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Background and aims <p>Replanting broadleaved saplings under pine trees is an effective measure to optimize the forest structure, and it is important to assess the interspecific interaction between replanted saplings and understory vegetation in the early stage.</p> Methods <p>We measured the interspecific relationship and nitrogen uptake of supplementary broadleaved saplings (<i>Michelia maudiae</i>, <i>Schima superba</i>, and <i>Liquidambar formosana</i>) and an understory shrub (<i>Loropetalum chinense</i>) under a <i>Pinus elliottii</i> plantation. This was accomplished by setting up double- and single-root bag experiments with a <sup>15</sup>N isotope labelling method.</p> Results <p>The three supplementary broadleaved species and an understory shrub (<i>L. chinense</i>) showed a preference for ammonium nitrogen over nitrate nitrogen. The effects of interspecific interactions on root mycorrhizal colonization rates and root branching were not significant, but there were obvious effects on specific root length, root biomass, and nitrogen uptake rate. When the replanted broadleaved trees mixed with <i>L. chinense</i>, the growth of their roots was inhibited, while that of the <i>L. chinense</i> was promoted. However, when <i>L. chinense</i> roots were mixed with <i>M. maudiae</i> or <i>L. formosana</i> roots, their inorganic nitrogen uptake rate decreased compared with when grown alone. The interactions of <i>L. chinense</i> × <i>M. maudiae</i> and <i>L. chinense</i> × <i>L. formosana</i> exhibited interspecific competition in root uptake of inorganic nitrogen, while <i>L. chinense</i> × <i>S. superba</i> exhibited a neutral interaction. <i>S. superba</i> adopted a strategy of constant root biomass with a slightly increased nitrogen uptake rate in response to interaction, and <i>L. chinense</i> exhibited higher root biomass and enhanced morphological traits (i.e., higher specific root length).</p> Conclusion <p>The nitrogen uptake amount of <i>L. chinense</i> was higher when coexisting with <i>S. superba</i>, compared with that of <i>M. maudiae</i> and <i>L. formosana</i>. This indicates that <i>S. superba</i> is more suitable than <i>M. maudiae</i> and <i>L. formosana</i> to be underplanted as a supplementary species to optimize the structure of pure pine forest.</p>

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Uptake of inorganic nitrogen between understory shrubs and replanted broadleaved trees in a subtropical plantation

  • 期刊论文

  • 发表日期：

    2025年8月19日

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  • Qianyuan Liu,
  • Liang Kou,
  • Shengwang Meng,
  • Fengting Yang,
  • Xiaoli Fu,
  • Huimin Wang

摘要

Background and aims

Replanting broadleaved saplings under pine trees is an effective measure to optimize the forest structure, and it is important to assess the interspecific interaction between replanted saplings and understory vegetation in the early stage.

Methods

We measured the interspecific relationship and nitrogen uptake of supplementary broadleaved saplings (Michelia maudiae, Schima superba, and Liquidambar formosana) and an understory shrub (Loropetalum chinense) under a Pinus elliottii plantation. This was accomplished by setting up double- and single-root bag experiments with a 15N isotope labelling method.

Results

The three supplementary broadleaved species and an understory shrub (L. chinense) showed a preference for ammonium nitrogen over nitrate nitrogen. The effects of interspecific interactions on root mycorrhizal colonization rates and root branching were not significant, but there were obvious effects on specific root length, root biomass, and nitrogen uptake rate. When the replanted broadleaved trees mixed with L. chinense, the growth of their roots was inhibited, while that of the L. chinense was promoted. However, when L. chinense roots were mixed with M. maudiae or L. formosana roots, their inorganic nitrogen uptake rate decreased compared with when grown alone. The interactions of L. chinense × M. maudiae and L. chinense × L. formosana exhibited interspecific competition in root uptake of inorganic nitrogen, while L. chinense × S. superba exhibited a neutral interaction. S. superba adopted a strategy of constant root biomass with a slightly increased nitrogen uptake rate in response to interaction, and L. chinense exhibited higher root biomass and enhanced morphological traits (i.e., higher specific root length).

Conclusion

The nitrogen uptake amount of L. chinense was higher when coexisting with S. superba, compared with that of M. maudiae and L. formosana. This indicates that S. superba is more suitable than M. maudiae and L. formosana to be underplanted as a supplementary species to optimize the structure of pure pine forest.