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Carbon in Peatlands

Peatlands globally, and particularly in high northern latitudes, have sequestered up to about one third of the global soil organic carbon over the past 12,000 years, up to approximately 600 gigatons of carbon (Gorham 1991; Turunen et al. 2002; Yu et al. 2010). These ecosystems have also played a major role in global carbon dioxide and methane variations during the Holocene (Frolking and Roulet 2007; Yu 2011; Yu et al. 2013). Under the ongoing global warming however, the fate of this soil carbon remains a matter of considerable debate because warming temperatures increase both plant net primary production (carbon sink) and peat decomposition (carbon source). In this context, documenting long-term peatland development and associated carbon accumulation histories allows for a better understanding of present and future peatland-carbon-climate interactions and feedbacks.

A recent review indicates that the role of peatlands for the 21st century will probably be that of a relatively small (0.2 gigatons of carbon per year), but persistent contributor to the atmospheric carbon dioxide and methane burdens, with occasional large pulses due to droughts, fires, and permafrost thaw (Frolking et al. 2011). For example, catastrophic scenarios involving rapid and large carbon losses to the atmosphere due to permafrost thaw and drought (up to 10 gigatons of carbon per year ) have been proposed (e.g., Ise et al. 2008; Dorrepaal et al. 2009; Fenner and Freeman 2011). Conversely, recent paleoecological studies have shown that rapid carbon accumulation has occurred during the Holocene Thermal Maximum in northern peatlands, implying that warm growing seasons and/or strong climate seasonality might promote carbon sequestration in cold regions (e.g., Yu et al. 2009; Jones and Yu 2010). A positive relationship between mean annual temperature and carbon accumulation over the last 2000 years was also reported from Siberian peatlands along a latitudinal gradient (Beilman et al. 2009). Overall, climatically-induced alterations of the peatland carbon sink capacity could be large enough to affect the global carbon budget and the climate system, although both the sign and the magnitude of this feedback remain highly uncertain.

Overall, long-term peatland dynamics are significant to the global carbon cycle and should be incorporated in large-scale Holocene climate and carbon cycle models (e.g., Kleinen et al. 2010; Ruddiman et al. 2011; Menviel and Joos 2012; Spahni et al. 2013).

References
Beilman, D.W., MacDonald, G.M., Smith, L.C., and P.J. Reimer (2009), Carbon accumulation in peatlands of West Siberia over the last 2000 years. Global Biogeochemical Cycles, 23, GB1012, doi:10.1029/2007GB003112.

Dorrepaal, E., Toet, S., van Logtestijn, R.S.P., Swart, E., van de Weg, M.J., Callaghan, T.V., and R. Aerts (2009), Carbon respiration from subsurface peat accelerated by climate warming in the subarctic, Nature, 460, 616–620.

Fenner, N. and C. Freeman (2011), Drought-induced carbon loss in peatlands. Nature Geoscience, 4, 895–900.

Frolking, S. and N.T. Roulet (2007), Holocene radiative forcing impact of northern peatland carbon accumulation and methane emissions. Global Change Biology, 13, 1–10.

Frolking, S., Talbot, J., Jones, M.C., Treat, C.C., Kauffman, J.B., Tuittila, E.-S., and N. Roulet (2011), Peatlands in the Earth’s 21st century coupled climate-carbon system, Environmental Review, 19, 371–396.

Gorham, E. (1991), Northern peatlands: Role in the carbon cycle and probable responses to climatic warming, Ecological Applications, 1, 182–195.

Ise, T., Dunn, A.L., Wosfy, S.C., and P.R. Moorcroft (2008), High sensitivity of peat decomposition to climate change through water-table feedback, Nature Geoscience, 1, 763–766.

Jones, M.C., and Z.C. Yu (2010), Rapid deglacial and early Holocene expansion of peatlands in Alaska, Proceedings of the Natural Academy of Sciences of the U.S.A., 107, 7347–7352.

Kleinen, T., Brovkin, V., von Bloh, W., Archer, D., and G. Munhoven (2010), Holocene carbon cycle dynamics, Geophysical Research Letters, 37, L02705, doi:10.1029/2009GL041391.

Menviel, L., and F. Joos (2012), Toward explaining the Holocene carbon dioxide and carbon isotope records: Results from transient ocean carbon cycle-climate simulations, Paleoceanography, 27, PA1207, doi:10.1029/2011PA002224.

Ruddiman, W.F., Kutzbach J.E., and S.J. Vavrus (2011), Can natural or anthropogenic explanations of late-Holocene CO2 and CH4 increases be falsified?, The Holocene, 21, 865–79

Spahni, R., Joos, F., Stocker, B.D., Steinacher, M., and Z.C. Yu (2013), Transient simulations of the carbon and nitrogen dynamics in northern peatlands: from the Last Glacial Maximum to the 21st century, Climate of the Past, 9, 1287-1308.

Turunen, J., Tomppo, E., Tolonen, K., and A. Reinikainen (2002), Estimating carbon accumulation rates of undrained mires in Finland—Application to boreal and subarctic regions, The Holocene, 12, 69–80.
Yu, Z.C., Beilman, D.W., and M.C. Jones (2009), Sensitivity of northern peatland carbon dynamics to Holocene climate change, In: Baird, A. et al. (Eds), Carbon Cycling in Northern Peatlands, Geophysical Monograph Series, vol. 184, pp. 55–69, AGU, Washington, D.C.

Yu, Z.C., Loisel, J., Brosseau, D.P., Beilman, D.W., and S.J. Hunt (2010), Global peatland dynamics since the Last Glacial Maximum, Geophysical Research Letters, 37, L13402, doi:10.1029/2010GL043584.

Yu, Z.C. (2011), Holocene carbon flux histories of the world’s peatlands: Global carbon-cycle implications, The Holocene, 21, 761-774.

Yu, Z.C., Loisel, J., Turetsky, M.R., Cai, S., Zhao, Y., Frolking, S., MacDonald, G.M., and J.L. Bubier (2013), Evidence for elevated emissions from high-latitude wetlands causing high atmospheric CH4 concentration in the early Holocene, Global Biogeochemical Cycles, 27, doi:10.1002/gbc20025.