EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Microscale oxygen distribution to predict denitrification in structured soil

Maik Lucas1, Lena Rohe2, Hans-Jörg Vogel1, Reinhard Well2, and Steffen Schlüter1
Maik Lucas et al.
  • 1Helmholtz Centre for Environmental Research GmbH - UFZ , Soil System Sciences, Leipzig, Germany (
  • 2Thünen Institute of Climate-Smart Agriculture, Braunschweig, Germany

Different microbial species are capable of producing N2O through multiple pathways, and these can coexist within short distances due to different microenvironmental conditions in the heterogeneous soil structure. Denitrification in soil occurs predominantly in microbial hotspots where denitrifiers use nitrate as an alternative electron acceptor. Soil water content has a profound influence on denitrification because it determines the diffusion lengths of oxygen through air- and water-filled pores, as well as the diffusion of denitrification products from the source in the soil to the atmosphere. Predicting N2O emissions resulting from denitrification, however, is notoriously difficult without quantifying microscale hotspots.

In this experiment we evaluated results from an incubation experiment with undisturbed cores from two different soils having contrasting structures (cropland vs. meadow) at three different water contents. In addition to high-resolution gas chromatography, 15N-labeled nitrate solution allowed information on denitrification and its product ratios to be gained through IRMS measurements at selected time points. On the other hand, 7 needle-type optodes per core in combination with image analysis of images derived by X-ray tomography are used to quantify small scale diffusion distances and hotspots around POM. Last, a previous experiment, with the same but sieved soil and without particulate organic matter (POM), is used as a comparison to further investigate the influence local structure heterogeneity and POM on denitrification.

First results indicate that the reduction of diffusion pathways during sieving in the arable soil resulted in significantly lower emissions after sieving compared to the structured soil, while N2O+N2 emissions in the meadow soil were only slightly affected by sieving. For the first time, we were able to generate 3D images of O2 saturation by combining image-derived diffusion length information with the measured O2 concentrations. These allowed to explain high variabilities of N2O+N2 emissions from the field structured cores.

How to cite: Lucas, M., Rohe, L., Vogel, H.-J., Well, R., and Schlüter, S.: Microscale oxygen distribution to predict denitrification in structured soil, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14831,, 2023.