Abstract
Global nitrogen (N) enrichment promotes soil organic carbon (SOC) accumulation but often causes biodiversity loss in plants and soil microbes, creating a central challenge for achieving co-benefits of carbon accumulation and biodiversity conservation. The extent to which biodiversity contributes to SOC accumulation, and how these trade-offs can be mitigated under N enrichment remains poorly understood. Here, we conduct a global meta-analysis of N enrichment experiments encompassing 2141 observations from 275 studies to evaluate the contributions of plant, bacterial, and fungal diversity to SOC accumulation and to determine associated ecological thresholds. Our findings indicate that biodiversity, especially in plant communities, is the most important factor for SOC accumulation. We identify three distinct N thresholds characterized by different ecological responses: biodiversity loss accelerates at 50 kg N ha⁻¹ yr⁻¹, soil degradation persists at 200 kg N ha⁻¹ yr⁻¹, and SOC accumulation declines beyond this point. Given that the promoting effects of bacterial, fungal, and plant diversity on SOC diminish or even reverse at 50, 67, and 74 kg N ha⁻¹ yr⁻¹, respectively, we suggest limiting fertilization to around 50 kg N ha⁻¹ yr⁻¹, as the trade-off between biodiversity loss and SOC accumulation under N enrichment is potentially minimized.
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Data availability
All data generated and analyzed in this study have been deposited in the figshare repository (https://doi.org/10.6084/m9.figshare.30646841). Supplementary Data 1 contains the full citation information for all primary studies included in the meta-analysis. Source data are provided with this paper.
Code availability
The main R code used in this study is available at the figshare repository (https://doi.org/10.6084/m9.figshare.30646841).
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Acknowledgements
This work was supported by the National Key Research and Development Program of China (grant number: 2021YFD1900500; S.J.), National Science Foundation of China (grant number: 42477129; S.J.), and National Science Foundation for Excellent Young Scholars of China (grant number: 42122050; S.J.).
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S.J. and H.P. conceived the ideas and designed the methodology. H.P., Y.H., W.W., and S.L. contributed to the literature inclusion and data collection. H.P. performed the analyses and wrote the original draft. S.J. and G.W. reviewed the paper before submission.
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Pan, H., Hui, Y., Wu, W. et al. Critical thresholds for co-benefits of carbon accumulation and biodiversity conservation under global nitrogen enrichment. Nat Commun (2026). https://doi.org/10.1038/s41467-025-68090-9
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DOI: https://doi.org/10.1038/s41467-025-68090-9
