Beyond clay: towards an improved set of variables for predicting soil organic matter content

Craig Rasmussen, Katherine Heckman, William R. Wieder, Marco Keiluweit, Corey R. Lawrence, Asmeret Asefaw Berhe, Joseph C. Blankinship, Susan E. Crow, Jennifer L. Druhan, Caitlin E. Hicks Pries, Erika Marin-Spiotta, Alain F. Plante, Christina Schädel, Joshua P. Schimel, Carlos A. Sierra, Aaron Thompson, Rota Wagai

Research output: Contribution to journalArticlepeer-review

289 Scopus citations


Improved quantification of the factors controlling soil organic matter (SOM) stabilization at continental to global scales is needed to inform projections of the largest actively cycling terrestrial carbon pool on Earth, and its response to environmental change. Biogeochemical models rely almost exclusively on clay content to modify rates of SOM turnover and fluxes of climate-active CO2 to the atmosphere. Emerging conceptual understanding, however, suggests other soil physicochemical properties may predict SOM stabilization better than clay content. We addressed this discrepancy by synthesizing data from over 5,500 soil profiles spanning continental scale environmental gradients. Here, we demonstrate that other physicochemical parameters are much stronger predictors of SOM content, with clay content having relatively little explanatory power. We show that exchangeable calcium strongly predicted SOM content in water-limited, alkaline soils, whereas with increasing moisture availability and acidity, iron- and aluminum-oxyhydroxides emerged as better predictors, demonstrating that the relative importance of SOM stabilization mechanisms scales with climate and acidity. These results highlight the urgent need to modify biogeochemical models to better reflect the role of soil physicochemical properties in SOM cycling.

Original languageEnglish (US)
Pages (from-to)297-306
Number of pages10
Issue number3
StatePublished - Feb 1 2018


  • Biogeochemistry
  • Carbon cycle
  • Soil organic matter

ASJC Scopus subject areas

  • Environmental Chemistry
  • Water Science and Technology
  • Earth-Surface Processes


Dive into the research topics of 'Beyond clay: towards an improved set of variables for predicting soil organic matter content'. Together they form a unique fingerprint.

Cite this