Microbe-mineral interactions and the fate of soil carbon
Courtney Creamer, Andrea Foster, Corey Lawrence, Jack McFarland, Marjorie Schulz, Mark Waldrop
[email protected] 2014-67003-22043
Importance of microbes & minerals for stable carbon (C) formation
Cotrufo et al., 2015 Nature Geoscience
Underlying research question:
How does soil mineralogy and
microbial community structure influence the
stability of C with different chemistries
across micro to regional scales?
Activities span µm to km scalesActivity 1: Raman
spectroscopy development
Activity 2: Sterile and non-sterile experiments
Activity 3: Soil mesocosms
Activity 4: Climo-chronosequences
Repeat
Create microbial residues
Quantify released residues
Add plant-
derived DOC
Activity 5: Reactive transport modeling
Activities span µm to km scalesActivity 1: Raman
spectroscopy development
Activity 2: Sterile and non-sterile experiments
Activity 4: Climo-chronosequences
13C organics
Controls on C stabilization• Abiotic: Sorption,
aggregation• Biotic: Efficiency of
microbial processing • Influenced by C
chemistry, microbes, mineralogy, soil depth
Raman spectroscopy development
Non-destructive in-situ quantification of:Microbial 13C assimilation
Carbon chemistry and spatial distribution
X X X X
X X
13C CO2
3 weeks
Does mineralogy affect stabilization of dead microbial
residues?
X X
Cumulative respiration
7.3%
0.73%
Anabolism94% 13C
4% 13C
Dead microbes are stabilized on highly sorptive minerals
C stabilization affected by mineral and life status
Aluminum hydroxide:
Feldspar:
Live E. coliDead 13C Arthrobacter
Live and dead
74%
58%
52%
0.8%
C stabilization affected by mineral and life status
Aluminum hydroxide:
Feldspar:
Live E. coliDead 13C Arthrobacter
Live and dead
52%
0.8%
25%
10%Live microbes stabilized residues
Live microbes destabilized sorbed residues
What is the fate of added C with depth?
• Glucose– Efficient biotic
processing, low sorption
• Oxalate– Inefficient
processing, high sorption
Carbon
C/N
% ClaySSA m2 g∙ -1
Soil specific surface area (SSA) and % clay
Photo: Corey Lawrence
Photo: Corey Lawrence
Construction of in situ
incubation units
Recovered in soil (%)
Oxalate-derived C not stabilized long-term
A
A/B
B
100806040200
Recovered in soil (%)
Glucose-derived C stabilized through profile
A
A/B
B
100806040200
Vulnerability of stabilized C with depth
-27%
-53%
-81%
A
A/B
B
100806040200Recovered in soil (%)
Conclusions:• Efficient biotic processing is an important
driver of the stabilization of added C– Live microbes > dead residues – Glucose > oxalic acid
• No simple rule for C stabilization on minerals–Microbes can destabilize or stabilize C depending
on mineralogy – Deep carbon was vulnerable to oxidation
Future directionsActivity 1: Raman spectroscopy development
Activity 2: Sterile and non-sterile experiments
Activity 3: Soil mesocosms
Activity 4: Climo-chronosequences
Repeat
Create microbial residues
Quantify released residues
Add plant-
derived DOC
Activity 5: Reactive transport modeling
Future directionsActivity 1: Raman spectroscopy development
Activity 2: Sterile and non-sterile experiments
Activity 3: Soil mesocosms
Activity 4: Climo-chronosequences
Repeat
Create microbial residues
Quantify released residues
Add plant-
derived DOC
Activity 5: Reactive transport modeling
• Raman applications:• Generate
parameters for microbially explicit models
• Extrapolation to larger regions• Mechanisms of C
stabilization and loss
• Applied questions on land use change • Increase soil
carbon and understanding vulnerability
Thank you!Tim Hyland and the Staff
at Wilder Ranch State Park
USGS Colleagues:Marjorie Schulz
Sabrina SevilgenSharon Mehlman
Andrea FosterFunding:
USDA (2014-67003-22043)