Dear All,
not only in all known to me textbooks, but also in my academic environment, plants are only discussed as carbon sinks and therefore planting forests is said to be one of the main strategies to reverse or reduce some effects of climate change.
But: About 10 years ago a german team from MPI published - and that seemed to be a shock for some climate researchers - that plants (especially forests) are able to produce tremendous amounts of methane under "normal" aerobic conditions autonomously (1). There were even attempts to link the ending phase of the ice ages with forest growth in the way that besides volcanic or solar activity forests were responsible for the warm up (and not vice versa).
Still in any lectures at my institution only common methane sources (microbes, anaerobic environments as bogs and swamps, cattles, humans,...) are discussed with students while - as said - plants are only considered as carbon sinks.
How so? Do you know something about the latest discoveries in this field (maybe i missed some relevant publications)? Are plants excluded as methane sources because of new investigations? Or is it an open (and not well known) problem that is not recognized broadly by environmental scientists?
Thank you
(1) Keppler F, Hamilton JTG, Brass M et al (2006) Methane emissions from terrestrial plants under aerobic conditions. Nature 439, 187-191.
Dear Aleksander,
I did a PhD on the ethylene production of Phaseolus Vulgaris L. and Marchantia Polymorpha L.
With the technique I used, I could measure methane, ethylene, ethane and propane as low molecular weight hydrocarbons at the sub-ppb level using a cryogenic pre-concentration technique. The plants were monitored in an open flow system, with very low backgrounds of the chemical species mentioned. The only hydrocarbon which was measurable with this system is ethylene, no methane, ethane or propane which were below the detection level of the measuring system (0.01 ppbv). It should be mentioned that I always removed the soil when I measured the plants in this system whereby the plants were watered with a glassfiber sheet substrate. If the soil was not removed some other of the hydrocarbons popped up above their detection limits.
It is my conviction that a large majority of plants do not emit methane, but when the soils wherein they grow are measured along with the plants growing on them, methane is bound to be measured as well.
Hence, methane is emitted by soils and not by the plants growing in these soils. Only the separate measurement of soil and plant has corroborated this finding, as I did in my PhD.
Hence, the measuring method has to be critically evaluated on the presence of soil in the measurement protocol or not!
Best regards,
Frank
Dear Aleksander,
I did a PhD on the ethylene production of Phaseolus Vulgaris L. and Marchantia Polymorpha L.
With the technique I used, I could measure methane, ethylene, ethane and propane as low molecular weight hydrocarbons at the sub-ppb level using a cryogenic pre-concentration technique. The plants were monitored in an open flow system, with very low backgrounds of the chemical species mentioned. The only hydrocarbon which was measurable with this system is ethylene, no methane, ethane or propane which were below the detection level of the measuring system (0.01 ppbv). It should be mentioned that I always removed the soil when I measured the plants in this system whereby the plants were watered with a glassfiber sheet substrate. If the soil was not removed some other of the hydrocarbons popped up above their detection limits.
It is my conviction that a large majority of plants do not emit methane, but when the soils wherein they grow are measured along with the plants growing on them, methane is bound to be measured as well.
Hence, methane is emitted by soils and not by the plants growing in these soils. Only the separate measurement of soil and plant has corroborated this finding, as I did in my PhD.
Hence, the measuring method has to be critically evaluated on the presence of soil in the measurement protocol or not!
Best regards,
Frank
Today we even have household application of biogas production and has been confirmed to save forest cover and improve biodiversity. The carbon sink in this scenario is the biomass accumulation that is transformed to combustible methane for heating and even electricity generation.
@Frank: Thank you for your interesting hints.
But there is a problem: The studies of the team did also use plants without soil in their studies (even in vitro experiments), and especially in further investigations they made Methionine responsible for the methane production inside the plants under some circumstances. Also, they found, UV radiation releases Methane from Pectine in Plants.
In further steps they said, that this is especially relevant for algae in oceans, what makes the whole interpretation even more confusing (ocean-methane-problem).
Kalthoff F, Benzing K, Comba Peter et al (2014) Abiotic methanogenesis from organosulphur compounds under ambient conditions. Nature Communications.
Hi Aleksander, I did not read yet the technique some authors that discovered methane as a plant emission. Did they use a closed measuring system, or an open flow system. Anyhow with both techniwues it is critical that the background hydrocarbons are removed from the input stream in the measuring chamber. If one does not, one measures methane from the input flow background! This background methane fluxif not to high must be subtracted from the methane flux measured with plants. Evidently if background and plant flux are equal, there is no methane flux from plants at all!
Can you send me some papers on the measuring technique used by folks that measured methane from plants? I can assure you that in this business a lot of artifacts are possible.
Thanks beforehand,
Frank
@Frank: I posted the Papers (Name, Year, Title, Magazine) under my question and under the second answer. I don't have the full-text at the moment, just summaries in german language (because german teams made the studies).
Hi Aleksander,
Sorry for answering rather late. I will try to find the papers you refer to, to figger out how the measurements were technically conceived. This may shed light on the origin of methane, plants or soils especially soils with a different carbon content.
Cheers,
Frank
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