Analysis of soil carbon transit times and age distributions using network theories

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The long-term soil carbon dynamics may be approximated by networks of linear compartments, permitting theoretical analysis of transit time (i.e., the total time spent by a molecule in the system) and age (the time elapsed since the molecule entered the system) distributions. We compute and compare these distributions for different network. configurations, ranging from the simple individual compartment, to series and parallel linear compartments, feedback systems, and models assuming a continuous distribution of decay constants. We also derive the transit time and age distributions of some complex, widely used soil carbon models (the compartmental models CENTURY and Rothamsted, and the continuous-quality Q-Model), and discuss them in the context of long-term carbon sequestration in soils. We show how complex models including feedback loops and slow compartments have distributions with heavier tails than simpler models. Power law tails emerge when using continuous-quality models, indicating long retention times for an important fraction of soil carbon. The responsiveness of the soil system to changes in decay constants due to altered climatic conditions or plant species composition is found to be stronger when all compartments respond equally to the environmental change, and when the slower compartments are more sensitive than the faster ones or lose more carbon through microbial respiration. Copyright 2009 by the American Geophysical Union.






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Manzoni, S, GG Katul and A Porporato (2009). Analysis of soil carbon transit times and age distributions using network theories. Journal of Geophysical Research: Biogeosciences, 114(4). p. G04025. 10.1029/2009JG001070 Retrieved from

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Gabriel G. Katul

George Pearsall Distinguished Professor

Gabriel G. Katul received his B.E. degree in 1988 at the American University of Beirut (Beirut, Lebanon), his M.S. degree in 1990 at Oregon State University (Corvallis, OR) and his Ph.D degree in 1993 at the University of California in Davis (Davis, CA).  He currently holds a distinguished Professorship in Hydrology and Micrometeorology at the Department of Civil and Environmental Engineering at Duke University (Durham, NC).   He was a visiting fellow at University of Virginia (USA) in 1997, the Commonwealth Science and Industrial Research Organization (Australia) in 2002, the University of Helsinki (Finland) in 2009,  the FulBright-Italy Distinguished Fellow at Politecnico di Torino (Italy) in 2010, the École polytechnique fédérale de Lausanne (Switzerland) in 2013,  Nagoya University (Japan) in 2014, University of Helsinki (Finland) in 2017, the Karlsruher Institute for Technology (Germany) in 2017, Princeton University (USA) in 2020, and CzechGlobe (Brno - Czech Republic) in 2023. He received several honorary awards, including the inspirational teaching award by the students of the School of the Environment at Duke University (in 1994 and 1996), an honorary certificate by La Seccion de Agrofisica de la Sociedad Cubana de Fisica in Habana (in 1998), the Macelwane medal and became thereafter a fellow of the American Geophysical Union (in 2002), the editor’s citation for excellence in refereeing from the American Geophysical Union (in 2008), the Hydrologic Science Award from the American Geophysical Union (in 2012), the John Dalton medal from the European Geosciences Union (in 2018), and the Outstanding Achievements in Biometeorology Award from the American Meteorological Society (in 2021) and later became an elected fellow of the American Meteorological Society (in 2024).  Katul was elected to the National Academy of Engineering (in 2023) for his contributions in eco-hydrology and environmental fluid mechanics.  He served as the Secretary General for the Hydrologic Science Section at the American Geophysical Union (2006-2008).  His research focuses on micro-meteorology and near-surface hydrology with emphasis on heat, momentum, carbon dioxide, water vapor, ozone, particulate matter (including aerosols, pollen, and seeds) and water transport in the soil-plant-atmosphere system as well as their implications to a plethora of hydrological, ecological, atmospheric and climate change related problems.

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