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Aims <p>Mountain ecosystems are vital carbon (C) and nitrogen (N) reservoirs, mitigating climate change through substantial soil organic matter (SOM) stocks. However, their vulnerability to climate shifts necessitates understanding altitudinal patterns in the sequestration, stabilization, δ<sup>13</sup>C and δ<sup>15</sup>N signatures of C and N within SOM.</p> Methods <p>We investigated C/N concentrations, stocks, and δ<sup>13</sup>C/δ<sup>15</sup>N signatures in bulk SOM and its physically fractionated components: free light fraction (LFOM), intra-aggregate particulate organic matter (IPOM), and mineral-associated organic matter (MOM) along the altitudinal gradient (1300–3400&#xa0;m) on Taibai Peak, Qinling Mountains.</p> Results <p>Unimodal patterns emerged for soil C and N concentrations and C stocks in SOM, LFOM, and IPOM, peaking at 3000&#xa0;m elevation in the evergreen coniferous forest, indicating maximum sequestration potential. At the 3000&#xa0;m peak, IPOM held the highest C and N proportions, while MOM was lowest, suggesting primary reliance on physical stabilization within aggregates over chemical stabilization to soil C and N pools. Unprotected LFOM-C/N proportions decreased with elevation, indicating enhanced soil C and N stabilization. The deciduous broad-leaved forest (1300&#xa0;m) showed lowest soil C and N stabilization (highest LFOM-C/N proportions), while the alpine shrub meadow (3400&#xa0;m) exhibited highest soil C and N stability (lowest LFOM-C/N proportions, highest MOM-C proportion). The δ<sup>13</sup>C and δ<sup>15</sup>N were most enriched at 3400&#xa0;m elevation in alpine shrub meadow. Depleted δ<sup>15</sup>N in SOM, IPOM, and MOM between 2800–3000&#xa0;m suggests a relatively closed N cycle.</p> Conclusions <p>Elevation-driven variations in climate, vegetation, soil, and microbes govern soil C and N pool dynamics within SOM. This work elucidates elevation-specific mechanisms regulating soil C/N stability and vulnerability in mountain ecosystems, informing predictions of their climate change response.</p>

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Shifts and drivers in soil carbon and nitrogen sequestration and stabilization along a 2100-m altitudinal gradient from temperate forests to alpine shrub meadow

  • 期刊论文

  • 发表日期：

    2025年12月11日

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  • Wen Yang,
  • Rou Pan,
  • Tingting Nong,
  • Yuxuan Zhao,
  • Xiangyu Liu,
  • Huan Zhang,
  • Bin Yan,
  • Shuqing An,
  • Xiaoli Cheng

摘要

Aims

Mountain ecosystems are vital carbon (C) and nitrogen (N) reservoirs, mitigating climate change through substantial soil organic matter (SOM) stocks. However, their vulnerability to climate shifts necessitates understanding altitudinal patterns in the sequestration, stabilization, δ13C and δ15N signatures of C and N within SOM.

Methods

We investigated C/N concentrations, stocks, and δ13C/δ15N signatures in bulk SOM and its physically fractionated components: free light fraction (LFOM), intra-aggregate particulate organic matter (IPOM), and mineral-associated organic matter (MOM) along the altitudinal gradient (1300–3400 m) on Taibai Peak, Qinling Mountains.

Results

Unimodal patterns emerged for soil C and N concentrations and C stocks in SOM, LFOM, and IPOM, peaking at 3000 m elevation in the evergreen coniferous forest, indicating maximum sequestration potential. At the 3000 m peak, IPOM held the highest C and N proportions, while MOM was lowest, suggesting primary reliance on physical stabilization within aggregates over chemical stabilization to soil C and N pools. Unprotected LFOM-C/N proportions decreased with elevation, indicating enhanced soil C and N stabilization. The deciduous broad-leaved forest (1300 m) showed lowest soil C and N stabilization (highest LFOM-C/N proportions), while the alpine shrub meadow (3400 m) exhibited highest soil C and N stability (lowest LFOM-C/N proportions, highest MOM-C proportion). The δ13C and δ15N were most enriched at 3400 m elevation in alpine shrub meadow. Depleted δ15N in SOM, IPOM, and MOM between 2800–3000 m suggests a relatively closed N cycle.

Conclusions

Elevation-driven variations in climate, vegetation, soil, and microbes govern soil C and N pool dynamics within SOM. This work elucidates elevation-specific mechanisms regulating soil C/N stability and vulnerability in mountain ecosystems, informing predictions of their climate change response.