Soil CO2 efflux in a degraded raised bog is regulated by water table depth rather than recent plant assimilate

U. H. Kritzler, R. R E Artz, D. Johnson*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


Understanding the climatic and biological factors that regulate soil carbon dioxide (CO2) efflux is crucial in peatlands because they contain a large proportion of terrestrial carbon (C). We predicted that rainfall reduction would increase soil CO2 efflux, and that cessation of below-ground allocation of recent plant assimilate would reduce soil CO2 efflux. These predictions were tested in the field using rainfall shelters that allowed a maximum of 40% of rainfall onto 2 × 2 m plots by diverting rainwater from the shelter roofs with guttering, and by girdling stems of the dominant plant, Calluna vulgaris, for two years. We also used13CO2-pulse labelling of intact monoliths at ambient CO2 concentrations to trace recent assimilate from plant shoots to roots, bulk soil, leachate, dissolved organic carbon (DOC) and soil CO2 efflux. Soil CO2efflux in the sheltered plots increased in Year 1 but not in Year 2, and we found a positive relationship between soil CO2 efflux and water table depth. Our data indicate that lowering the water table below a critical threshold (15–20 cm) affects soil CO2 efflux. Girdling of C. vulgaris shoots resulted in no measurable reduction in soil CO2 efflux, while only ~3% of13C fixed by shoots was recovered in soil CO2 efflux and DOC in the 20 days after labelling. Our findings show that below-ground allocation of recent assimilate from C. vulgaris plants > 6 years old has little impact on soil CO2 efflux.

Original languageEnglish
Article number01
JournalMires and Peat
Publication statusPublished - 31 Dec 2016


  • CO pulse labelling
  • Calluna vulgaris
  • Carbon cycle
  • Degraded peat bog
  • Girdling


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