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<p>Establishing plantations represents an effective nature-based solution for enhancing terrestrial carbon sinks and mitigating climate change; however, plantation productivity and carbon sequestration capacity are generally constrained by soil nitrogen (N) availability. Stand density regulation is an important silvicultural practice for alleviating N limitation and maximizing carbon sequestration potential, yet the mechanisms through which stand density influences soil N availability and transformation rates remain insufficiently elucidated. Here, we aimed to explore these mechanisms by examining key N-cycling microbes and associated substrate availability. To address this aim, we selected 25 plots of 40-year-old <i>Pinus sylvestris</i> var. <i>mongolica</i> stands across a stand density gradient (350–1,500 ind·ha<sup>–1</sup>). In these stands, we measured needle litter characteristics, soil physicochemical properties, soil microbial and ammonia oxidizer communities, and net N mineralization (N<sub>min</sub>) and nitrification rates (N<sub>nitri</sub>). We found that soil N availability decreased with increasing stand density, evidenced by the significantly negative relationships between stand density and soil nitrate concentrations and N<sub>min</sub> and N<sub>nitri</sub>. The decline in N<sub>min</sub> was related to reduced β-<i>N</i>-acetylglucosaminidase activities with increasing stand density. Similarly, the decrease in N<sub>nitri</sub> was associated with the negative effect of stand density on <i>amoA</i> gene abundance of ammonia-oxidizing bacteria. Collectively, these results suggest that stand density regulates soil N availability and transformation rates by mediating relevant microbial drivers and underscore the importance of stand density management in alleviating N limitation and enhancing plantation ecological functions.</p>

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Microbial regulation of soil nitrogen dynamics along a stand density gradient of Mongolian pine plantations

  • 期刊论文

  • 发表日期：

    2026年7月14日

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  • Yansong Zhang,
  • Yi Wang,
  • Dehui Zeng,
  • Qingwei Wang,
  • Dapao Yu,
  • Guigang Lin

摘要

Establishing plantations represents an effective nature-based solution for enhancing terrestrial carbon sinks and mitigating climate change; however, plantation productivity and carbon sequestration capacity are generally constrained by soil nitrogen (N) availability. Stand density regulation is an important silvicultural practice for alleviating N limitation and maximizing carbon sequestration potential, yet the mechanisms through which stand density influences soil N availability and transformation rates remain insufficiently elucidated. Here, we aimed to explore these mechanisms by examining key N-cycling microbes and associated substrate availability. To address this aim, we selected 25 plots of 40-year-old Pinus sylvestris var. mongolica stands across a stand density gradient (350–1,500 ind·ha–1). In these stands, we measured needle litter characteristics, soil physicochemical properties, soil microbial and ammonia oxidizer communities, and net N mineralization (Nmin) and nitrification rates (Nnitri). We found that soil N availability decreased with increasing stand density, evidenced by the significantly negative relationships between stand density and soil nitrate concentrations and Nmin and Nnitri. The decline in Nmin was related to reduced β-N-acetylglucosaminidase activities with increasing stand density. Similarly, the decrease in Nnitri was associated with the negative effect of stand density on amoA gene abundance of ammonia-oxidizing bacteria. Collectively, these results suggest that stand density regulates soil N availability and transformation rates by mediating relevant microbial drivers and underscore the importance of stand density management in alleviating N limitation and enhancing plantation ecological functions.