Collaborative Research: Tracing the fate, age, and ecohydrologic significance of rock moisture

干旱的频率和严重程度增加了了解森林水源的重要性。在没有土壤水分的地方，木本植物通常获得储存在风化基岩下面裂隙和孔洞中的水(岩石水分)。然而，与土壤地幔相比，人们对储存在基岩中的水以及植物可能如何接触到水知之甚少。需要更好的工具来识别不同物种如何获取岩石水分，以了解降雨量的变化如何影响当地水资源。这项实验通过同位素示踪剂跟踪水在土壤、基岩和树木中的流动，以记录森林水如何利用地下水补给和溪流的影响，特别是在干旱期间。新的水追踪工具将被评估并传达给学生和早期职业科学家，以便这些工具可以被广泛应用，以更好地了解气候变化下水资源的命运。研究是在北加州一片古老森林中的一个集中表征和监测的山坡上进行的。实验结果将为树木在旱季何时何地供水以及它们的水分吸收如何影响地下水补给和径流提供直接的同位素证据。这项研究克服了以前在追踪岩石水分方面的挑战，利用独特的能力，利用专门的采样基础设施，通过非饱和、裂隙的基岩追踪水分。在旱季开始时，标签水将被注入基岩中。在接下来的旱季和雨季，标记的水将通过地下-植物-大气连续体进行追踪。该项目还将通过测量短命的天然放射性同位素的浓度来估计水池的水龄和通过时间。来自标签水和放射性同位素的估计通过时间将独立用于评估岩石水分的命运及其生态水文意义。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Increased frequency and severity of drought is amplifying the importance of understanding where forests source water. Where soil water is unavailable, woody plants commonly access water stored in the underlying fractures and pores of weathered bedrock (rock moisture). However, in contrast to the soil mantle, little is known about water stored in bedrock and how accessible it may be to plants. Better tools for fingerprinting how different species access rock moisture are needed to understand how shifts in precipitation could impact local water resources. This experiment tracks water flow through soil, bedrock, and trees via isotopic tracers to document how forest water use influences of groundwater recharge and stream flow, especially during drought. New tools for tracing water will be evaluated and communicated to students and early career scientists, so that these tools can be widely applied to better understand the fate of water resources under changing climate.The research is conducted at an intensively characterized and monitored hillslope in a Northern Californian old-growth forest. Experimental results will provide direct, isotopic evidence for when and where trees source water during the dry season and how their water uptake impacts groundwater recharge and streamflow. The study overcomes previous challenges with tracing rock moisture by leveraging the unique capability to trace water through unsaturated, fractured bedrock using specialized sampling infrastructure. Labeled water will be injected into the bedrock at the start of the dry season. That labeled water will be tracked through the subsurface-plant-atmosphere continuum in the dry and wet seasons that follow. The project will also estimate water age and transit time of water pools by measuring concentrations of short-lived naturally occurring radio-isotopes. Estimated transit times from labeled water and radio-isotopes will be used independently to evaluate the fate of rock moisture and its ecohydrologic significance.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.