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Methane emissions from terrestrial plants under aerobic conditions


Methane is an important greenhouse gas and its atmospheric concentration has almost tripled since pre-industrial times1,2. It plays a central role in atmospheric oxidation chemistry and affects stratospheric ozone and water vapour levels. Most of the methane from natural sources in Earth's atmosphere is thought to originate from biological processes in anoxic environments2. Here we demonstrate using stable carbon isotopes that methane is readily formed in situ in terrestrial plants under oxic conditions by a hitherto unrecognized process. Significant methane emissions from both intact plants and detached leaves were observed during incubation experiments in the laboratory and in the field. If our measurements are typical for short-lived biomass and scaled on a global basis, we estimate a methane source strength of 62–236 Tg yr-1 for living plants and 1–7 Tg yr-1 for plant litter (1 Tg = 1012 g). We suggest that this newly identified source may have important implications for the global methane budget and may call for a reconsideration of the role of natural methane sources in past climate change.

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Figure 1: Release rates and isotopic signatures of CH 4 formed by leaf tissue incubated in the dark.
Figure 2: Mixing ratios and δ 13 C values of CH 4 formed by intact plants.

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We thank R. Conrad, J. Kesselmeier and D. Harper for comments on the manuscript; B. Knape, P. Franz, R. Shaheen, F. Kleinbongardt, V. Mallinger, R. Runck and C. McRoberts for technical assistance; the Botanical Garden of the University of Heidelberg for providing plant species from tropical regions; and the European Commission for a Marie Curie-Research Training Grant (F.K.). The ISOSTRAT project in Heidelberg was funded by the BMBF within the AFO2000 project.

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Correspondence to Frank Keppler.

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This file contains Supplementary Tables 1 and 2, and Supplementary Figures 1–4. (DOC 127 kb)

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Keppler, F., Hamilton, J., Braß, M. et al. Methane emissions from terrestrial plants under aerobic conditions. Nature 439, 187–191 (2006).

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