Abstract Understanding flow and transport processes in the critical zone relies heavily on characterising the interactions between evaporation and vegetation uptake of soil water; however, the magnitude, sources, and ages of these water fluxes are rarely well-constrained. We adapted the StorAge Selection (SAS) function framework to estimate the residence time of stored water, and transit times of eco-hydrologic fluxes, at multiple soil depths in typical soil-vegetation units in the humid, energy-limited Scottish Highlands. Modelling water and stable isotope fluxes within the soil-vegetation units indicated that rapid movement of young water through the soils occurred at both sites, creating relatively stable water residence times in the soils with depth and time. Estimation of the evaporation profile had limited temporal variability with a high preference for near-surface water (0 – 5 cm soil depth, long-term mean age: 50 – 65 days) due to relatively frequent precipitation. Root uptake profiles revealed higher temporal variability, favouring deeper water (5 – 15 cm) during drier periods and near-surface (0 – 5 cm) during wet periods (long-term mean age: 6 – 15 days older than evaporation). The model structure provides a tool to help constrain water storage–flux–age interactions in the upper part of the critical zone and understand how soil–vegetation systems influence groundwater recharge and catchment-scale hydrology.

中文翻译：

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使用存储选择功能评估土壤水、蒸发和蒸腾的混合模式和水龄

摘要 了解临界区的流动和运输过程在很大程度上依赖于表征土壤水分蒸发和植被吸收之间的相互作用；然而，这些水通量的大小、来源和年龄很少受到很好的限制。我们调整了存储选择 (SAS) 函数框架，以估计在潮湿、能源有限的苏格兰高地典型土壤植被单元的多个土壤深度下储存水的停留时间和生态水文通量的传输时间。对土壤-植被单元内的水和稳定同位素通量进行建模表明，年轻水在两个地点都发生在土壤中的快速运动，从而在土壤中随着深度和时间的推移创造了相对稳定的水停留时间。由于相对频繁的降水，蒸发剖面的估计具有有限的时间可变性，对近地表水（0-5 厘米土壤深度，长期平均年龄：50-65 天）的高度偏好。根系吸收剖面显示更高的时间变异性，在干燥时期有利于更深的水（5-15 厘米），在潮湿时期有利于近地表（0-5 厘米）（长期平均年龄：比蒸发早 6-15 天）。模型结构提供了一种工具，有助于限制临界区上部的蓄水-通量-年龄相互作用，并了解土壤-植被系统如何影响地下水补给和集水区规模的水文。在干燥期有利于更深的水 (5 – 15 cm) 和在潮湿期的近地表 (0 – 5 cm)（长期平均年龄：比蒸发早 6 – 15 天）。模型结构提供了一种工具，有助于限制临界区上部的蓄水-通量-年龄相互作用，并了解土壤-植被系统如何影响地下水补给和集水区规模的水文。在干燥期有利于更深的水 (5 – 15 cm) 和在潮湿期的近地表 (0 – 5 cm)（长期平均年龄：比蒸发早 6 – 15 天）。模型结构提供了一种工具，有助于限制临界区上部的蓄水-通量-年龄相互作用，并了解土壤-植被系统如何影响地下水补给和集水区规模的水文。