Long-term bare fallow soil fractions reveal thermo-chemical
properties controlling soil organic carbon dynamics

Chassé, Mathieu; Luftalla, Suzanne; Cécillon, Lauric; Baudin, François; Abiven, Samuel; Chenu, Claire; Barré, Pierre

doi:10.5194/bg-2020-176

Cited by 2 publications

(2 citation statements)

References 54 publications

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“…The vertisol SOC also showed high thermal stability (T 50 -CO 2pyrolysis, T 50 -CO 2 -oxidation), low radiocarbon signature (Δ 14 C) and oxygen content (OI) for both the topsoil and subsoil. This suggests a substantial abundance of pyrogenic SOC that could partly explained the unusually high turnover time of vertisol SOC 40 , though a partial contribution of fossil C from volcanic CO 2 emission or inherited from the parent material could also possibly be involved 7 .…”

Section: Mineral Control Of Soc Dynamics Across Depthmentioning

confidence: 99%

Bioenergetic control of soil carbon dynamics across depth

et al. 2022

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Soil carbon dynamics is strongly controlled by depth globally, with increasingly slow dynamics found at depth. The mechanistic basis remains however controversial, limiting our ability to predict carbon cycle-climate feedbacks. Here we combine radiocarbon and thermal analyses with long-term incubations in absence/presence of continuously 13C/14C-labelled plants to show that bioenergetic constraints of decomposers consistently drive the depth-dependency of soil carbon dynamics over a range of mineral reactivity contexts. The slow dynamics of subsoil carbon is tightly related to both its low energy density and high activation energy of decomposition, leading to an unfavourable ‘return-on-energy-investment’ for decomposers. We also observe strong acceleration of millennia-old subsoil carbon decomposition induced by roots (‘rhizosphere priming’), showing that sufficient supply of energy by roots is able to alleviate the strong energy limitation of decomposition. These findings demonstrate that subsoil carbon persistence results from its poor energy quality together with the lack of energy supply by roots due to their low density at depth.

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Section: Mineral Control Of Soc Dynamics Across Depthmentioning

confidence: 99%

Bioenergetic control of soil carbon dynamics across depth

et al. 2022

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“…1 h per sample) and at a reasonable cost (less than USD 60) using Rock-Eval ® ; it is thermally stable (i.e. high activation energy), and it is depleted in hydrogen (Barré et al, 2016;Hemingway et al, 2019;Gregorich et al, 2015;Poeplau et al, 2019;Chassé et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

A robust initialization method for accurate soil organic carbon simulations

et al. 2022

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Abstract. Changes in soil organic carbon (SOC) stocks are a major source of uncertainty for the evolution of atmospheric CO2 concentration during the 21st century. They are usually simulated by models dividing SOC into conceptual pools with contrasted turnover times. The lack of reliable methods to initialize these models, by correctly distributing soil carbon amongst their kinetic pools, strongly limits the accuracy of their simulations. Here, we demonstrate that PARTYSOC, a machine-learning model based on Rock-Eval® thermal analysis, optimally partitions the active- and stable-SOC pools of AMG, a simple and well-validated SOC dynamics model, accounting for effects of soil management history. Furthermore, we found that initializing the SOC pool sizes of AMG using machine learning strongly improves its accuracy when reproducing the observed SOC dynamics in nine independent French long-term agricultural experiments. Our results indicate that multi-compartmental models of SOC dynamics combined with a robust initialization can simulate observed SOC stock changes with excellent precision. We recommend exploring their potential before a new generation of models of greater complexity becomes operational. The approach proposed here can be easily implemented on soil monitoring networks, paving the way towards precise predictions of SOC stock changes over the next decades.

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Long-term bare fallow soil fractions reveal thermo-chemical properties controlling soil organic carbon dynamics

Cited by 2 publications

References 54 publications

Bioenergetic control of soil carbon dynamics across depth

Bioenergetic control of soil carbon dynamics across depth

A robust initialization method for accurate soil organic carbon simulations

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