Controls on the Composition of Persistent Microbial-derived Organic Matter in Soil
EMSL Project ID
51642
Abstract
Current estimates suggest that soils contain 1.5 x 10^12 tons of carbon, or roughly three times more carbon than the atmosphere, and represent a giant reservoir for potential greenhouse gas emission or sequestration. The majority of C in soils is in the form of soil organic matter (SOM). Research suggests that the majority of SOM is of microbial origin in the form of microbial residues. It is unknown how the production and persistence of microbially derived SOM varies with biological inputs (plant and microbial) and inherent properties of the soil (e.g. mineralogy, texture). For example, plant inputs and soil geochemistry influence soil microbial biomass, community composition and turnover times that underlay SOM formation, cycling, and long-term storage. Yet the generalizable mechanisms regulating accrual and long-term stabilization of microbial residues are still unclear. Using a 12 month, 13C-labeling soil incubation, we are testing the hypotheses that (H1) microbial-derived SOM accumulation varies between microbial communities selected by crop inputs, (H2) the quantity of microbial residues that accrue and persist is positively correlated with the abundance of poorly crystalline iron minerals in soil, and (H3) persistent microbial residues accrue in "Hot Spots" on minerals where iron is present at the organo-mineral interface. Soils were collected from sandy loams at the Kellogg Biological Station (KBS) in MI, and silty loams at the Arlington Agricultural Research Station (AARS) in WI. These soils were amended with 13C-labeled glucose, which was rapidly incorporated into microbial biomass. By tracking 13C over time, we are measuring the persistence and form of microbial derived molecules. We propose to complement our incubation experiment with sequential extractions allowing us to quantify incorporation of the 13C label into different biomolecular pools using EA-IRMS. Preliminary data suggests a large fraction (~65-70%) of persistent microbial residues are unextractable from solids. We propose to investigate the mechanisms binding persistent microbial residues to mineral surfaces by examining the mineralogy of two contrasting soils with XRD, XPS, and Mossbauer spectroscopy. Finally, we propose to use SEM and NanoSIMS for elemental mapping of mineral surfaces to spatially resolve how different mineral components interact with persistent microbial residues. By collaborating with EMSL we will be able to develop a fundamental understanding of the ecological, biogeochemical and microbial processes regulating the accumulation and persistence of microbial residues in soil while advancing the goals of DOE, BER, and EMSL.
Project Details
Project type
Exploratory Research
Start Date
2020-12-01
End Date
2021-11-27
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members