Circumpolar assessment of permafrost C quality and its vulnerability over time using long-term incubation data

High‐latitude ecosystems store approximately 1700 Pg of soil carbon (C), which is twice as much C as is currently contained in the atmosphere. Permafrost thaw and subsequent microbial decomposition of permafrost organic matter could add large amounts of C to the atmosphere, thereby influencing the g...

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Published in:	Global change biology Vol. 20; no. 2; pp. 641 - 652
Main Authors:	Schädel, Christina, Schuur, Edward A. G., Bracho, Rosvel, Elberling, Bo, Knoblauch, Christian, Lee, Hanna, Luo, Yiqi, Shaver, Gaius R., Turetsky, Merritt R.
Format:	Journal Article
Language:	English
Published:	Oxford Blackwell Publishing Ltd 01.02.2014 Wiley-Blackwell
Subjects:	Alaska Animal and plant ecology Animal, plant and microbial ecology Arctic Regions Atmosphere Biological and medical sciences boreal forest C decomposition Carbon - metabolism Carbon Cycle Carbon dioxide Climate Change Climatology. Bioclimatology. Climate change Decomposition Earth, ocean, space Ecosystem Exact sciences and technology External geophysics Forestry Fundamental and applied biological sciences. Psychology General aspects General forest ecology Generalities. Production, biomass. Quality of wood and forest products. General forest ecology Latitude Meteorology Models, Biological Organic matter Permafrost Seasons Siberia Soil - chemistry Soil depth soil organic carbon Soil sciences Synecology Temperature Terrestrial ecosystems tundra Turnover time Russian Federation United States Eurasia America Siberia Alaska North America Organic carbon Boreal forest Incubation C decomposition soil organic carbon Decomposition Permafrost Vulnerability Long term Dynamical climatology Climate change Soils Quality Siberia Alaska Polar region Tundra tundra boreal forest climate change
ISSN:	1354-1013, 1365-2486, 1365-2486
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Summary:	High‐latitude ecosystems store approximately 1700 Pg of soil carbon (C), which is twice as much C as is currently contained in the atmosphere. Permafrost thaw and subsequent microbial decomposition of permafrost organic matter could add large amounts of C to the atmosphere, thereby influencing the global C cycle. The rates at which C is being released from the permafrost zone at different soil depths and across different physiographic regions are poorly understood but crucial in understanding future changes in permafrost C storage with climate change. We assessed the inherent decomposability of C from the permafrost zone by assembling a database of long‐term (>1 year) aerobic soil incubations from 121 individual samples from 23 high‐latitude ecosystems located across the northern circumpolar permafrost zone. Using a three‐pool (i.e., fast, slow and passive) decomposition model, we estimated pool sizes for C fractions with different turnover times and their inherent decomposition rates using a reference temperature of 5 °C. Fast cycling C accounted for less than 5% of all C in both organic and mineral soils whereas the pool size of slow cycling C increased with C : N. Turnover time at 5 °C of fast cycling C typically was below 1 year, between 5 and 15 years for slow turning over C, and more than 500 years for passive C. We project that between 20 and 90% of the organic C could potentially be mineralized to CO2 within 50 incubation years at a constant temperature of 5 °C, with vulnerability to loss increasing in soils with higher C : N. These results demonstrate the variation in the vulnerability of C stored in permafrost soils based on inherent differences in organic matter decomposability, and point toward C : N as an index of decomposability that has the potential to be used to scale permafrost C loss across landscapes.
Bibliography:	Department of Energy NICCR and TES U.S. National Parks and Inventory Monitoring Program ark:/67375/WNG-FTSTFCWB-5 Figure S1. Observed and modeled respiration rates for five randomly selected soil samples (a-e). The samples are the same as in Table S3. Table S1. Soil sample parameters for each individual soil core. Table S2. Prior parameter range for C pool partitioning coefficients (fi) and decay rates (ki). Table S3. Comparison of data-model fit and C loss for three time frames using a 2-pool and a 3-pool model for five randomly selected soil samples. Table S4. Correlations between model parameters. Table S5. MLE (97.5% CI) for all parameters and potential C loss for 1, 10, and 50 incubations years for all 121 soil samples. Table S6. Multiple regression results for estimated parameters and C loss (MLE, upper and lower limit of 97.5% CI) for 50 incubation years at 5 °C. NSF CAREER Program Danish National Research Foundation - No. CENPERM DNRF100 NSF Bonanza Creek LTER National Science Foundation Vulnerability of Permafrost Carbon Research Coordination Network - No. 955713 istex:3EA6E3F6248D9FA2CE5EEBC18ED0E19E47AF1145 European Union FP7-ENVIRONMENT - No. GA282700 ArticleID:GCB12417 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 14 ObjectType-Article-1 ObjectType-Feature-2 content type line 23
ISSN:	1354-1013 1365-2486 1365-2486
DOI:	10.1111/gcb.12417