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PI-Submitted Research Highlights for
Terrestrial Ecosystem Science Program

Dual Role of Microorganisms in Soil Organic Matter Dynamics

Julie D. Jastrow
Argonne National Laboratory

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23 August 2017

Soil microbes function as both decomposers and synthesizers of soil organic matter

The Science 
The concept of a soil “microbial carbon pump” is proposed as a mechanism for integrating how the contrasting breakdown and synthesis activities of microorganisms — coupled with the “entombment” of microbial residues via organo-mineral interactions — influence soil organic matter dynamics and persistence.

The Impact
A conceptual framework was developed to inspire new research aimed at the role of microorganisms in the formation of persistent soil organic matter. New understanding on this topic is essential for model development and for informing national and global discussions on the sustainability and vulnerability of soils, including related impacts on food and biofuel production, ecosystem services, environmental health, and climate.

Summary
The dynamic balance between inputs of organic materials versus losses (via decomposition or transport) regulates soil organic matter cycling. In this context, microbes are widely investigated as major mediators of decomposition, particularly through the effects of their extracellular enzymes. Less studied is the impact of microbial growth and death on the creation of soil organic matter. Because the living biomass of microbes in soil is small, microbial contributions to soil organic matter formation have been underappreciated. But, the rapid life cycle of microbes can produce large amounts of organic residues over time. Even though microbial residues can be intrinsically easy to decompose, recent studies suggest a significant portion can be stabilized in soils by intimate physical and chemical associations with soil minerals. In this perspective article, the contrasting metabolic roles that microbes play in soil organic matter dynamics (i.e., catabolic breakdown and anabolic formation) are reviewed. The concept of a soil “microbial carbon pump” is borrowed from marine literature and coupled with the “entombing effect” (stabilization via organo-mineral interactions) to create a framework for stimulating and guiding new research efforts targeted at the role of microbial synthesis and turnover in the formation of persistent soil organic matter.

Contacts (BER PM)
Daniel Stover
SC-23.1
Daniel.Stover@science.doe.gov (301-903-0289)

(BER-funded PI Contact)
Julie D. Jastrow
Argonne National Laboratory
jdjastrow@anl.gov (630-252-3226)

(Lead PI Contact)
Chao Liang
Chinese Academy of Sciences
cliang823@gmail.com

Funding
This work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences, the National Natural Science Foundation of China, the National Key Research and Development Program of China, and the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research.

Publications
Liang, C., J.P. Schimel, & J.D. Jastrow, “The importance of anabolism in microbial control over soil carbon storage.” Nature Microbiology 2, 17105 (2017). [doi:10.1038/nmicrobiol.2017.105].

TES SFA


In the transformation and cycling of carbon compounds produced by plant photosynthesis, the soil “microbial carbon pump” moves carbon derived from microbial synthesis into soil, where it can become stabilized by the “entombing effect”. The yin-yang symbol represents how the microbial carbon pump is driven by the counterbalanced activities of different microbial functional groups that together drive the movement of carbon from vegetation to soil organic matter. (Image Credit: Xuefeng Zhu, Institute of Applied Ecology, Chinese Academy of Sciences)

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