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

干旱的频率和严重程度增加，使了解森林水源的重要性更加突出。在土壤水不可用的地方，木本植物通常会获得储存在风化基岩的裂缝和孔隙中的水（岩石水分）。然而，与土壤地幔相比，人们对基岩中储存的水以及植物如何获取水知之甚少。需要更好的工具来识别不同物种如何获得岩石水分，以了解降水的变化如何影响当地的水资源。该实验通过同位素示踪剂跟踪通过土壤，基岩和树木的水流，以记录森林用水如何影响地下水补给和水流，特别是在干旱期间。新的追踪水的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。这项研究是在加利福尼亚州北方古老森林的一个山坡上进行的。实验结果将提供直接的同位素证据，树木在旱季的水源，以及它们的吸水量如何影响地下水补给和径流。该研究克服了以前的挑战，通过利用独特的能力，通过非饱和，断裂基岩使用专门的采样基础设施跟踪水跟踪岩石水分。标记的水将在旱季开始时注入基岩。在接下来的旱季和雨季，这些被标记的水将通过地下-植物-大气连续体被追踪。该项目还将通过测量自然存在的短寿命放射性同位素的浓度来估计水池的水龄和通行时间。来自标记水和放射性同位素的估计过境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，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估。

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.