Preprints
https://doi.org/10.5194/essd-2022-240
https://doi.org/10.5194/essd-2022-240
 
08 Sep 2022
08 Sep 2022
Status: this preprint is currently under review for the journal ESSD.

Quantifying stocks in exchangeable base cations in permafrost: a reserve of nutrients about to thaw

Elisabeth Mauclet1, Maëlle Villani1, Arthur Monhonval1, Catherine Hirst1, Edward A. G. Schuur2, and Sophie Opfergelt1 Elisabeth Mauclet et al.
  • 1Earth and Life Institute, Université catholique de Louvain, Louvain-la-Neuve, Belgium
  • 2Center for Ecosystem Society and Science, Northern Arizona University, Flagstaff, AZ, USA

Abstract. Permafrost ecosystems are limited in nutrients for vegetation development and constrain the biological activity to the active layer. Upon Arctic warming, permafrost degradation exposes large amounts of soil organic carbon (SOC) to decomposition and minerals to weathering, but also releases organic and mineral soil material that may directly influence the soil exchange properties (cation exchange capacity and base saturation). The soil exchange properties are key for nutrient base cation supply (Ca2+, K+, Mg2+) for vegetation growth and development. In this study, we investigate the distribution of soil exchange properties within typical Arctic tundra permafrost soils at Eight Mile Lake (Interior Alaska, USA) because they will dictate the potential reservoir of newly thawed nutrients and thereby influence soil biological activity and vegetation nutrient sources. Our results highlight a difference in the SOC distribution within soil profiles according to the permafrost thaw. The poorly thawed permafrost soils (active layer thickness; ALT ≤ 60 cm) present more organic material in surface (i.e., organic layer thickness; OLT ≥ 40 cm) than the highly thawed permafrost soil (i.e., ALT > 60 cm and OLT < 40 cm). In turn, this difference in SOC distribution directly affects the soil exchange complex properties. However, the low bulk density of organic-rich soil layers leads to much lower CEC density in surface (~9 400 cmolc m-3) than in the mineral horizons of the active layer (~16 000 cmolc m-3) and in permafrost soil horizons (~12 000 cmolc m-3). As a result of the overall increase in CEC density with depth and the overall increase in base saturation with depth (from ~20 % in organic surface to 65 % in permafrost soil horizons), the average total stock in exchangeable base cations (Ca2+, K+, Mg2+ and Na+ in g m-3) is more than 2-times higher in the permafrost than in the active layer. More specifically, the stocks in base cations in the upper part of permafrost about to thaw in the following are ~ 860 g m-3 for Caexch, 45 g m-3 for Kexch, 200 g m-3 for Mgexch and 150 g m-3 for Naexch. This first order estimate is a needed step for future ecosystem prediction models to provide constraint on the size of the reservoir in exchangeable nutrients (Ca, K, Mg) about to thaw.

Elisabeth Mauclet et al.

Status: open (until 03 Nov 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on essd-2022-240', Matthias Siewert, 21 Sep 2022 reply

Elisabeth Mauclet et al.

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Characterization of permafrost soil exchange properties and quantification of stocks in soil exchangeable base cations Mauclet, Elisabeth; Villani, Maëlle; Monhonval, Arthur; Hirst, Catherine; Schuur, Edward A. G.; Opfergelt, Sophie https://doi.org/10.14428/DVN/FQVMEP

Elisabeth Mauclet et al.

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Short summary
Permafrost ecosystems are limited in nutrients for vegetation development and constrain the biological activity to the active layer. Upon Arctic warming, permafrost degradation exposes organic and mineral soil material that may directly influence the capacity of the soil to retain key nutrients for vegetation growth and development. Here, we demonstrate that the average total stock in exchangeable nutrients (Ca, K, Mg, Na) is more than two times higher in the permafrost than in the active layer.