Tracing the Influence of Exudate Chemistry, Microbiology, and Mineralogy on the Decomposition and Stabilization of Root-Derived Carbon
EMSL Project ID
48912
Abstract
Soils store more carbon (C) than the atmosphere and biosphere combined, yet the fundamental mechanisms that regulate this vast pool of C remain elusive. Plant roots are the dominant source of C in soil, but it is the soil microbial community that determines the fate of this C. The rhizosphere, a dynamic root-soil interface, is the primary site of C transformation in soil, where the exchange of C, nutrients, and biomolecules between the plant and rhizosphere microbial community orchestrates transformation and ultimate stabilization of root-derived C. Through collaboration with EMSL scientists, we propose to delineate the transformation of root C by the rhizosphere microbiome (via metaproteomics and metatranscriptomics) and define the root and microbial products that become stabilized through adsorption to mineral surfaces (13C-NMR and FTICR-MS). In short, we propose to develop a molecular-scale map and a mechanistic understanding of the fate of plant-derived C, and the potential for soil C stabilization.
The root-associated microbiome utilizes and transforms root-derived carbon to cell materials and products. We will characterize these microbial transformations using isotopically-enabled metaproteomics (at EMSL) and transcriptomics (already ongoing in our lab). Resulting microbial products and materials can be stabilized through mineral association. Association with soil minerals provides the greatest organic carbon protection, with some mineral-associated carbon persisting for thousands of years. However, we know that not all mineral-associated C is protected from microbial degradation. Our previous work tracking plant C into soil under elevated CO2 showed that while soil minerals initially stabilized new plant-derived C, plant and soil dynamics later caused C release from soil minerals, and a subsequent release of microbially-respired CO2.
To understand the mechanisms of stabilization and C release from mineral associations, our EMSL research includes molecular characterization of plant-microbe-mineral interactions in the rhizosphere. Coupled with our ongoing DOE-funded work tracing association of plant-derived C with soil minerals using stable isotope labeling, we plan to address the fundamental mechanisms that control SOM stabilization by chemically characterizing: C compounds exuded by roots, those transformed by the rhizosphere microbial community, those associated with soil minerals, and those that are subsequently released from soil mineral surfaces into soil pore water. We will use 13C-Nuclear Magnetic Resonance Spectrometry (NMR) to characterize mineral-associated C compounds, and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS) to characterize dissolved organic C and organo-mineral complexes in soil pore water with high resolution. By linking microbial decomposition in the rhizosphere with SOM stabilization processes, this data will allow us to build a mechanistic understanding of processes controlling the fate of C in soils. Understanding the plant-microbe-mineral feedbacks within the rhizosphere may allow us to predict how soil C cycling will change as climate change alters plant-derived C inputs to soil (quantity and composition), the soil microbial community, and ultimately how much C is stored in soils.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2015-10-01
End Date
2017-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members