Multiple model forms needed to capture true uncertainty of soil carbon fate in a changing world.
Organic matter in soils is persistent because of its physical isolation from soil microbes, but the extent to which these protected soil carbon pools may be vulnerable to environmental change remains uncertain. This uncertainty is reflected in projections of soil carbon change simulated by this project’s models, which disagree as to whether soils will gain or lose carbon through the end of this century.
The results from this study illustrate that models disagree on the sign and magnitude of global soil changes through 2100, largely because of the divergent responses of Arctic systems. These results reflect different assumptions about the nature of soil carbon persistence and vulnerabilities, underscoring the challenges associated with setting allowable greenhouse gas emission targets that will limit global warming to 1.5°C.
Soils store carbon, lots of carbon. Because of these large carbon stocks, exchanges of carbon dioxide (CO2) between soils and the atmosphere are large, and the potential responses of soil carbon stocks and fluxes to projected changes in climate are uncertain. The understanding of factors responsible for the persistence of these vast soil carbon stores has changed dramatically, and models need to widely implement these new ideas. The research team, led by the University of Colorado, Boulder, evaluated three models that make different assumptions about factors responsible for persistence of carbon in soils. Their results show that, although the different model formulations produce similar estimates for initial soil carbon stocks, they show large spread in the fate of soil carbon under projected changes in soil temperature, moisture, and plant growth through the end of this century. These results highlight that greater attention is needed to develop and test model formulations that are consistent with observations and understanding—especially in the Arctic, which has large soil carbon stores that are likely to experience rapid change in upcoming decades.
BER Program Manager
U.S. Department of Energy Office of Science, Office of Biological and Environmental Research
Earth and Environmental Systems Sciences Division (SC-33.1)
Environmental System Science
University of Colorado, Boulder & National Center for Atmospheric Research
This work was supported by the Terrestrial Ecosystem Science (TES) program of the Office of Biological and Environmental Research (BER) under awards TES DE- SC0014374 and BSS DE-SC0016364), within the U.S. Department of Energy (DOE) Office of Science; U.S. Department of Agriculture (USDA) National Institute of Food and Agriculture (NIFA, 2015-67003-23485); DOE BER RUBISCO Science Focus Area (SFA); and National Aeronautics and Space Administration (NASA) Interdisciplinary Science Program (ISP, award number NNX17AK19G). B. Sulman was supported under award NA14OAR4320106 from the National Oceanic and Atmospheric Administration (NOAA) and U.S. Department of Commerce (DOC) and by the Next-Generation Ecosystem Experiments (NGEE)–Arctic project, supported by TES BER, within the DOE Office of Science.
Wieder, W. R., B. N. Sulman, M. D. Hartman, C. D. Koven, and M. A Bradford. “Arctic soil governs whether climate change drives global losses or gains in soil carbon.” Geophysical Research Letters 46(24), 14486–95 (2019). [DOI:10.1029/2019GL085543].
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