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Background and aims <p>Climate change and anthropogenic nitrogen (N) deposition are altering terrestrial nutrient cycles, but their integrative effects on depth-resolved soil–microbe–plant N cycling remain poorly understood. This study aimed to disentangle how reduced precipitation and N enrichment influence soil N retention, microbial <sup>15</sup>N assimilation, and plant N uptake across soil depths and plant species.</p> Methods <p>A field experiment was conducted in a temperate forest in northeastern China using four treatments (control, N addition, precipitation reduction, and combined treatment), where N addition was applied at 50&#xa0;kg N·ha⁻<sup>1</sup>·yr⁻<sup>1</sup> and precipitation reduction excluded 30% of throughfall (~ 210&#xa0;mm·yr⁻<sup>1</sup>). <sup>15</sup>N tracers (<sup>15</sup>NH₄Cl and K<sup>15</sup>NO₃) applied at two soil depths (0–5&#xa0;cm and 5–15&#xa0;cm) and sampled at two post-labeling intervals (24&#xa0;h and 72&#xa0;h).</p> Results <p>Reduced precipitation significantly suppressed plant biomass (− 21% to − 43%) and microbial biomass nitrogen (MBN, − 17.3% to − 36.2%) relative to the control. N addition substantially enhanced soil <sup>15</sup>N retention (by 38.5%–67.9%) and microbial <sup>15</sup>N assimilation (by 45.2%–73.1%), with more persistent effects at depth and over time. <i>Adonis vernalis</i> exhibited 1.7- to 2.5-fold greater <sup>15</sup>N uptake and 1.6- to 2.3-fold higher biomass accumulation compared to the others. Multivariate analyses revealed strong positive correlations among NH₄⁺–N, microbial <sup>15</sup>N assimilation, and plant <sup>15</sup>N uptake (r = 0.82–0.89), supporting a tightly coupled and form-specific soil–microbe–plant N pathway.</p> Conclusions <p>These findings demonstrate that N addition and reduced precipitation have distinct, depth-specific effects on soil-microbe-plant N coupling: surface layers respond with rapid microbial assimilation and plant uptake, whereas deeper horizons retain <sup>15</sup>N longer through microbial immobilization and access by drought-tolerant roots. This highlights the need to incorporate depth stratification and species-specific N responses in ecosystem nutrient modeling under changing climate regimes.</p>

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Depth-dependent nitrogen coupling among soil, microbe, and plant under altered precipitation and nitrogen input

  • 期刊论文

  • 发表日期：

    2025年11月20日

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  • Yibo Li,
  • Mingxin Zhou,
  • Xingliang Xu

摘要

Background and aims

Climate change and anthropogenic nitrogen (N) deposition are altering terrestrial nutrient cycles, but their integrative effects on depth-resolved soil–microbe–plant N cycling remain poorly understood. This study aimed to disentangle how reduced precipitation and N enrichment influence soil N retention, microbial 15N assimilation, and plant N uptake across soil depths and plant species.

Methods

A field experiment was conducted in a temperate forest in northeastern China using four treatments (control, N addition, precipitation reduction, and combined treatment), where N addition was applied at 50 kg N·ha⁻1·yr⁻1 and precipitation reduction excluded 30% of throughfall (~ 210 mm·yr⁻1). 15N tracers (15NH₄Cl and K15NO₃) applied at two soil depths (0–5 cm and 5–15 cm) and sampled at two post-labeling intervals (24 h and 72 h).

Results

Reduced precipitation significantly suppressed plant biomass (− 21% to − 43%) and microbial biomass nitrogen (MBN, − 17.3% to − 36.2%) relative to the control. N addition substantially enhanced soil 15N retention (by 38.5%–67.9%) and microbial 15N assimilation (by 45.2%–73.1%), with more persistent effects at depth and over time. Adonis vernalis exhibited 1.7- to 2.5-fold greater 15N uptake and 1.6- to 2.3-fold higher biomass accumulation compared to the others. Multivariate analyses revealed strong positive correlations among NH₄⁺–N, microbial 15N assimilation, and plant 15N uptake (r = 0.82–0.89), supporting a tightly coupled and form-specific soil–microbe–plant N pathway.

Conclusions

These findings demonstrate that N addition and reduced precipitation have distinct, depth-specific effects on soil-microbe-plant N coupling: surface layers respond with rapid microbial assimilation and plant uptake, whereas deeper horizons retain 15N longer through microbial immobilization and access by drought-tolerant roots. This highlights the need to incorporate depth stratification and species-specific N responses in ecosystem nutrient modeling under changing climate regimes.