Emission of methane, carbon monoxide, carbon dioxide and short-chain hydrocarbons from vegetation foliage under ultraviolet irradiation.

Wesley T Fraser,David S Reay,Emanuel Blei,Stephen C Fry,Keith A Smith,Mark F Newman,Andy R Mcleod

doi:10.1111/pce.12489

Wesley T Fraser, David S Reay + Show 5 more

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https://doi.org/10.1111/pce.12489

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Abstract

The original report that plants emit methane (CH 4) under aerobic conditions caused much debate and controversy. Critics questioned experimental techniques, possible mechanisms for CH 4 production and the nature of estimating global emissions. Several studies have now confirmed that aerobic CH 4 emissions can be detected from plant foliage but the extent of the phenomenon in plants and the precise mechanisms and precursors involved remain uncertain. In this study, we investigated the role of environmentally realistic levels of ultraviolet (UV) radiation in causing the emission of CH 4 and other gases from foliage obtained from a wide variety of plant types. We related our measured emissions to the foliar content of methyl esters and lignin and to the epidermal UV absorbance of the species investigated. Our data demonstrate that the terrestrial vegetation foliage sampled did emit CH 4, with a range in emissions of 0.6–31.8 ng CH 4 g−1 leaf DW h−1, which compares favourably with the original reports of experimental work. In addition to CH 4 emissions, our data show that carbon monoxide, ethene and propane are also emitted under UV stress but we detected no significant emissions of carbon dioxide or ethane.

Highlights

Methane (CH4) is a naturally occurring gas in the Earth’s atmosphere, currently at a global mean concentration of 1803 nL L−1, and is a known potent greenhouse gas with an atmospheric lifetime of 12.4 years and 100 year global warming potential that is 28 times that of carbon dioxide (CO2) (IPCC 2013)
carbon monoxide (CO), CH4, C2H4 and C3H8 net emission rates from leaves were all enhanced under UV radiation and significantly different from equivalent leaves not exposed to UV radiation when tested across all species by the Mann– Whitney test (P < 0.001)
While the level of replication in our study precludes conclusions about differences between individual species, we detected a net production of CH4 from the leaves tested and our analysis clearly demonstrates that UV radiation can produce a net CH4 emission from terrestrial vegetation foliage

Summary

Introduction

Methane (CH4) is a naturally occurring gas in the Earth’s atmosphere, currently at a global mean concentration of 1803 nL L−1, and is a known potent greenhouse gas with an atmospheric lifetime of 12.4 years and 100 year global warming potential that is 28 times that of carbon dioxide (CO2) (IPCC 2013). Small increases in CH4 concentration will result in a large increase in warming potential and natural and anthropogenic sources and sinks need to be identified and accurately quantified in order to calculate a global CH4 budget. Concentrations in the tropics continued to be highly variable throughout and it may require careful study to understand the detail of their contribution to the global CH4 budget. The most recent review of three decades of global CH4 sources and sinks suggests that a rise in natural wetland and fossil fuel emissions probably accounts for the increase in global CH4 levels after 2006, with uncertainty about the relative contributions of these sources (Kirschke et al 2013)

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