EGU21-7442, updated on 04 Mar 2021
https://doi.org/10.5194/egusphere-egu21-7442
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Analysing the relationship of CO2 and O2 concentrations and flux patterns in forest soils

Valentin Gartiser, Verena Lang, and Martin Maier
Valentin Gartiser et al.
  • Forest Research Institute BadenWürttemberg (FVA), Wonnhalde 4, 79100 Freiburg, Germany

Soils act as bioreactors for the production and consumption of different gases. CO2 is usually produced in soils due to the oxidation of organic material. Under aerobic conditions, this production is coupled to a consumption of O2 resulting in concentration profiles that increase with depth for CO2 and decrease for O2. Depending on the organic material present, the exchange of O2 and CO2 is approximately equimolar in well aerated soils. This can be deduced from vertical gradients of both gases which should reflect the ratio of their diffusion coefficient (Massmann 1998). The ratio between the CO2 and O2 flux is often called the respiratory coefficient. However, certain soil types or conditions may invoke anaerobe processes that may lead to a decoupling of CO2 production and O2 consumption. Such a decoupling can also result from oxidation of minerals or dissolution and relocation of carbonates.

Here we present long-term data of soil CO2 and O2 concentrations from forest sites in South West Germany. Gas samples were collected passively starting 1998 until now using permanently installed gas wells at different depths. The samples were then analysed using gas chromatography for CO2 and O2 (and additionally N2, Ar, N2O, CH4, and C2H4).

CO2 and O2 fluxes were calculated using the gradient approach (Maier et al 2020). At sites with well aerated soils, the observed CO2 and O2 fluxes followed a clear linear relationship, with high effluxes of CO2 corresponding to high influxes of O2. The exchange was furthermore approximately equimolar with the calculated fluxes following a -1:1 trend.

We will compare these data from well aerated soils to concentration data of CO2 and O2 from less well-aerated soils with temporally suboxic conditions to further analyse the respiratory coefficient under oxygen limited conditions. Furthermore, diffusion-coefficient-normalised gradients are calculated to obtain information about the stoichiometry of the production and consumption patterns involved.

 

Literature:

Maier M, Gartiser V, Schengel A, Lang V. Long Term Soil Gas Monitoring as Tool to Understand Soil Processes. Applied Sciences. 2020; 10(23):8653.

Massman, W J. A review of the molecular diffusivities of H2O, CO2, CH4, CO, O3, SO2, NH3, N2O, NO, and NO2 in air, O2 and N2 near STP. Atmospheric Environment 1998; 32(6), 1111–1127

 

How to cite: Gartiser, V., Lang, V., and Maier, M.: Analysing the relationship of CO2 and O2 concentrations and flux patterns in forest soils, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7442, https://doi.org/10.5194/egusphere-egu21-7442, 2021.

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