EGUsphere

Copernicus Publications

Göttingen, Germany

10.5194/egusphere-2022-1083

Soil minerals mediate climatic control of soil C cycling on annual to centennial timescales

Beem-Miller

Jeffrey Prescott

https://orcid.org/0000-0003-0955-6622

¹ Rasmussen

Craig

https://orcid.org/0000-0003-4344-4800

² Hoyt

Alison May

¹ ³ Schrumpf

Marion

¹ Guggenberger

Georg

https://orcid.org/0000-0002-6962-8264

⁴ Trumbore

Susan

https://orcid.org/0000-0003-3885-6202

Department of Biogeochemical Processes, Max Planck Institute for Biogeochemistry, Jena, Germany

Department of Environmental Science, The University of Arizona, Tucson, AZ, USA

Department of Earth System Science, Stanford University, Stanford, CA, USA

Institute of Soil Science, Leibniz University Hannover, Hannover, Germany

Horizon 2020

11 11 2022

2022 1 27

2022

This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/

This article is available from https://egusphere.copernicus.org/preprints/2022/egusphere-2022-1083/

The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2022/egusphere-2022-1083/egusphere-2022-1083.pdf

Climate and parent material both affect soil C persistence, yet the relative importance of climatic versus mineralogical controls on soil C dynamics remains unclear. To test this, we collected soil samples in 2001, 2009, and 2019 along a combined gradient of parent material (andesite, basalt, granite) and climate (mean annual temperature (MAT): 6.5 °C “cold”, 8.6 °C “cool”, 12.0 °C “warm”). We measured the radiocarbon of heterotrophically respired CO2 (∆14Crespired) and bulk soil C (∆14Cbulk) as proxies for transient and persistent soil C, and characterized mineral assemblages using selective dissolution. Using linear regression, we observed that MAT was not a significant predictor of either ∆14Cbulk or ∆14Crespired, yet climate was highly significant as a categorical variable. Climate explained more variance in ∆14Cbulk and ∆14Crespired over 0–0.1 m, but parent material explained more from 0.1–0.3 m. Cool site soil C was more persistent (lower ∆14Cbulk) than cold or warm climate sites, and also more persistent on andesitic soils, followed by basaltic and then granitic soils. Poorly crystalline metal oxides (PCMs) (but not crystalline metal oxides) were significantly (p < 0.1) correlated with ∆14Cbulk, ∆14Crespired, and ∆14Crespired - ∆14Cbulk, indicating their importance for soil C cycling on both short and long timescales. The change in ∆14Crespired observed over the study period was linearly related to MAT for the granite soils with the lowest PCM content, but not in the andesitic and basaltic soils with higher PCM content. This link between PCM abundance and the decoupling of MAT and soil C cycling rates suggests PCMs may attenuate the temperature sensitivity of decomposition.