Water-stable isotopes provide a valuable tool for tracing plant-water interactions, particularly evapotranspiration (ET) partitioning and leaf water dynamics at the plant-atmosphere interface. However, process-based investigations of plant/leaf development and the associated isotopic dynamics of water fluxes involving isotope enrichment at plant-atmosphere interfaces at the ecosystem scale remain challenging. In this study, in situ isotopic measurements and tracer-aided models were used to study the dynamic interactions between vegetation growth and the isotopic dynamics of water fluxes (ET, soil evaporation, and transpiration) involving isotope enrichment in canopy leaves in a multispecies grassland ecosystem. The day-to-day variations in the isotopic compositions of ET flux were mainly controlled by plant growth, which could be explained by the significant logarithmic relationship determined between the leaf area index and transpiration fraction. Leaf development promoted a significant increase in the isotopic composition of ET and led to a slight decrease in the isotopic composition of water in canopy leaves. The transpiration (evaporation) isoflux acted to increase (decrease) the δ¹⁸O of water vapor, and the total isoflux impacts depended on the seasonal tradeoffs between transpiration and evaporation. The isotopic evidence in ET fluxes demonstrates the biotic controls on day-to-day variations in water/energy flux partitioning through transpiration activity. This study emphasizes that stable isotopes of hydrogen and oxygen are effective tools for quantitative evaluations of the hydrological component partitioning of ecosystems and plant-climate interactions.

水稳定同位素为追踪植物-水相互作用提供了一种有价值的工具，特别是植物-大气界面处的蒸散 (ET) 分配和叶水动力学。然而，基于过程的植物/叶发育研究以及涉及生态系统规模植物-大气界面同位素富集的水通量的相关同位素动力学仍然具有挑战性。在这项研究中，原位同位素测量和示踪辅助模型用于研究植被生长与涉及多物种草原生态系统冠层叶中同位素富集的水通量（ET、土壤蒸发和蒸腾）同位素动力学之间的动态相互作用. ET 通量同位素组成的日常变化主要受植物生长控制，这可以通过叶面积指数和蒸腾分数之间确定的显着对数关系来解释。叶片发育促进了ET同位素组成的显着增加，并导致冠层叶片中水的同位素组成略有下降。蒸腾作用（蒸发）等通量用于增加（减少）δ¹⁸ O 的水蒸气和总等通量影响取决于蒸腾和蒸发之间的季节性权衡。ET 通量中的同位素证据证明了通过蒸腾活动分配的水/能量通量的日常变化的生物控制。本研究强调，氢和氧的稳定同位素是定量评估生态系统水文成分划分和植物-气候相互作用的有效工具。