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

Permafrost soil organic matter (de)composition in times of global warming

Cornelia Rottensteiner1, Victoria Martin1, Alberto Canarini1, Hannes Schmidt1, Leila Hadžiabdić1, Julia Horak1, Moritz Mohrlok1, Carolina Urbina Malo1, Willeke A'Campo2, Luca Durstewitz2, Julia Wagner2, Rachele Lodi3, Niek Speetjens4, George Tanski4, Michael Fritz5, Hugues Lantuit5, Gustaf Hugelius2, and Andreas Richter1
Cornelia Rottensteiner et al.
  • 1Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria (
  • 2Department of Physical Geography, Stockholm University, Stockholm, Sweden
  • 3Department of Environmental Sciences, Informatics and Statistics, and CNR Institute of Polar Sciences, Ca'Foscari University, Venice, Italy
  • 4Department of Earth and Climate, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
  • 5Helmholtz Centre for Polar and Marine Research, Alfred Wegener Institute, Potsdam, Germany

The Arctic warms four times faster than the global average, resulting in widespread permafrost thaw. Organic matter that was stored in permanently frozen soil for up to millennia now becomes available to microbial decomposition. Warming might also alter microbial community composition and physiology and thus change the decomposition potential of soils. Our current knowledge about permafrost soil organic matter (SOM) composition and decomposition is limited, particularly in regard to the heterogeneity of permafrost landscapes, thus hampering our ability to predict possible permafrost soil feedbacks to climate change. The objective of this study was to characterize SOM and microbial community composition of the active layer and the upper permanently frozen soil from permafrost-affected polygonal lowland tundra.

We collected more than 80 soil samples from four different soil layers (organic, mineral, cryoturbated, permanently frozen) from three developmental stages of ice-wedge polygons (low-center, flat-center, high-center polygons) in NW Canada, and analyzed organic matter composition by a pyrolysis-GC/MS fingerprinting approach and microbial community composition by amplicon sequencing of the 16S rRNA gene (bacteria, archaea) and the ITS1 region (fungi).

Our results suggest that the spatial heterogeneity of permafrost soils is not only reflected in soil physical parameters, but also in the chemical composition of organic matter and the composition of microbial communities. The organic soil layer comprised both the highest microbial diversity and the most diverse SOM composition. The distribution of major compound classes (carbohydrates, lignins, lipids, N-compounds, phenols & aromatics) differed between organic, mineral, cryoturbated and permanently frozen organic matter. This pattern followed a gradient from low to high organic matter degradation with soil depth. Soil organic matter composition also differed among polygon types, indicating different decomposition pathways, likely depending on differences in vegetation and soil water availability. We also found distinct microbial communities for soils from low-center polygons, possibly driven by prevailing anoxic conditions in this landscape unit. Bacterial and archaeal communities differed among all soil layers, while only fungal communities from the organic soils differed from the other layers.

The observed differences in SOM and microbial community composition among soil layers and polygon types highlight the importance of considering spatial heterogeneity when studying permafrost soils. Moreover, our results might help to explain observed differences in microbial decomposition patterns on different spatial scales and emphasize the need to include aspects of permafrost soil heterogeneity to finetune current ecosystem and climate models.

This study is part of the EU H2020 project “Nunataryuk”.

How to cite: Rottensteiner, C., Martin, V., Canarini, A., Schmidt, H., Hadžiabdić, L., Horak, J., Mohrlok, M., Urbina Malo, C., A'Campo, W., Durstewitz, L., Wagner, J., Lodi, R., Speetjens, N., Tanski, G., Fritz, M., Lantuit, H., Hugelius, G., and Richter, A.: Permafrost soil organic matter (de)composition in times of global warming, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14026,, 2023.

Supplementary materials

Supplementary material file