Human activities, including the use of fossil fuels, have increased the amount of available nitrogen globally. This increased nitrogen availability can alter plant communities and lead to decreased plant species diversity. One challenge to understanding the impacts of nitrogen enrichment is that communities exhibit a wide range of responses. Why do some communities respond strongly while others do not, and can we identify factors that indicate which communities are most vulnerable? This project will test whether plant traits associated with nitrogen use (e.g., specific leaf area, leaf carbon to nitrogen ratios, and leaf nitrogen to phosphorus ratios) can help to understand ecological responses to nitrogen enrichment. It will address two questions: 1) does nitrogen enrichment cause a shift toward species with certain traits, and 2) are there stronger diversity declines in communities composed of species with certain traits and/or with a narrower range of traits prior to enrichment? Encompassing 260 species in 35 nitrogen fertilization experiments in 10 habitats across the United States, the research will quantify relationships among leaf traits and changes in species composition due to nitrogen enrichment. This research will be the first to use large-scale, multisystem variation in plant traits to predict the impacts of nitrogen enrichment. This project will support the research of a doctoral student. Data will be made publicly available for further studies and educational opportunities, and an interactive website will be created to help high school students visualize nitrogen enrichment threats in different communities.
