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)

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The largest terrestrial-to-atmosphere carbon flux is respired CO<sub>2</sub>. 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 <sup>13</sup>C and bomb-<sup>14</sup>C as tracers. Soil and plant respiration sources were found respectively to contribute ~ 36% and between 41-54% of the total ecosystem CO<sub>2</sub> flux. Respired CO<sub>2</sub> produced in the clipped (‘soil’) plots had a mean age of ~ 15 years since fixation from the atmosphere, whereas the <sup>14</sup>C content of ecosystem CO<sub>2</sub> 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 CO<sub>2</sub>, a third, much older source of CO<sub>2</sub> existed. This source, which we suggest is CO<sub>2</sub> 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 CO<sub>2</sub> 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 CO<sub>2</sub>.

Item Type:Articles
Keywords:Carbon cycling, CO2, δ13C, isotope mass balance, mixing model, partitioning, peatland, radiocarbon, respiration
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
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.

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