Research Starter Grant: Using Stable Isotopes to Identify the Components of Forest Canopy Evapotranspiration

植物叶片的同位素组成提供了每单位植物生长所损失的水分的信息。此外，最近的数据表明，碳和氢同位素测量可以用来确定森林冠层中的水蒸气是来自土壤、通过蒸发还是来自植物。在本研究中，我们将研究叶片和冠层水汽的同位素组成，以了解和预测植被对降水潜在变化的响应，并确定植被对生态系统尺度水循环的可能反馈。该项目旨在测试在加州大学河滨分校（UCR）附近的加州大学自然保护区系统的詹姆斯圣哈辛托山保护区有关植被-大气水循环的三个假设。这三种假设将植物生理学与生态系统水平的过程结合起来，并将在了解植被对预测降水变化的响应的背景下进行评估。该项目将直接支持UCR开发新的稳定同位素设施，从而为最先进的科学基础设施做出贡献。它还将促进一位新助理教授的专业发展，并促进他与具有相似兴趣的当地科学家先锋小组的互动。此外，詹姆斯保护区的工作将受益于该地区正在进行的密集研究，该地区已成为创新和实验技术的温床。这项调查的新颖性将为向学生传授这项技术并进一步使用它提供机会。

The isotopic composition of plant leaves provides information about the amount of water lost per unit of plant growth. Further, recent data show that carbon and hydrogen isotope measurements can be used to determine whether water vapor in the forest canopy came from the soil, via evaporation, or from plants. In this study, the isotopic composition of leaves and canopy water vapor will be investigated to understand and predict the responses of vegetation to potential changes in precipitation, and to identify possible vegetation feedbacks to ecosystem-scale water cycling. The project is designed to test three hypotheses relating vegetation-atmosphere water cycling at the James San Jacinto Mountain Reserve of the University of California Natural Reserve System, near University of California, Riverside (UCR). The three hypotheses integrate plant physiology to ecosystem-level processes, and will be evaluated in the context of understanding the responses of vegetation to predicted changes in precipitation regime. This project will support directly the development of new stable isotope facilities at UCR, and thus contribute to state-of-the-art scientific infrastructure. It also will promote the professional development of a new assistant professor, and his interaction with a pioneering group of local scientists with similar interests. Furthermore, work at the James Reserve will benefit, and benefit from, intensive on-going studies at that location, which has become a hotbed of innovative and experimental techniques. The novelty of this investigation will allow opportunities to teach this technique to students and further its use.