Preprints
https://doi.org/10.5194/bg-2021-227
https://doi.org/10.5194/bg-2021-227

  10 Sep 2021

10 Sep 2021

Review status: this preprint is currently under review for the journal BG.

Large Herbivores Affecting Permafrost – Impacts of Grazing on Permafrost Soil Carbon Storage in Northeastern Siberia

Torben Windirsch1,2, Guido Grosse1,2, Mathias Ulrich3, Bruce C. Forbes4, Mathias Göckede5, Juliane Wolter1,6, Marc Macias-Fauria7, Johan Olofsson8, Nikita Zimov9, and Jens Strauss1 Torben Windirsch et al.
  • 1Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany
  • 2University of Potsdam, Department for Geosciences, Potsdam, Germany
  • 3University of Leipzig, Institute for Geography, Leipzig, Germany
  • 4Arctic Centre, University of Lapland, Rovaniemi, Finland
  • 5Max Planck Institute for Biogeochemistry, Department Biogeochemical Signals, Jena, Germany
  • 6University of Potsdam, Institute of Biochemistry and Biology, Potsdam, Germany
  • 7University of Oxford, School of Geography and the Environment, Biogeosciences Lab, Oxford, Great Britain
  • 8Umeå University, Department of Ecology and Environmental Science, Umeå, Sweden
  • 9Northeast Science Station, Pacific Institute for Geography, Far-Eastern Branch of Russian Academy of Science, Chersky, Republic of Sakha (Yakutia), Russia

Abstract. The risk of carbon emissions from permafrost ground is linked to ground temperature and thus in particular to thermal insulation by vegetation and organic soil layers in summer and snow cover in winter. This ground insulation is strongly influenced by the presence of large herbivorous animals browsing for food. In this study, we examine the potential impact of large herbivore presence on the ground carbon storage in thermokarst landscapes of northeastern Siberia. Our aim is to understand how intensive animal grazing may affect permafrost thaw and hence organic matter decomposition, leading to different ground carbon storage, which is significant in the active layer. Therefore, we analysed sites with differing large herbivore grazing intensity in the Pleistocene Park near Chersky and measured maximum thaw depth, total organic carbon content and decomposition state by δ13C isotope analysis. In addition, we determined sediment grain size composition as well as ice and water content. We found the thaw depth to be shallower and carbon storage to be higher in intensively grazed areas compared to extensively and non-grazed sites in the same thermokarst basin. The intensive grazing presumably leads to a more stable thermal ground regime and thus to increased carbon storage in the thermokarst deposits and active layer. However, the high carbon content found within the upper 20 cm on intensively grazed sites could also indicate higher carbon input rather than reduced decomposition, which requires further studies. We connect our findings to more animal trampling in winter, which causes snow disturbance and cooler winter ground temperatures during the average annual 225 days below freezing. This winter cooling overcompensates ground warming due to the lower insulation associated with shorter heavily grazed vegetation during the average annual 140 thaw days. We conclude that intensive grazing influences the carbon storage capacities of permafrost areas and hence might be an actively manageable instrument to reduce net carbon emission from these sites.

Torben Windirsch et al.

Status: open (until 23 Oct 2021)

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Torben Windirsch et al.

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Large herbivores affecting terrestrial permafrost in northeastern Siberia: biogeochemical and sediment characteristics under different grazing intensities Windirsch, T., Grosse, G., Ulrich, M., Forbes, B. C., Göckede, M., Zimov, N., Macias-Fauria, M., Olofsson, J., Wolter, J., and Strauss, J. https://doi.pangaea.de/10.1594/PANGAEA.933446

Torben Windirsch et al.

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Short summary
With global warming, permafrost thaw and associated carbon release are of increasing importance. We examined how large herbivorous animals affect Arctic landscapes and how they might contribute to reduction of these emissions. We show that over a short timespan of roughly 25 years, these animals have already changed the vegetation and landscape. On pastures in a permafrost area in Siberia we found smaller thaw depth and higher carbon content than in surrounding non-pasture areas.
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