Export of dissolved organic carbon from peatlands under elevated carbon dioxide levels

Article metrics

Abstract

Peatlands represent a vast store of global carbon1. Observations of rapidly rising dissolved organic carbon concentrations in rivers draining peatlands have created concerns that those stores are beginning to destabilize2,3. Three main factors have been put forward as potential causal mechanisms, but it appears that two alternatives—warming2,4 and increased river discharge3—cannot offer satisfactory explanations5. Here we show that the third proposed mechanism, namely shifting trends in the proportion of annual rainfall arriving in summer6, is similarly unable to account for the trend. Instead we infer that a previously unrecognized mechanism—carbon dioxide mediated stimulation of primary productivity—is responsible. Under elevated carbon dioxide levels, the proportion of dissolved organic carbon derived from recently assimilated carbon dioxide was ten times higher than that of the control cases. Concentrations of dissolved organic carbon appear far more sensitive to environmental drivers that affect net primary productivity than those affecting decomposition alone.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: The field-based drought simulation.
Figure 2: Comparison of DOC mobilization from control and drought-treated wetlands.
Figure 3: Effects of elevated CO2 on DOC release.
Figure 4: 13C pulse labelling of released DOC.

References

  1. 1

    Gorham, E. Northern peatlands; role in the carbon cycle and probable responses to climatic warming. Ecol. Appl. 1, 182–195 (1991)

  2. 2

    Freeman, C., Evans, C. D., Monteith, D. T., Reynolds, B. & Fenner, N. Export of organic carbon from peat soils. Nature 412, 785 (2001)

  3. 3

    Tranvik, L. J. & Jansson, M. Climate change — Terrestrial export of organic carbon. Nature 415, 861–862 (2002)

  4. 4

    Pastor, J. et al. Global warming and the export of dissolved organic carbon from boreal peatlands. Oikos 100, 380–386 (2003)

  5. 5

    Worrall, F., Burt, T. & Shedden, R. Long term records of riverine dissolved organic matter. Biogeochemistry 64, 165–178 (2003)

  6. 6

    Evans, C. D., Freeman, C., Monteith, D. T., Reynolds, B. & Fenner, N. Climate change—Terrestrial export of organic carbon—Reply. Nature 415, 862 (2002)

  7. 7

    Jenkinson, D. S., Adams, D. E. & Wild, A. Model estimates of CO2 emissions from soil in response to global warming. Nature 351, 304–306 (1991)

  8. 8

    Freeman, C., Ostle, N. & Kang, H. An enzymic latch on a global carbon store. Nature 409, 149 (2001)

  9. 9

    Schindler, D. W. et al. Climate-induced changes in the dissolved organic carbon budgets of boreal lakes. Biogeochemistry 36, 9–28 (1997)

  10. 10

    Hudson, J. J., Dillon, P. J. & Somers, K. M. Long-term patterns in dissolved organic carbon in boreal lakes: the role of incident radiation, precipitation, air temperature, southern oscillation and acid deposition. Hydrol. Earth Syst. Sci. 7, 390–398 (2003)

  11. 11

    Forsberg, C. Will an increased greenhouse impact in Fennoscandia give rise to more humic and coloured lakes? Hydrobiologia 229, 51–58 (1992)

  12. 12

    Tipping, E. et al. Climatic influences on the leaching of dissolved organic matter from upland UK moorland soils, investigated by a field manipulation experiment. Environ. Int. 25, 83–95 (1999)

  13. 13

    Houghton, J. T. et al. (eds) Climate Change 2001: The Scientific Basis (Cambridge Univ. Press, Cambridge, 2001)

  14. 14

    Oechel, W. C. et al. Transient nature of CO2 fertilization in arctic tundra. Nature 371, 500–503 (1994)

  15. 15

    Mitsch, W. J. & Gosselink, J. G. Wetlands (Van Nostrand Reinhold, New York, 1993)

  16. 16

    Norby, R. J., Cotrufo, M. F., Ineson, P., O'Neill, E. G. & Canadell, J. G. Elevated CO2, litter chemistry, and decomposition: a synthesis. Oecologia 127, 153–165 (2001)

  17. 17

    Jones, T. H. et al. Impacts of rising atmospheric carbon dioxide on model terrestrial ecosystems. Science 280, 441–443 (1998)

  18. 18

    Aerts, R., Wallen, B. & Malmer, N. Growth-limiting nutrients in Sphagnum-dominated bogs subject to low and high atmospheric nitrogen supply. J. Ecol. 80, 131–140 (1992)

  19. 19

    Woodin, S., Graham, B., Killick, A., Skiba, U. & Cresser, M. Nutrient limitation of the long-term response of heather [Calluna-vulgaris (l) hull] to CO2 enrichment. New Phytol. 122, 635–642 (1992)

  20. 20

    Zangerl, A. R. & Bazzaz, F. A. The response of plants to elevated CO2. 2. Competitive interactions among annual plants under varying light and nutrients. Oecologia 62, 412–417 (1984)

  21. 21

    Hutchin, P. R., Press, M. C., Lee, J. A. & Ashenden, T. W. Elevated concentrations of CO2 may double methane emissions from mires. Glob. Change Biol. 1, 125–128 (1995)

  22. 22

    Van der Heijden, E., Jauhiainen, J., Silvola, J., Vasander, H. & Kuiper, P. J. C. Effects of elevated atmospheric CO2 concentration and increased nitrogen deposition on growth and chemical composition of ombrotrophic Sphagnum balticum and oligo-mesotrophic Sphagnum papillosum. J. Bryol. 22, 175–182 (2000)

  23. 23

    Berendse, F. et al. Raised atmospheric CO2 levels and increased N deposition cause shifts in plant species composition and production in Sphagnum bogs. Glob. Change Biol. 7, 591–598 (2001)

  24. 24

    Dacey, J. W. H., Drake, B. G. & Klug, M. J. Stimulation of methane emission by carbon dioxide enrichment of marsh vegetation. Nature 370, 47–49 (1994)

  25. 25

    Megonigal, J. P. & Schlesinger, W. H. Enhanced CH4 emissions from a wetland soil exposed to elevated CO2 . Biogeochemistry 37, 77–88 (1997)

  26. 26

    Ziska, L. H. et al. Long-term growth at elevated carbon dioxide stimulates methane emission in tropical paddy rice. Glob. Change Biol. 4, 657–665 (1998)

  27. 27

    Strom, L., Ekberg, A., Mastepanov, M. & Christensen, T. R. The effect of vascular plants on carbon turnover and methane emissions from a tundra wetland. Glob. Change Biol. 9, 1185–1192 (2003)

  28. 28

    Waddington, J. M. & Roulet, N. T. Groundwater flow and dissolved carbon movement in a boreal peatland. J. Hydrol. 191, 122–138 (1997)

  29. 29

    Kuzyakov, Y. Review: Factors affecting rhizosphere priming effects. J. Plant Nutr. Soil Sci. 165, 382–396 (2002)

  30. 30

    Wetzel, R. G. Gradient-dominated ecosystems— Sources and regulatory functions of dissolved organic matter in freshwater ecosystems. Hydrobiologia 229, 181–198 (1992)

Download references

Acknowledgements

We are grateful to the Royal Society, the Welsh Assembly Government and the Natural Environment Research Council, UK, for funding this research.

Author information

Correspondence to C. Freeman.

Ethics declarations

Competing interests

C.F. has obtained support from United Utilities for an NERC-CASE PhD studentship. C.F. has accepted a Royal Society industry fellowship that would involve work (part-time) at Welsh Water from October 2004 to October 2008.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Freeman, C., Fenner, N., Ostle, N. et al. Export of dissolved organic carbon from peatlands under elevated carbon dioxide levels. Nature 430, 195–198 (2004) doi:10.1038/nature02707

Download citation

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.