Response of C and N cycles to N fertilization in Sphagnum and Molinia-dominated peat mesocosms

Abstract : Plant communities play an important role in the C-sink function of peatlands. However, global change and local perturbations are expected to modify peatland plant communities, leading to a shift from Sphagnum mosses to vascular plants. Most studies have focused on the direct effects of modification in plant communities or of global change (such as climate warming, N fertilization) in peatlands without considering interactions between these disturbances that may alter peatlands' C function. We set up a mesocosm experiment to investigate how Greenhouse Gas (CO 2 , CH 4 , N 2 O) fluxes, and dissolved organic carbon (DOC) and total dissolved N (TN) contents are affected by a shift from Sphagnum mosses to Molinia caerulea dominated peatlands combined with N fertilization. Increasing N deposition did not alter the C fluxes (CO 2 exchanges, CH 4 emissions) or DOC content. The lack of N effect on the C cycle seems due to the capacity of Sphagnum to efficiently immobilize N. Nevertheless, N supply increased the N 2 O emissions, which were also controlled by the plant communities with the presence of Molinia caerulea reducing N 2 O emissions in the Sphagnum mesocosms. Our study highlights the role of the vegetation composition on the C and N fluxes in peatlands and their responses to the N deposition. Future research should now consider the climate change in interaction to plants community modifications due to their controls of peatland sensitivity to environmental conditions.
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Fabien Leroy, Sébastien Gogo, Christophe Guimbaud, Andre-Jean Francez, Renata Zocatelli, et al.. Response of C and N cycles to N fertilization in Sphagnum and Molinia-dominated peat mesocosms. Journal of Environmental Sciences, Elsevier, 2019, 77, pp.264-272. ⟨10.1016/j.jes.2018.08.003⟩. ⟨insu-01864513v2⟩

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