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<p>Following extensive drought-induced tree mortality, robust regeneration material is essential to withstand the initial establishment shock and restore affected areas. Bare and exposed sites are especially vulnerable, making the identification of effective mitigation measures particularly important. We analyzed stem xylem responses of sessile oak (ring-porous) and Norway spruce (conifer) subjected to two treatments intended to enhance survival under limited water availability. Hydrogel in the substrate (H) and a 50&#xa0;% crown reduction (CR) were applied to saplings exposed to contrasting water regimes during a two-year experiment. Under drought, oak showed strong anatomical acclimation: despite reduced growth, conductivity-related traits, including vessel diameter (D<sub>H</sub>) and total vessel lumen area (TVLA), increased, while functional xylem area (F<sub>X</sub>) remained unchanged. Spruce responded more conservatively, mainly preserving F<sub>X</sub>. CR induced pronounced anatomical changes in oak, reducing vessel dimensions by up to 40&#xa0;% and shifting xylem towards a hydraulically safer configuration, whereas H had negligible effects. In spruce, neither CR nor H produced consistent anatomical adjustments, and F<sub>X</sub> was influenced mainly by water availability. Therefore, only CR had a clear effect in oak, resulting in safer xylem resembling that of well-watered plants. Because CR does not alleviate drought-induced growth reduction, potential trade-offs with competitive ability must be considered. These findings highlight species-specific acclimation patterns and suggest that CR may help mitigate drought stress in oak, though its effectiveness and the role of reduction intensity require further testing. Future studies should also assess the potential for long-lasting benefits of early CR and H application, including potential belowground responses.</p>

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Crown reduction mitigates drought effects on xylem anatomy and function in sessile oak and Norway spruce

  • 期刊论文

  • 发表日期：

    2026年3月19日

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  • Sergei Mikhailov,
  • Janko Arsić,
  • Marko Stojanović,
  • Roman Plichta,
  • Petr Horáček

摘要

Following extensive drought-induced tree mortality, robust regeneration material is essential to withstand the initial establishment shock and restore affected areas. Bare and exposed sites are especially vulnerable, making the identification of effective mitigation measures particularly important. We analyzed stem xylem responses of sessile oak (ring-porous) and Norway spruce (conifer) subjected to two treatments intended to enhance survival under limited water availability. Hydrogel in the substrate (H) and a 50 % crown reduction (CR) were applied to saplings exposed to contrasting water regimes during a two-year experiment. Under drought, oak showed strong anatomical acclimation: despite reduced growth, conductivity-related traits, including vessel diameter (DH) and total vessel lumen area (TVLA), increased, while functional xylem area (FX) remained unchanged. Spruce responded more conservatively, mainly preserving FX. CR induced pronounced anatomical changes in oak, reducing vessel dimensions by up to 40 % and shifting xylem towards a hydraulically safer configuration, whereas H had negligible effects. In spruce, neither CR nor H produced consistent anatomical adjustments, and FX was influenced mainly by water availability. Therefore, only CR had a clear effect in oak, resulting in safer xylem resembling that of well-watered plants. Because CR does not alleviate drought-induced growth reduction, potential trade-offs with competitive ability must be considered. These findings highlight species-specific acclimation patterns and suggest that CR may help mitigate drought stress in oak, though its effectiveness and the role of reduction intensity require further testing. Future studies should also assess the potential for long-lasting benefits of early CR and H application, including potential belowground responses.