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<p><UnorderedList Mark="Bullet"> <ItemContent> <p>Gross N<sub>2</sub>O emission and N<sub>2</sub>O uptake were simultaneously quantified using <sup>15</sup>N<sub>2</sub>O pool dilution.</p> </ItemContent> <ItemContent> <p>N<sub>2</sub>O uptake varies by land use: forest &gt; grassland &gt; vegetable &gt; orchard &gt; upland.</p> </ItemContent> <ItemContent> <p>N<sub>2</sub>O uptake can be of the same order of magnitude as gross emission and net emissions.</p> </ItemContent> <ItemContent> <p>High SOC and <i>nosZ</i> clade II abundance jointly promoted soil N<sub>2</sub>O uptake.</p> </ItemContent> </UnorderedList></p><p>Empirical data on soil nitrous oxide (N<sub>2</sub>O) uptake and gross N<sub>2</sub>O emission remain scarce compared to net emission measurements, limiting mechanistic understanding of how land use regulates N<sub>2</sub>O source-sink dynamics. Using <sup>15</sup>N<sub>2</sub>O pool dilution technology, we quantified gross N<sub>2</sub>O emission across five contrasting land uses (upland, vegetable, orchard, grassland, and forest) in the black soil region of northeast China to explore biotic and abiotic drivers of N<sub>2</sub>O uptake. Forest and agricultural soils exhibited divergent N<sub>2</sub>O uptake: forest soils showed the highest cumulative uptake (17.65 µg N kg<sup>−1</sup> soil), associated with sandy texture (55.07%), high soil organic carbon (SOC; 29.33 g kg<sup>−1</sup>), and abundant <i>nosZ</i> clade II denitrifiers (4.23×10<sup>8</sup> copies g<sup>−1</sup> dry soil). In contrast, long-term cultivated upland soils displayed minimal uptake (8.19 µg N kg<sup>−1</sup> soil), coinciding with clay-rich texture (25.10%), depleted SOC (8.54 g kg<sup>−1</sup>), and reduced <i>nosZ</i> clade II abundance (0.27×10<sup>8</sup> copies g<sup>−1</sup> dry soil). Piecewise structural equation modeling (piecewise SEM) illustrated that the abundance of <i>nosZ</i> clade I and II genes were positively correlated with SOC, with a standardized path coefficient of <i>β</i> = 0.71 (<i>p</i> &lt; 0.001). Both sand content (<i>β</i> = 0.42, <i>p</i> &lt; 0.05) and <i>nosZ</i> gene abundance (<i>β</i> = 0.36, <i>p</i> &lt; 0.05) had positive direct effects on N<sub>2</sub>O uptake. Notably, <i>nosZ</i> clade II abundance was 15-fold higher in forest than upland soils and strongly correlated with SOC (<i>R</i><sup>2</sup> = 0.68, <i>p</i>&lt;0.05), suggesting this non-denitrifying functional group is associated with N<sub>2</sub>O reduction in high-carbon ecosystems. Our results suggest that contrasting land uses mediate divergent N<sub>2</sub>O uptake by altering <i>nosZ</i> clade II communities and carbon availability. Specifically, agricultural intensification coincides with SOC depletion and reduced <i>nosZ</i> clade II, potentially weakening N<sub>2</sub>O sink function. In contrast, forest preservation maintains high uptake potential. Mitigation strategies could center on restoring SOC and reducing tillage in agricultural soils to boost <i>nosZ</i> clade II-mediated N<sub>2</sub>O uptake, and protecting forest ecosystems to maintain their high N<sub>2</sub>O sink capacity.</p>

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Contrasting land uses mediate divergent N2O uptake through nosZ clade II and carbon availability: Evidence from 15N2O pool dilution in black soils

  • 期刊论文

  • 发表日期：

    2026年7月18日

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  • Hongshan Liu,
  • Xiangzhou Zheng,
  • Baobao Pan,
  • Hong Ding,
  • Yuefen Li,
  • Yushu Zhang

摘要

Gross N2O emission and N2O uptake were simultaneously quantified using 15N2O pool dilution.

N2O uptake varies by land use: forest > grassland > vegetable > orchard > upland.

N2O uptake can be of the same order of magnitude as gross emission and net emissions.

High SOC and nosZ clade II abundance jointly promoted soil N2O uptake.

Empirical data on soil nitrous oxide (N2O) uptake and gross N2O emission remain scarce compared to net emission measurements, limiting mechanistic understanding of how land use regulates N2O source-sink dynamics. Using 15N2O pool dilution technology, we quantified gross N2O emission across five contrasting land uses (upland, vegetable, orchard, grassland, and forest) in the black soil region of northeast China to explore biotic and abiotic drivers of N2O uptake. Forest and agricultural soils exhibited divergent N2O uptake: forest soils showed the highest cumulative uptake (17.65 µg N kg−1 soil), associated with sandy texture (55.07%), high soil organic carbon (SOC; 29.33 g kg−1), and abundant nosZ clade II denitrifiers (4.23×108 copies g−1 dry soil). In contrast, long-term cultivated upland soils displayed minimal uptake (8.19 µg N kg−1 soil), coinciding with clay-rich texture (25.10%), depleted SOC (8.54 g kg−1), and reduced nosZ clade II abundance (0.27×108 copies g−1 dry soil). Piecewise structural equation modeling (piecewise SEM) illustrated that the abundance of nosZ clade I and II genes were positively correlated with SOC, with a standardized path coefficient of β = 0.71 (p < 0.001). Both sand content (β = 0.42, p < 0.05) and nosZ gene abundance (β = 0.36, p < 0.05) had positive direct effects on N2O uptake. Notably, nosZ clade II abundance was 15-fold higher in forest than upland soils and strongly correlated with SOC (R2 = 0.68, p<0.05), suggesting this non-denitrifying functional group is associated with N2O reduction in high-carbon ecosystems. Our results suggest that contrasting land uses mediate divergent N2O uptake by altering nosZ clade II communities and carbon availability. Specifically, agricultural intensification coincides with SOC depletion and reduced nosZ clade II, potentially weakening N2O sink function. In contrast, forest preservation maintains high uptake potential. Mitigation strategies could center on restoring SOC and reducing tillage in agricultural soils to boost nosZ clade II-mediated N2O uptake, and protecting forest ecosystems to maintain their high N2O sink capacity.