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

Vulnerability of Permafrost CarbonResearch Coordination 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:

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)

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

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

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)

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

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)

Carbon Decomposition Model

itotii raCkdt(t)dC

1; itot

ii raCC

ra

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

from passive C pool

from slow C pool

from fast C pool

total C-flux (measured)

Partitioning Incubation CO2-C Flux

Turnover Time

Slow C poolFast C pool Passive C pool

500-10,000Years

Model Parameter

orgmin<1m

min>1m

Turnover time (years)

0

1

2

3

4

5

Soil type

orgmin<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

Carbon Pool Sizes

Slow C pool Passive C poolFast C pool

C pool 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.

Multiple regression tableVariable

C:N

depth

%N

Vegetation type

Bulk density

pH

Data were transformed to meet assumption of normality

Carbon Loss and C:N

1 year 10 year 50 year10 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

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

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

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

Implications

Carbon Pools x Thaw Trajectories xIncubation Rates =Potential Carbon Loss