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June 15th, 2005

Nitrogen fertilization of soil puts rare plant species at risk

Katherine Suding (former INSTAAR postdoc; assistant professor, UC Irvine) led a team from eight universities in compiling data from previous and ongoing nitrogen-loading experiments on the alpine tundra of Niwot Ridge and in eight other ecosystems across North America. They found that rare plant species are six times more likely than abundant species to be lost due to nitrogen fertilization of soil.

While nitrogen increases the production of most plants, an excess amount of it creates competition among plants for space that tends to drive rare plants out of existence, causing a loss of biodiversity. The team determined that other plant traits may put abundant plant species at risk in some settings: short height (short plants receive less sunlight in the midst of taller plants); the ability to convert atmospheric nitrogen, via bacteria, into a form that plants can use (the cost of supporting the bacteria hurts the plants); and a short life span (longer-living plants do not have to start the life cycle all over again).

The teams' work on nearly a thousand plant species will help predict how patterns of plant diversity will decline as N availability continues to increase globally in terrestrial ecosystems due to human activities.

The project was initiated through the Niwot Ridge Long-Term Ecological Research (LTER) site, administered by INSTAAR, including experiments by Tim Seastedt (INSTAAR) and Bill Bowman (INSTAAR). A subsequent larger effort was funded through the LTER network office. Additional INSTAAR contributions include data compilation assistance by Dan Liptzin. Publication of the research was highlighted in the 15 April issue of Science. Suding will return to INSTAAR this summer to continue research activities on Niwot Ridge and Colorado locales.

The paper was published in the March 22, 2005 issue of Proceedings of the National Academy of Sciences of the United States of America.