College of Natural Resources, University of Idaho, Moscow, ID, 83844, USA.
Bordeaux Sciences Agro, UMR INRA-ISPA 1391, Gradignan, 33195, France.
Plant Cell Environ. 2018 Mar;41(3):576-588. doi: 10.1111/pce.13121. Epub 2018 Jan 29.
From 2011 to 2013, Texas experienced its worst drought in recorded history. This event provided a unique natural experiment to assess species-specific responses to extreme drought and mortality of four co-occurring woody species: Quercus fusiformis, Diospyros texana, Prosopis glandulosa, and Juniperus ashei. We examined hypothesized mechanisms that could promote these species' diverse mortality patterns using postdrought measurements on surviving trees coupled to retrospective process modelling. The species exhibited a wide range of gas exchange responses, hydraulic strategies, and mortality rates. Multiple proposed indices of mortality mechanisms were inconsistent with the observed mortality patterns across species, including measures of the degree of iso/anisohydry, photosynthesis, carbohydrate depletion, and hydraulic safety margins. Large losses of spring and summer whole-tree conductance (driven by belowground losses of conductance) and shallower rooting depths were associated with species that exhibited greater mortality. Based on this retrospective analysis, we suggest that species more vulnerable to drought were more likely to have succumbed to hydraulic failure belowground.
从 2011 年到 2013 年，德克萨斯州经历了有记录以来最严重的干旱。这一事件为评估四个共存木本物种（包括槲栎、德克萨斯州柿、腺叶朴和蓝刺柏）对极端干旱的物种特异性反应和死亡率提供了一个独特的自然实验。我们使用对幸存树木的后干旱测量结果，并结合回溯过程建模，检验了可能促进这些物种多样化死亡率模式的假设机制。这些物种表现出广泛的气体交换反应、水力策略和死亡率。多种提出的死亡率机制指标与跨物种的观察到的死亡率模式不一致，包括等/异水度、光合作用、碳水化合物枯竭和水力安全裕度的衡量标准。与表现出更高死亡率的物种相比，春季和夏季整树导水率（由地下导水率损失驱动）和根系较浅的大量损失与物种更容易受到干旱的影响有关。基于这种回顾性分析，我们认为更容易受到干旱影响的物种更有可能因地下水力衰竭而屈服。
