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| Titel |
Integrating plant-microbe interactions to understand soil C stabilization with the MIcrobial-MIneral Carbon Stabilization model (MIMICS) |
| VerfasserIn |
Stuart Grandy, Will Wieder, Cynthia Kallenbach, Lisa Tiemann |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250099763
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| Publikation (Nr.) |
 EGU/EGU2014-15579.pdf |
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| Zusammenfassung |
| If soil organic matter is predominantly microbial biomass, plant inputs that build biomass
should also increase SOM. This seems obvious, but the implications fundamentally change
how we think about the relationships between plants, microbes and SOM. Plant residues that
build microbial biomass are typically characterized by low C/N ratios and high lignin
contents. However, plants with high lignin contents and high C/N ratios are believed to
increase SOM, an entrenched idea that still strongly motivates agricultural soil
management practices. Here we use a combination of meta-analysis with a new
microbial-explicit soil biogeochemistry model to explore the relationships between
plant litter chemistry, microbial communities, and SOM stabilization in different
soil types. We use the MIcrobial-MIneral Carbon Stabilization (MIMICS) model,
newly built upon the Community Land Model (CLM) platform, to enhance our
understanding of biology in earth system processes. The turnover of litter and SOM in
MIMICS are governed by the activity of r- and k-selected microbial groups and
temperature sensitive Michaelis-Menten kinetics. Plant and microbial residues are
stabilized short-term by chemical recalcitrance or long-term by physical protection.
Fast-turnover litter inputs increase SOM by >10% depending on temperature in clay
soils, and it’s only in sandy soils devoid of physical protection mechanisms that
recalcitrant inputs build SOM. These results challenge centuries of lay knowledge
as well as conventional ideas of SOM formation, but are they realistic? To test
this, we conducted a meta-analysis of the relationships between the chemistry of
plant liter inputs and SOM concentrations. We find globally that the highest SOM
concentrations are associated with plant inputs containing low C/N ratios. These results
are confirmed by individual tracer studies pointing to greater stabilization of low
C/N ratio inputs, particularly in clay soils. Our model and meta-analysis results
suggest that current ideas about plant-microbe-SOM relationships are unraveling. If
so, our reconsideration of the mechanisms stabilizing SOM will also challenge
long-held views about how to optimize plant community management to increase SOM. |
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