Preprints
https://doi.org/10.5194/egusphere-2023-2983
https://doi.org/10.5194/egusphere-2023-2983
22 Dec 2023
 | 22 Dec 2023
Status: this preprint is open for discussion.

The influence of land use and management on the behaviour and persistence of soil organic carbon in a subtropical Ferralsol

Laura Hondroudakis, Peter M. Kopittke, Ram C. Dalal, Meghan Barnard, and Zhe H. Weng

Abstract. A substantial carbon (C) debt has been accrued due to long-term cropping for global food production emitting carbon dioxide from soil. However, the factors regulating the persistence of soil organic C (SOC) remain unclear, with this hindering our ability to develop effective land management strategies to sequester C in soil. Using a Ferralsol from semi-arid subtropical Australia, alteration of bulk C contents and fractions due to long-term land use change (up to 72 y) were examined with a focus on understanding whether SOC lost due to cropping could be restored by subsequent conversion back to pasture or plantation. It was found that use of soil from cropping for 72 y resulted in the loss of > 70 % of both C and N contents. Although conversion of cropped soil to pasture or plantation for up to 39 y resulted in an increase in both C and N, the C content of all soil fractions were not restored to the original values observed under remnant vegetation. The loss of C with cropping was most pronounced from the particulate organic matter fraction, whilst in contrast, the portion of the C that bound strongly to the soil mineral particles (i.e., the mineral-associated fraction) was most resilient. Indeed, microbial-derived aliphatic C was enriched in the fine fraction of mineral-associated organic matter (< 53 µm). Our findings were further confirmed using synchrotron-based micro-spectroscopic analyses of intact microaggregates which highlighted that binding of C to soil mineral particles is critical to SOC persistence in disturbed soil. The results of the present study extend our conceptual understanding of C dynamics and behaviour at the fine scale where C is stabilised and accrues, but it is clear that restoring C in soils in semi-arid landscapes of subtropical regions poses a challenge.

Laura Hondroudakis, Peter M. Kopittke, Ram C. Dalal, Meghan Barnard, and Zhe H. Weng

Status: open (until 14 Mar 2024)

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Laura Hondroudakis, Peter M. Kopittke, Ram C. Dalal, Meghan Barnard, and Zhe H. Weng
Laura Hondroudakis, Peter M. Kopittke, Ram C. Dalal, Meghan Barnard, and Zhe H. Weng

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Short summary
Land use change to cropping is known to greatly reduced organic carbon and nitrogen concentrations, but much remains unknown about the mechanisms influencing their persistence in soil. In a soil from a subtropical Australian cropping system, we demonstrate that organic carbon is protected by mineral-associations, but not particulate forms. Importantly, we also show that reversion from cropping to pasture or plantation can partially restore this organic carbon.