Tracing and Closing the Water Balance in a Vegetated Lysimeter
Tracing and Closing the Water Balance in a Vegetated Lysimeter
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DOI：
10.1029/2020wr029049
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发表时间：
2021-04-01
影响因子：
5.4
通讯作者：
Rinaldo, Andrea
中科院分区：
文献类型：
--
作者：
Benettin, Paolo;Nehemy, Magali F.;Rinaldo, Andrea
土壤水分平衡的关闭是生态水文学的基础。但是，用水文信息来封闭土壤水分平衡，并不能洞察通过深层排水或土壤蒸发和蒸腾作用组合通过土柱的水的年龄分布。这是目前我们学科中的一大挑战；追踪水平衡是下一步需要做的。在这里，我们报告了一个受控示踪剂实验的结果，该实验旨在关闭土壤水分平衡并追踪其个别成分。这是在种植了一棵柳树的2.5米(3)蒸渗仪上进行的。我们在蒸渗仪的顶部施加了25毫米的同位素浓缩水，并通过土壤水、底部排水和植物木质部对其进行了43天的跟踪。然后我们对系统进行破坏性采样，以量化剩余的同位素质量。收集了900多个水样进行稳定同位素分析，以追踪标记灌溉。然后，我们使用这些数据来量化标记灌溉何时何地成为植物吸收或深度渗漏的来源。水分平衡流出以蒸散为主(88%)。对蒸腾通量的跟踪进一步表明，蒸腾作用是1-2个月前以降水形式下降的土壤水分。在蒸腾作用中的示踪突破是复杂的，不同于在土壤中或在底部排水中观察到的突破曲线。由于缺乏从旅行时间到蒸腾作用的直接实验数据，这些结果提供了第一个平衡闭合，其中跟踪了所有相关的流出。
Closure of the soil water balance is fundamental to ecohydrology. But closing the soil water balance with hydrometric information offers no insight into the age distribution of water transiting the soil column via deep drainage or the combination of soil evaporation and transpiration. This is a major challenge in our discipline currently; tracing the water balance is the needed next step. Here we report results from a controlled tracer experiment aimed at both closing the soil water balance and tracing its individual components. This was carried out on a 2.5 m(3) lysimeter planted with a willow tree. We applied 25 mm of isotopically enriched water on top of the lysimeter and tracked it for 43 days through the soil water, the bottom drainage, and the plant xylem. We then destructively sampled the system to quantify the remaining isotope mass. More than 900 water samples were collected for stable isotope analysis to trace the labeled irrigation. We then used these data to quantify when and where the labeled irrigation became the source of plant uptake or deep percolation. Evapotranspiration dominated the water balance outflow (88%). Tracing the transpiration flux showed further that transpiration was soil water that had fallen as precipitation 1-2 months prior. The tracer breakthrough in transpiration was complex and different from the breakthrough curves observed within the soil or in the bottom drainage. Given the lack of direct experimental data on travel time to transpiration, these results provide a first balance closure where all the relevant outflows are traced.