Understanding the movement of water in terrestrial ecosystems and determining the soil depths from which mature trees take up water has become an important research priority. Here, we test the suitability of a dynamic ²H pulse-labelling experiment for assessing (1) the fate of a simulated precipitation event as it moves through the ecohydrological system and (2) the water uptake depths of different tree species in a mature temperate forest. We applied ²H-labelled water as a single pulse to the top soil using a sprinkler system and then allowed it to infiltrate into deeper soil layers by washing it through the soil column with a sequence of non-²H-labelled irrigation pulses. We then followed this ²H-enriched irrigation pulse over a period of 81 days in different depths of the soil and in the xylem of four tree species (Fagus sylvatica, Quercus petraea, Picea abies and Pinus sylvestris). Our experiment shows infiltration and mixing of the irrigation pulse in the soil occurs within a few days. Furthermore, we found that tree species differed significantly in their use of shallow (−10- to −30-cm soil depth) and deep (−80-cm soil depth) soil water. We also found immediate uptake of infiltrating mobile soil water by trees, which questions the recently established two-water-worlds hypothesis. Our study demonstrated that a dynamic ²H-labelled irrigation pulse is a useful approach to (1) assess how water from a precipitation event infiltrates into a forest ecosystem and (2) assess the water uptake depths of different temperate tree species.

中文翻译：

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动态 2H 灌溉脉冲标记揭示了土壤中降水的快速渗透和混合以及温带森林中树木特定物种的吸水深度

了解陆地生态系统中水的运动并确定成熟树木吸水的土壤深度已成为重要的研究重点。在这里，我们测试了动态² H 脉冲标记实验的适用性，以评估（1）模拟降水事件在生态水文系统中移动时的命运和（2）成熟温带中不同树种的吸水深度森林。我们使用喷水灭火系统将² H 标记的水作为单个脉冲施加到表层土壤中，然后通过使用一系列非² H 标记的灌溉脉冲将其冲洗穿过土柱，使其渗入更深的土壤层。然后我们按照这个²81 天期间，在不同深度的土壤和四种树种（山毛榉、栎属、云杉和樟子松）的木质部中的富氢灌溉脉冲。我们的实验表明，灌溉脉冲在土壤中的渗透和混合会在几天内发生。此外，我们发现树种在使用浅层（-10 至-30 厘米土壤深度）和深层（-80 厘米土壤深度）土壤水方面存在显着差异。我们还发现树木会立即吸收渗透的流动土壤水，这对最近建立的两个水世界假说提出了质疑。我们的研究表明，动态²H 标记的灌溉脉冲是一种有用的方法，可以 (1) 评估降水事件中的水如何渗入森林生态系统，以及 (2) 评估不同温带树种的吸水深度。