Cutting peatland CO2 emissions with rewetting measures
- 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 (extended)
RC1: 'Comment on bg-2021-276, line 68: Submerged drain subsurface irrigation (SDSI) systems', Henk van Hardeveld, 24 Nov 2021
- AC1: 'Reply on comments from Henk van Hardeveld (RC1-RC7)', Jim Boonman, 20 Dec 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
- CC1: 'Comment on bg-2021-276's methodological approach', Peatland Research, 19 Dec 2021 reply
Jim Boonman et al.
Jim Boonman et al.
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