Strong mineralogic control of soil organic matter composition in response to nutrient addition across diverse grassland sites

Qian Zhao, Stephen J. Callister, Allison M. Thompson, Ravi K. Kukkadapu, Malak M. Tfaily, Lisa M. Bramer, Nikolla P. Qafoku, Sheryl L. Bell, Sarah E. Hobbie, Eric W. Seabloom, Elizabeth T. Borer, Kirsten S. Hofmockel

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Soil organic matter (SOM) dynamics are central to soil biogeochemistry and fertility. The retention of SOM is governed initially by interactions with minerals, which mediate the sorption of chemically diverse organic matter (OM) molecules via distinct surface areas and chemical functional group availabilities. Unifying principles of mineral-OM interactions remain elusive because of the multi-layered nature of biochemical-mineral interactions that contribute to soil aggregate formation and the heterogeneous nature of soils among ecosystems. This study sought to understand how soil mineralogy as well as nitrogen (N) enrichment regulate OM composition in grassland soils. Using a multi-site grassland experiment, we demonstrate that the composition of mineral-associated OM depended on the clay content and specific mineral composition in soils across the sites. With increasing abundance of ferrihydrite (Fh) across six different grassland locations, OM in the hydrophobic zone became more enriched in lipid- and protein-like compounds, whereas the kinetic zone OM became more enriched in lignin-like molecules. These relationships suggest that the persistence of various classes of OM in soils may depend on soil iron mineralogy and provide experimental evidence to support conceptual models of zonal mineral-OM associations. Experimental N addition disrupted the accumulation of protein-like molecules in the hydrophobic zone and the positive correlation of lignin-like molecules in the kinetic zone with Fh content, compared to unfertilized soils. These data suggest that mineralogy and clay content together influence the chemical composition not only of mineral-associated OM, but also of soluble compounds within the soil matrix. If these relationships are prevalent over larger spatial and temporal scales, they provide a foundation for understanding SOM cycling and persistence under a variety of environmental contexts.

Original languageEnglish (US)
Article number137839
JournalScience of the Total Environment
StatePublished - Sep 20 2020

Bibliographical note

Funding Information:
This work was funded by National Science Foundation ( NSF ) award to K. S. Hofmockel ( NSF-DEB-1556418 ) and FY16 Laboratory Directed Research and Development program at Pacific Northwest National Laboratory a multiprogram national laboratory operated by Battelle for the U.S. Department of Energy (contract DE-AC05-76RL01830 ). We thank collaborators from the Nutrient Network ( ) providing us soil property data. We also thank lead investigators, Dana M. Blumenthal (USDA-Agricultural Research Service), Cynthia S. Brown (Colorado State University), Scott L. Collins (University of New Mexico), Julia A. Klein (Colorado State University), Johannes M. H. Knops (University of Nebraska) at each site for operations and maintenance. Coordination and data management of Nutrient Network project have been supported by E. T. Borer, S. E. Hobbie, and E. W. Seabloom from the National Science Foundation Research Coordination Network (NSF-DEB-1042132) and Long-Term Ecological Research (NSF-DEB-1234162 to Cedar Creek LTER) programs, and the UMN Institute on the Environment (DG-0001-13). The research was performed at EMSL, a DOE Office of Science User Facility sponsored by the Office of Biological and Environmental Research.

Publisher Copyright:
© 2020 Elsevier B.V.


  • Chemical composition
  • Ecosystem service
  • Fertilization
  • Mineralogy
  • Organo-mineral complex
  • Zonal structure

PubMed: MeSH publication types

  • Journal Article

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