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。如果一个生态系统接收了太多的氮，通常是很清楚的，因为离开生态系统的水和气体中有高水平的氮。然而，目前还不清楚干旱地区（如沙漠）的生态系统如何对增加的氮做出反应。旱地占地球陆地面积的三分之一。重要的是要了解增加的氮将如何影响这些生态系统。该项目还将通过培训本科生、研究生和博士后研究员来培养科学人才。这些学生中的许多人将通过西班牙裔服务机构获得。对公立K-12学校的宣传活动将在加州南部举行。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。该项目对于了解干旱生态系统的功能尤其重要。 该项目将评估降水量相对较少的流域的氮动态。研究地点位于加州南部，并接受不同程度的大气氮沉降。该项目的总体目标是制定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输入。还将对土壤和水中的氮进行测量。这些测量结果将用于改进地球化学模型。该模型将测试流域对氮添加的反应。在这项研究中，测量和建模相结合的方法将推进水文学在流域尺度上驱动氮动态的作用的理论。该奖项反映了NSF的法定使命，并被认为是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的支持。

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.