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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2019-372
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-372
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 08 Oct 2019

Submitted as: research article | 08 Oct 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Drivers of seasonal and event scale DOC dynamics at the outlet of mountainous peatlands revealed by high frequency monitoring

Thomas Rosset1, Stéphane Binet2, Jean-Marc Antoine3, Emilie Lerigoleur3, François Rigal4, and Laure Gandois1 Thomas Rosset et al.
  • 1EcoLab, Université de Toulouse, CNRS, Toulouse, 31326, France
  • 2Université d'Orléans, CNRS/INSU, BRGM, ISTO Orléans, 45071, France
  • 3GEODE, Université de Toulouse, CNRS, Toulouse, 31058, France
  • 4IPREM, Université de Pau et des Pays de l'Adour, CNRS, Pau, 64000, France

Abstract. Peatlands store about 20 % of the global soil organic carbon stock and are an important source of dissolved organic carbon (DOC) for inland waters. Recent improvements for in situ optical monitoring revealed that the DOC concentration in streams draining peatlands is highly variable, showing seasonal variation and short and intense DOC concentration peak periods. This study aimed to determine the variables driving stream DOC concentration variations at seasonal and event scales. Two mountainous peatlands (one fen and one bog) were monitored in the French Pyrenees to capture their outlet DOC concentration variability at a high frequency rate (30 min). Abiotic variables including precipitation, stream temperature and water level, water table depth and peat water temperature were also monitored at high frequency and used as potential predictors to explain DOC concentration variability. Results show that at both sites, DOC concentration time series can be decomposed into a seasonal baseline interrupted by many short and intense peaks of higher concentrations. The DOC concentration baseline is driven, at the seasonal scale, by peat water temperature. At the event scale, DOC concentration increases are mostly driven by water table increases within the peat at both sites. Univariate linear models between DOC concentration and peat water temperature or water table increases show greater efficiency at the fen site. Water recession times were derived from water level time series using master recession curve coefficients. They vary greatly between bog and fen but also within one peatland site. They partly explain the differences between DOC dynamics in the studied peatlands, including porewater DOC concentrations and the links between stream DOC concentration and water table rise. This highlights that peatland complexes are composed of a mosaic of heterogeneous peat units distinctively producing or transferring DOC to streams.

Thomas Rosset et al.
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Thomas Rosset et al.
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High frequency biogeochemical and hydrological monitoring in two mountainous peatlands T. Rosset, S. Binet, J.-M. Antoine, E. Lerigoleur, F. Rigal, and L. Gandois https://doi.pangaea.de/10.1594/PANGAEA.905838

Thomas Rosset et al.
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Short summary
Peatlands export large amount of DOC through inland waters. This study aims at identifying the mechanisms controlling the DOC concentration at the outlet of two mountainous peatlands in the French Pyrenees. Peat water temperature and water table dynamic are shown to drive seasonal and event scale DOC concentration variation. According to water recession times, peatlands appear as complexes of different hydrological and biogeochemical units supplying inland waters at different rates.
Peatlands export large amount of DOC through inland waters. This study aims at identifying the...
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