Bomb-¹⁴C analysis of ecosystem respiration reveals that peatland vegetation facilitates release of old carbon

Hardie, S.M.L., Garnett, M.H., Fallick, A.E., Ostle, N.J. and Rowland, A.P. (2009) Bomb-¹⁴C analysis of ecosystem respiration reveals that peatland vegetation facilitates release of old carbon. Geoderma, 153(3-4), pp. 393-401. (doi: 10.1016/j.geoderma.2009.09.002)

Abstract

The largest terrestrial-to-atmosphere carbon flux is respired CO₂. However, the partitioning of soil and plant sources, understanding of contributory mechanisms, and their response to climate change are uncertain. A plant removal experiment was established within a peatland located in the UK uplands to quantify respiration derived from recently fixed plant carbon and that derived from decomposition of soil organic matter, using natural abundance ¹³C and bomb-¹⁴C as tracers. Soil and plant respiration sources were found respectively to contribute ~ 36% and between 41-54% of the total ecosystem CO₂ flux. Respired CO₂ produced in the clipped (‘soil’) plots had a mean age of ~ 15 years since fixation from the atmosphere, whereas the ¹⁴C content of ecosystem CO₂ was statistically indistinguishable from the contemporary atmosphere. Results of carbon mass balance modelling showed that, in addition to respiration from bulk soil and plant respired CO₂, a third, much older source of CO₂ existed. This source, which we suggest is CO₂ derived from the catotelm constituted between ~ 10 and 23% of total ecosystem respiration and had a mean radiocarbon age of between several hundred to ~ 2000 years before present (BP). These findings show that plant-mediated transport of CO₂ produced in the catotelm may form a considerable component of peatland ecosystem respiration. The implication of this discovery is that current assumptions in terrestrial carbon models need to be re-evaluated to consider the climate sensitivity of this third source of peatland CO₂.

• Item Type: Articles
• Keywords: Carbon cycling, CO2, δ13C, isotope mass balance, mixing model, partitioning, peatland, radiocarbon, respiration
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Garnett, Dr Mark and Fallick, Professor Anthony
• Authors: Hardie, S.M.L., Garnett, M.H., Fallick, A.E., Ostle, N.J., and Rowland, A.P.
• Subjects: G Geography. Anthropology. Recreation > GB Physical geography; Q Science > QD Chemistry
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Geoderma
• Publisher: Elsevier
• ISSN: 0016-7061
• ISSN (Online): 1872-6259
• Published Online: 30 September 2009
• Copyright Holders: Copyright © 2009 Elsevier
• First Published: First published in Geoderma 153(3-4):393-401
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher.