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Title: Global patterns and controls of soil organic carbon dynamics as simulated by multiple terrestrial biosphere models: Current status and future directions

Soil is the largest organic carbon (C) pool of terrestrial ecosystems, and C loss from soil accounts for a large proportion of land-atmosphere C exchange. Therefore, a small change in soil organic C (SOC) can affect atmospheric carbon dioxide (CO₂) concentration and climate change. In the past decades, a wide variety of studies have been conducted to quantify global SOC stocks and soil C exchange with the atmosphere through site measurements, inventories, and empirical/process-based modeling. However, these estimates are highly uncertain, and identifying major driving forces controlling soil C dynamics remains a key research challenge. This study has compiled century-long (1901–2010) estimates of SOC storage and heterotrophic respiration (Rh) from 10 terrestrial biosphere models (TBMs) in the Multi-scale Synthesis and Terrestrial Model Intercomparison Project and two observation-based data sets. The 10 TBM ensemble shows that global SOC estimate ranges from 425 to 2111 Pg C (1 Pg = 10¹⁵ g) with a median value of 1158 Pg C in 2010. The models estimate a broad range of Rh from 35 to 69 Pg C yr⁻¹ with a median value of 51 Pg C yr⁻¹ during 2001–2010. The largest uncertainty in SOC stocks exists in the 40–65°N latitude whereas the largestmore » cross-model divergence in Rh are in the tropics. The modeled SOC change during 1901–2010 ranges from –70 Pg C to 86 Pg C, but in some models the SOC change has a different sign from the change of total C stock, implying very different contribution of vegetation and soil pools in determining the terrestrial C budget among models. The model ensemble-estimated mean residence time of SOC shows a reduction of 3.4 years over the past century, which accelerate C cycling through the land biosphere. All the models agreed that climate and land use changes decreased SOC stocks, while elevated atmospheric CO₂ and nitrogen deposition over intact ecosystems increased SOC stocks—even though the responses varied significantly among models. Model representations of temperature and moisture sensitivity, nutrient limitation, and land use partially explain the divergent estimates of global SOC stocks and soil C fluxes in this study. In addition, a major source of systematic error in model estimations relates to nonmodeled SOC storage in wetlands and peatlands, as well as to old C storage in deep soil layers.« less
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  1. Auburn Univ., AL (United States). International Center for Climate and Global Change Research, School of Forestry and Wildlife Sciences
  2. Northern Arizona Univ., Flagstaff, AZ (United States). School of Earth Sciences and Environmental Sustainability and Dept. of Civil Engineering, Construction Management, and Environmental Engineering
  3. Northern Arizona Univ., Flagstaff, AZ (United States). School of Earth Sciences and Environmental Sustainability and Center for Ecosystem Science and Society
  4. Carnegie Institution for Science, Stanford, CA (United States). Dept. of Global Ecology
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division and Climate Change Science Inst.
  6. Laboratoire des Sciences du Climat et de l'Environnement, Gif sur Yvette (France)
  7. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Atmospheric Sciences and Global Change Div.
  8. National Inst. for Environmental Studies, Tsukuba (Japan)
  9. Univ. of Illinois, Urbana-Champaign, IL (United States). Dept. for Atmospheric Sciences
  10. Tsinghua Univ., Beijing (China). Depart. of Hydraulic Engineering
  11. Montana State Univ., Bozeman, MT (United States). Dept. of Ecology
  12. National Snow and Ice Data Center; Boulder, CO (United States)
  13. National Aeronautics and Space Administration, Mountain View, CA (United States). Ames Research Center,
  14. Univ. of Maryland, College Park, MD (United States). Dept. of Atmospheric and Oceanic Science
Publication Date:
OSTI Identifier:
Grant/Contract Number:
AC05-76RL01830; NNX10AG01A; NNH10AN681
Accepted Manuscript
Journal Name:
Global Biogeochemical Cycles
Additional Journal Information:
Journal Volume: 29; Journal Issue: 6; Journal ID: ISSN 0886-6236
American Geophysical Union (AGU)
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States