Recent European heatwaves have significantly impacted forest ecosystems, leading to increased plant water stress. Advances in land surface models aim to improve the representation of vegetation drought responses by incorporating plant hydraulics into the plant functional type (PFT) classification system. However, reliance on PFTs may inadequately capture the diverse plant hydraulic traits (PHTs), potentially biasing transpiration and vegetation water stress representations. The detection of vegetation drought stress is further complicated by the mixing of different tree species and forest patches. This study uses the Community Land Model version 5.0 to simulate an experimental mixed-forest catchment with configurations representing standalone, patched mixed, and fully-mixed forests. Biome-generic, PFT-specific, or species-specific PHTs are employed. Results emphasize the crucial role of accurately representing mixed forests in reproducing observed vegetation water stress and transpiration fluxes for both broadleaf and needleleaf tree species. The dominant vegetation fraction is a key determinant, influencing aggregated vegetation response patterns. Segregation level in PHT parameterizations shapes differences between observed and simulated transpiration fluxes. Simulated root water potential emerges as a potential metric for detecting vegetation stress periods. However, the model's plant hydraulic system has limitations in reproducing the long-term effects of extreme weather events on needleleaf tree species. These findings highlight the complexity of modeling mixed forests and underscore the need for improved representation of plant diversity in land surface models to enhance the understanding of vegetation water stress under changing climate conditions.

中文翻译：

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通过联合使用树水监测和地表建模来检测混合森林生态系统中的植被压力


最近的欧洲热浪严重影响了森林生态系统，导致植物水分压力增加。地表模型的进展旨在通过将植物水力学纳入植物功能类型（PFT）分类系统来改善植被干旱反应的表征。然而，对 PFT 的依赖可能不足以捕获不同的植物水力特征 (PHT)，从而可能使蒸腾作用和植被水分胁迫表征产生偏差。由于不同树种和森林斑块的混合，植被干旱胁迫的检测变得更加复杂。本研究使用社区土地模型 5.0 版来模拟实验性混合林流域，其配置代表独立、斑块混合和完全混合森林。采用生物群系通用、PFT 特异性或物种特异性 PHT。结果强调了准确表示混交林在再现阔叶树种和针叶树种观测到的植被水分胁迫和蒸腾通量方面的关键作用。占主导地位的植被比例是影响总体植被响应模式的关键决定因素。 PHT 参数化中的分离水平决定了观察到的蒸腾通量与模拟的蒸腾通量之间的差异。模拟根水势成为检测植被胁迫期的潜在指标。然而，该模型的植物液压系统在再现极端天气事件对针叶树种的长期影响方面存在局限性。这些发现凸显了混合林建模的复杂性，并强调需要改进地表模型中植物多样性的表示，以增强对气候条件变化下植被水分胁迫的理解。