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Stimulation of organic N mineralization by N‒acquiring enzyme activity alleviates soil microbial N limitation following afforestation in subtropical karst areas

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Abstract

Aims

Stoichiometry of soil extracellular enzymes such as the ratios of carbon (C)‒, nitrogen (N)‒, and phosphorus (P)‒acquiring enzymes as well as their vector length and angle are used to reveal the biogeochemical equilibrium between microbial nutrient requirements and soil nutrient availability. However, the dynamics of soil extracellular enzymes activities and microbial N limitation following afforestation remain poorly understood in karst rocky desertification areas.

Methods

Soil samples were collected from Dodonaea viscosa plantations after 0, 10, 20, and 40 years of afforestation following the abandonment of croplands in a karst rocky desertification area, and a natural restored shrubland soil was served as the control. The activities of C, N, and P extracellular enzymes were measured and the stoichiometric and vector ratios of extracellular enzymes were calculated to quantify microbial nutrient limitation.

Results

The stoichiometric ratio of soil C: N:P acquisition enzymes was 0.63:1.48:1.0, with a vector angle of 34.7 in croplands, indicating high microbial N limitation. Compared to the croplands, D. viscosa afforestation significantly increased soil C‒, N‒, and P‒acquiring enzyme activities and gradually increased C: N:P stoichiometric ratio and vector angle to 0.75:1.39:1–0.76:1.17:1 and 34.9–38.2, respectively, indicating that afforestation alleviated microbial N limitation. Furthermore, gross N mineralization and gross ammonium immobilization rates increased by 140‒278% and 340‒801% following afforestation due to the increase in soil organic C and total N contents and the > 2 mm soil aggregates. The vector angle positively correlated with β‒N‒acetylglucosaminidase activity, gross N mineralization, and gross ammonium immobilization. Notably, the vector angle of extracellular enzymes following 40‒year afforestation was still 6.63% lower than that of the shrubland soil.

Conclusion

Our results suggested that afforestation could substantially increase gross N mineralization through stimulating β‒N‒acetylglucosaminidase activity and gross ammonium immobilization, thereby reducing microbial N limitation. However, this limitation persists even following long‒term afforestation in karst rocky desertification areas.

Research highlights

  • Afforestation improves soil structure and increases organic matter content.

  • Afforestation stimulates the activities of soil C‒, N‒, and P‒acquiring enzymes.

  • Afforestation increases gross N mineralization and NH4+ immobilization rates.

  • Afforestation alleviates soil microbial N limitation in subtropical karst areas.

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Data availability

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

References

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Acknowledgements

We extend our appreciation to the reviewers for their time in reviewing our manuscript and providing clear and insightful suggestions, as well as their valuable contribution to improving the scientific quality of our manuscript.

Funding

This research was supported by the National Natural Science Foundation of China (42177243), the Guangxi Science and Technology Planning Project, China (2023GXNSFFA026010), the Guilin Scientific Research and Technology Development Project, China (2020010905), the Natural Resource Science and Technology Strategic Research Project, China (2023-ZL-03), the Geological Survey Project, China (DD20240095) and the Guangxi Bagui Scholarship Program to Dejun Li.

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Authors and Affiliations

Authors

Contributions

Lijun Liu: Writing‒original draft, Investigation, Formal analysis. Qilin Zhu: Software, Writing‒review & editing. Dongni Wen: Investigation. Lin Yang: Investigation. Kang Ni: Investigation. Xingliang Xu: Writing‒review & editing. Jianhua Cao: Investigation, Methodology. Lei Meng: Investigation, Methodology. Jinling Yang: Investigation, Methodology. Jinxing Zhou: Investigation, Methodology. Tongbin Zhu: Conceptualization, Writing‒review & editing, Funding acquisition. Christoph Müller: Methodology.

Corresponding author

Correspondence to Tongbin Zhu.

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Conflict of interest

The authors declare that they have no known competing financial interest or personal relationships that could have appeared to influence the work reported in this paper.

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Responsible Editor: Jorge Durán.

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Supplementary file 1 (DOCX 537 KB)

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Liu, L., Zhu, Q., Wen, D. et al. Stimulation of organic N mineralization by N‒acquiring enzyme activity alleviates soil microbial N limitation following afforestation in subtropical karst areas. Plant Soil (2024). https://doi.org/10.1007/s11104-024-06668-w

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  • DOI: https://doi.org/10.1007/s11104-024-06668-w

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