Nitrogen deposition sources and patterns in the Greater Yellowstone Ecosystem determined from ion exchange resin collectors, lichens, and isotopes.

Over the past century, atmospheric nitrogen deposition (N) has increased across the western United States due to agricultural and urban development, resulting in degraded ecosystem quality. Regional patterns of N are often estimated by coupling direct measurements from large-scale monitoring networks and atmospheric chemistry models, but such efforts can be problematic in the western US because of complex terrain and sparse sampling. This study aimed not only to understand N patterns in mountainous ecosystems but also to investigate whether isotope values of lichens and throughfall deposition can be used to determine N sources, and serve as an additional tool in ecosystem health assessments.