circumpolar assessment of organic matter decomposibility as a control over potential permafrost...
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Circumpolar Assessment of Organic Matter Decomposibility as a Control Over
Potential Permafrost Carbon Loss
Dr. Ted SchuurDepartment 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
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Vulnerability of Permafrost CarbonResearch Coordinati on Network (RCN)
PIs: Ted Schuur, A. David McGuireSteering Committee: Josep G. Canadell, Jennifer W. Harden, Peter Kuhry, Vladimir E. Romanovsky, Merritt R. TuretskyPostdoctoral Researcher: Christina Schädel
Workshop: May 2013; Annual Meeting @ AGU
http://www.biology.ufl.edu/permafrostcarbon/
Core funding: Additional Workshop funding:
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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 PgLand Use Change 151 Pg
Permafrost Zone C Emissions: Future?7-11% Loss? 120-195 Pg Expert Survey (Schuur 2013) (162-288 Pg CO2-Ceq)
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2) Permafrost Carbon QualityLeads: Christina Schädel, T. SchuurIncubation synthesis to determine pool sizes and decomposition rates;Network of long-term soil incubation experiments
1) Permafrost Carbon QuantityLeads: Gustaf Hugelius, C. Tarnocai, J. HardenSpatially distributed estimates of deep SOC storage;Quantifying uncertainties in circumpolar permafrost SOC storage
5) Modeling Integration & UpscalingLeads: Dave McGuire P. Canadell, D. Lawrence, Charles Koven, D. HayesEvaluation 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
4) ThermokarstLeads: Guido Grosse, B. SannellMetadata analysis of physical processes/rates;Analysis of thermokarst inventories; Distribution of thermokarst features in the Arctic
3) Anaerobic/Aerobic IssuesLeads: David Olefeldt, M. Turetsky Synthesis of CO2 and CH4 fluxes from northern lakes and wetlands;Controls on methane emission in permafrost environments
Data syntheses in formats for biospheric or climate modelsWorking Group Activities
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Permafrost Carbon Network MembersCurrent number of: Members: 135+Institutions: 70Countries: 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
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Soil Organic Matter Decomposition
Schmidt et al. 2011
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)
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Permafrost Zone Incubation Database40 incubation studies (34 published, 6 unpublished)~500 unique soil samples
Incubation length (days)
0 500 1000 1500 2000 4500
Num
ber of studies
0
2
4
6
8
10
12
14
16
18
long-term incubation synthesis
SOC (%)
0 10 20 30 40 50
Sam
pling depth (m
)
0
5
10
15
20
25
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Soil Incubation SynthesisLab 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)
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Carbon Decomposition Model
itotii raCkdt
(t)dC
1; itot
ii raC
Cra
C-pool dynamics
Partitioning coefficient
3-pool model
Cf Cs Cp = Ctot-(Cf+Cs)
rs rprf R
Schädel et al. 2013 Oecologia
n
iirR
1
Total respiration
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from passive C pool
from slow C pool
from fast C pool
total C-flux (measured)
Partitioning Incubation CO2-C Flux
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Turnover Time
Slow C poolFast C pool Passive C pool
500-10,000Years
Model Parameter
orgm
in<1m
min>1m
Tu
rnover tim
e (years)
0
1
2
3
4
5
Soil type
orgm
in<1m
min>1m
0
5
10
15
20
25
30
35p<0.05 n.s.
Time in ‘incubation years’; continuous flux at 5 deg C
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Carbon Pool Sizes
Slow C pool Passive C poolFast C pool
C p
ool size (% of total C
)
0
2
4
6
8
10
12
Soil type
0
20
40
60
80
100p<0.01
p<0.01
n.s.
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Multiple regression tableVariable
C:N
depth
%N
Vegetation type
Bulk density
pH
Data were transformed to meet assumption of normality
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Carbon Loss and C:N
1 year 10 year 50 year
10 years
C:N
0 20 40 60 80
1 year
0 20 40 60 80
C loss (%
of initial C)
0
20
40
60
80
10050 years
0 20 40 60 80
p<0.01 p<0.01 p<0.01
Time in ‘incubation years’; continuous flux at 5 deg C
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1year
boreal tundra
C loss (%
of initial C)
0
5
10
15
20
2510year
boreal tundra0
20
40
60
80
10050year
boreal tundra0
20
40
60
80
100
Carbon Loss and Vegetation Type
p=0.018 p=0.04 n.s.
1 year 10 year 50 year
Time in ‘incubation years’; continuous flux at 5 deg C
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Results Summary
Simple C:N and vegetation type metrics can be used to scale across landscapes and soil maps
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
Full incubation dataset can determine sensitivity to changing environmental conditions
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Carbon Quantity Working Group
ModelingWorking Group
spatial extent inventory 3m depth
Permafrost thaw trajectories with IPCC scenarios
Hugelius et al. 2012
Harden et al. 2012
Future Upscaling
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Implications
Carbon Pools x Thaw Trajectories xIncubation Rates =Potential Carbon Loss