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Different root exudates C/N ratios accelerate CO2 emission from paddy soil
  • +9
  • Guan Cai,
  • Muhammad Shahbaz,
  • Tida Ge,
  • yajun Hu,
  • Baozhen Li,
  • Yuhuai Liu,
  • Qiong Liu,
  • Olga Shibistova,
  • Leopold Sauheitl,
  • Jinshui Wu,
  • Georg Guggenberger,
  • Zhenke Zhu
Guan Cai
Institute of Soil Science, Leibniz Universität Hannover, Hannover 30419, Germany

Corresponding Author:guan@ifbk.uni-hannover.de

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Muhammad Shahbaz
Sveriges Lantbruksuniversitet Fakulteten for landskapsplanering tragards- och djurbruksvetenskap
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Tida Ge
Institude of Subtropical Agriculture, The Chinese Academy of Sciences
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yajun Hu
Key Laboratory of Agro-ecological Processes in Subtropical Region & Changsha Research Station for Agricultural and Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, 410125, China
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Baozhen Li
Chinese Academy of Sciences
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Yuhuai Liu
Institute of Soil Science
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Qiong Liu
University of Bayreuth
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Olga Shibistova
Institute of Soil Science
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Leopold Sauheitl
Institute of Soil Science, Leibniz Universität Hannover, Hannover 30419, Germany
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Jinshui Wu
Chinese Acad Sci
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Georg Guggenberger
Leibniz University Hannover
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Zhenke Zhu
Institude of Subtropical Agriculture, The Chinese Academy of Sciences
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Abstract

Root exudates can greatly modify microbial activity and soil organic matter (SOM) mineralization. However, the mechanism of root exudation and its stoichiometric ratio of C/N controlling upon paddy soil C mineralization are poorly understand. In this study, we used a mixture of glucose, oxalic acid, and alanine as root exudate mimics, employing three C/N stoichiometric ratios (CN6, CN10, and CN80) to explore the underlying mechanisms involved in C mineralization. The input of root exudates enhanced CO2 emission by 1.8–2.3-fold than that of the control. Artificial root exudates with low C/N ratios (CN6 and CN10) increased the metabolic quotient (qCO2) by 12% over those obtained at higher stoichiometric ratios (CN80 and C-only), suggesting a relatively high energy demand for microorganisms to acquire organic N from SOM by increasing N-hydrolase production. The stoichiometric ratios of enzymes (β-1,4-glucosidase to β-1,4-N-acetyl glucosaminidase) promoting organic C degradation compared to those involved in organic N degradation showed a significant positive correlation with qCO2; the stoichiometric ratios of microbial biomass (MBC/MBN) were positively correlated with carbon use efficiency. This suggests that root exudates with higher C/N ratios entail an undersupply of N for microorganisms, triggering the release of N-degrading extracellular enzymes. This in turn decreases SOM mineralization, implying the C/N ratio of root exudates to be a controlling factor. Our findings show that the C/N stoichiometry of root exudates controls C mineralization by the specific response of the microbial biomass through the release of C- and N-releasing extracellular enzymes to adjust for the microbial C/N ratio.
23 Aug 2021Submitted to Land Degradation & Development
24 Aug 2021Submission Checks Completed
24 Aug 2021Assigned to Editor
27 Aug 2021Reviewer(s) Assigned
19 Nov 2021Review(s) Completed, Editorial Evaluation Pending
21 Nov 2021Editorial Decision: Revise Minor
29 Nov 20211st Revision Received
13 Dec 2021Submission Checks Completed
13 Dec 2021Assigned to Editor
14 Dec 2021Review(s) Completed, Editorial Evaluation Pending
24 Dec 2021Editorial Decision: Revise Minor
26 Dec 20212nd Revision Received
28 Dec 2021Submission Checks Completed
28 Dec 2021Assigned to Editor
02 Jan 2022Review(s) Completed, Editorial Evaluation Pending
03 Jan 2022Editorial Decision: Accept