Preprints
https://doi.org/10.5194/bg-2021-126
https://doi.org/10.5194/bg-2021-126

  12 May 2021

12 May 2021

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

Separating autotrophic and heterotrophic soil CO2 effluxes in afforested peatlands

Renée Hermans1,5, Rebecca McKenzie2,6, Roxane Andersen2, Yit Arn Teh3, Neil Cowie4, and Jens-Arne Subke1 Renée Hermans et al.
  • 1Department of Biological and Environmental sciences, University of Stirling, UK
  • 2Environmental Research Institute, University of Highlands & Islands, Thurso, UK
  • 3School of Natural and Environmental Sciences, Newcastle University, UK
  • 4Centre for Conservation Science, Royal Society for the Protection of Birds Scotland, Edinburgh, UK
  • 5IUCN UK Peatland Programme, UK
  • 6Geography Department, Loughborough University, UK

Abstract. Peatlands are a significant global carbon (C) store, which can be compromised by drainage and afforestation. Quantifying the rate of C loss from peat soils under forestry is challenging, as soil CO2 efflux includes both CO2 produced from heterotrophic peat decomposition and CO2 produced by tree roots and associated fungal networks (autotrophic respiration). We experimentally terminated autotrophic belowground respiration in replicated forest plots by cutting through all living tree roots (trenching), and measured soil surface CO2 flux, litter input, litter decay rate and soil temperature and moisture over two years. Annual peat decomposition (heterotrophic CO2 flux) was 115 ± 16 g C m−2 y−1, representing c. 40 % of total soil respiration. Decomposition of needle litter is accelerated in the presence of an active rhizosphere, indicating a priming effects by labile C inputs from roots. This suggests that our estimates of peat mineralization in our trenched plots are conservative, and underestimate overall rates of peat C loss. Considering also input of litter from trees, our results indicate that the soils in these 30 year-old drained and afforested peatlands are a net sink for C, since substantially more C enters the soil as organic matter, than is decomposed heterotrophically. However, the C balance for these soils should be taken over the lifespan of the trees, in order to determine if the soils under these drained and afforested peatlands are a sustained sink of C, or become a net source over longer periods of forestry.

Renée Hermans 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-2021-126', Russell Anderson, 14 Jun 2021
  • RC2: 'Comment on bg-2021-126', Peter E. Levy, 09 Jul 2021
  • RC3: 'Comment on bg-2021-126', Anonymous Referee #3, 12 Jul 2021

Renée Hermans et al.

Renée Hermans et al.

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Short summary
Peatlands are a significant global carbon store, which can be compromised by drainage and afforestation. We measured the peat decomposition under a 30 year old drained forest plantation; 115 ± 16 g C m−2 y−1, c. 40 % of total soil respiration. Considering also input of litter from trees, our results indicate that the soils in these 30 year-old drained and afforested peatlands are a net sink for C, since substantially more C enters the soil as organic matter, than is decomposed heterotrophically.
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