Novel meteorological methods for measuring trace gas fluxes

The paper deals with flux measurements in two contexts: small plots and plant canopies. Mass balance methods have been developed for small experimental plots with lateral dimensions of tens of metres rather than the 1 m typical of chambers or the hundreds of metres required for conventional micrometeorological estimates. The general method relies on the conservation of mass to equate the differences in horizontal fluxes across upwind and downwind boundaries of a test plot with the surface flux within the plot along the line of the wind. Applications to soil and animal experiments are discussed. Lagrangian descriptions of transport now supplant older, but inappropriate gradient-diffusion theory for inferring fluxes and source-sink distributions of scalars in plant canopies. An inverse Lagrangian theory due to M. R. Raupach provides a relatively simple observational and computational scheme for making such inferences from measurements of mean concentration profiles and canopy turbulence. The scheme and a range of applications are described.

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

Atmospheric Measurement Techniques ◽

10.5194/amt-14-4445-2021 ◽

2021 ◽

Vol 14 (6) ◽

pp. 4445-4460

Author(s):

Lukas Kohl ◽

Markku Koskinen ◽

Tatu Polvinen ◽

Salla Tenhovirta ◽

Kaisa Rissanen ◽

...

Keyword(s):

Measurement System ◽

Trace Gas ◽

Environmental Drivers ◽

Gas Flux ◽

Technical Problems ◽

Gas Fluxes ◽

Plant Foliage ◽

Trace Gas Fluxes ◽

Flux Measurements ◽

Plant Shoots

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.

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Technical Note: Possible errors in flux measurements due to limited digitalization

10.5194/amt-2018-150 ◽

2018 ◽

Author(s):

Thomas Foken ◽

Wolfgang Babel ◽

Christoph Thomas

Keyword(s):

Net Ecosystem Exchange ◽

Technical Note ◽

Trace Gas ◽

Instrument Error ◽

Small Magnitude ◽

Gas Fluxes ◽

Sonic Anemometers ◽

Trace Gas Fluxes ◽

Flux Measurements ◽

Water Vapour Fluxes

Abstract. Recently reported trends of carbon dioxide uptakes pose the question if trends may results of the digitalization of gas analysers and sonic anemometers used in the 1990s. Simulating a 12-bit digitalization and the instrument error reported for the R2 and R3 sonic anemometers elsewhere, the influence of these deficits in comparison to the 16-bit digitalization were quantified. Both issues have an effect only on trace gas fluxes of small magnitude, mainly for the carbon rather than for the water vapour fluxes. The influence on the annual net ecosystem exchange is negligible.

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Possible errors in flux measurements due to limited digitalization

Atmospheric Measurement Techniques ◽

10.5194/amt-12-971-2019 ◽

2019 ◽

Vol 12 (2) ◽

pp. 971-976 ◽

Cited By ~ 2

Author(s):

Thomas Foken ◽

Wolfgang Babel ◽

Christoph Thomas

Keyword(s):

Carbon Dioxide ◽

Net Ecosystem Exchange ◽

Trace Gas ◽

Small Magnitude ◽

Carbon Dioxide Uptake ◽

Gas Fluxes ◽

Sonic Anemometers ◽

Trace Gas Fluxes ◽

Flux Measurements ◽

Water Vapour Fluxes

Abstract. Recently reported trends of carbon dioxide uptake pose the question of whether trends may be the result of the limited digitalization of gas analysers and sonic anemometers used in the 1990s. Modifying a 12 bit digitalization and the instrument error reported for the Gill R2 and R3 sonic anemometers found elsewhere, the influence of these deficits in comparison to the now commonly used 16 bit digitalization were quantified. Both issues have an effect only on trace gas fluxes of small magnitude, mainly for the carbon dioxide rather than for the water vapour fluxes. The influence on the annual net ecosystem exchange is negligible, because other errors resulting from gap filling routines, for example, are much larger.

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Approaches to Scaling of Trace Gas Fluxes in Ecosystems

10.1016/s0167-5117(98)x8020-1 ◽

1999 ◽

Keyword(s):

Trace Gas ◽

Gas Fluxes ◽

Trace Gas Fluxes

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Towards reliable measurements of trace gas fluxes at plant surfaces

New Phytologist ◽

10.1111/nph.17310 ◽

2021 ◽

Vol 230 (6) ◽

pp. 2097-2099

Author(s):

Lukas Kohl ◽

Markku Koskinen ◽

Mari Pihlatie

Keyword(s):

Trace Gas ◽

Gas Fluxes ◽

Trace Gas Fluxes ◽

Plant Surfaces

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Dynamic global vegetation modelling for prediction of plant functional types and biogenic trace gas fluxes

Global Ecology and Biogeography ◽

10.1046/j.1365-2699.1999.00152.x ◽

1999 ◽

Vol 8 (6) ◽

pp. 473-488 ◽

Cited By ~ 30

Author(s):

Christopher S. Potter ◽

Steven A. Klooster

Keyword(s):

Plant Functional Types ◽

Trace Gas ◽

Functional Types ◽

Vegetation Modelling ◽

Gas Fluxes ◽

Trace Gas Fluxes ◽

Global Vegetation

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An ecosystem-scale perspective of the net land methanol flux: synthesis of micrometeorological flux measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-7413-2015 ◽

2015 ◽

Vol 15 (13) ◽

pp. 7413-7427 ◽

Cited By ~ 18

Author(s):

G. Wohlfahrt ◽

C. Amelynck ◽

C. Ammann ◽

A. Arneth ◽

I. Bamberger ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Dominant Role ◽

Terrestrial Ecosystem ◽

Surface Wetness ◽

Flux Synthesis ◽

Leaf Level ◽

Flux Measurements ◽

The Rich ◽

Study Sites ◽

Source Sink

Abstract. Methanol is the second most abundant volatile organic compound in the troposphere and plays a significant role in atmospheric chemistry. While there is consensus about the dominant role of living plants as the major source and the reaction with OH as the major sink of methanol, global methanol budgets diverge considerably in terms of source/sink estimates, reflecting uncertainties in the approaches used to model and the empirical data used to separately constrain these terms. Here we compiled micrometeorological methanol flux data from eight different study sites and reviewed the corresponding literature in order to provide a first cross-site synthesis of the terrestrial ecosystem-scale methanol exchange and present an independent data-driven view of the land–atmosphere methanol exchange. Our study shows that the controls of plant growth on production, and thus the methanol emission magnitude, as well as stomatal conductance on the hourly methanol emission variability, established at the leaf level, hold across sites at the ecosystem level. Unequivocal evidence for bi-directional methanol exchange at the ecosystem scale is presented. Deposition, which at some sites even exceeds methanol emissions, represents an emerging feature of ecosystem-scale measurements and is likely related to environmental factors favouring the formation of surface wetness. Methanol may adsorb to or dissolve in this surface water and eventually be chemically or biologically removed from it. Management activities in agriculture and forestry are shown to increase local methanol emission by orders of magnitude; however, they are neglected at present in global budgets. While contemporary net land methanol budgets are overall consistent with the grand mean of the micrometeorological methanol flux measurements, we caution that the present approach of simulating methanol emission and deposition separately is prone to opposing systematic errors and does not allow for full advantage to be taken of the rich information content of micrometeorological flux measurements.

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