Collaborative Research: How can we assess nitrogen saturation in xeric ecosystems? Accounting for water, time, and nitrogen availability

大气氮沉降有可能对生态系统产生负面影响。如果一个生态系统吸收了过多的氮，通常是很清楚的，因为离开生态系统的水和气体中的氮含量很高。然而，目前还不清楚干旱地区（如沙漠）的生态系统如何对添加的氮做出反应。旱地覆盖了地球陆地表面的三分之一。了解添加的氮将如何影响这些生态系统是很重要的。该项目还将通过培养本科生、研究生和博士后的科学方法来建设科学队伍。这些学生中的许多人将通过西班牙裔服务机构获得帮助。加州南部的公立K-12学校将开展拓展活动。这项研究将有助于预测环境变化将如何影响生态系统过程和服务，如清洁的空气和水。这个项目对于了解干旱生态系统的功能特别重要。该项目将评估降水相对较少的流域的氮动力学。研究地点位于加州南部，大气中的氮沉降水平不同。该项目的总体目标是开发一个更好的评估氮饱和度的框架。该研究将氮饱和理论扩展到干燥系统。它将解释季节转换期间降雨的脉冲性质。该项目将使用被动收集器和空间建模来量化大气氮的输入。土壤和水中的氮含量也将进行测量。这些测量结果将用于改进生物地球化学模型。该模型将测试流域对氮添加的反应。本研究中测量和建模相结合的方法将推动围绕水文在流域尺度上驱动氮动力学作用的理论。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

Atmospheric nitrogen deposition has the potential to negatively affect ecosystems. It is usually clear if an ecosystem has received too much nitrogen because there are high levels of nitrogen in water and gas leaving the ecosystem. However, it is unclear how ecosystems in dry places, such as deserts, respond to added nitrogen. Drylands cover a third of Earth's land surface. It is important to understand how added nitrogen will affect these ecosystems. This project will also build the scientific workforce by training undergraduate students, graduate students, and postdoctoral associates in scientific methods. Many of these students will be reached through a Hispanic serving institution. Outreach activities to public K-12 schools will take place in southern California. This research will help predict how environmental change will affect ecosystem processes and services, such as clean air and water. This project will be especially important for understanding how dry ecosystems function. This project will evaluate nitrogen dynamics in watersheds receiving relatively little precipitation. The study sites are in southern California and receive different levels of atmospheric nitrogen deposition. The overall goal of the project is to develop a better framework for assessing nitrogen saturation. The research will expand nitrogen saturation theory to dry systems. It will account for the pulsed nature of rainfall during seasonal transitions. The project will quantify atmospheric nitrogen inputs using passive collectors and spatial modeling. Nitrogen measurements will also take place in the soil and water. These measurements will then be used to improve a biogeochemical model. The model will test watershed responses to nitrogen addition. The combined approaches of measurement and modeling in this study will advance theory surrounding the role of hydrology in driving nitrogen dynamics at the watershed scale.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.