EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Molecular Changes in Dissolved Organic Matter After Soil Rewetting

Alice Orme1,2, Simon Benk2, Markus Lange2, Christian Zerfaß1, Georg Pohnert1, and Gerd Gleixner2
Alice Orme et al.
  • 1Friedrich Schiller University, Jena, Germany
  • 2Max Planck Institute for Biogeochemistry, Jena, Germany

The intensity and occurrence of droughts is projected to increase due to climate change. Dried soils release high concentrations of dissolved organic matter (DOM) into subsurface waters when they are rewet, the so-called rewetting peak. To more accurately predict the role of rewetting of soils after drought on the carbon cycle in a changing climate, it is important to understand the processes behind this DOM release.

The DOM rewetting peak origin is disputed between soil organic matter (SOM) from breakdown of soil particles; accumulated root exudates; and microbial release due to a change in osmotic potential through osmolytes or cell bursting. To better understand the origin of the rewetting DOM peak, we took a rewetting series of soil water samples from different vegetation types between December 2018 and April 2019 for targeted and untargeted metabolomics. Initial results using untargeted ultrahigh-resolution mass spectrometry analysis revealed a clear temporal trend, indicating that vegetation-independent molecular changes occur following rewetting. An increase in O/C and a decrease in H/C over time was observed which is attributed to microbial decomposition, supported by a decrease in m/z over time. We also observed an increase in the content of lipidic compounds (R > 0.6) following rewetting. This indicates that cells do not burst upon rewetting and, over time, microbial activity increases, suggesting that the DOM rewetting peak is caused by a lack of decomposition, rather than a high production, of organic matter.

How to cite: Orme, A., Benk, S., Lange, M., Zerfaß, C., Pohnert, G., and Gleixner, G.: Molecular Changes in Dissolved Organic Matter After Soil Rewetting, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14616,, 2021.

Display materials

Display file

Comments on the display material

to access the discussion