Recent studies have highlighted the importance of understanding ecohydrological drought feedbacks to secure water resources under a changing climate and increasing anthropogenic impacts. In this study, we monitored and modelled feedbacks in the soil–plant-atmosphere continuum to the European drought summer 2018 and the following 2 years. The physically based, isotope-aided model EcH₂O-iso was applied to generic vegetation plots (forest and grassland) in the lowland, groundwater-dominated research catchment Demnitzer Millcreek (NE Germany; 66 km²). We included, inter alia, soil water isotope data in the model calibration and quantified changing “blue” (groundwater recharge) and “green” (evapotranspiration) water fluxes and ages under each land use as the drought progressed. Novel plant xylem isotope data were excluded from calibration but were compared with simulated root uptake signatures in model validation. Results indicated inter-site differences in the dynamics of soil water storage and fluxes with contrasting water age both during the drought and the subsequent 2 years. Forest vegetation consistently showed a greater moisture stress, more rapid recovery and higher variability in root water uptake depths from a generally younger soil water storage. In contrast, the grassland site, which had more water-retentive soils, showed higher and older soil water storage and groundwater recharge fluxes. The damped storage and flux dynamics under grassland led to a slower return to younger water ages at depth. Such evidence-based and quantitative differences in ecohydrological feedbacks to drought stress in contrasting soil-vegetation units provide important insights into Critical Zone water cycling. This can help inform future progress in the monitoring, modelling and development of climate mitigation strategies in drought-sensitive lowlands.

中文翻译：

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2018-2020年中欧长期干旱异常下森林和草地生态水文反馈建模

最近的研究强调了了解生态水文干旱反馈对于在气候变化和人为影响不断增加的情况下确保水资源的重要性。在这项研究中，我们监测并模拟了土壤-植物-大气连续体对 2018 年欧洲干旱夏季和随后两年的反馈。基于物理的同位素辅助模型 EcH ₂ O-iso 应用于低地、地下水占主导地位的研究集水区 Demnitzer Millcreek（德国东北部；66 公里²）。我们在模型校准中包括了土壤水同位素数据等，并量化了随着干旱的进展，每种土地利用下“蓝色”（地下水补给）和“绿色”（蒸发蒸腾）水通量和年龄的变化。新的植物木质部同位素数据被排除在校准之外，但在模型验证中与模拟的根吸收特征进行了比较。结果表明，在干旱期间和随后的 2 年中，土壤储水和通量的动态变化与不同的水龄存在差异。森林植被始终表现出更大的水分胁迫，更快速的恢复和根系吸水深度的更大变异性，来自通常较年轻的土壤储水量。相比之下，具有更多保水土壤的草地，显示出更高和更老的土壤储水量和地下水补给通量。草地下的阻尼存储和通量动态导致较慢的深度返回到较年轻的水年龄。在对比土壤-植被单元中，对干旱胁迫的生态水文反馈的这种基于证据的和定量的差异为关键区水循环提供了重要的见解。这有助于为干旱敏感低地气候减缓战略的监测、建模和制定方面的未来进展提供信息。