An automated system for trace gas flux measurements from plant foliage and other plant compartments

Lukas Kohl,Kaisa Rissanen,Salla Tenhovirta,Alessandro Zanetti,Marjo Patama,Tatu Polvinen,Markku Koskinen,Mari Pihlatie

doi:10.5194/amt-14-4445-2021

Lukas Kohl, Kaisa Rissanen + Show 6 more

Open Access

https://doi.org/10.5194/amt-14-4445-2021

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Abstract

Abstract. Plant shoots can act as sources or sinks of trace gases including methane and nitrous oxide. Accurate measurements of these trace gas fluxes require enclosing of shoots in closed non-steady-state chambers. Due to plant physiological activity, this type of enclosure, however, leads to CO2 depletion in the enclosed air volume, condensation of transpired water, and warming of the enclosures exposed to sunlight, all of which may bias the flux measurements. Here, we present ShoTGa-FluMS (SHOot Trace Gas FLUx Measurement System), a novel measurement system designed for continuous and automated measurements of trace gas and volatile organic compound (VOC) fluxes from plant shoots. The system uses transparent shoot enclosures equipped with Peltier cooling elements and automatically replaces fixated CO2 and removes transpired water from the enclosure. The system is designed for measuring trace gas fluxes over extended periods, capturing diurnal and seasonal variations, and linking trace gas exchange to plant physiological functioning and environmental drivers. Initial measurements show daytime CH4 emissions of two pine shoots of 0.056 and 0.089 nmol per gram of foliage dry weight (d.w.) per hour or 7.80 and 13.1 nmolm-2h-1. Simultaneously measured CO2 uptake rates were 9.2 and 7.6 mmolm-2h-1, and transpiration rates were 1.24 and 0.90 molm-2h-1. Concurrent measurement of VOC emissions demonstrated that potential effects of spectral interferences on CH4 flux measurements were at least 10-fold smaller than the measured CH4 fluxes. Overall, this new system solves multiple technical problems that have so far prevented automated plant shoot trace gas flux measurements and holds the potential for providing important new insights into the role of plant foliage in the global CH4 and N2O cycles.

Highlights

Plants have recently been recognized as potential sources and sinks of atmospheric trace gases including the greenhouse gases methane (CH4) and nitrous oxide (N2O) (e.g. Keppler et al, 2006; Machacova et al, 2016; Carmichael et al, 2014; Pangala et al, 2015; Machacova et al, 2019)
Concurrent measurement of volatile organic compound (VOC) emissions demonstrated that potential effects of spectral interferences on CH4 flux measurements were at least 10-fold smaller than the measured CH4 fluxes
Initial tests of ShoTGa-clim2 showed that cooling was not necessary as the enclosure chambers do not warm significantly compared to the ambient temperature due to the low thermal energy emitted by the LED-based lighting system

Summary

Introduction

Plants have recently been recognized as potential sources and sinks of atmospheric trace gases including the greenhouse gases methane (CH4) and nitrous oxide (N2O) (e.g. Keppler et al, 2006; Machacova et al, 2016; Carmichael et al, 2014; Pangala et al, 2015; Machacova et al, 2019). L. Kohl et al.: Automatic shoot trace gas measurements a century, few direct measurements of the CH4 and N2O exchange of plant shoots and/or foliage have been reported far (Machacova et al, 2016; Sundqvist et al, 2012; Takahashi et al, 2012). No continuous measurements of tree shoot CH4 or N2O exchange have yet been conducted. This lack of available shoot flux data stands in contrast to reports of CH4 and N2O emissions from plant foliage under laboratory conditions and widespread speculation about their role in the global CH4 and N2O cycles This lack of available shoot flux data stands in contrast to reports of CH4 and N2O emissions from plant foliage under laboratory conditions and widespread speculation about their role in the global CH4 and N2O cycles (e.g. Keppler et al, 2006; Lenhart et al, 2018)

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