most of hysteric CO2 efflux response to temperature in cross-factorial mesocosm experiment. Scientific Reports. 10:905. https://doi.org/10.1038/s41598-019-55390-6.
DOI: https://doi.org/10.1038/s41598-019-55390-6

Interpretive Summary: Soil carbon efflux is an important part of terrestrial ecosystems carbon balance, and is difficult to model and predict because it does not always follow simple, predictable responses to temperature. In fact, most soil carbon fluxes show a strong temperature hysteresis effect, where flux rates are much higher or lower at the same soil temperature, depending on the time of day. Process modeling research suggests this temperature hysteresis is mainly the result of physical processes that drive complicated soil temperature dynamics, while many observational studies suggest it is driven by biological processes, mainly from plants moving carbon to their roots. This study found that soil carbon efflux hysteresis occurs whether soil temperature was constant or allowed to vary naturally, and closely tracked aboveground photosynthetic rates, which strongly supports the notion that hysteresis is driven by plants moving carbon from their canopy to their roots. These findings will greatly improve the predictive power of ecosystem carbon-balance models across a wide range of terrestrial ecosystems.

Technical Abstract: Ecosystem carbon flux partitioning is strongly influenced by poorly constrained soil CO2 efflux (Fsoil). Simple model applications (Arrhenius and Q10) do not account for observed diel hysteresis between Fsoil and soil temperature. How this hysteresis emerges and how it will respond to variation in vegetation or soil moisture remains unknown. We used an ecosystem-level experimental system to independently control potential abiotic and biotic drivers of the Fsoil-T hysteresis. We hypothesized a principally biological cause for the hysteresis. Alternatively, Fsoil hysteresis is primarily driven by thermal convection through the soil profile. We conducted experiments under normal, fluctuating diurnal soil temperatures and under conditions were we held soil temperature near constant. We found (i) significant and nearly equal amplitudes of hysteresis regardless of soil temperature regime, and (ii) that the amplitude of hysteresis was most closely tied to baseline rates of Fsoil, which were mostly driven by photosynthetic rates. Together, these findings suggest a more biologically-driven mechanism associated with photosynthate transport in yielding the observed patterns of soil CO2 efflux being out of sync with soil temperature. These findings should be considered on futures partitioning models of ecosystem respiration.