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。通常很清楚一个生态系统是否吸收了太多的氮，因为离开生态系统的水和气体中有高水平的氮。然而，目前尚不清楚沙漠等干旱地区的生态系统对添加的氮素有何反应。旱地覆盖了地球陆地表面的三分之一。重要的是要了解添加的氮素将如何影响这些生态系统。该项目还将通过对本科生、研究生和博士后助理进行科学方法培训来建设科学队伍。这些学生中的许多人将通过西班牙裔服务机构获得帮助。南加州将开展面向公立K-12学校的外展活动。这项研究将有助于预测环境变化将如何影响生态系统的过程和服务，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为重要。该项目将评估降水量相对较少的流域的氮素动态。这些研究地点位于加利福尼亚州南部，接收到不同水平的大气氮沉积。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。这项研究将把氮饱和理论推广到干燥系统。它将解释季节性过渡期间降雨的脉动性质。该项目将使用被动收集器和空间建模来量化大气氮输入。还将在土壤和水中进行氮素测量。然后，这些测量将被用于改进生物地球化学模型。该模型将测试分水岭对氮素添加的反应。这项研究中的测量和建模相结合的方法将推动关于水文学在推动流域尺度上的氮素动态方面的作用的理论。这一奖项反映了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。

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.