• Root water uptake is a key ecohydrological process for which a physically based understanding has been developed in the past decades. However, due to methodological constraints, knowledge gaps remain about the plastic response of whole plant root systems to a rapidly changing environment.
• We designed a laboratory system for nondestructive monitoring of stable isotopic composition in plant transpiration of a herbaceous species (Centaurea jacea) and of soil water across depths, taking advantage of newly developed in situ methods. Daily root water uptake profiles were obtained using a statistical Bayesian multisource mixing model.
• Fast shifts in the isotopic composition of both soil and transpiration water could be observed with the setup and translated into dynamic and pronounced shifts of the root water uptake profile, even in well watered conditions.
• The incorporation of plant physiological and soil physical information into statistical modelling improved the model output. A simple exercise of water balance closure underlined the nonunique relationship between root water uptake profile on the one hand, and water content and root distribution profiles on the other, illustrating the continuous adaption of the plant water uptake as a function of its root hydraulic architecture and soil water availability during the experiment.

中文翻译：

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通过同位素分析调查矢车菊对土壤水分有效性的根系可塑性响应

• 根系吸水是关键的生态水文过程，在过去的几十年中，人们已经从根源上获得了基于物理的理解。但是，由于方法上的限制，关于整个植物根系对快速变化的环境的塑性响应的知识差距仍然存在。
• 我们利用新开发的原位方法，设计了一个实验室系统，用于对草本物种（Centaurea jacea）和土壤水的植物蒸腾过程中的稳定同位素组成进行无损监测。使用统计贝叶斯多源混合模型获得每日根系吸水曲线。
• 通过设置可以观察到土壤和蒸腾水的同位素组成快速变化，即使在灌溉条件良好的条件下，也能转化为根系吸水特征的动态变化和明显变化。
• 将植物生理和土壤物理信息纳入统计模型可改善模型输出。一项简单的水平衡闭合练习强调了一方面根系吸水状况与另一方面的水含量和根系分布状况之间的非唯一关系，说明了植物吸水作为根系水力结构和功能的持续适应性。实验过程中的土壤水分利用率。