| 英文摘要: | It has received less attention than climate change, but nitrogen deposition from air pollution could also have major ecological effects. One well-documented effect of adding nitrogenous fertilizers to grasslands is loss of species due to heightened competition. Although deposition from the air is so far mostly adding smaller amounts of nitrogen, accumulated effects could cause similar losses. This project will advance our understanding of how nitrogen deposition is likely to affect biodiversity in grasslands worldwide in the future. In partnership with an international network of research sites, researchers will measure incoming nitrogen, accumulation of nitrogen in the soil, and abundances of plant species over three years to discover which levels of nitrogen deposition are likely to trigger species loss. Because reducing nitrogen pollution can be economically costly, it is important to be able to weigh these costs against benefits to conservation of diversity and other resources such as grazing lands. Research results will thus be disseminated to managers in the U.S. to help inform policy with science. The project will also train technicians and undergraduate students and provide research experiences for two high school teachers who will pass on their knowledge to classes.
The project will test the hypothesis that the relationship between nitrogen deposition and species loss is determined by previous nitrogen availability, co-limitation of plant growth by other nutrients, climate, and species traits. At about 30 of the 75 sites in the international Nutrient Network, researchers and collaborators will install nitrogen addition treatments designed to mimic accelerated deposition and deploy ion-exchange resin collectors to measure nitrogen availability to plants. These treatments and measurements will be combined with existing nutrient treatments and measurements of nitrogen input, climate, and plant species composition to provide a large data set for Bayesian analyses. |