Molecular and microscopic insights into the formation of soil organic matter in a red pine rhizosphere

Alice C. Dohnalkova, Malak M. Tfaily, A. Peyton Smith, Rosalie K. Chu, Alex R. Crump, Colin J. Brislawn, Tamas Varga, Zhenqing Shi, Linda S. Thomashow, James B. Harsh, C. Kent Keller

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Microbially-derived carbon inputs to soils play an important role in forming soil organic matter (SOM), but detailed knowledge of basic mechanisms of carbon (C) cycling, such as stabilization of organic C compounds originating from rhizodeposition, is scarce. This study aimed to investigate the stability of rhizosphere-produced carbon components in a model laboratory mesocosm of Pinus resinosa grown in a designed mineral soil mix with limited nutrients. We utilized a suite of advanced imaging and molecular techniques to obtain a molecular-level identification of newly-formed SOM compounds, and considered implications regarding their degree of long-term persistence. The microbes in this controlled, nutrient-limited system, without pre-existing organic matter, produced extracellular polymeric substances that formed associations with nutrient-bearing minerals and contributed to the microbial mineral weathering process. Electron microscopy revealed unique ultrastructural residual signatures of biogenic C compounds, and the increased presence of an amorphous organic phase associated with the mineral phase was evidenced by X-ray diffraction. These findings provide insight into the formation of SOM products in ecosystems, and show that the plant-and microbially-derived material associated with mineral matrices may be important components in current soil carbon models.

Original languageEnglish (US)
Article number4
JournalSoil Systems
Issue number1
StatePublished - Dec 2017
Externally publishedYes


  • 16S sequencing
  • Carbon cycle
  • Electron microscopy
  • Fourier-transform ion cyclotron resonance mass spectrometry
  • Mineral weathering
  • Mineral-organic associations
  • Rhizosphere
  • Soil microbiome
  • Soil organic matter

ASJC Scopus subject areas

  • Soil Science
  • Earth-Surface Processes


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