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

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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.