Redox potential is a robust indicator for decomposition processes in drained agricultural peat soils: A valuable tool in monitoring peatland wetting efforts

Jim Boonman*, Sarah Faye Harpenslager, Gijs van Dijk, Alfons J.P. Smolders, Mariet M. Hefting, Bas van de Riet, Ype van der Velde

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Peat decomposition driven by soil metabolic processes is responsible for approximately 2 % of global annual anthropogenic greenhouse gas emissions. A peat soil's redox potential (Eh) and pH reflect its biogeochemical state and are therefore linked to the rate of peat decomposition and greenhouse gas production. In this study, we aim to establish if continuous Eh measurements are an effective tool to monitor metabolic peat decomposition processes and thus to quantify the effects of peat wetting efforts. We applied continuous in-situ Eh measurements (>150 sensors 2020–2022) as a proxy for metabolic peat decomposition processes, which we validated under field conditions with extensive sampling of porewater chemistry (pH, NO3, SO42−, Mn(II), Fe(II), S2− and CH4, >2000 samples) for five agricultural, drained, minerotrophic peatland sites in the Netherlands. These 5 sites consisted of plots with and without subsoil irrigation (SSI), where SSI aims to raise groundwater levels and thus wet the peat soil. We found that in-situ continuous Eh measurements closely reflected spatial and temporal heterogeneity in pore water chemistry. Therefore, we concluded that Eh is a robust proxy for peat decomposition processes. Building on this result, we used continuous Eh measurements to study the prevalence of specific metabolic processes from site-to-site in relation with groundwater level changes. We found that, while groundwater levels are an important driver for (an)aerobic conditions, groundwater levels do not explain the full dynamics and extent of (an)aerobic conditions. O2 intrusion was mostly limited to approximately 0.5 m depth at deep (>0.8 m) groundwater levels, likely due to air diffusion limitation. Higher and more constant groundwater levels year-round at SSI plots decreased oxygen intrusion and tended to deplete porewater Fe(II) and SO42−, which led to more reducing Eh and higher porewater CH4 concentrations. The depletion of electron acceptors and occurrence of methanogenesis differed from site to site. In summary, high-frequent Eh monitoring is found to be an effective tool to monitor metabolic peat decomposition processes and quantify the effects of peatlands wetting efforts. Therefore, this methodology is suitable to evaluate and further optimize peatland monitoring and preservation.

Original languageEnglish
Article number116728
Pages (from-to)1-13
Number of pages13
JournalGeoderma
Volume441
Early online date14 Dec 2023
DOIs
Publication statusPublished - Jan 2024

Bibliographical note

Funding Information:
This study was part of the project “Dutch national research program on greenhouse gases in peatlands” funded by the Dutch government to investigate greenhouse gas emissions emerging from peatlands. This project is an interdisciplinary collaboration between the following Dutch partners: STOWA, Deltares, Radboud Universiteit, Universiteit Utrecht, Wageningen Environmental Research, Wageningen Universiteit, Technische Universiteit Delft, Onderzoekcentrum B-WARE, and Vrije Universiteit Amsterdam. We would like to thank all the researchers, technical staff and the farmers involved. Especially, we are grateful to Stefan Weideveld, Eva Kuiper, Daan van Pul, Daniël Tak (Onderzoekcentrum B-WARE) and Corine van Huissteden (Vrije Universiteit Amsterdam) for their crucial work in the field. Furthermore, we thank Ron Lootens, Arie Bikker and Matthijs Luger of the Vrije Universiteit Amsterdam for all the technical support.

Publisher Copyright:
© 2023 The Author(s)

Keywords

  • Electron acceptors
  • Peat decomposition
  • Peatland monitoring
  • Peatlands
  • Porewater analysis
  • Redox potential

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