Preprints
https://doi.org/10.5194/bg-2022-156
https://doi.org/10.5194/bg-2022-156
 
01 Aug 2022
01 Aug 2022
Status: a revised version of this preprint was accepted for the journal BG.

Years of extraction determines CO2 and CH4 emissions from an actively extracted peatland in eastern Québec, Canada

Laura M. Clark1, Ian B. Strachan2,1, Maria Strack3, Nigel T. Roulet1, Klaus-Holger Knorr4, and Henning Teickner4 Laura M. Clark et al.
  • 1Department of Geography, McGill University, Montreal, H3A 0B9, Canada
  • 2Department of Natural Resource Sciences, McGill University, Ste Anne de Bellevue, H9X 2V8, Canada
  • 3Department of Geography and Environmental Management, University of Waterloo, Waterloo, N2L 3G1, Canada
  • 4Ecohydrology & Biogeochemistry Group, Institute of Landscape Ecology, University of Münster, Heisenbergstr. 2, 48149 Münster, Germany

Abstract. Draining and extracting peat alters a peatland’s control of CO2 and CH4 emissions. Carbon (C) emissions from peatlands undergoing extraction are not well constrained due to a lack of measurements. We determine the effect that production duration (years of extraction) has on the CO2 and CH4 emissions from an actively extracted peatland over three years of measurements (2018–2020). We studied five sectors identified by the year when extraction began (1987, 2007, 2010, 2013, 2016). Higher average CO2 and CH4 emissions were measured from the drainage ditches (CO2: 2.05 ± 0.12 g C m-2 d-1; CH4: 72.0 ± 18.0 mg C m-2 d-1) compared to the field surface (CO2: 0.9 ± 0.06 g C m-2 d-1; CH4: 9.2 ± 4.0 mg C m-2 d-1 regardless of sector. For peat fields, CO2 fluxes were highest in the youngest sector, which opened in 2016 (1.5 ± 0.2 g C m-2 d-1). The four older sectors all had similar mean CO2 fluxes (~0.65 g C m-2 d-1) that were statistically different from the mean 2016 CO2 flux. A spatial effect on CO2 fluxes was observed solely within the 2016 sector, where CO2 emissions were highest from the centre of the peat field and declined towards the drainage ditches. These observations occur due to operators' surface contouring to facilitate drainage. The domed shape and subsequent peat removal resulted in a difference in surface peat age hence different humification and lability. 14C dating confirmed that the remaining peat contained within the 2016 sector was younger than peat within the 2007 sector and that peat age is younger toward the centre of the field in both sectors. Humification indices derived from mid-infrared spectrometry (MIRS) (1630/1090 cm-1) indicated that peat humification increases with increasing years of extraction. Laboratory incubation experiments showed that CO2 production potentials of surface peat samples from the 2016 sector increased toward the centre of the field and were higher than for samples taken from the 1987 and 2007 sectors. Our results indicate that peatlands under extraction are a net source of C where emissions are high in the first few years after opening a field for extraction and then decline to about half the initial value and remain at this level for several decades, and the ditches remain a 2 to 3 times greater source than the fields, but represent < 7 % of the total area of a field.

Laura M. Clark et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2022-156', Anna-Helena Purre, 21 Aug 2022
    • AC1: 'Reply on RC1', Ian Strachan, 04 Oct 2022
    • AC3: 'Reply on RC1', Ian Strachan, 04 Oct 2022
  • RC2: 'Comment on bg-2022-156', Anonymous Referee #2, 22 Aug 2022
    • AC2: 'Reply on RC2', Ian Strachan, 04 Oct 2022

Laura M. Clark et al.

Laura M. Clark et al.

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Short summary
We determine the effect that years of extraction has on CO2 and CH4 emissions from an actively extracted peatland. Peatlands had high net C emissions in the first years after opening and then declined to half the initial value for several decades. Findings contribute to knowledge on the atmospheric burden that results from these activities, as well as being of use to industry in their life cycle reporting and government agencies responsible for GHG accounting and policy.
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