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Key message <p>Increasing crown transparency shortens phloem production in co-occurring <i>Pinus sylvestris</i> L.&#xa0;and <i>Juniperus communis</i> L.&#xa0;and shifts carbon allocation from growth to defense metabolism in <i>Pinus sylvestris</i>&#xa0;L..</p> Context <p>Climate warming intensifies drought stress in temperate forests, altering carbon allocation and tree vitality. Crown transparency (CT) is a widely used indicator of canopy decline, but its relationship with secondary phloem development and metabolism remains unclear.</p> Aims <p>We examined how CT influences intra-annual phloem phenology in <i>Pinus sylvestris</i> L.&#xa0;and <i>Juniperus communis&#xa0;</i>L., and metabolomic profiles in <i>P. sylvestris</i>, at a drought-prone submontane site (Tyrol, Austria), testing whether increasing CT alters phloem phenology and metabolomic profiles.</p> Methods <p>We combined microcore sampling, Gompertz modeling, and untargeted GC–MS metabolomics across CT classes, linking anatomical development with biochemical composition.</p> Results <p>Phloem onset was CT-independent in <i>P. sylvestris</i> but delayed in <i>J. communis</i> with higher CT. Increasing CT shortened phloem formation and reduced cell production in both species. In <i>P. sylvestris</i>, xylem-to-phloem ratios decreased with CT. Low-CT trees showed higher hexoses, arabinose, and redox-active metabolites, whereas high-CT trees accumulated phenolics and showed reduced metabolic flexibility, indicating a shift toward stress-related metabolism.</p> Conclusion <p>CT links structural and metabolic stem responses and coordinates phloem phenology with carbon allocation strategies.</p>

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Effects of crown transparency on phloem formation and metabolomic profiles in Pinus sylvestris L. co-occurring with Juniperus communis L. at a drought-prone site

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月30日

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  • Marion Fink,
  • Moritz Stegner,
  • Stefan Mayr,
  • Walter Oberhuber

摘要

Key message

Increasing crown transparency shortens phloem production in co-occurring Pinus sylvestris L. and Juniperus communis L. and shifts carbon allocation from growth to defense metabolism in Pinus sylvestris L..

Context

Climate warming intensifies drought stress in temperate forests, altering carbon allocation and tree vitality. Crown transparency (CT) is a widely used indicator of canopy decline, but its relationship with secondary phloem development and metabolism remains unclear.

Aims

We examined how CT influences intra-annual phloem phenology in Pinus sylvestris L. and Juniperus communis L., and metabolomic profiles in P. sylvestris, at a drought-prone submontane site (Tyrol, Austria), testing whether increasing CT alters phloem phenology and metabolomic profiles.

Methods

We combined microcore sampling, Gompertz modeling, and untargeted GC–MS metabolomics across CT classes, linking anatomical development with biochemical composition.

Results

Phloem onset was CT-independent in P. sylvestris but delayed in J. communis with higher CT. Increasing CT shortened phloem formation and reduced cell production in both species. In P. sylvestris, xylem-to-phloem ratios decreased with CT. Low-CT trees showed higher hexoses, arabinose, and redox-active metabolites, whereas high-CT trees accumulated phenolics and showed reduced metabolic flexibility, indicating a shift toward stress-related metabolism.

Conclusion

CT links structural and metabolic stem responses and coordinates phloem phenology with carbon allocation strategies.