Scientists to Examine Negative Impacts of Pollutant Nitrogen on Plant Diversity

Nitrogen is a beneficial plant fertilizer in small amounts, but large amounts cause negative impacts on ecosystems, such as water pollution, acidification of soils, increased productivity of invasive species, increased probability of wildfire, and a decline of native plant diversity.

Over the past century human activities have more than quadrupled the amount of plant-available nitrogen inputs from the atmosphere compared to natural inputs. What impact does this have on plant species diversity across the United States?

A group of scientists, including researchers at the University of California, Riverside, has received a one-year $100,000 grant from the John Wesley Powell Center for Analysis and Synthesis of the U.S. Geological Survey to examine the evidence for impacts of pollutant nitrogen on plant species diversity across the United States. Specifically, the group, called the Powell Center Working Group on Diversity and Nitrogen Deposition, will synthesize data sets on the impacts of nitrogen deposition on plant diversity.

"Documentation of the impacts of nitrogen deposition on plant diversity are generally lacking in the U.S., but observations from Europe indicate biodiversity losses in areas with high levels of nitrogen pollution," said Edith B. Allen, a professor of plant ecology in the Department of Botany and Plant Sciences and the grant's principal investigator at UC Riverside. Other principal investigators are at the U.S. Geological Survey and the University of Colorado at Boulder.

Nitrogen's primary sources are agriculture, industry and automobile emissions. Nitrogen deposition refers to the input of reactive nitrogen species from the atmosphere to the biosphere. The pollutants that contribute to nitrogen deposition derive mainly from nitrogen oxides and ammonia.

Allen and her colleagues will evaluate patterns of plant diversity within plant communities along gradients ranging from high to low nitrogen deposition. The group will determine the gradients from a nationwide deposition model as well as measured deposition data from the Environmental Protection Agency and other agencies.

"We have already obtained plant diversity data from government and private sources," said Allen, a member of UCR's Center for Conservation Biology. "We will use our results to refine critical loads of nitrogen inputs that cause losses in diversity, and we will make available critical load data to regulatory agencies so that they can set air quality standards to preserve biodiversity."

The Powell Center Working Group on Diversity and Nitrogen Deposition has a total of 16 collaborators from the United States and Europe. At UCR, Allen will be joined in the research by Robert Johnson, an assistant specialist in the Center for Conservation Biology.

The John Wesley Powell Center for Analysis and Synthesis serves as a catalyst for innovative thinking in earth system science research by providing scientists from different backgrounds a place and time to focus on multi-faceted issues. Its working groups come together around information related to complex questions or phenomena.