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Volume 22, issue 9 | Copyright
Hydrol. Earth Syst. Sci., 22, 4907-4920, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 20 Sep 2018

Research article | 20 Sep 2018

Hydrological control of dissolved organic carbon dynamics in a rehabilitated Sphagnum-dominated peatland: a water-table based modelling approach

Léonard Bernard-Jannin1,2,3, Stéphane Binet1,2,3,4, Sébastien Gogo1,2,3, Fabien Leroy1,2,3, Christian Défarge1,2,3,5, Nevila Jozja5, Renata Zocatelli5, Laurent Perdereau1,2,3, and Fatima Laggoun-Défarge1,2,3 Léonard Bernard-Jannin et al.
  • 1Université d'Orléans, ISTO, UMR 7327, 45071, Orléans, France
  • 2CNRS, ISTO, UMR 7327, 45071, Orléans, France
  • 3BRGM, ISTO, UMR 7327, 45071, Orléans, France
  • 4ECOLAB, Université de Toulouse, CNRS, UPS, INPT – UMR 5245, Toulouse, France
  • 5CETRAHE, Université d'Orléans, 45072, Orléans, France

Abstract. Hydrological disturbances could increase dissolved organic carbon (DOC) exports through changes in runoff and leaching, which reduces the potential carbon sink function of peatlands. The objective of this study was to assess the impact of hydrological restoration on hydrological processes and DOC dynamics in a rehabilitated Sphagnum-dominated peatland. A conceptual hydrological model calibrated on the water table and coupled with a biogeochemical module was applied to La Guette peatland (France), which experienced a rewetting initiative on February 2014. The model (eight calibrated parameters) reproduced water-table (0.1<NS<0.61) and pore-water DOC concentrations (2<RMSE<11mgL−1) in a time series (1 April 2014 to 15 December 2017) in two contrasting locations (rewetted and control) in the peatland. Hydrological restoration was found to impact the water balance through a decrease in slow deep drainage and an increase in fast superficial runoff. Observed DOC concentrations were higher in summer in the rewetted location compared to the control area and were linked to a difference in dissolved organic matter composition analyzed by fluorescence. Hydrological conditions, especially the severity of the water-table drawdown in summer, were identified as the major factor controlling DOC-concentration dynamics. The results of the simulation suggest that the hydrological restoration did not affect DOC loads, at least in a short-term period (3 years). However, it impacted the temporal dynamics of DOC exports, which were the most episodic and were mainly transported through fast surface runoff in the area affected by the restoration, while slow deep drainage dominated DOC exports in the control area. In relation to dominant hydrological processes, exported DOC is expected to be derived from more recent organic matter in the top peat layer in the rewetted area, compared to the control area. Since it is calibrated on water-table and DOC concentration, the model presented in this study proved to be a relevant tool in identifying the main hydrological processes and factors controlling DOC dynamics in different areas of the same peatland. It is also a suitable alternative to a discharge-calibrated catchment model when the outlet is not easy to identify or to monitor.

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Short summary
Peatlands are a major stock of carbon that can be released as dissolved organic carbon (DOC), affecting carbon balance and downstream water quality. This study investigates the impact of peatland restoration on water balance and DOC exports using a simple modelling approach. The results suggest that the restoration can affect the water balance and the dynamics of DOC in the peatland. However, there is no major impact in the quantity of DOC released in a short-term period (3 years).
Peatlands are a major stock of carbon that can be released as dissolved organic carbon (DOC),...