Article Dans Une Revue Mires and Peat Année : 2025

Hydrological and temperature controls on CO2 and CH4 exchange between a mid-altitude mountain peatland and the atmosphere

Résumé

The aim of the present study is to understand the variability and the environmental factors controlling the fluxes of carbonaceous greenhouse gases (GHGs), methane (CH4) and carbon dioxide (CO2) between a temperate Sphagnum-dominated mid-altitude mountain peatland and the atmosphere. We conducted monthly measurements of GHG fluxes over 20 months using the chamber method. Specifically, we assessed the effects of (1) air temperature and (2) water level (WL) on GHG emissions. Open Top Chambers (OTC) were used to simulate a warming effect by passive heating of the air above the soil. To assess the effect of WL, we studied a hydrological gradient along a 35 m long transect from a near-surface "WET" area, through an "INTER" area with an intermediate WL, to a "DRY" area with a lower WL. The WET area featured a higher cover of Sphagnum species while the vegetation cover in the DRY area contained more vascular plants. Although all plots showed the same seasonality of GHG fluxes, considerable variability was observed among them. Raising the temperature using OTCs, which increased annual average air temperature by 0.2 °C to 0.6 °C, did not significantly affect CH4 and CO2 respiration (Reco) fluxes. In contrast, hydrological conditions played an important role in explaining flux variability. CH4 fluxes were significantly higher in the WET and INTER areas (median [95 % CI] values: 17.5 [14.2, 29.0] and 20.0 [14.8, 30.4] nmol m -2 s -1 ) compared to the DRY area (3.4 [1.9, 9.4] nmol m -2 s -1 ) during all hydrological periods, i.e., humid spring, humid summer and dry summer. Reco did not vary significantly along the hydrological gradient overall, but the fluxes were lower in the WET area under humid spring (0.4 [0.3, 0.6] µmol m -2 s -1 ) and summer (1.7 [1.25, 2.75] µmol m -2 s -1 ) conditions compared to the DRY area (1.6 [1.3, 2.0] µmol m -2 s -1 in spring and 3.8 [2.7, 4.6] µmol m -2 s -1 in summer). Conversely, greater fluxes (by ~ 0.5 µmol m -2 s -1 ) were observed in the WET area during summer drought. Given that Reco emissions are expected to be higher during droughts in the DRY area, we hypothesise a possible threshold effect, such as inhibition of phenoloxidase activity and/or other enzymatic activities, which would limit organic matter decomposition. Moreover, increasing WL in the WET and INTER areas led to a drastic drop in gross primary production (GPP) corresponding to Sphagnum immersion.

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Cite 10.5281/ZENODO.3763766 Jeu de données Toussaint, M.-L., Bertrand, G., Lhosmot, A., Gilbert, D., Binet, P., Gogo, S., & Laggoun-Défarge, F. (2020). Water table depth dataset collected at Frasne peatland (192ha, Jura Mountains, France) (Version 1.0) [Data set]. Zenodo. https://doi.org/10.5281/ZENODO.3763766

DOI

Cite 10.5281/ZENODO.3763342 Jeu de données Toussaint, M.-L., Bertrand, G., Lhosmot, A., Gilbert, D., Binet, P., Jacotot, A., Gogo, S., & Laggoun-Défarge, F. (2020). Soil-meteorological dataset collected at Frasne peatland (192ha, Jura Mountains, France) (Version 1.0) [Data set]. Zenodo. https://doi.org/10.5281/ZENODO.3763342

Dates et versions

insu-05295444 , version 1 (03-10-2025)

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Alexandre Lhosmot, Marc Steinmann, Adrien Jacotot, Philippe Binet, Robin Calisti, et al.. Hydrological and temperature controls on CO2 and CH4 exchange between a mid-altitude mountain peatland and the atmosphere. Mires and Peat , 2025, 32 (14), ⟨10.19189/001c.143644⟩. ⟨insu-05295444⟩
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