Vortragsreihe Ökologie und Umweltforschung WS 2009/10

Produzieren Pflanzen tatsächlich Methan?

Eingeladen durch G. Gebauer.

Almost four years ago, Keppler et al. (2006) reported from laboratory experiments that living plants, plant litter and the structural plant component pectin emit CH₄ to the atmosphere under aerobic conditions. These observations caused considerable controversy amongst the scientific community and the general public because of their far-reaching implications. This was mainly for two reasons: firstly, it is generally accepted knowledge that the reduced compound CH₄ can only be produced naturally from organic matter by methanogens in the absence of oxygen, or at high temperatures, e.g. in biomass burning. The fact that no mechanism for an ‘aerobic’ production of CH₄ had been identified at the molecular level in plants added to the consternation. Secondly, the first extrapolations from laboratory measurements to the global scale indicated that these emissions could constitute a substantial fraction of the total global emissions of CH₄.

After publication of the findings of Keppler et al., their extrapolation procedure was severely criticised, and other up-scaling calculations suggested a lower, though still potentially significant plant source of CH₄ emissions. However, it became clear, that without further insight into the mechanism of the ‘aerobic’ production of CH₄, any up-scaling approach would have considerable uncertainties and thus be of questionable value. Therefore, the principle scientific questions are now: if, by how much, and by what mechanisms is CH₄ emitted from dead plant matter and living vegetation. Some subsequent studies could not confirm the original findings of Keppler et al., however, several more recent studies including stable isotope studies have now confirmed CH₄ formation from both dead plant tissues and living intact plants. An overview of the current state of the art and the most recent findings will be given in this presentation.

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