Hydraulic failure explains much of the increased rates of drought-induced tree mortality around the world, underlining the importance of understanding how species distributions are shaped by their vulnerability to embolism. Here we determined which physiological traits explain species climatic limits among temperate rainforest trees in a region where chronic water limitation is uncommon. We quantified the variation in stem embolism vulnerability and leaf turgor loss point among 55 temperate rainforest tree species in New Zealand and tested which traits were most strongly related to species climatic limits. Leaf turgor loss point and stem P50 (tension at which hydraulic conductance is at 50% of maximum) were uncorrelated. Stem P50 and hydraulic safety margin were the most strongly related physiological traits to climatic limits among angiosperms, but not among conifers. Morphological traits such as wood density and leaf dry matter content did not explain species climatic limits. Stem embolism resistance and leaf turgor loss point appear to have evolved independently. Embolism resistance is the most useful predictor of the climatic limits of angiosperm trees. High embolism resistance in the curiously overbuilt New Zealand conifers suggests that their xylem properties may be more closely related to growing slowly under nutrient limitation and to resistance to microbial decomposition.

中文翻译：

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温带雨林树种的气候极限可以通过被子植物中的木质部栓塞抗性来解释，而不能通过针叶树来解释。

水力衰竭解释了世界上因干旱引起的树木死亡率上升的原因，这突出了理解物种分布如何因其易受栓塞影响而形成的重要性。在这里，我们确定了哪些生理特性解释了在长期缺水不常见的地区的温带雨林树木中物种的气候限制。我们量化了新西兰55种温带雨林树种中茎栓塞脆弱性和叶片膨大损失点的变化，并测试了哪些性状与物种气候极限最相关。叶片膨大损失点与茎P50（水力导流在最大导流率的50％时的张力）不相关。在被子植物中，茎P50和水力安全系数是与气候极限关系最密切的生理特征，但不在针叶树中。木材密度和叶片干物质含量等形态特征无法解释物种的气候极限。茎抗栓塞性和叶片膨大损失点似乎是独立发生的。抗栓塞性是被子植物树气候极限的最有用的预测指标。在奇特地过建的新西兰针叶树中，较高的抗栓塞性表明它们的木质部性质可能与在养分限制下缓慢生长以及对微生物分解的抵抗力密切相关。抗栓塞性是被子植物树气候极限的最有用的预测指标。奇特的新西兰针叶树具有较高的抗栓塞性，这表明它们的木质部性质可能与在营养限制下缓慢生长以及对微生物分解的抵抗力密切相关。抗栓塞性是被子植物树气候极限的最有用的预测指标。奇特的新西兰针叶树具有较高的抗栓塞性，这表明它们的木质部性质可能与在营养限制下缓慢生长以及对微生物分解的抵抗力密切相关。