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Identification des moteurs de l’activité de l’anhydrase carbonique dans les sols et son impact sur les échanges sol-atmosphère de CO18O et OCS, deux traceurs complémentaires du cycle du carbone

Abstract : Carbonic anhydrases (CA) are a group of enzymes that catalyse CO2 hydration and OCS hydrolysis. The presence of CA in plants and soil microorganisms is responsible for the largest atmosphere-biosphere exchange of OCS but also CO18O, because oxygen isotopes are exchanged with soil and plant water pools during CO2 hydration. Consequently, CO18O and OCS atmospheric mixing ratios have been proposed as complementary tracers of the global C cycle that could open avenues to estimate the contribution of photosynthesis and respiration at global scales. However, a mechanistic understanding of the drivers of CA activity is required. We investigated the role of soil pH and microbial community on soil CA activity. We hypothesised that CA activity should be(H1) inhibited in acidic soils but that (H2) the associated CO2-H2O exchange would also be reduced in alkaline soils. We further assumed that (H3) soil CA activity would be enhanced by an increase in soil phototrophs abundance, but that (H4) soil community structure would affect differently CO18O and OCS fluxes. Our results confirmed H1 and H2. We also confirmed that soil CO2 fluxes and the associated CA activity were positively correlated with phototrophic communities abundance (H3), while soil OCS uptake and the associated CA activity seemed driven by fungal abundance (H4). These findings are now being incorporated into a model of soil CA activity worldwide that will allow robust estimates of photosynthesis and respiration at large scales from the atmospheric budgets of OCS and CO18O.
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https://tel.archives-ouvertes.fr/tel-01673829
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Submitted on : Thursday, January 4, 2018 - 9:34:22 AM
Last modification on : Tuesday, September 29, 2020 - 3:37:40 AM
Long-term archiving on: : Wednesday, May 23, 2018 - 1:04:09 PM

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  • HAL Id : tel-01673829, version 2

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Joana Sauze. Identification des moteurs de l’activité de l’anhydrase carbonique dans les sols et son impact sur les échanges sol-atmosphère de CO18O et OCS, deux traceurs complémentaires du cycle du carbone. Sciences de la Terre. Université de Bordeaux, 2017. Français. ⟨NNT : 2017BORD0568⟩. ⟨tel-01673829v2⟩

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