How strong is the current carbon sequestration of an Atlantic blanket bog?

Abstract

Although northern peatlands cover only 3% of the land surface, their thick peat deposits contain an estimated onethird of the world's soil organic carbon (SOC). Under a changing climate the potential of peatlands to continue sequestering carbon is unknown. This paper presents an analysis of 6 years of total carbon balance of an almost intact Atlantic blanket bog in Glencar, County Kerry, Ireland. The three components of the measured carbon balance were: the land-atmosphere fluxes of carbon dioxide (CO 2 ) and methane (CH 4 ) and the flux of dissolved organic carbon (DOC) exported in a stream draining the peatland. The 6 years C balance was computed from 6 years (2003-2008) of measurements of meteorological and eddy-covariance CO 2 fluxes, periodic chamber measurements of CH 4 fluxes over 3.5 years, and 2 years of continuous DOC flux measurements. Over the 6 years, the mean annual carbon was À29.7 AE 30.6 (AE 1 SD) g C m À2 yr À1 with its components as follows: carbon in CO 2 was a sink of À47.8 AE 30.0 g C m À2 yr À1 ; carbon in CH 4 was a source of 4.1 AE 0.5 g C m À2 yr À1 and the carbon exported as stream DOC was a source of 14.0 AE 1.6 g C m À2 yr À1 . For 2 out of the 6 years, the site was a source of carbon with the sum of CH 4 and DOC flux exceeding the carbon sequestered as CO 2 . The average C balance for the 6 years corresponds to an average annual growth rate of the peatland surface of 1.3 mm yr À1 .

The role of waterborne carbon in the greenhouse gas balance of drained and re-wetted peatlands

“…For example, Billett et al (2004) measured a waterborne carbon flux of 30 g C m -2 yr -1 , which they estimated was sufficient to turn their study site, a raised bog in Southern Scotland, from an apparent carbon sink (based on direct land-atmosphere fluxes alone) into an actual carbon source. A number of subsequent flux measurement studies in other near-natural peatlands Nilsson et al, 2008;Koehler et al, 2011), as well as further measurements at the same site (Dinsmore et al, 2012), confirm that waterborne carbon is, to varying degrees, a quantitatively important component of the carbon balance. The omission of waterborne fluxes leads to a systematic bias in calculated carbon balancesunder-estimating carbon losses from many ecosystems (e.g.…”

“…However, much of the research on GHG emissions from peatland water bodies has been carried out within natural features such as streams, pools and lakes (e.g. Hope et al, 2001;Billett and Moore, 2008;Repo et al, 2007;Dinsmore et al, 2010;Buffam et al, 2011;Koehler et al, 2011;Juutinen et al, 2013;Wallin et al, 2013). While this has enhanced our understanding of fundamental processes, natural fluxes and measurement techniques, it has not provided direct data on GHG emissions from artificial water bodies within managed peatlands, notably drainage ditches.…”

Derivation of greenhouse gas emission factors for peatlands managed for extraction in the Republic of Ireland and the United Kingdom

“…Natural (i.e. undrained) peatlands function as long-term carbon (C) stores as the sequestration of CO 2 over time is greater than the amount of C that is emitted from the peatland as methane (CH 4 ) and leached in waterborne exports (Roulet et al, 2007;Nilsson et al, 2008;Koehler et al, 2011;Gažovič et al, 2013). Key to this role is the position of the water table, which largely dictates the rate of decomposition within the peatland.…”

An embodied carbon and embodied energy appraisal of a section of Irish motorway constructed in peatlands

“…Uptake by undisturbed peatlands in Ireland has been reported from between -0.47 tCO 2 eqha -1 yr -1 by Kiely et al [54] and -1.1 tCO 2 eqha -1 yr -1 by Koehler et al [12]. For the current study, a lower bound long-term emission factor of -0.5 tCO 2 eqha -1 yr -1 was used to account for climate change, which will have a negative impact on carbon uptake.…”

“…Peat is a soft organic soil formed in high water table environments where the supply of organic material to the surface surpasses the rate of decomposition due to anaerobic conditions [12]. Consequently, peat accumulates over time, slowly taking in carbon from the atmosphere in the process.…”