• A classic theory proposes that plant xylem cannot be both highly efficient in water transport and resistant to embolism, and therefore a hydraulic efficiency–safety trade‐off should exist. However, the trade‐off is weak, and many species exhibit both low efficiency and low safety, falling outside of the expected trade‐off space. It remains unclear under what climatic conditions these species could maintain competitive fitness.
• We compiled hydraulic efficiency and safety traits for 682 observations of 499 woody species from 178 sites world‐wide and measured the position of each observation within the proposed trade‐off space.
• For both angiosperms and gymnosperms, observations from sites with high climatic seasonality, especially precipitation seasonality, tended to have higher hydraulic safety and efficiency than observations from sites with low seasonality. Specifically, high vapour pressure deficit, high solar radiation, and low precipitation during the wet season were driving factors.
• Strong climatic seasonality and drought in both dry and wet seasons appear to be ecological filters that select for species with co‐optimized safety and efficiency, whereas the opposite environmental conditions may allow the existence of plants with low efficiency and safety.

中文翻译：

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木质部水力效率和安全性之间的权衡取舍：气候季节性至关重要

• 一个经典的理论提出，植物木质部既不能在水运输方面高效，又不能抗栓塞，因此应该在水力效率与安全性之间进行权衡。但是，权衡取舍很弱，许多物种都表现出低效率和低安全性，落在了预期的取舍空间之外。尚不清楚这些物种在什么气候条件下可以保持竞争适应性。
• 我们汇总了来自全球178个站点的499种木本植物的682个观测值的水力效率和安全性状，并测量了每个观测值在建议的折衷空间内的位置。
• 对于被子植物和裸子植物，从气候季节特别是降水季节的地点观察到的水力安全性和效率比季节低地点的水力安全性和效率更高。特别地，在湿季高蒸气压亏空，高太阳辐射和低降水是驱动因素。
• 干旱和潮湿季节的强烈气候季节变化和干旱似乎是选择具有共同优化的安全性和效率的物种的生态过滤器，而相反的环境条件可能允许存在效率和安全性低的植物。