Collaborative Proposal: MSA: Controls on coupled nitrogen and carbon cycles of watersheds across eco-regions

Title: Collaborative Proposal: MSA: Controls on coupled nitrogen and carbon cycles of watersheds across eco-regions<br/><br/>Nitrogen is a critical nutrient that supports life. Too much can cause problems such as unsightly algal blooms or coastal dead zones where fish cannot live. The fate of nitrogen is closely tied to the fate of carbon in plants and soil. However, the connection between nitrogen and carbon remains poorly understood. In particular, little is known about carbon and nitrogen interactions across different landscapes, from the tropics to the arctic. This project will help better understand what controls nitrogen leaving watersheds through streams. It will take advantage of data collected by the National Ecological Observatory Network across the nation's diverse environments. This research is important as people add more nitrogen to the land through air pollution, fertilizers, and septic systems. It will also help understand how much carbon the environment can absorb as carbon dioxide increases in the atmosphere. The project will result in new data sets that will be shared with other researchers. The project team will work with schools and local communities to explain how what happens on land affects water quality. Findings will be translated to be useful for policy makers. A diverse group of students will learn how to use environmental sensor technology. <br/><br/>Consistent input and output measurements for terrestrial and aquatic ecosystems collected by NEON will be used to address the overarching question: "How tightly are watershed carbon (C) and nitrogen (N) cycles coupled across biomes and how is this coupling influenced by physical environmental conditions (climate and hydrology), vegetation characteristics, and legacies from past disturbance?" Hypotheses will be tested related to the role of watershed carbon to nitrogen ratios, precipitation, storminess, temperature, and disturbance using 1) ongoing NEON sensor, manually-collected, and remote sensing measurements to estimate watershed N inputs, N outputs and net ecosystem C exchange (NEE), 2) a terrestrial ecosystem model (PnET) to scale NEE to the entire watershed draining to streams, and 3) analysis of watershed net N and C fluxes against potential explanatory data for each domain. Twenty-two NEON watersheds defined by wadeable streams and proximity of NEE measurements will be used, incorporating a wide range of watershed characteristics. Watershed budget estimates will include estimates of uncertainty in both C and N fluxes and sinks. Scientific findings will be translated into education and policy relevant information with groups such as LTER Schoolyard program and the Science Policy Exchange.<br/><br/>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.