Preprints
https://doi.org/10.5194/egusphere-2022-1083
https://doi.org/10.5194/egusphere-2022-1083
 
11 Nov 2022
11 Nov 2022
Status: this preprint is open for discussion.

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

Jeffrey Prescott Beem-Miller1, Craig Rasmussen2, Alison May Hoyt1,3, Marion Schrumpf1, Georg Guggenberger4, and Susan Trumbore1 Jeffrey Prescott Beem-Miller et al.
  • 1Department of Biogeochemical Processes, Max Planck Institute for Biogeochemistry, Jena, Germany
  • 2Department of Environmental Science, The University of Arizona, Tucson, AZ, USA
  • 3Department of Earth System Science, Stanford University, Stanford, CA, USA
  • 4Institute of Soil Science, Leibniz University Hannover, Hannover, Germany

Abstract. 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.

Jeffrey Prescott Beem-Miller et al.

Status: open (until 09 Jan 2023)

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Jeffrey Prescott Beem-Miller et al.

Jeffrey Prescott Beem-Miller et al.

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Short summary
We compared the age of persistent soil organic matter as well as active emissions of carbon dioxide from soils across a gradient of climate and geology. We found that clay minerals are more important than mean annual temperature for both persistent and actively cycling soil carbon, and that they may attenuate the sensitivity of soil organic matter decomposition to temperature. Accounting for geology and soil development could therefore improve estimates of soil carbon stocks and changes.