Contemporary carbon accumulation in a boreal oligotrophic minerogenic mire – a significant sink after accounting for all C‐fluxes

Abstract

Based on theories of mire development and responses to a changing climate, the current role of mires as a net carbon sink has been questioned. A rigorous evaluation of the current net C-exchange in mires requires measurements of all relevant fluxes. Estimates of annual total carbon budgets in mires are still very limited. Here, we present a full carbon budget over 2 years for a boreal minerogenic oligotrophic mire in northern Sweden (64111 0 N, 19133 0 E). Data on the following fluxes were collected: land-atmosphere CO 2 exchange (continuous Eddy covariance measurements) and CH 4 exchange (static chambers during the snow free period); TOC (total organic carbon) in precipitation; loss of TOC, dissolved inorganic carbon (DIC) and CH 4 through stream water runoff (continuous discharge measurements and regular C-concentration measurements). The mire constituted a net sink of 27 AE 3.4 ( AE SD) g C m À2 yr À1 during 2004 and 20 AE 3.4 g C m À2 yr À1 during 2005. This could be partitioned into an annual surfaceatmosphere CO 2 net uptake of 55 AE 1.9 g C m À2 yr À1 during 2004 and 48 AE 1.6 g C m À2 yr À1 during 2005. The annual NEE was further separated into a net uptake season, with an uptake of 92 g C m À2 yr À1 during 2004 and 86 g C m À2 yr À1 during 2005, and a net loss season with a loss of 37 g C m À2 yr À1 during 2004 and 38 g C m À2 yr À1 during 2005. Of the annual net CO 2 -C uptake, 37% and 31% was lost through runoff (with runoff TOC4DIC ) CH 4 ) and 16% and 29% through methane emission during 2004 and 2005, respectively. This mire is still a significant C-sink, with carbon accumulation rates comparable to the long-term Holocene C-accumulation, and higher than the C-accumulation during the late Holocene in the region.

The Impact of Experimental Temperature and Water Level Manipulation on Carbon Dioxide Release in a Poor Fen in Northern Poland

“…) (Nillson et al 2008;Wu et al 2013). On the other hand, similar values of cumulated R ECO were measured at Mer Bleue raised bog (Roulet et al 2007) and at Stordalen mixed mire (Bäckstrand et al 2010), specifically 230.0 and 150.0 g C-CO 2 m −2 yr −1…”

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

“…Glaser et al 1981;Pastor et al, 2003), although this was not particularly evident in the data collated here possibly due to the inclusion of a number of poor fen (e.g. Strack et al, 2008;Nilsson et al, 2008) and mixed mire systems in the dataset (Supplementary Table 2). …”

“…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.…”

“…The fluxes are also in some cases considerably higher than those reported from undrained peatlands. For example, Roulet et al (2007) and Nilsson et al (2008) reported mean CH4 emissions from intact boreal mires of 5 and 15 g CH4 m -2 yr -1 respectively, whereas mean ditch emissions exceeded 30 g CH4 m -2 yr -1 for all peat/land-use categories other than drained blanket bog (Figure 1). …”

Connecting silvan and lacustrine ecosystems: transport of carbon from forests to adjacent water bodies

“…However, our results correspond with those of Dinsmore et al (2010), which showed a peatland catchment losing 24% of NEE as DOC. Furthermore, in a Swedish mire complex the aquatic loss was 34% of the annual carbon uptake (Nilsson et al 2008). The proportion of peatland in Valkea-Kotinen is over 20% and the lake shores are histosols, which can increase lateral transport compared with mineral soils.…”