As global climate change leads to increased spatial and temporal heterogeneity in precipitation patterns, seasonal droughts are becoming more frequent in subtropical monsoon regions. Some conifer species despite having high embolism resistance, still succumb to the effects of climatic drought. Therefore, assessing a plant’s drought resistance based solely on hydraulic traits does not provide a comprehensive picture. Cunninghamia lanceolata (C. lanceolata), a species extensively cultivated in the subtropical monsoon regions due to its rapid growth, drought resistance, and high economic value, plays a dominant role in fast-growing and high-yielding forestry. Investigating the drought response of C. lanceolata is crucial for ensuring sustainable timber production, maintaining ecosystem balance, and enhancing ecological hydrological functions. To this end, from July 2022 to October 2023, we conducted a comparative experiment simulating seasonal drought on 15-year-old C. lanceolata. We assessed the embolism resistance of C. lanceolata by constructing vulnerability curves and analyzed its water use patterns using hydrogen and oxygen isotope compositions. The research findings indicate that in October 2022, the hydraulic safety margin (HSM50) of C. lanceolata increased from 0.99 ± 0.23 MPa to 1.12 ± 0.13 MPa under water input exclusion, suggesting that C. lanceolata can enhance its xylem embolism resistance to counteract short-term drought stress. Despite the ability of C. lanceolata to adjust its root distribution, C. lanceolata primarily relies on shallow soil moisture for survival, with the maximum water uptake from the 0–10 cm soil layer reaching up to 53.0 %±9.0 %. This mismatch between the tree’s water use pattern and soil moisture dynamics exacerbates drought stress during the dry season, leading to irreversible embolism accumulation over prolonged seasonal droughts. During the 2023 dry season, the natural percentage loss of conductivity (NPLC) in C. lanceolata trees from both the drought and control groups significantly increased to 27.45 ± 1.03 % and 19.60 ± 1.05 %, respectively, both higher than in the 2022 dry season (increases of 8.06 ± 3.01 % and 8.58 ± 2.36 %, respectively). Therefore, we believe that HSM can only assess a plant’s short-term resistance to sudden drought but cannot accurately determine its long-term adaptability to repeated extreme drought stress. A comprehensive assessment should be made by considering both the tree’s water use patterns and hydraulic characteristics.

中文翻译：

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杉木 不能 仅依靠木质部栓塞抗性 来承受长期的季节性干旱


随着全球气候变化导致降水模式的时空异质性增加，亚热带季风地区的季节性干旱变得越来越频繁。一些针叶树物种尽管具有很高的抗栓塞性，但仍然屈服于气候干旱的影响。因此，仅根据水力特性评估植物的抗旱性并不能提供全面的情况。杉木 （C. lanceolata） 是一种在亚热带季风地区广泛种植的物种，由于其生长迅速、抗旱性和高经济价值，在快速生长和高产林业中发挥着主导作用。研究杉木的干旱响应对于确保可持续木材生产、维持生态系统平衡和增强生态水文功能至关重要。为此，从 2022 年 7 月到 2023 年 10 月，我们对 15 年生杉木进行了模拟季节性干旱的比较实验。我们通过构建脆弱性曲线评估了杉木的抗栓性，并使用氢和氧同位素组成分析了其水分使用模式。研究结果表明，2022 年 10 月，杉木在水输入排除下的水力安全边际 （HSM50） 从 0.99 ± 0.23 MPa 增加到 1.12 ± 0.13 MPa，表明杉木可以增强其木质部栓塞抵抗力以抵消短期干旱胁迫。尽管杉木能够调整其根系分布，但杉木主要依靠浅层土壤水分生存，0-10 cm 土层的最大吸水率高达 53.0 %±9.0 %。 树木的水分利用模式与土壤水分动态之间的这种不匹配加剧了旱季的干旱胁迫，导致在长期的季节性干旱中不可逆的栓塞积累。在 2023 年旱季，干旱组和对照组杉木的自然电导率损失百分比 （NPLC） 分别显著增加到 27.45 ± 1.03% 和 19.60 ± 1.05 %，均高于 2022 年旱季（分别增加 8.06 ± 3.01% 和 8.58 ± 2.36%）。因此，我们认为 HSM 只能评估植物对突发干旱的短期抵抗力，而不能准确判断其对反复极端干旱胁迫的长期适应性。应通过考虑树木的用水模式和水力特性来进行全面评估。