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 Research Coordination Network (RCN) 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 Workshop: May 2013; Annual AGU 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: (2012) Fossil Fuel Emissions365 Pg Land Use Change151 Pg Permafrost Zone C Emissions: Future? 7-11% Loss? Pg Expert Survey (Schuur 2013)( Pg CO 2 -C eq )

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 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 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 4) Thermokarst Leads: Guido Grosse, B. Sannell Metadata analysis of physical processes/rates; Analysis of thermokarst inventories; Distribution of thermokarst features in the Arctic 3) Anaerobic/Aerobic Issues Leads: David Olefeldt, M. Turetsky Synthesis of CO 2 and CH 4 fluxes from northern lakes and wetlands; Controls on methane emission in permafrost environments Data syntheses in formats for biospheric or climate models Working Group Activities

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 Schmidt et al )Chemical recalcitrance (plant & microbial inputs plus transformation in soils) 2)Physical Interactions (disconnection, sorption) 3)Microbial communities (enzyme pathways) 4)Environmental controls (pH, Temp, H 2 O, O 2, etc)

Permafrost Zone Incubation Database 40 incubation studies (34 published, 6 unpublished) ~500 unique soil samples long-term incubation synthesis

Soil Incubation Synthesis  Lab incubations from permafrost zone (121 samples; 8 studies)  Long-term incubations (1 year+)  Normalized to 5°C (Q 10 =2.5)  Upland boreal, tundra soils (Organic, surface 1m)

Carbon Decomposition Model C-pool dynamics Partitioning coefficient 3-pool model CfCf CsCs C p = C tot -(C f +C s ) rsrs rprp rfrf R Schädel et al Oecologia Total respiration

from passive C pool from slow C pool from fast C pool total C-flux (measured) Partitioning Incubation CO 2 -C Flux

Turnover Time Slow C poolFast C poolPassive C pool ,000 Years Model Parameter p<0.05n.s. Time in ‘incubation years’; continuous flux at 5 deg C

Carbon Pool Sizes Slow C poolPassive C poolFast C pool p<0.01 n.s.

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 1 year10 year50 year p<0.01 Time in ‘incubation years’; continuous flux at 5 deg C

Carbon Loss and Vegetation Type p=0.018p=0.04 n.s. 1 year10 year50 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 Modeling Working Group  spatial extent  inventory 3m depth  Permafrost thaw trajectories with IPCC scenarios Hugelius et al Harden et al Future Upscaling

Implications Carbon Pools x Thaw Trajectories x Incubation Rates = Potential Carbon Loss