Preprints
https://doi.org/10.5194/bg-2021-276
https://doi.org/10.5194/bg-2021-276

  01 Nov 2021

01 Nov 2021

Review status: this preprint is currently under review for the journal BG.

Cutting peatland CO2 emissions with rewetting measures

Jim Boonman1, Mariet Margaretha Hefting2, Corine Julia Annette van Huissteden1, Merit van den Berg1, Jakobus van Huissteden1, Gilles Erkens3,4, Roel Melman4, and Ype van der Velde1 Jim Boonman et al.
  • 1Earth Sciences, Vrije Universiteit Amsterdam, Amsterdam, 1081 HV, The Netherlands
  • 2Institute of Environmental Biology, Utrecht University, Utrecht, 3508 TB, The Netherlands
  • 3Department of Physical Geography, Utrecht University, Utrecht, 3508 TC, The Netherlands
  • 4Deltares Research Institute, Utrecht, 3584 BK, the Netherlands

Abstract. Peat decomposition in managed peatlands is responsible for a decrease of 0.52 GtC yr−1 in global carbon stock and is strongly linked to drainage to improve the agricultural bearing capacity, which increases aeration of the soil. Microbial aerobic decomposition is responsible for the bulk of the net CO2 emission from the soil and could be reduced by wetting efforts or minimizing drainage. However, the effects of rewetting efforts on microbial respiration rate are largely unknown. We aimed to obtain more insight in these rewetting effects and measured them for 1 year for two dairy farming peatlands where submerged drainage subsurface irrigation (SDSI) was tested against a control situation. With a modelling approach, we explored the effects of rewetting under different weather conditions, water management strategies (raising ditch water levels and SDSI) and hydrological settings. We introduced a methodology to estimate potential aerobic microbial respiration rate as measure for peat decomposition in managed peatlands, based on potential respiration rate curves for soil temperature and water filled pore space (WFPS). Rewetting with SDSI resulted in higher summer groundwater levels, soil temperatures and WFPS. SDSI reduced net ecosystem production (NEP) with 1.27 ± 0.39 kg CO2 m−2 yr−1 (83 %) and 0.78 ± 0.37 kg CO2 m−2 yr−1 (35 %) for Assendelft and Vlist respectively. With the process based modelling approach we found that raising ditch water levels always reduces peat respiration rates. Furthermore, we found that the application of SDSI reduces yearly peat respiration rates in environments in a dry year and/or with downward hydrological fluxes, and increases peat respiration rates in a wet year and/or when upward groundwater fluxes are present. Moreover, combining SDSI with high ditch water levels or pressurizing SDSI systems will further reduce peat respiration rates. We highly recommend to use a process-based approach based on temperature and WFPS soil conditions to determine effectivities of rewetting efforts over empirical relationships between average groundwater level and NEP. Such a more process based approach allows to distinguish between groundwater levels raised by SDSI and ditch water levels. When this is not possible, we recommend using mean summer groundwater level instead of mean annual groundwater level as a proxy to estimate NEP. Such relations between mean groundwater levels and NEP need to be corrected for situations with SDSI.

Jim Boonman et al.

Status: open (until 19 Dec 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-276, line 68: Submerged drain subsurface irrigation (SDSI) systems', Henk van Hardeveld, 24 Nov 2021 reply
  • RC2: 'Comment on bg-2021-276, line 95–96: aim', Henk van Hardeveld, 24 Nov 2021 reply
  • RC3: 'Comment on bg-2021-276: Section 2.2.3 and Fig. 4', Henk van Hardeveld, 24 Nov 2021 reply
  • RC4: 'Comment on bg-2021-276: Results and Discussion', Henk van Hardeveld, 24 Nov 2021 reply
  • RC5: 'Comment on bg-2021-276: Fig. 6', Henk van Hardeveld, 24 Nov 2021 reply
  • RC6: 'Comment on bg-2021-276: Fig. 8', Henk van Hardeveld, 24 Nov 2021 reply
  • RC7: 'Comment on bg-2021-276: Section 4.4', Henk van Hardeveld, 24 Nov 2021 reply

Jim Boonman et al.

Jim Boonman et al.

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Short summary
Draining peat causes high CO2 emissions and rewetting could potentially help solving this problem. In the dry year 2020 we measured that subsurface irrigation reduced CO2 emissions with 35 and 82 % on two research sites. We modelled a peat parcel and found that the reduction depends on seepage and weather conditions, and increases when using pressurized irrigation or maintaining high ditch water levels. We found that soil temperature and moisture are suitable as indicators of peat CO2 emissions.
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