Circumpolar Assessment of Organic
Matter Decomposibility as a Control Over
Potential Permafrost Carbon Loss
Dr. Ted Schuur
Department of Biology, University of Florida
February, 2013
Co-Authors: Christina Schädel, Rosvel Bracho, Bo Elberling,
Christian Knoblauch, Agnieszka Kotowska, Hanna Lee, Yiqi Luo,
Massimo Lupascu, Susan Natali, Gaius Shaver, Merritt Turetsky
Vulnerability of Permafrost Carbon
Researc h Coordination Network (RCN)
http://www.biology.ufl.edu/permafrostcarbon/
PIs: Ted Schuur, A. David McGuire
Steering Committee: Josep G. Canadell, Jennifer W. Harden, Peter
Kuhry, Vladimir E. Romanovsky, Merritt R. Turetsky
Postdoctoral Researcher: Christina Schädel
Core funding:
Additional
Workshop funding:
Workshop: May 2013; Annual Meeting @ AGU
Permafrost Carbon Feedback to Climate
What is the magnitude, timing, and form of the
permafrost carbon release to the atmosphere in
a warmer world?
Cumulative C Emissions: 1850-2005 (2012)
Fossil Fuel Emissions
365 Pg
Land Use Change
151 Pg
Permafrost Zone C Emissions: Future?
7-11% Loss?
120-195 Pg
Expert Survey (Schuur 2013) (162-288 Pg CO2-Ceq)
Working Group Activities
Data syntheses in formats for biospheric or climate models
1) Permafrost Carbon Quantity
Leads: Gustaf Hugelius, C. Tarnocai, J. Harden
Spatially distributed estimates of deep SOC storage;
Quantifying uncertainties in circumpolar permafrost SOC storage
2) Permafrost Carbon Quality
Leads: Christina Schädel, T. Schuur
Incubation synthesis to determine pool sizes and decomposition rates;
Network of long-term soil incubation experiments
3) Anaerobic/Aerobic Issues
Leads: David Olefeldt, M. Turetsky
Synthesis of CO2 and CH4 fluxes from northern lakes and wetlands;
Controls on methane emission in permafrost environments
4) Thermokarst
Leads: Guido Grosse, B. Sannell
Metadata analysis of physical processes/rates;
Analysis of thermokarst inventories;
Distribution of thermokarst features in the Arctic
5) Modeling Integration & Upscaling
Leads: Dave McGuire P. Canadell, D. Lawrence, Charles Koven, D. Hayes
Evaluation of thermal and carbon dynamics of permafrost-carbon models;
State-of-the-art assessment of the vulnerability of permafrost carbon and its effects on the climate
system
Permafrost Carbon Network Members
Current number of:
Members: 135+
Institutions: 70
Countries: 16
Working Groups
1) Carbon Quantity: 28 members
2) Carbon Quality: 27 members
3) An/Aerobic: 27 members
4) Thermokarst: 33 members
5) Modeling Integration: 50 members
Soil Organic Matter Decomposition
1) Chemical recalcitrance
(plant & microbial inputs
plus transformation in
soils)
2) Physical Interactions
(disconnection, sorption)
3) Microbial
communities
(enzyme pathways)
4) Environmental controls
(pH, Temp, H2O, O2 , etc)
Schmidt et al. 2011
Permafrost Zone Incubation Database
40 incubation studies
(34 published, 6 unpublished)
~500 unique soil samples
18
Number of studies
14
12
long-term incubation synthesis
10
8
6
4
2
Sampling depth (m)
0
16
5
10
15
20
25
0
0
500
1000
1500
2000
Incubation length (days)
4500
0
10
20
30
SOC (%)
40
50
Soil Incubation Synthesis
Lab incubations from
permafrost zone
(121 samples;
8 studies)
 Long-term
incubations (1 year+)
 Normalized
to 5°C (Q10=2.5)
Upland boreal, tundra
soils
(Organic, surface <1m,
deep soils >1m)
Carbon Decomposition Model
Total respiration
n
R   ri
3-pool model
i 1
C-pool dynamics
Cf Cs
rf
Cp = Ctot-(Cf+Cs)
rs
rp
R
dCi (t)
 k i C tot ra i
dt
Partitioning coefficient
Ci
rai 
; rai  1
Ctot
Schädel et al. 2013 Oecologia
Partitioning Incubation CO2-C Flux
total C-flux (measured)
from passive C pool
from slow C pool
from fast C pool
Turnover Time
5
Slow C pool
p<0.05
4
35
30
3
20
2
15
500-10,000
Years
Model
Parameter
10
1
5
m
in
>1
in
<1
m
m
Soil type
m
m
in
>1
m
in
<1
m
or
g
0
m
0
Passive C pool
n.s.
25
or
g
Turnover time (years)
Fast C pool
Time in ‘incubation years’; continuous flux at 5 deg C
Carbon Pool Sizes
12
Slow C pool
n.s.
10
Passive C pool
100
p<0.01
80
8
60
6
40
4
2
20
0
0
Soil type
m
m
in
>1
m
in
<1
m
or
g
m
m
in
>1
m
in
<1
m
or
g
m
in
>1
m
m
in
<1
m
p<0.01
or
g
C pool size (% of total C)
Fast C pool
Multiple regression table
Variable
C:N
depth
%N
Vegetation type
Bulk density
pH
Data were transformed to meet assumption of normality
Carbon Loss and C:N
C loss (% of initial C)
1 year
100
10 year
50 year
1 year
10 years
50 years
p<0.01
p<0.01
p<0.01
80
60
40
20
0
0
20
40
60
80 0
20
40
60
80
0
20
40
60
C:N
Time in ‘incubation years’; continuous flux at 5 deg C
80
Carbon Loss and Vegetation Type
1 year
10 year
C loss (% of initial C)
1year
25
50 year
10year
p=0.018
100
50year
p=0.04
100
20
80
80
15
60
60
10
40
40
5
20
20
0
0
0
boreal
tundra
boreal
tundra
n.s.
boreal
tundra
Time in ‘incubation years’; continuous flux at 5 deg C
Results Summary
Vulnerability ranges from ~20% loss in organic soils to <5-10%
for mineral soils [5 deg C; 10 incubation years]
Vulnerability of boreal soils > tundra soils, but this difference
diminishes over time
Simple C:N and vegetation type metrics can be used to scale
across landscapes and soil maps
Full incubation dataset can determine sensitivity to changing
environmental conditions
Future Upscaling
Carbon Quantity
Working Group
spatial extent
 inventory 3m depth
Hugelius et al. 2012
Modeling
Working Group
Permafrost thaw
trajectories with IPCC
scenarios
Harden et al. 2012
Implications
Carbon Pools x
Thaw Trajectories x
Incubation Rates =
Potential Carbon Loss